Interesting then the rado has a specific headphone tap, and most likely has significantly higher output impedance/lower damping factor than the EC.
It might also be why is sounds more mid centric.
Pretty much all DHT’s get more linear as you increase load. The higher impedance output tap reduces the plate load, resulting in a more traditional load line.
Having said that, I put a dummy load switch on my 2A3 amp to see what the difference was, and it was WAY more subtle than I expected,
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The EC and Radu are very different amps sonically, thought both builders love that big bake light knob.
Radu being that warm, bottom heavy, romantic seducing mids and vocals, and totally inoffensive top end. Traditional WE style 300B to the core. I also know there are many traditional amp archetypes with specific names for 300b builds. I dont know the difference, but this seems the poster child for what most reference as the 300b sound. Big on macro and stage size.
The Studio B is just… EC Studio sound. Tbh i wonder if one day people will say theyre building a Uthus style dht amp. More balanced, things are grand but not over the top.
The PSVane ACME tubes that worked great in the Radu were a detriment in the EC. I know Craig suggests the lower end bloomier warmer tubes, GLs and EHs, he also said the new WEs are probably best but didnt suggest them. While Radu had ACMEs and EMLs in that amp. I imagine Elrogs would slot in well there too and may be one set that fits both amps.
I have no doubt transformers play a big roll. Craig’s being special mable audio kits with the tertiary winding as well, before that cine mag and tribute as well as others. Sadly many of his sources shut down or retired. The Radu used Hashimotos, and he seems to be big on japanese transformers i general (ie Tango etc). I get a feeling the japanese kits give a rounder more traditional sound. None of this even touches cores, chokes, regulators, taps, etc.
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@Souldriver , just because choices in life are great to have and I’m oh so curious to see what you wind up w/, I’m just throwing darts randomly though 
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I know you said you wanted to replace the amp, but maybe a DHT DAC could open up options for your “end game” amp and you can still keep the DHT sounds in your chain from your DAC. I not too familiar with any Lampizator DAC, so I am not sure if your DAC is already a DHT DAC, but I came across a Big 7 DAC and thought you might like something like this.
Lampizator Big 7 SE MK2 Dac in USAM:
I never dealt with this seller, so if you do engage with him, always proceed with caution.
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Oh there are options plenty. Even ZOTL SET amps. https://davidberning.com/
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I thought he dropped dead 
maybe i’m mistaken.
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Hello,
As a tip, you’ve already had one or two tube amplifiers.
So you already know what you like.
So you should decide for yourself whether you prefer the pentode or triode sound.
Believe it or not, there are audio patients who only have a preference for one and can’t do anything with the other.
Personally I like both but my preference is more for the pentode, sweeter end, and has a bit more volume to my ear.
Not that I don’t like the triode mode, but sometimes I miss something.
Another tip I like to give is the design itself.
You should also have something in your DIY where you can access tubes for at least 10 years.
The greater the variety, the better you will be able to stock up for the next few years.
Why I say this is that if you like the amplifier in the end and a lot of it is the way you wanted it, you won’t give it away and you will learn to love it.
It doesn’t matter if it’s for stereo or headphone amplification.
The Zmf Aegis in the diy version is a good example of this, if you still have something like this as a stereo amplifier it is a very good match.
The rest is then to fill the drawers with tubes for personal sound customisation.
In the end, it’s not about how much money you spend on the amplifier, but what you spend it on.
There are actually tube amps out there if you meet the right people who will build you something that doesn’t have to cost a lot.
These amplifiers not only fulfil their personal purpose but can also be impressive in terms of sound.
They are often even better than what you hear in the shop.
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Yes. It looks like the builders who have gotten back and spoke to me all have suggested 300B as probably the best fit. Thankfully there is a bunch of new production options that tend to last, but it gets pricey quick. But the fun of rolling, or finding and using NOS as it doesnt exist for the 300bs. Some have said 2a3 may suit the needs but may end up being less engaging or harder to get deep deep bass from. Most have suggested against 45s for my needs, but i think it would be cool to have a nice but inexpensive 45 to see what that tube and 1 watt can do.
Bass isn’t the issue, that’s really a function of cap sizes and the transformer.
2a3 amps do tend to be a bit more linear, less mid forwards, 45’s can be the same way.
You’ll get closer to 2W from a good 45 amp.
Generally for what you describe I think your in the 300B space, or the bigger triodes 211’s, 242’s 845’s, those give you a lot more umph than a 300B, but as you increase output, costs go up, noise floors rise, it’s all a trade off.
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I had some very productive phone calls today with 2 builders. Both taking very different approaches.
