DIY TUBE PREAMP HELP PLEASE

[Califmike33]

That is just so ridiculous what a world we live in when you have to fake capacitors potentiometers and electronic parts.

 

[Califmike33]

Anybody have any feedback on this company are they any good?

http://www.tubes4hifi.com/

 

[Lavane]

Anybody have any feedback on this company are they any good?

http://www.tubes4hifi.com/

I've built the ST-70 amplifier and a pair of the M-125 mono blocks. Solid kits with great instructions and they sound very good. As for the preamps, I haven't had any exposure to those kits.
People seem to like Roy's preamp kits though. I've read his instructions aren't as thorough as the instructions Bob had for his amp kits?

 

[Califmike33]

I got another question for you guys do tube preamps pair better with a class d amp or a class a b?

 

[FlaCharlie]

I got another question for you guys do tube preamps pair better with a class d amp or a class a b?

I don't think it has much to do with the type of amp. It's mostly about impedance matching.

From a technical standpoint, the rule of thumb is that the output impedance of the preamp should ideally be about 10% of the input impedance of the amp.

I don't think following, or not following, the rule of thumb is an accurate predictor of sonic synergy, though.

SS and Class D amps tend to have input impedances in the 10k to 20k range while tube amps are often 100k. So, again from a purely technical standpoint, tube amps tend to work well with a wider variety of preamps. SS preamps tend to have very low output impedance, under 1k, so they can typically be used with any amp. Tube preamps must be designed with output impedance in mind in order to meet the rule of thumb.

While synergy plays a role, as it does with any combination, that aspect is not so easy to predict. Lots of people use combinations that don't follow the rule of thumb yet they like the results. For example, on paper, the little FX type preamps are not a very good match for a Class D or SS amp yet that's probably how most owners use them.

 

[Califmike33]

Thanks Charlie for that explanation. I guy i follow on youtube THOMAS STEREO says that tube pre amp fills the gap of whats missing on class d amps and they work well. He claims its the best setup is a tube pre and class d amp. Again everybody likes different flavours, so that may ring true for some but not others. Trying to decide if i want to go full tube for headphones and speakers or go preamp tube and class d for the amp, hmmmmmmmmmmm.


Im a little nervous charlie about building that boggie factor amp, point to point looks hard vs PCB.

 

[Ian C.]

Not sure what your expectations are, but I'm doing one of the Marantz 7 clone tube preamps, point-to-point, right now and there is zero documentation. Zero, as in none whatsoever. Way bigger project than I thought I was getting into.

 

[Califmike33]

Where did you get the kit? I've seen them on eBay. Yeah point-to-point just to me is jumping off the cliff if you haven't built other kits.

I plan on using the Emotiva bas x A2 mini for the amp, it has a great headphone amp inside and a small footprint. So i just want to add some tube flavor from a diy preamp.

The eBay china kits seem ok but no directions at all. I think Tubes4hifi have some great options but there pricey, but they have a great reputation for bang-for-the-buck kits I have heard there follow along directions are not the best. I guess Roy the owner there says on his website he will help you to a point, like 20 mins to be exact, then he charges by the minute.

Then you have the Elekits, solid , good following, there not cheap either. Im like the sp13 at tubes4hifi, seems like a good kit.

 

[rothwellaudio]

I guy i follow on youtube THOMAS STEREO says that tube pre amp fills the gap of whats missing on class d amps and they work well.

Sounds like total BS. What, exactly, is "missing" with a class D amp? And how does the preamp know what's missing, and what does it fill it in with?
Don't take too much notice of what that guy says.

 

[Califmike33]

 

[Califmike33]

He talks about what's missing on class d amps that they tend to sound dry etc etc and a tube preamp sort of fills in the areas that are missing on class d according to him.

 

[rothwellaudio]

He talks about what's missing on class d amps that they tend to sound dry etc etc and a tube preamp sort of fills in the areas that are missing on class d according to him.

Yeah, total BS.
There are lots of different ways to make a tube preamp, yet somehow they all have this magic property of "filling in" stuff that's missing?

 

[Califmike33]

Here is a guy on eBay that has loads of DIY kits , cases, clones, etc, thought i would share it with you guys.



https://www.ebay.com/str/pinshuche?...uid=G-qt1-8jQt2&widget_ver=artemis&media=COPY

 

[FlaCharlie]

I guy i follow on youtube THOMAS STEREO says that tube pre amp fills the gap of whats missing on class d amps and they work well. He claims its the best setup is a tube pre and class d amp. . . . Trying to decide if i want to go full tube for headphones and speakers or go preamp tube and class d for the amp, hmmmmmmmmmmm.

