Build This Tube Amp With A Screwdriver

[FlaCharlie]

So for those who can't read schematics, I'll try to explain all the connections using the following wiring diagrams. While they're not step-by-step instructions like you'd find in a kit, they should be fairly easy to follow.

Here's the wiring diagram for the 6SL7 input tube which plugs into the center socket:


The connections close to the center of the diagram are numbered. They're the screws on the octal socket that go to the tube pins. You can see the orientation of the locator pin / keyway. The locator pin prevents the tube from being inserted the wrong way. Notice that, unlike the diagrams found in tube data sheets, the sequence here is counter-clockwise since we're looking at the top of the socket. The sockets have numbers molded into the plastic but they're tiny and difficult to see.

The connections further from the center are on the terminal strips. For simplicity, only one connection ( O ) is shown but each one actually represents a pair and connections can be made to either one of the pair since they are connected to each other.

Note that parts from Pins 4 and 5 of the 6SL7 go to 3 connections. Those 3 are on the larger 8 position terminal strip that's located in the center / on the rear side of the amp. I'll post a diagram of the entire 8 position strip later. Obviously, there will be some redundancy as some connections will appear on two different diagrams.

The parts / connections on Pins 1 and 2 of the 6SL7 go to a smaller terminal strip which only has 3 terminals. That strip is located in the center / on the front side of the amp.

Here's an in-progress pic that shows some of that. I meant to take more of them but once I started wiring things up I got on a roll and didn't take many pics.



Here's the wiring diagram for the Left Channel EL34. The connections on the right side are on the 3 position barrier strip mounted on the front side of the amp. The connections on the left side are on the 4 position barrier strip mounted towards the rear of the amp.


Here's an in-progress pic of that:



Similarly, here's the wiring diagram for the Right Channel EL34. Again, the connections on the right side are on the 3 position barrier strip mounted on the front side of the amp and the connections on the left side are on the 4 position barrier strip mounted towards the rear of the amp.


Note that Pin 8 (the cathode) and Pin 1 (G3) must be connected at the socket with a wire. Some tubes make this connection internally but the EL34 does not so the jumper wire is necessary. Also, the EL34 does not have a Pin 6. So I'm using that connection (Pin 6) on the socket as a tie point. This makes it easier to mount the grid stopper resistor since the resistor body should be mounted as close to the grid pin as possible. The grid stopper is the dark brown resistor in the pic. Pin 5 is the grid pin.

Here's an in-progress pic of the 6SL7 and the Right EL34:



Here's the wiring diagram for the SMPS terminal strip, which has 6 positions:



And here's a pic of it wired up:



The SMPS terminal strip is mounted with nylon spacers so there's a gap between the bottom of the terminal strip and the board. This allows the green wires in the pic, which are the 6.3v heater wires, to run underneath the terminal strip on their way to the tube sockets. The orange wire, which is the heater ground, connects to the SMPS terminal strip as shown in the diagram.

Here's the wiring diagram for the 8 position terminal strip, which is mounted in the center / rear of the amp. Again, some of these connections are also described on other diagrams.


Here's a pic of the amp from the rear showing how I've mounted the IEC socket that connects the SMPS to the AC supply coming from the wall. I've used a combination IEC connector / fuse / switch and mounted it with a pair of 2" L brackets.




Looks like I've reached the 10 pic limit for posting pics in a single post so I'll continue in another post . . .

 

[FlaCharlie]

Here's a pic of the connections between the IEC socket and the SMPS. I'm using crimp / push on connectors on the switch. Those were sourced from AliExpress but I'm sure you can find them elsewhere too. The connection to the SMPS is made with crimp on spade connectors which can typically be found at places like Lowe's, Home Depot or Harbor Freight but you could just make these connections with the bare wires.



Prospective builders can use a variety of methods to wire up the AC connection from the wall to the input of the SMPS.

IEC sockets just allow you to use a removable power cord. They are available in a variety of configurations. You could use an IEC that also houses a fuse but has no switch or an IEC connector that has no switch and no fuse.

Of course, you don't need to use an IEC at all, it's just a convenience. You could just connect the bare wires of a 3 wire cord directly to the SMPS, plug the other end into a power strip and switch it on and off using the power strip.

The SMPS has an internal fuse and various protection circuitry so it will go into protection mode if there is an issue. I just wanted to be doubly sure so I used an additional fuse. I'm using a 2A fast blow. You can also use a chassis mount fuse holder that uses crimp connections if you only want to add a fuse.