Builder 1:
The first builder wants to take a much more grand approach, which I am down with, but it comes with a steep real estate cost. It would be a conservative 3w from 2-stages, 300B power tubes, EML 20A drivers, GZ34 regulators with Monolith Nano Core iron and chokes, and rod coleman regulators. Basically they said component wise there is not much more you can do that is higher. So, great! Right? It would be 2 pieces, which is fine. But each one is huge. 21”x15”, also ~50lbs EACH! I just dont think i have the space. With that weight it needs to go on the floor as i dont trust my desk to hold that all. If it goes on the floor the headphones cables may not reach either. He can use an alternate chassis but it is basically the same size but on it’s side. This doesnt really work either. It is cool, but probably excessive. He admitted anything else would involve compromises or a design theory / end goal change. He also gave the option that speaker taps could be added but he would suggest the transform then be set to 4/32ohm vs the 8/64 that would better match the headphones. (I may be mis remembering the lower values here) The point was also that if it ever needed to be sold, speaker capabilities help resale and well, it is basically a speaker amp already. No real surprises here, except i thought a power supply box would be much smaller.
If i wanted a speaker and headphone amp where i had the space to plop it down I can see pursuing this more.
Builder 2:
In contrast to the first builder, this one emphasized doing more in a smaller and lower powered package based off the 71A power tube delivering a staggering .75w! Trannies would be Hitachi Finemet (finemet = nanocrystal, and i think that is Hitachi’s patent name). Overall size would be ~18”x11”, and I am sure it would still weigh a ton. He believes more power for my headphones would just increase noise vs being truly useful. To @Deleeh 's point, i worry about tube availability as i do not believe there is new production. The nos seems inexpensive and apparently theyre not super rare, but yeah. I dont have a tube tester to just grab em off ebay or something. A few things that are to note…
Positives:
- First off he has the same music tastes, this makes talking about preferences much easier and it feels like it is the same language vs a different dialect.
- He also owns a PF LCD-2, which given that it is the harder of the two to drive properly, this should help.
- He is able to do a volume bypass or a stepped attenuator with a fully open top step, i can use the lampi to control volume.
- He is anal about noise and hum, even incorporating many things into the chassis to stem microphonic and any tranny vibration
Negatives:
- He seems to be very ok running the tubes hit and hard. Or at least to their stated limits. I believe others try to take it easy on tubes.
- He also made some remarks that other builders seem to have a gig with one audio company so they want to push people towards similar amps for their ease (i dont believe this is founded and tbh it is ok if they do).
- Their product styling isnt my favorite. No amp to try or compare to, a total faith purchase.
Neutral or Just not Sure:
- I said i was ok with 2 boxes for a seperate power section, he said a properly designed power section wouldnt ever need this. Ehh, i tend to believe that even with a perfectly designed power section there is credit to literally having them spaced out.
- Seems very set on the parts he uses and selects. I am not here to say xyz is better and it does seem he has done the ear testing to back his views.
- Same a bit with his view on cables, but that is just an odd contradictory stating that they arent that big but then specifies gauge and some vintage WE wire he sources.
- He also believes that the whole volume control should be used not just the first 3rd, which i dont know either way outside usually pots sound better higher up.
- His favorite headphone is a Klipsch hp-3. No digs there i just dont know how those sound or how to translate that into how he describes things.
A pretty decent eye opener for both sides. And makes me want to hear more things.
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The PSU for my DIY 2A3 amp weighs close to 30lbs FWIW, the weight is all in the transformers. Using 20A’s as a pre tube means you need at least one additional transformer
The Rod Coleman regulators are more complex than the ones I use, and have two heat generating devices , so more heatsinks, more weight.
I can easily see hitting 50lbs with oversized transformers and a big box.
I can’t see how the amp itself hits that though, interstage transformers weigh very little and there is only so big you need to go on output transformers.
I honestly wouldn’t worry about it, for less common tubes there is plenty of “stock”, you replace them every 4 or 5 years, prices will continue to rise, but bear in mind, outside the highly desirable tubes, you can still buy most NOS tubes at prices lower than their adjusted new prices would have been (tubes were never cheap things).
Practically at tolerable listening levels, your never putting more than a few 100mW into any headphone, the Susvara included. Some headphones do seem to respond on amps with more power, it’s completely unclear to me why (it has absolutely nothing to do with current delivery).
Having said that what is true is that tubes are more linear at the lower end of their power band.
Don’t underestimate this, one of the things I wish I’d had hindsight on in my own amp is how bad microphonics, from the case can be. My tubes are all hard mounted to the top plate and plugging in headphones the tubes literally ring for 30+ seconds afterwards.
I’m not sure that’s true of others generally, look at the suggested load line rom the 2A3 data sheet, it’s right on (or depending on your model slightly over) the maximum 15W plate dissipation, and those numbers are commonly used in amps.
It’s all tradeoffs, if you build a separate power section (I did it for convenience) you have to run multiple voltages some invariably with some ripple or even AC through an umbilical and that can introduce noise of it’s own.