Im a little nervous charlie about building that boggie factor amp, point to point looks hard vs PCB.

Well I'm a tube fan and I seem to prefer a setup that includes tubes. Of course this is all subjective and YMMV. And, while I prefer an all tube setup, I do enjoy the Class D amps I have too.

I don't think that Class D is "missing" anything but, in my limited experience with them, I find that Class D amps sound different with a tube preamp than they do by themselves. Different combinations of gear sound different. As you would expect.

I like having and listening to gear that sounds different from other gear and I enjoy all sorts of combinations. I have 3 inexpensive Class D amps and they each use a different chip. When I listen to them I mostly do so without any tubes in the mix. But that's because I have several systems set up at any given moment so I always have alternatives that are tube. For example, here at my computer I have a Class D amp powering one system and a DIY tube amp (a Bugle 45 SET) to choose from.

If I only owned one amp, which was Class D, I would probably use a tube preamp with it, though. That's just my preference.

Building something point to point is actually not all that difficult.

For me the most time consuming aspect of DIY is deciding on a physical layout. Using a circuit board simplifies that process somewhat, although you may still need to deal with some layout decisions. Some kits are just a board and parts and others provide everything you need and there are no decisions for you to make.

After you decide on a layout it's just drilling holes (I use a simple step type drill bit and a hand held drill) and using basic nuts and bolts to fasten down the tube sockets and terminal strips. With a circuit board you're sticking the lead of resistor or cap through a hole and adding solder. With point to point you're using a needle nose pliers to bend the lead around the lug of a terminal strip and soldering it. There's really not much difference between the two.

Of course, if you're not concerned about having a more "finished" look you could just do a very tidy breadboard type build using sockets and terminal strips that don't even require soldering at all. Everything is just attached to a piece of wooden board. Someone posted something like that recently on the Tube forum but I forget which thread it was in. That's what I use when I breadboard stuff but it's far from tidy.

There are two aspects of circuit board construction that can present problems if the board is not well designed. Although those who design circuit boards can probably point out other examples.

With point to point, if you're using AC to heat the tubes, standard procedure is to twist the heater wires which reduces the chance that the electrical field will radiate hum to other parts of the circuit. And you have more freedom to position the wires away from sensitive areas. Obviously, traces on a board can not be twisted and there are space constraints so layout is very important. No doubt some designers choose to use DC to minimize this issue, but that adds complexity and expense.

Another possible issue concerns tube sockets that are mounted on the board. Tube rolling is popular and every time a tube is inserted and removed the board flexes a bit. A board that's cheap and thin will flex more and this puts stress on solder joints. With point to point the sockets are mounted to the chassis and problems are less likely.

And, for the DIYer, another limitation is that it's very difficult (perhaps nearly impossible) to make any changes to the circuit if you use a board. With point to point you can rewire to your heart's content, if you want to try something different. If you hear about a mod to your circuit, give it try. Don't like the result, wire it back like it was.

Another issue with boards is that if, for whatever reason, something goes wrong and a part burns up then the board can be damaged. This may require you to replace the board. But there is no guarantee that replacement boards will be available at any given point in the future. I've read numerous stories about gear that ended up in the landfill because the board was damaged and no replacement was available, often because the manufacturer is no longer in business. With point to point the damaged part can typically be removed and replaced without disturbing the rest of the circuit.

As I see it, the primary advantage of circuit boards is economics. They are very cheap to produce in quantity and they are faster to build, which means a higher profit margin for the manufacturer.

No doubt there are other advantages. I admit I'm not that familiar with them and I know nothing about how to design them. I'm quite sure that it would be totally impractical, probably impossible, to build most modern electronics using point to point. But for the tube circuits that most of us on here are building, point to point is perfectly viable and, it seems to me, it offers some advantages.

Lots of people build quality kits that use circuit boards, though, and they are quite satisfied. One reason why I probably prefer point to point is just familiarity. I learned how to work on tube gear because I started out collecting and restoring vintage gear and most all of it is point to point.

 

[Califmike33]

Well thank you for that Charlie that makes a lot of sense. I think since I've only done a couple of vintage stereo recaps and only really worked on a circuit board is probably why I'm leaning that way because I'm somewhat familiar with it. I did burn a couple tracers up when I first started on the circuit board and had the repair them but in the end it worked and it sounded good.

And like you said there is a lot that can go wrong with the circuit board and you're right about the mods you can always go back and just unsolder it and resolder it and fix it and move stuff around circuit board you're kind of stuck with the layout.

I like the tube sound but I also like class d sound it's why I'm thinking of getting a preamp to put a little bit of tube flavor into it.