Here are pics of the speaker connections and the RCA inputs:




For the RCA inputs and speaker outputs I'm using a wall plate that's typically used for home theater installations. There are a couple different types of these. Some plates have small square holes and use connectors that snap into place. I'm using the type that has the speaker binding posts and RCA jacks fastened to the wall plate with nuts. Either type should work fine.

You'll usually find these plates with either all speaker connections or all RCA already installed. The one here originally had 8 speaker connections. I removed 4 of them and filled two of the empty holes with RCA jacks that were removed from some of the square snap-in types. So now I've got 4 speaker connections and 2 RCAs mounted onto a single plate. The RCA jacks are female to female.

The 8 position terminal strip diagram that I posted earlier shows how the RCA inputs are wired.

You could use a plate that has 6 connections instead of 8. I bought the 8 connection plate so that I would have 4 extra speaker connectors that I could use later for other projects.

If you want to build it like I have here (without solder) you want to make sure that the connectors themselves do not require solder. Some listings for these only show the outside connections and you can't tell if the inside connections require solder or not. You need to be able to see pics that show both sides of the connectors so you can confirm that they're the right type.

For the speaker connections I'm using banana plugs on speaker side. They also use screws to attach the speaker wires. On the amp side of the wall plate the bare wires from the OT (output transformer) are screwed into the binding posts.

Here's the wiring diagram:


Here's a pic of the speaker posts that are used in the wall plates and the handy RCA plugs with screw connectors that I'm using on the amp side of the wall plate.



This is just one method of making these connections. You don't need to use one of these wall plates. For example, the OT (output transformer) secondary wires and the speaker wires could be connected with screws using one of the same type of terminal strips that are used elsewhere. Vintage amps typically use screw terminals to connect the speakers.

For the RCA inputs you could just cut an interconnect cable and use the screw connections / terminal strips on the wire end. The end that still has a plug can either be left long enough to connect to a source or it could be kept very short. If kept short you could then use a female to female RCA adapter to connect separate / longer cables.

These days I mostly stream audio or play CDs through a DAC that has a volume control. So I've just built this as a power amp with no volume control. Volume controls with screw connections are available if you want to add one.

Next up, a parts list . . .

 

[FlaCharlie]

So finally I'll discuss which parts I used . . .

First, I'll list them according to which part of the circuit they're associated with and what their function is. Later I'll try to post some parts numbers from Digi-Key, which is where I usually buy things like resistors and capacitors. Other major suppliers like Mouser are fine too but I would not buy these parts on eBay or AliExpress. Digi-Key has a free shipping option which is especially handy for small parts orders. Here's a link with details:

http://www.audiokarma.org/forums/in...hipping-on-parts-orders.739513/#post-10018562

Resistors are 1/2w (0.5w) carbon film unless noted. You can use metal film if you prefer. The ones marked * are used as grid stoppers. For those I prefer to use carbon comp types but many people use carbon film or metal film.

6SL7 or 12SL7
Triode section #1:
100k grid leak resistor
220 Ω grid stopper resistor*
AA Battery
Battery Holder w/wire leads
100k plate load resistor (I'm using 1w but 1/2w is OK too)
330k feedback resistor
39k feedback resistor

Triode section #2:
100k grid leak resistor
220 Ω grid stopper resistor*
AA Battery
Battery Holder w/wire leads
100k plate load resistor (I'm using 1w but 1/2w is OK too)
330k feedback resistor
39k feedback resistor

EL34 x 2
470k grid leak resistor
680 Ω grid stopper resistor*
200 Ω 5w cathode resistor (wirewound)
220uf 25v cathode bypass capacitor (electrolytic)
1.8k screen resistor
0.22uf coupling capacitor (400v or higher)

Note on coupling caps: Obviously, you can go down the boutique rabbit hole if you like but basic caps from Digi-Key or other reputable sources are fine. I splurged a bit because I wanted to try the Mundorf Aluminum Oils that Stephe recommends. They are available from Parts Connexion and cost ~$48 shipped.

I don't typically spend a lot of time trying different caps but I had tried several types that I had on hand when I was breadboarding this experimentally with a similar circuit. The ones that sounded best in that comparison, before I ordered the Mundorfs, were probably the cheapest I had in stock. I think I must have bought them 20 years ago when I was first stocking my shop. They are unbranded but I think I may have gotten them from Antique Electronics. The drawer they were in was labelled Metallized Polyester and they were the last two left in that value. The Mundorfs did sound better to me but I didn't think they were head and shoulders better. The concept of diminishing returns is quite real, IMO. I often find that spending considerably more results in only an incremental improvement and sometimes no improvement at all.

