I want to build a simple SET mono amp. Suggestions on classic schematics?

I have a fair amount of experience fixing gear professionally. Mostly SS but some tube stuff. I haven't really delved into doing a lot of building or mods though. I'd like to get my feet wet by building a couple simple single ended triode monoblocks. Partly because it won't require much custom fabrication and I want to try some tubes in my system! I have basically unlimited access to basic parts. Might have to order some tubes and probably transformers.

Can anyone point me in the direction of some classic schematics or books of schematics of SETs in particular? I'd rather work from something classic, simple and time tested than some anonymous internet DIYer's design (not that there's anything wrong with that!). Maybe 5-10 Watts, power amp only and preferably mono as I'd like to smoke as few parts as possible as I experiment with a prototype!

Thanks in advance!

How deep are your pockets? A 2a3 amp is nice. Building a el-84 tube is more realistic. Do a search in the tube amp section. Lots of schematics there. BTW, building mono's is more expensive. Dual power supplies etc.

For getting your feet wet. Try a RH-84 amp. Few parts and great sound. It uses pentode but, you can change it to triode design.

Its hard to beat the el-84 for sound to cost ratio.

Mark

Here is the single ended 2A3 amp I built:
http://jelabsarch.blogspot.com/2012/08/radiotron-se2a3_5.html

Said to be a good design (I like mine).

I built this one as my first SE amp:
http://diyaudioprojects.com/Schematics/Mikael-Abdellah-SE-KT88-Amplifier.htm

It's very simple as you can see, but that doesn't mean it sounds bad, quite the opposite. I built mine as dual monoblocks (shared power supply) as I wanted to keep the cost down. The great thing about this amp is that you can run it in UL Triode & Pentode modes with the addition of a few components and a switch. You can also run a few different types of tubes KT88 EL34 6L6 KT66, etc. That's another reason I built this amp, as I wanted to try out different tubes and modes to compare the sound of each.

Search around on the web and you'll find a LOT of information from people who built this amp.

Good luck!
Glenn

Big, small, cheap or 'spensive?
Flea-power or beefy?
Also, "classic" in the sense of "old" or in terms of "well-established and well respected"?

I will offer one primary suggestion. I am a little biased (no pun intended) as a variation of this circuit, built by AK's own "Redboy" is my daily driver. Not exactly high-end, but I still like it a lot. SE 2A3.
http://jelabsarch.blogspot.com/2012/06/je-labs-simple-452a3.html

Another classic (in both senses of the word above) SE amp topology would be a single-ended EL84 amp like the old Zenith console hifi amp, or an EICO AF-4, or the triode mode variant of the Zenith amp sold by Steve Deckert as the Decware "Zen" SE-84 amp. A bit of digging on the web ought to turn up a schematic for this super simple, low powered but good sounding SE amp.

You shouldn't be able to build a bad sounding SE amp if you use a 2A3 or an EL84 (in either triode or "normal" mode, truth be told) and even halfway decent output iron.

Another time-honored fleapower SE triode amp is Bob Danielak's "Darling" amp family using the 1626 tube for outputs.


http://home.comcast.net/~ottoamps/darling.html

Not to hijack but...

For either the SE 2A3 or the "Darling", what's a realistic cost (including tubes and iron) to put one of these together? I've been interested in doing a SET build myself but, like most projects, I usually have a $ amount in mind then find that I've spent 4-5 times that amount when it's all done.

I would think that one ought to be able to build a nice stereo SE 2A3 amp from scratch and no "junkbox" components (i.e., all bits and pieces purchased new) for a kilobuck or less. Any needed components that one can scrounge or acquire used/cheap will reduce that cost.

sebrof said:

Here is the single ended 2A3 amp I built:
http://jelabsarch.blogspot.com/2012/08/radiotron-se2a3_5.html

Said to be a good design (I like mine).

Click to expand...

I like this one a lot. I think I'm gonna go with it. What tubes did you use? I was thinking about subbing 6D6's for the 6C6,s cause they're stupid expensive. I think I'm gonna start with Chinese tubes and upgrade later to NOS for the 2A3's. Probably same with the output irons. Damn expensive too!


You know how many watts it puts out? can you describe your impression of the sound? What kind of speakers are you driving it with? What kind of pre are you using? Would love to see some pictures of yours too!

Thanks!

kahlfin1k said:

I like this one a lot. I think I'm gonna go with it. What tubes did you use? I was thinking about subbing 6D6's for the 6C6,s cause they're stupid expensive.

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I use 6C6 drivers, they are about $15 pair from Tube Depot or others, or eBay. I use JJ 2A3-40s and I recently subbed a 5AR4 rectifier for the 5R4 which seemed to give it a little more jump.
I tried Old Stock Sylvania 2A3s that tested as new. They were nice, but a little laid back and not quite as much bass, but that was on speakers I no longer have so with my current speakers it may be a different story.

kahlfin1k said:

Probably same with the output irons. Damn expensive too!

Click to expand...