There are loads of kits out there I mean tons of kits to build a tube preamp. There's a bunch of threads like the one you showed me where I could do point to point there's no shortage of options.

I keep reading about some of these kids I'm looking at that their marantz 7 circuit another maybe a carey circuit another one I was looking at is a rogue circuit copy clone. No I have to admit I don't know anything about those circuits but I'm guessing if they're trying to clone it they must have some type of reputation to the original.

So I'm just looking around looking at kits and looking at threads on DIY builds trying to make it a decision it's a little overwhelming cuz there's so many of them to choose from and I have no clue what they sound like.

 

[Lavane]

I had fun uilding the Simple Universal Preamp. Not much to them. Not even a cathode follower, just a simple single gain stage using a single dual triode and a tube recrifier.
It can use a 12AU7, 12AY7, 12AT7, 12AX7 or 12AZ7. Although anything more than a 12AY7 is a lot of gain. I tried a 12AU7 and a 12AY7 and liked the 12AY7.
It's cheap to roll tubes in and so far has worked well with all the tube amps I've tried it with. I did add the bypass cap option and put them on a switch. It sounds better to me with the caps in circuit at low volumes, out at higher volumes.
It's point to point, but a low parts count.

 

[FlaCharlie]

I'm looking at that their marantz 7 circuit another maybe a carey circuit another one I was looking at is a rogue circuit copy clone. No I have to admit I don't know anything about those circuits but I'm guessing if they're trying to clone it they must have some type of reputation to the original. . . . it's a little overwhelming cuz there's so many of them to choose from and I have no clue what they sound like.

I can understand how you would be overwhelmed and, yes, it's hard to guess how something will sound. That's why I prefer to breadboard projects before I build something.

The Chinese will clone anything but they seem to mostly choose circuits from companies that have some brand recognition so they can capitalize on that. I seriously doubt that their decisions are based on sonics and they often call them clones even though they don't follow the original circuit. It's not just the Chinese, of course. Tube manufacturers sell new production "Tung-Sol", "Gold Lion", "Mullard", etc tubes in an attempt to capitalize on the reputation of the original companies. Unfortunately, tube newbies often don't realize that the tubes are not the same. But I digress . . . as I often do.

For example, StepheK's first "preamp shootout" on YT included 3 preamps. One was the popular Marantz 7 "clone", which was the one she considered the worst of the 3. And two of the three sounded like SS, not tubey at all.

She's planning a updated shootout soon which will include the winner of the previous one and 4 others. The details on those plans start at the around the 11:40 point in her latest channel update here:

She will be including the one Lavane built. She also built one of those after the earlier shootout and liked it. She has a detailed, step by step, point to point, build series on it:

That basic circuit design is the same as what I used in my Boogie Factor 1626. As you can see from the pic Lavane posted, there really isn't much to building something like this. Not quite as simple as soldering parts to a circuit board but not really complicated either.

I'm usually a bit skeptical about designs that are meant to appeal to tube rollers. The ideal operating points of those tubes are all somewhat different. Unless there is some provision to adjust the operating points, there are bound to be compromises made in order to allow for tube rolling. If it was optimized to use a particular tube type, the operating points / parts values might be different.

For example, it uses a 100k plate load resistor. Another "rule of thumb" says that plate resistors should be at least 3x the plate resistance of the tube. The 12AX7 has a plate resistance between 62.5k and 80k according to the data sheet.

Also, I notice that @Lavane says that it works well with all the tube amps he's used it with. But what about SS or Class D? Perhaps he'll comment. It seems like most of the interest in tube preamps is coming from people who want to add that proverbial "tube goodness" to their SS / Class D systems.

The output impedance of a simple design like this is mostly determined by the plate resistance of the tube. For example, the 12AY7 has a plate resistance of 25k ohms. So, on paper, it doesn't even follow the rule of thumb for a tube amp with a 100k input impedance and it's very far from a Class D, which might be as low a 10k or 20k.

BTW, the SE 6BQ5 amp that Stephe uses in the shootout was built from one of my projects. It's good for comparing preamps because it has no input tubes, only the 6BQ5 output tubes. Its input impedance is quite high at 470k, so it's very easy to drive and, as a result, input impedance issues are less likely to be apparent.

But again, I'm not sure how audible an impedance mismatch might be. Perhaps it's not audible at all. I don't usually concern myself with things that are not technically ideal if they aren't audible but when I build stuff I do try to respect guidelines like this when I can.