That said, part of the fun of a breadboard style build is that it makes it very easy to experiment with different parts. So have fun with it. It's a subjective hobby so YMMV.

Power Supply
SMPS - listed as "250w / 300v 0.6A / 6.3v 4A / 12.6v 4A" on eBay and AliExpress
Model # ending in -U1 is preferred / see earlier post
for comments on Model # ending in -52

1k dropping resistor
22uf 450v electrolytic capacitor
250 Ω 5w resistor (wirewound) (omit if using 12SL7 instead of 6SL7)
100 Ω resistor (isolates the heater supply ground from signal ground)
100 Ω resistor (1w metal oxide) (isolates the signal ground from safety ground)
0.1uf 630v capacitor (isolates the signal ground from safety ground)
2A Fuse

Tubes
I haven't done any serious tube rolling in this build.

I'm using some JJ E34L output tubes. I had a quad of them that I bought years ago. I had used them in some vintage PP amps (Pilot 260, Eico HF-87) but they still test as new. They're easy to find. Antique Electronic Supply (tubesandmore.com) lists them for $24 each. They're a reliable source for other items too.

The only types of 6SL7s I've tried are a USA Raytheon with black glass and an RCA short bottle with clear glass. Both are used tubes but test as new in my Hickok with well balanced triodes. The big dealer near me, Radio Electric Supply (vacuumtubes.net), lists NOS Raytheons for $25 and the RCAs for $40, also NOS. I've also used a Raytheon branded Japanese 12SL7, which also sounds fine. They list 12SL7s for $5 each.

Another very large dealer is vacuumtubesinc.com in Orlando.

I prefer using old production tubes but there are new production 6SL7s available. Oddly, they seem to cost more. There is also a Russian version that I've heard is decent.

I avoid the "boutique" dealers who write flowery descriptions of how a tube sounds. And I have no problem using strong or new testing used tubes.

Output Transformers
Should have 3.5k or 5k primary with an UL tap
rated for at least 10w

Obviously, you can use any OT you prefer, even ones that cost $1000. The cost of OTs will be the biggest variable when it comes to total build cost. Check physical sizes and adjust your build accordingly.

The OTs I'm using were purchased from AliExpress. They're not "branded", at least not in English.

A wide variety are sold. Many look very similar and some are obviously exactly the same. The sellers are not the manufacturer, they probably all get them from the same distributor. The same OTs are often sold by different sellers at prices that vary considerably. Some sellers sell pairs and others list them individually. Shipping prices vary wildly. If you see a high shipping price for a single unit that price usually does not double if you order two. You've got to put a pair of them in a cart to find out what the total will be.

So spend some time comparing what's out there at any given moment.

AliExpress OT listings have some limited specs in the descriptions which can be useful for comparing them to other AliExpress OTs but, beyond dimensions and weight, I would be hesitant to use them to compare with OTs made elsewhere. I consider any of the specs that might impact performance to be questionable.

I mostly chose the ones I'm using based on price and the claim that they have 38H of inductance, which is higher than many of the others sold there. Inductance supposedly affects bass response and higher is better. They cost ~$80 for the pair including shipping. I also bought some that are 5k for a different project. They're apparently from the same manufacturer (based on a label on the bottom) and they cost me ~$90 shipped. (Some folks here (@Lavane @Tom Bavis) have used the smaller 5w OTs that seem to be made by the same manufacturer and they have reported good results.) Perhaps they will comment?

Slightly larger ones, rated at 13w are also available. I think I saw some of those for ~$110 shipped. And higher wattage ones are listed too but prices are higher.

Bottom line . . . I'm very happy with the sound I'm hearing using them. My last project (the Cockeyed Monkey) used the 15w GXSE OTs from Edcor, which are a popular choice for DIY builds. I believe that Stephe and Analog Ethos use the Edcors. They cost about twice as much (~$160) and you need to add shipping to that.

For another SMPS project, which I breadboarded previously, I'm using the Hi-Fi OTs from Musical Power Supplies (MPS). Those also sound really good but they won't work here because none of his OTs have UL taps. But if you're building a different circuit, take a look.

I have no way to measure but, to my ear, these Chinese OTs seem to work just as well as the Edcors and the MPS. But I can't compare them directly because they are not suited for the same circuit.

Notably, they claim to use Z11 laminations. I know zilch about transformers but from what I've read that material is considered higher quality than what Edcor and MPS use. I recall reading that MPS, who are mostly known for guitar stuff, was trying to source Z11 in an effort to improve the quality of their Hi-Fi offerings. Of course there's probably no way to tell if they are actually using Z11. But it's worth mentioning.