I had James transformers model HS6112. Sounded nice, but when I put a pair of Electraprint transformers in that I got from a friend it totally changed the amp for the better. How these EPs would compare to better James, or good Edcore, etc. I do not know, but I will say the OPTs matter a lot.

kahlfin1k said:

You know how many watts it puts out? can you describe your impression of the sound?

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3 or 4 watts probably.
With the right speakers it is easy to listen to, never harsh, good bass, and what I would call a very real sounding presentation. By real I mean that instruments sound like what they are, lots of tone. Draws you in vs. blows you away.

kahlfin1k said:

What kind of speakers are you driving it with? What kind of pre are you using? Would love to see some pictures of yours too!
Thanks!

Click to expand...

It's an integrated. Pics of my system, speakers, amp are on my system page in my signature. PM me if you want more.

sebrof said:

I use 6C6 drivers, they are about $15 pair from Tube Depot or others, or eBay. I use JJ 2A3-40s and I recently subbed a 5AR4 rectifier for the 5R4 which seemed to give it a little more jump.
I tried Old Stock Sylvania 2A3s that tested as new. They were nice, but a little laid back and not quite as much bass, but that was on speakers I no longer have so with my current speakers it may be a different story.


I had James transformers model HS6112. Sounded nice, but when I put a pair of Electraprint transformers in that I got from a friend it totally changed the amp for the better. How these EPs would compare to better James, or good Edcore, etc. I do not know, but I will say the OPTs matter a lot.


3 or 4 watts probably.
With the right speakers it is easy to listen to, never harsh, good bass, and what I would call a very real sounding presentation. By real I mean that instruments sound like what they are, lots of tone. Draws you in vs. blows you away.


It's an integrated. Pics of my system, speakers, amp are on my system page in my signature. PM me if you want more.

Click to expand...

Thanks so much for the response. I have one other question and it's probably a total noob one. How is the Humbucking pot supposed to be wired? Were do the 2 points (circled in red) go?

Also did what impedance did you use for the output? The output irons I ordered have 4 and 8 ohm secondaries.

Thanks!

kahlfin1k said:

Thanks so much for the response. I have one other question and it's probably a total noob one. How is the Humbucking pot supposed to be wired? Were do the 2 points (circled in red) go?

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They get tied to pins 1 and 4 of the Triodes along with the 2.5v from the heater transformer.

kahlfin1k said:

Also did what impedance did you use for the output? The output irons I ordered have 4 and 8 ohm secondaries.

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This will depend on your speakers. I ended up rewiring my transformers for 16 ohms because my woofer is 16 ohms. I would try both taps and see (that's pretty much what I did, 4, 8, 16 ohms and 16 sounded best).

kahlfin1k said:

I have a fair amount of experience fixing gear professionally. Mostly SS but some tube stuff. I haven't really delved into doing a lot of building or mods though. I'd like to get my feet wet by building a couple simple single ended triode monoblocks. Partly because it won't require much custom fabrication and I want to try some tubes in my system! I have basically unlimited access to basic parts. Might have to order some tubes and probably transformers.

Can anyone point me in the direction of some classic schematics or books of schematics of SETs in particular? I'd rather work from something classic, simple and time tested than some anonymous internet DIYer's design (not that there's anything wrong with that!). Maybe 5-10 Watts, power amp only and preferably mono as I'd like to smoke as few parts as possible as I experiment with a prototype!

Thanks in advance!

Click to expand...

6V6 is a fine sounding very tough octal pentode which make great bass this is one of the special audio tubes. I you want to take it up a notch look for some 6AQ5 which is a ruggidized miniture version of a 6v6 and is much less micophonic due to its smaller size. They uses to use these in auto and mobile radio. Another fine tube often overlooked in NA is the 6BM8 which in Japan is considered in the same way the 300B is here. Excellent tube top notch and small so not microphonic. The 6BQ5 is also a fine tube though not to the level of the 6BM8 imo. Hope this is of interest. Best regards Moray James.

http://www.diyaudio.com/forums/tubes-valves/63441-ecl82-6bm8-pp-stereo.html
http://www.lh-electric.net/projects/tiny3w.html
https://www.tube-town.net//diy/sv-6bm8/svetlana-6bm8.html
http://www2u.biglobe.ne.jp/~hu_amp/6bm8a_e.htm
http://www.datasheetarchive.com/6BM8-datasheet.html
http://www.atatan.com/~s-ito/amp/yakinori.html

vfr800fiman said:

I built this one as my first SE amp:
http://diyaudioprojects.com/Schematics/Mikael-Abdellah-SE-KT88-Amplifier.htm

It's very simple as you can see, but that doesn't mean it sounds bad, quite the opposite. I built mine as dual monoblocks (shared power supply) as I wanted to keep the cost down. The great thing about this amp is that you can run it in UL Triode & Pentode modes with the addition of a few components and a switch. You can also run a few different types of tubes KT88 EL34 6L6 KT66, etc. That's another reason I built this amp, as I wanted to try out different tubes and modes to compare the sound of each.