For example, when I was breadboarding tubes for the Boogie Factor I only tried low gain tubes, mu of 10 or less, because that was the prime design consideration. It's based on the premise that, since most amps don't need any gain at all to produce full power, why use a high gain tube and then dump most of the gain to ground?

I chose the 1626 based on how it sounded to me, although a couple of others were close. I calculated the output impedance as ~1.39k but, truthfully, that aspect was not one of the prime considerations. If I had liked the sound of another tube better I would have used it even if the output impedance was considerably higher. But it is a nice bonus and provides a better "on paper" impedance match with SS / Class D.

OK, earlier I mentioned seeing a pic of a tidy breadboard build which demonstrates how you can build something without building a chassis and with almost no soldering. Not recommended if you have small kids or curious pets, though I suppose you could add a cover if you find that style of construction appealing to you. Here's the pic:

 

[Califmike33]

Makes a lot of sense Charlie I'm new to this and I'm soaking up all your wisdom.

I did watch that shoot out with Stephe was surprised me was the amp on the far left in this with the silver face that look like the same amp as the sp10 tubes4hifi. If the sound is going through the tubes here's what I don't understand she said that amp had no tube sound she said it sounded really clean super clean but it did not have tube sound how can it not have tube sound if the sounds going through the tubes I don't understand that?. She then said the middle one which I'm guessing was the marant 7 was the worst of the bunch the one to her right was the best of the bunch with the wood knob.

I don't know a lot about this but I know I've looked at some marant sevens I looked at some Conrad Johnson amps and you're right the clones are not clones they're stealing the name and the reputation to sell their product it sort of resembles the layout if you look at the pictures between the real thing and the clone there is a resemblance but it is definitely not an exact clone.

As far as drilling holes in chassis and stuff I got no problem with that I was a cabinet maker I had my own cabinet making business I've drilled holes and diy things together for 25 years I don't have a problem with that. And I guess if I had step by step instructions I could do the point the point wiring it's just I got to have step-by-step instructions cuz obviously I've never done this before and I don't have anything else to fall back on if I get stuck.

As far as some of these kits that you can buy these clones and other kits a lot of them I think lack instructions thorough instructions now if there's a huge thread on here or another forum with the build obviously you've got people that'll back you up and help you with it but when you don't have a thread I think you're asking for trouble depending on your experience.

If you look further back in this thread there's a guy that said he's working on a marantz 7 clone and it comes with no instructions and he says it looks like he bit off a lot more than he could chew with it that's another thing I don't understand is how these Chinese clones can come out yet they don't give you one damn piece of paper that tells you how to put it together they just assume you already know how to do it.

Tubes4hifi from what I've read the SP 14 is a killer amp that hits way above its price point. As I look at their website the sp10 looks like a Conrad Johnson clone it looks like the same thing I see on eBay and AliExpress it looks like the exact same amp but $100 higher am I wrong?.

You know this boogie Factor amp I got to take your word for it then it sounds really good this is probably the one I'm going to end up building and with your help offered that makes me feel a little more easy about it. Charlie any idea cost wise what it would cost me to build that boogie Factor?

Again I appreciate everybody that has contributed to this red and everybody's feedback.

 

[Lavane]

I can understand how you would be overwhelmed and, yes, it's hard to guess how something will sound. That's why I prefer to breadboard projects before I build something.

The Chinese will clone anything but they seem to mostly choose circuits from companies that have some brand recognition so they can capitalize on that. I seriously doubt that their decisions are based on sonics and they often call them clones even though they don't follow the original circuit. It's not just the Chinese, of course. Tube manufacturers sell new production "Tung-Sol", "Gold Lion", "Mullard", etc tubes in an attempt to capitalize on the reputation of the original companies. Unfortunately, tube newbies often don't realize that the tubes are not the same. But I digress . . . as I often do.

For example, StepheK's first "preamp shootout" on YT included 3 preamps. One was the popular Marantz 7 "clone", which was the one she considered the worst of the 3. And two of the three sounded like SS, not tubey at all.

She's planning a updated shootout soon which will include the winner of the previous one and 4 others. The details on those plans start at the around the 11:40 point in her latest channel update here:

She will be including the one Lavane built. She also built one of those after the earlier shootout and liked it. She has a detailed, step by step, point to point, build series on it:

That basic circuit design is the same as what I used in my Boogie Factor 1626. As you can see from the pic Lavane posted, there really isn't much to building something like this. Not quite as simple as soldering parts to a circuit board but not really complicated either.

I'm usually a bit skeptical about designs that are meant to appeal to tube rollers. The ideal operating points of those tubes are all somewhat different. Unless there is some provision to adjust the operating points, there are bound to be compromises made in order to allow for tube rolling. If it was optimized to use a particular tube type, the operating points / parts values might be different.