Here are pics of the OT listing and some of the other items that were purchased from places like eBay and AliExpress. The descriptions can be used to search. These are not links and prices shown may not be current or the best deal. The sellers are not identified. Sellers come and go and deals change so all I can say is "shop around". Buy from whatever source you're comfortable with.

 

[Lavane]

Nice, thanks for posting a parts list. As for those cheap OPT's, they sound pretty good in the DG-1 modified Maggie 8600 I built from scratch. I don't think I would use them in this amp though. A 10 to 20 watt output transformer is what I would use personally. Maybe those smaller 15w Edcore's or the ones you posted.

 

[nikon f]

What was the total cost for this amplifier?

 

[FlaCharlie]

Nice, thanks for posting a parts list. As for those cheap OPT's, they sound pretty good in the DG-1 modified Maggie 8600 I built from scratch. I don't think I would use them in this amp though. A 10 to 20 watt output transformer is what I would use personally. Maybe those smaller 15w Edcore's or the ones you posted.

Yeah, those little 5w ones wouldn't be useful for this circuit due to their wattage rating. They don't have an UL tap either. But for circuit using a SE EL84 / 6BQ5 or 6V6 they look like a decent budget choice.

The 10w ones I'm using seem to be made by the same manufacturer, that's the only reason I mentioned the little 5w ones.

 

[FlaCharlie]

What was the total cost for this amplifier?

I haven't tallied it up. But the cost of the most expensive parts should give you an idea:

SMPS ~$40 shipped
OTs ~$80 shipped
EL 34s ~$50
6SL7 ~$30
Cage $20
Sockets ~$9
Barrier Strips ~$8

That's about $237. So depending on other choices I'm guessing maybe ~$300?

That's assuming you just use normal decent coupling caps, not the Mundorfs. And if you use a 12SL7 instead of a 6SL7 you can deduct ~$25 from the above. The 12SL7 is exactly the same tube, it just has a 12.6v heater.

Anytime you do a DIY project there are choices that each person must make. I've tried to explain how to economize in certain areas. For example, if you read through the thread I discuss some optional, lower cost, methods of connecting the AC, the speakers and the source.

And, remember, this is really more about using this SMPS and these build methods.

A different circuit could be built for a somewhat lower cost. For example, a SE design that uses a 6BQ5 or 6V6 could use the little 5w OTs mentioned above. I think Lavane told me he paid $34 for the pair he's using. So that would reduce the above cost by $46.

Using all 12.6v tubes would also reduce the cost. A 12V6 could be used instead of a 6V6, for example. For a design that uses either a single 12SN7 or 12SL7 and a pair of 12V6 output tubes the total cost of tubes would only be ~$15 or so for quality American tubes.

The Russian versions of the EL84 or 6V6 are also good choices.

 

[Lavane]

The Russian Reflektor 6H9C along with a few more can be used instead of the 6SL7 too. That would even save a few more bucks.
I used them in a PP amp and they sounded pretty good. I still have a pair of them along with a quad of JJ KT-77's.

 

[BrassTeacher]

I am disappointed that there are no jokes about the dangers of working with high voltage under the influence of alcohol

 

[Dandy]

Thanks for taking an original and educational approach to a project FlaCharlie. By default, it also illustrates how helpful it is to be able to read a schematic and solder.

For my last breadboard project (stereo EL84 PP), I put the completed breadboard with transformers into a vintage suitcase. Just flip up the case lid when on. Having the case sides around it gives a degree of enclosure.

 

[FlaCharlie]

Thanks for taking an original and educational approach to a project FlaCharlie. By default, it also illustrates how helpful it is to be able to read a schematic and solder.

For my last breadboard project (stereo EL84 PP), I put the completed breadboard with transformers into a vintage suitcase. Just flip up the case lid when on. Having the case sides around it gives a degree of enclosure.

I agree. This method can be used by anyone but it's especially useful for someone who has avoided DIY because they're unsure about their abilities. Hopefully it will encourage them and give them the confidence to delve into the hobby further and expand their skill set.

The low cost is an additional benefit. If someone has very limited resources they might consider a project like this to be more appealing than a traditional build.

Love the suitcase idea! I'm very much into repurposing so I'm always looking at stuff with an eye to incorporate it into a build.

 

[Lavane]

I agree. This method can be used by anyone but it's especially useful for someone who has avoided DIY because they're unsure about their abilities. Hopefully it will encourage them and give them the confidence to delve into the hobby further and expand their skill set.