Search around on the web and you'll find a LOT of information from people who built this amp.

Good luck!
Glenn

Click to expand...

Great project with a lot of easy options!

kahlfin1k said:

I have a fair amount of experience fixing gear professionally. Mostly SS but some tube stuff. I haven't really delved into doing a lot of building or mods though. I'd like to get my feet wet by building a couple simple single ended triode monoblocks. Partly because it won't require much custom fabrication and I want to try some tubes in my system! I have basically unlimited access to basic parts. Might have to order some tubes and probably transformers.

Can anyone point me in the direction of some classic schematics or books of schematics of SETs in particular? I'd rather work from something classic, simple and time tested than some anonymous internet DIYer's design (not that there's anything wrong with that!). Maybe 5-10 Watts, power amp only and preferably mono as I'd like to smoke as few parts as possible as I experiment with a prototype!

Thanks in advance!

Click to expand...

Lots of good recommendations to start.

You can go as far as you want!

Whats below is some of what can ultimately be done. Thought some people might like a look even if its farther then you would like to go.

10 watts can drive a 98db/watt speaker to the same loudness as the 1.6 watt amp below does with 105db/watt speakers.

I designed this 1.6 watt 45 amplifier for a friend it can be configured for 45,2A3 or a 300B as the amplifier is a modular design. He has highly modified LaScala's which aren't a problem at 105db/watt for his 45 amp. Its his dream SET amplifier.

You shouldn't under rate yourself. If my friend who built a pair of monster monoblocks can do it you can undertake any project you put your mind to! he didn't know a whole heck of a lot about tube circuits. I tutored him via e-mail as he did the building. He wanted 1930's styling and I must say it looks it.

In the photo below is a George Wright 3.5 watt 2A3 monoblock used to contrast his 1.6 watt BOS45 monoblock. BTW you wouldn't know you were listening to a 1 watt anything and subjectively there is just no comparison to the 3.5 watt amplifier, the 1.6 watt wins hands down and even makes the 3.5 watts sound a bit wimpy. But then again he has about $3000 in it with some boutique parts. The design certainly can be scaled down to suit. Later I convinced him to go to bridged tube rectification a rarity in tube audio but well worth the effort.

The design is certainly far from classical but then so is the sound far from typical SET sound as well.

Your about 200 miles from the guy that built a pair of these and it could be arranged for you to hear them.



I would use the 6D22S's (30 second turn on delay) and they can operate on 5 volts with no issues as well to replace the 5Z3's in the second schematic that uses a single high voltage transformer vs the two paralleled in the first schematic.



SET12

SET12 said:

Great project with a lot of easy options!



Lots of good recommendations to start.

You can go as far as you want!

Whats below is some of what can ultimately be done. Thought some people might like a look even if its farther then you would like to go.

10 watts can drive a 98db/watt speaker to the same loudness as the 1.6 watt amp below does with 105db/watt speakers.

I designed this 1.6 watt 45 amplifier for a friend it can be configured for 45,2A3 or a 300B as the amplifier is a modular design. He has highly modified LaScala's which aren't a problem at 105db/watt for his 45 amp. Its his dream SET amplifier.

You shouldn't under rate yourself. If my friend who built a pair of monster monoblocks can do it you can undertake any project you put your mind to! he didn't know a whole heck of a lot about tube circuits. I tutored him via e-mail as he did the building. He wanted 1930's styling and I must say it looks it.

In the photo below is a George Wright 3.5 watt 2A3 monoblock used to contrast his 1.6 watt BOS45 monoblock. BTW you wouldn't know you were listening to a 1 watt anything and subjectively there is just no comparison to the 3.5 watt amplifier, the 1.6 watt wins hands down and even makes the 3.5 watts sound a bit wimpy. But then again he has about $3000 in it with some boutique parts. The design certainly can be scaled down to suit. Later I convinced him to go to bridged tube rectification a rarity in tube audio but well worth the effort.

The design is certainly far from classical but then so is the sound far from typical SET sound as well.

Your about 200 miles from the guy that built a pair of these and it could be arranged for you to hear them.

I would use the 6D22S's (30 second turn on delay) and they can operate on 5 volts with no issues as well to replace the 5Z3's in the second schematic that uses a single high voltage transformer vs the two paralleled in the first schematic.

View attachment 443095View attachment 443097View attachment 443102View attachment 443103View attachment 443104

SET12

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gygdsuydgsad9732y87y73 oops! My keyboard malfunctioned from all the drool on it!

sebrof said:

They get tied to pins 1 and 4 of the Triodes along with the 2.5v from the heater transformer.



This will depend on your speakers. I ended up rewiring my transformers for 16 ohms because my woofer is 16 ohms. I would try both taps and see (that's pretty much what I did, 4, 8, 16 ohms and 16 sounded best).

Click to expand...

Thanks! I think I'm going to do a 4 and 8 ohm tap with a shared ground so I have some flexibility.

What value mains fuse did you use?