For example, it uses a 100k plate load resistor. Another "rule of thumb" says that plate resistors should be at least 3x the plate resistance of the tube. The 12AX7 has a plate resistance between 62.5k and 80k according to the data sheet.

Also, I notice that @Lavane says that it works well with all the tube amps he's used it with. But what about SS or Class D? Perhaps he'll comment. It seems like most of the interest in tube preamps is coming from people who want to add that proverbial "tube goodness" to their SS / Class D systems.

The output impedance of a simple design like this is mostly determined by the plate resistance of the tube. For example, the 12AY7 has a plate resistance of 25k ohms. So, on paper, it doesn't even follow the rule of thumb for a tube amp with a 100k input impedance and it's very far from a Class D, which might be as low a 10k or 20k.

BTW, the SE 6BQ5 amp that Stephe uses in the shootout was built from one of my projects. It's good for comparing preamps because it has no input tubes, only the 6BQ5 output tubes. Its input impedance is quite high at 470k, so it's very easy to drive and, as a result, input impedance issues are less likely to be apparent.

But again, I'm not sure how audible an impedance mismatch might be. Perhaps it's not audible at all. I don't usually concern myself with things that are not technically ideal if they aren't audible but when I build stuff I do try to respect guidelines like this when I can.

For example, when I was breadboarding tubes for the Boogie Factor I only tried low gain tubes, mu of 10 or less, because that was the prime design consideration. It's based on the premise that, since most amps don't need any gain at all to produce full power, why use a high gain tube and then dump most of the gain to ground?

I chose the 1626 based on how it sounded to me, although a couple of others were close. I calculated the output impedance as ~1.39k but, truthfully, that aspect was not one of the prime considerations. If I had liked the sound of another tube better I would have used it even if the output impedance was considerably higher. But it is a nice bonus and provides a better "on paper" impedance match with SS / Class D.

OK, earlier I mentioned seeing a pic of a tidy breadboard build which demonstrates how you can build something without building a chassis and with almost no soldering. Not recommended if you have small kids or curious pets, though I suppose you could add a cover if you find that style of construction appealing to you. Here's the pic:
View attachment 2820734

As for that simple preamp, as I said, you really don't need anymore gain than what a 12AU7 will provide. I just found the the 12AY7 sounded better to me.
But that could be anything. Different brand tubes of the same type can sound a little different. So between the RCA clear top 12AU7 and the Sylvania 12AY7, the Sylvania just sounded a bit better to me.
When it comes to that "tube" sound, if I come across a tube amp that sounds "tubey", I tend to think something is wrong with it. Some think that tube sound means overly warm. Usually meaning rolled off highs and maybe even rolled off bottom end. If that's the case, something is wrong with the amp. Poor design, not so good output transformers, worn out parts like out of spec caps and resistors, or even worn out tubes. My amps are clean, clear and detailed sounding.
I think the biggest difference between SS and tubes is the harmonic distortion.
Tubes tend to produce even order harmonics that is pleasing to many peoples ears. While SS I'd odd order harmonics which can come off sounding dry, harsh or analytical to some. Everyone is different. Over the years I've just found tube equipment to sound better to my ears. I don't get the ear fatigue I can get from some SS gear. I don't have any Class D amps other than a couple Crown amps that use a Class D amp to drive a discrete output stage. They're clean and clear with plenty of power, but sound flat and dry. I can't listen to them for very long. The frequency response and distortion specs are great, but they just don't sound as good as my other SS amps. They do make for great subwoofer amps though since they have built in DSP.

 

[Califmike33]

I've had a couple headphone tube amps you're right I think maybe there's a misconception when you say to be sound people tend to think warm gooey soft. Until recently when I owned my first headphone amp I didn't know that they could be that detailed still I thought it was all based on distortion and to get the tube sound you had to give up clarity and definition. But there's definitely something to tubes there's that holographic sound takes the edge off of stuff in some ways it's hard to describe.

Yeah I've heard class d described in many ways harsh analytical dry flat. There are many people that are happy with just listening to a class d I think now that I've tasted the tube sound I got to have tubes somewhere in the mix I can't just listen to a class D.

No I've never heard a class a single ended tube amp my tube amp is a OTL so is there a big difference between a class a tube amp and an OTL as far as the sound quality?.

One other question for you experienced guys let's say I built a tube amp put together a kit point to point circuit board whatever it is is there a way to add a headphone jack to an existing tube amp that doesn't have one let's say I built the boogie Factor is there a way to put in to where I could listen to it also with headphones?