The low cost is an additional benefit. If someone has very limited resources they might consider a project like this to be more appealing than a traditional build.

Love the suitcase idea! I'm very much into repurposing so I'm always looking at stuff with an eye to incorporate it into a build.

Maybe a small critter cage would work to put the amp into. It would be completely enclosed. You could even get one with a small door and try your hand at "ship in a bottle" type build.

 

[Mr Boochie]

So a few years ago I picked up a Switch Mode Power Supply (SMPS) that's designed for tube circuits. It has separate outputs for 6.3v and 12.6v heaters and a 300v output for the B+. But other projects took precedence so it sat on the shelf for a long time. Some folks over at DIYAudio had messed around with them with varying results. I culled as much info as I could from them and I finally got around to using it on my breadboard setup to power a basic SE circuit. The obvious attractions are low cost and simplicity.

This piqued my interest in extending that element of simplicity to the rest of the amp. I get the sense that there are a lot of folks who might be interested in building a DIY tube amp but are hesitant to take the plunge because they are overwhelmed by the complexity. My goal here is to present something that is far less intimidating for newbies.

This is a project that anyone CAN build. Not just a simple circuit but something that is extremely easy to assemble while still using point to point wiring.

So I've dubbed this one the Simplissimo. I'm not sure if that's a real word or not but I like it.

The result is a design whose construction requires no soldering. You can build this amp with a screwdriver and a few basic hand tools. It's nothing earth shattering. The same construction techniques are commonly used when breadboarding which is the experimental process I always use when I build a DIY project from scratch. It's a simple technique where all the parts are mounted to a wooden board. So no chassis fabrication skills are needed either.

My breadboard experiments always end up looking like a rat's nest with so many clip leads running everywhere that it's scary. So I've eliminated that aspect. And while my experiments typically do have some soldered connections, this just takes the next step and eliminates them. I plan on posting a few designs that use breadboard style construction and this SMPS.

Just to be clear, this build isn't so much about using a particular tube or circuit. I'm just using this SMPS as a turn-key power supply solution and combining it with simplified build techniques. Any design that can be powered with ~300v B+ can be built like this and it's easy to experiment since everything is wired point to point. Want to compare pentode, triode and UL? Try a boutique coupling cap? A different feedback resistor value? A different biasing method? A screwdriver is all you need.

Of course, if a more traditional build is preferred, the same construction techniques can be combined with a conventional power supply and some type of chassis. I'll be posting a different circuit later that combines these breadboard techniques with the same type of bamboo box that I used for a chassis with my Boogie Factor 1626 preamp. https://www.audiokarma.org/forums/index.php?threads/1626-preamp-build.931276/

Those who have read my previous build threads know that I like to keep costs low by using repurposed materials and I often use inexpensive, "under the radar", tubes. I've strayed from that formula just a bit here in that this design uses tubes that are common and in current production. I have not abandoned the low budget, bang for the buck, approach. You should be able to build it for ~$250 to $300.

I'm not a designer or an engineer. I'm just a hobbyist / copy and paste builder. I try to incorporate elements from other designs and combine them in different ways. There are many popular SE circuits out there which use a triode to drive a variety of output tubes. So you'll find many of the same elements I'm using here elsewhere. Truth is, there's not much new under the sun when it comes to tube amps.

For simplicity I decided to stick with octal tubes only and to save space I opted to use a single, dual triode, input tube. So I experimented with both the 6SN7 or 6SL7 as inputs in combination with numerous output tubes including the 6V6, EL34, 6L6GC, the Russian 6n3ce and the 7591. I tried running triode, pentode, UL and E-Linear, though not all combinations with every different tube. I also tried a variety of biasing methods for the input tube and some other circuit variations.

In the end I chose the EL34 which offers a good combination of power and affordability with a 6SL7 on the input. No, I haven't abandoned the use of oddball tubes and the versions that follow will likely use some.

Building the same circuits over and over again is not my style. I usually try to incorporate at least a few "new to me" elements in my DIY projects. Gotta keep it fresh and interesting.

Although I have some vintage PP EL34 amps that I've restored, I've never built anything from scratch with an EL34 or a 6SL7. I've also never built an Ultra Linear (UL) amp or anything that uses local, plate-to-plate (aka Schade), feedback. And, though I used SMPSs to heat the tubes in my most recent amp, the Cockeyed Monkey ( https://www.audiokarma.org/forums/i...ckeyed-monkey-a-directly-coupled-set.1040847/ ), the use of a SMPS to power everything is also new to me.

The output section is just a basic UL EL34 design using local, plate-to-plate (aka Schade), feedback. The current popularity of Schade FB is often traced to the RH amp designs but it's really nothing new. I recently came across a schematic for a "house brand" radio that was sold in Western Auto stores starting in 1947. It uses Schade FB in its amplifier section, which consists of a 6SQ7 driving a 6V6 output tube.

This basic output section is now very common. One example is the Skunkie Designs EL34 amp. @StepheK is now selling handcrafted, custom built amps using the same basic output section for ~$2000 to $2500, I believe. The most expensive version uses the legendary ISO Tango OTs! Of course she also has a series of step-by-step videos on her YouTube channel for those who want to build it themselves.

And Analog Ethos sells SE EL34 kits using the same UL output section design for ~$1300 to $1600. Their instructions are superb and this is a great option for those who would rather not deal with chassis fabrication. I've also seen some schematics that use the same circuit with different output tubes, such as the 6V6. So the basic design is well known and respected.

For the input I'm using the 6SL7, which is a dual triode. And just like the amps mentioned above, I'm using one triode to drive each EL34.

Besides the use of a SMPS and breadboard construction techniques there are two main differences between the designs mentioned and this one. The most obvious one is that this PS only puts out ~300v, so I'm running the outputs at lower voltage and higher current while the others run higher voltage and lower current.

The other is that I use a AA battery to bias the 6SL7. I've used the same battery grid bias scheme for input tubes in other builds too. It's simple to implement and I like how it sounds. Because the tube does not draw current from the battery, the battery will last as long as its shelf life. For a common Alkaline that should be at least 3 to 4 years. For a lithium it's probably 8 to 10 years. You must use regular batteries in this application. You can not use rechargeables.

Of course you can try other bias schemes. For example, Stephe uses a combination of a resistor and an LED to bias the dual triode 5751 input tube in her amp. The 5751 is a 9 pin miniature that has the same amplification factor (mu 70) as the 6SL7, BTW. The Analog Ethos kit uses the more traditional combination of a cathode resistor and bypass cap to bias a dual triode 12AT7, another 9 pin miniature.

I tried both of these alternatives and preferred the battery method but YMMV. I encourage prospective builders to take full advantage of the breadboard and point-to-point construction methods used here. Break out the screwdriver and experiment!

Anyway, here's a pic of the finished amp. Yeah, it's not much to look at:

View attachment 3225403
And here's the schematic:

View attachment 3225404
Since most people who can't solder or fabricate a chassis probably can't read and build from a schematic either, I'll add some (hopefully) easy to follow wiring diagrams, a few in-progress pics and some construction notes, along with a basic parts list later. Oh, and if you're concerned about using breadboard construction because of the high voltages that are present, that will be addressed too. I'll do my best to try to present all this in a newbie friendly manner.

Again, my goal here is to encourage people to get into the DIY aspect of this hobby we all enjoy.

If you're DIY curious I encourage you to check out the excellent Skunkie Designs videos as well as other build channels on YouTube, the kits available from Analog Ethos and others, as well as the many AK threads that focus on restoring and modding amps pulled from old console stereos. What I'm presenting here is just another "intro to DIY" option.

Very nice!

Though the title reminds me of this old Jefferson Starship song, which I didn't like.

 

[FlaCharlie]

I usually buy parts from Digi-Key so the parts numbers below are from them but other big suppliers like Mouser should have equivalent parts. One thing I like about Digi-Key is that they have a free shipping option, which is especially nice on small orders like this.

Details here: http://www.audiokarma.org/forums/in...hipping-on-parts-orders.739513/#post-10018562

If you're in a hurry you can pay for shipping which increases the total cost by roughly 50%. But even if you pay for shipping the parts are still pretty cheap.

Carbon Film Resistors
2 - 100k . . . 2019-CF1/2CT52R104JCT-ND . . . 0.12 . . . 0.24
2 - 100k 1w . . . 13-FMP100JT-52-100KCT-ND . . . 0.20 . . . 0.40
2 - 470k . . . 2019-CF1/2CT52R474JCT-ND . . . 0.12 . . . 0.24
2 - 1.8k . . . 2019-CF1/2CT52R182JCT-ND . . . 0.14. . . 0.28
2 - 330k . . . 2019-CF1/2CT52R334JCT-ND . . . 0.14 . . . 0.28
2 - 39k . . . 2019-CF1/2CT52R393JCT-ND . . . 0.14 . . . 0.28
1 - 1k . . . 2019-CF1/2CT52R102JCT-ND . . . 0.12 . . . 0.12
1 - 100Ω . . . 2019-CF1/2CT52A101JCT-ND . . . 0.14 . . . 0.14

Carbon Comp Resistors
Note: These are different from the values I used (220 & 680 ohm) but values are not critical for grid stoppers. These are the closest values that Digi-Key had in stock.
Other suppliers may have the same values I used but at a higher price plus additional shipping.

You might even be able to omit them. They are used to prevent possible oscillation. Some tube types (those with high transconductance) are more susceptible to this and others not so much. I usually include them "just in case". On the other hand, I have a lot of vintage tube amps and I don't think any of them use grid stoppers. And most schematics for modern commercially available amps don't have them either.

2 - 100Ω CC . . . 273-OD101KE-ND . . . 0.84 . . . 1.68
2 - 560Ω CC . . . 273-OF561KE-ND . . . 0.95 . . . 1.90

Metal Oxide Resistor
1 - 100Ω 1w . . . RSMF1JT100RCT-ND . . . 0.22 . . . 0.22

Wirewound Resistors
2 - 200Ω 5w . . . 749-PAC500002000FAC000CT-ND . . . 1.64 . . . 3.28
1 - 250Ω 5w . . . 738-WW5JT250RCT-ND . . . 0.77 . . . 0.77

Electrolytic Capacitors
2 - 220uf 25v . . . 732-9283-1-ND . . . 0.54 . . . 1.08
1 - 22uf 450v . . . 493-5884-ND . . . 1.42 . . . 1.42

Film Capacitors
Note: The 0.22 uf coupling caps I've listed are Panasonic polypropylene.
If you prefer to use something else they can be deleted from the list.

2 - 0.22uf 630v . . . P12174-ND . . . 1.89 . . . 3.78
1 - 0.1uf 630v . . . 495-B32921C3104M026-ND . . . 0.52 . . . 0.52

Parts Total $16.87

 

[Mr Boochie]

Nice completeness!

 

[Lavane]

I had a thought. A way to make this solderless amp safer for the first time builder. Mount everything on an aluminum plate like I've been using lately in a few preamp and amp builds. Mount everything BUT the output transformers and tube sockets on the bottom. So up top is just the output transformers and tube sockets. Maybe put the SMPS up top too if a trany cover or project box can be found to cover it, along with adding some ventilation to Any cover used?
Then just make a nice wood base to put the aluminum plate in.
All the shocky bits would be safely enclosed. The only exposed shocking hazards would be the ends of the wires secured in the tube socket screw terminals.

 

[FlaCharlie]

I had a thought. A way to make this solderless amp safer for the first time builder. Mount everything on an aluminum plate like I've been using lately in a few preamp and amp builds. Mount everything BUT the output transformers and tube sockets on the bottom. So up top is just the output transformers and tube sockets. Maybe put the SMPS up top too if a trany cover or project box can be found to cover it, along with adding some ventilation to Any cover used?
Then just make a nice wood base to put the aluminum plate in.
All the shocky bits would be safely enclosed. The only exposed shocking hazards would be the ends of the wires secured in the tube socket screw terminals.

That's a very popular method of DIY construction. Metal top plate mounted on a wood base with all of the electrical connections on the bottom of the plate. I used that method for my first DIY build years ago. The circuit is the Bugle 45 SET designed by Gordon Rankin.

Instead of using a standard metal chassis from Hammond I ordered only their optional bottom cover and used it as a top plate. I stained some pieces of wood, screwed them together and mounted the plate.

The chassis used for my more recent amp builds just use wood as a top plate instead of metal.

For the Cockeyed Monkey I repurposed a bamboo serving tray that I found at Aldi as a top plate. I added wood around the sides like I did for the Bugle.

GloTone Cockeyed Monkey - A Directly Coupled SET

So here's my latest DIY amp, the Cockeyed Monkey . . . I always like to try some things that are "new to me" in my builds and this one has several elements that I've been meaning to try for a while. I had never built a directly coupled amp so I figured it was time. I decided on using this...

www.audiokarma.org

For the Nuance iSET I just repurposed a wooden box that I found. Flipped it over and the bottom is now the top plate.

The Nuance - My "Inverted SET" DIY Project

Here's my latest project, which I had breadboarded for most of last year. Yeah, I'm slow. Most of the discussion about Single Ended Triode amps (and amps in general) seems to center on the type of output tube that's being used. Traditionally, the SET outputs are all directly heated. Many...

www.audiokarma.org

For my Boogie Factor preamp build I repurposed a bamboo box which is sold at Target and WalMart for storing cutlery. Transformers and tubes on top, electrical connections underneath just like the others. Thread is linked in the first post.

Here's a pic.



Back in the first post I mentioned that I was planning a few projects that incorporate the basic elements I've used here, the SMPS and the no solder aspect.

One will be built in the same type of bamboo box that I used for the Boogie Factor. It uses a different circuit and tubes than the one above. I actually breadboarded that one first. The build was started and is partially done but it was delayed for reasons which I'll explain at a later date.

So then I moved on to develop the circuit presented above on the (experimental) breadboard.

As I mentioned earlier, I would encourage the use of a cage with the build presented here. I think that makes it reasonably safe. Certainly safer than running a Dynaco ST70 or ST35 without any cage, as many owners seem to do.

Yesterday afternoon, I started putting together the (experimental) breadboard for the third project using the same elements. In keeping with my general approach to DIY, it uses a circuit and tubes that are "new to me". I'm hoping to have it powered up later today.

If it pans out it will be constructed in a somewhat different manner. Basically, it will be built on two levels but the top will not be metal. The only things on the top will be the OTs and the tubes. Or maybe even just the tubes. The SMPS and all the connections will be mounted on the lower level.

 

[juliet lima]

What a great thread. Thanks OP

 

[Lavane]

That's a very popular method of DIY construction. Metal top plate mounted on a wood base with all of the electrical connections on the bottom of the plate. I used that method for my first DIY build years ago. The circuit is the Bugle 45 SET designed by Gordon Rankin.

Instead of using a standard metal chassis from Hammond I ordered only their optional bottom cover and used it as a top plate. I stained some pieces of wood, screwed them together and mounted the plate.

The chassis used for my more recent amp builds just use wood as a top plate instead of metal.

For the Cockeyed Monkey I repurposed a bamboo serving tray that I found at Aldi as a top plate. I added wood around the sides like I did for the Bugle.

GloTone Cockeyed Monkey - A Directly Coupled SET

So here's my latest DIY amp, the Cockeyed Monkey . . . I always like to try some things that are "new to me" in my builds and this one has several elements that I've been meaning to try for a while. I had never built a directly coupled amp so I figured it was time. I decided on using this...

www.audiokarma.org

For the Nuance iSET I just repurposed a wooden box that I found. Flipped it over and the bottom is now the top plate.

The Nuance - My "Inverted SET" DIY Project

Here's my latest project, which I had breadboarded for most of last year. Yeah, I'm slow. Most of the discussion about Single Ended Triode amps (and amps in general) seems to center on the type of output tube that's being used. Traditionally, the SET outputs are all directly heated. Many...

www.audiokarma.org

For my Boogie Factor preamp build I repurposed a bamboo box which is sold at Target and WalMart for storing cutlery. Transformers and tubes on top, electrical connections underneath just like the others. Thread is linked in the first post.

Here's a pic.

View attachment 3239669

Back in the first post I mentioned that I was planning a few projects that incorporate the basic elements I've used here, the SMPS and the no solder aspect.

One will be built in the same type of bamboo box that I used for the Boogie Factor. It uses a different circuit and tubes than the one above. I actually breadboarded that one first. The build was started and is partially done but it was delayed for reasons which I'll explain at a later date.

So then I moved on to develop the circuit presented above on the (experimental) breadboard.

As I mentioned earlier, I would encourage the use of a cage with the build presented here. I think that makes it reasonably safe. Certainly safer than running a Dynaco ST70 or ST35 without any cage, as many owners seem to do.

Yesterday afternoon, I started putting together the (experimental) breadboard for the third project using the same elements. In keeping with my general approach to DIY, it uses a circuit and tubes that are "new to me". I'm hoping to have it powered up later today.

If it pans out it will be constructed in a somewhat different manner. Basically, it will be built on two levels but the top will not be metal. The only things on the top will be the OTs and the tubes. Or maybe even just the tubes. The SMPS and all the connections will be mounted on the lower level.

I bought a plexi cover for the driver board in my ST-70. There was someone on ebay selling covers for the original type Dynaco driver boards, but haven't seen them for a while now.

 

[FlaCharlie]

I bought a plexi cover for the driver board in my ST-70. There was someone on ebay selling covers for the original type Dynaco driver boards, but haven't seen them for a while now.

That certainly looks much nicer than a cage. The only advantage of a cage is that it also eliminates the possibility that someone will touch the hot tubes.