The obvious issue is cross talk between the transformers, but he’s right in so far as long as the power transformers are rotated relative to the audio transformers it’s not really an issue.
Did he suggest DC or AC heaters?
Isn’t that what your paying a builder for (experience), I’d bet all of the have favorites and tend to always source from them.
Depends what he means by that, could just be referring to reasonable amounts of power, lower overall gain, or could be referring to lower input sensitivity, which I do think for a DAC like the Lampizator isn’t a bad thing.
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Weight, yeah. I figured both would top out at 75 max. Just the size needed for both, a 42" x 15" total footprint. And yeah having 20As as drivers is the main factor.
I would probably buy 2-3 sets from the builder while he can test them and in case the price spikes.
Yeah, and some headphones i feel there is a difference delivery when there is more power. Others not so much. I am rarely concerned about volume with headphones, more so the compatibility with some cans that perk up with power.
The Radu had very nice vented sockets and this builder makes his own in a more industrial style. Is that sound different from the weeeehhhhhh laser gun start up type noise one first power on?
You know what, the extreme details were left out. I spoke to this guy for an hour and a half. We jumped from the amp, to music, to design languages, to what concerts we are going to this summer. A very easy and friendly guy. He actually just texted me a pic from the Al DiMeola concert last night. But, I didnt get intended drivers, rectifier, or AC vs DC. I do know he uses WaveLength regulators. That company being known for guitar and pro audio.
Btw, @kerls this builder was invited to and got to tour Trent Reznors recording studio after meeting him at Nola’s Jazz fest one year.
Oh absolutely! And it is why I am spending the time talking to these guys and trying to understand myself while asking questions and figuring out why they ask me certain things. The comment is more of an “his way or the highway” things, which once again its not good or bad, but i felt was contrasting the first builder who was more go with the flow in that aspect. Going by your suggestion of not pushing my thoughts on a builder and instead dictating the need and have them handle the solution has me learning a lot. It raises a ton of questions too, but that is also my own lack of knowledge.
This remind me. @keithc do you have any additionsl info on the outputs of the lampi? The sheet say 2.8v RMS at 1khz -20db. I kind of only half trust the sheet as the fuse is listed wrong. I think most lampis are 3v, but this would still be stronger than most. Also are the rca and xlr outs the same, different plugs just for convenience?
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Yes it’s very obvious high pitched ringing sound, with the headphone jack being on the top, you hear the connector being inserted and a slow decay of the ringing that’s happening I assume on the top plate.
It’s “harmless”, since I never touch the amp when listening, but you have to wonder how small a vibration would impact what your hearing, and whether the plate resonates with other sounds on the room.
I think philosophically heater design is probably the single most controversial/religious aspect of tube amp design. AC vs high frequency AC vs DC vs voltage regulated DC, vs current regulated DC vs both.
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Hello,
I would actually say the following about performance.
Firstly, it depends on what headphones you already have, I would expect them to run smoothly.
Certainly power is not everything because 5 watts is not really an exaggeration.
But 1 watt would be the minimum that at least some planar headphones can be operated as well as 300 ohms.
More is of course better but not a must.
Secondly, the amplifier should of course also be able to drive headphones where there are others.
This is always a bit difficult, also because of the trend that manufacturers specify.
At the moment it is a mix between 150-16 ohms.
The circuit should also be quiet.
Something like Ampandsound has the problems you don’t want as an example.
These are things you should clarify that would be important.
About the tubes, I’ll summarise it like this.
You can use 45 2A3s, no problem, but your variety will be limited.
That also means less room for manoeuvre for the personal taste.
Not that these things are bad, and I would check the market beforehand.
If you’re unhappy with the amp, you’ll want to resell it.
As a tube bunny, you look at things like that to make sure the tube variety is there.
Or at least a selection, be it for your collection or as a replacement.
Otherwise nobody will buy the amplifier.
The market is still there but the really good ones are slowly disappearing and are becoming rarer even in the 6SN7,12au7/12At7/5751 range.look for EL34 Mullard Xf1 or 2,EL12 Siemens,Valvo,these are just a few examples.there is still a market but the price has reached a league where you don’t want to pay,not even in 5 years or 10 years.
For my Felkis Euforia 6080 Gec you already pay 200$+ for one tube and you need 2 of them.
Even for my Mcchanson Ultimate, which can drive quite a lot of tubes, there are prices for some genera where you say okay, no thanks.
So try to find a compromise here, also for you in terms of design.
A design that can perhaps do both with selectable switches for stereo and headphones with different tube configurations would be something.
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For those interested. There is a lot to read. But i feel I had a good back and forth with this builder and he has backed all his stances well. I just dont like that he seems to come across negative on other amp brands. I have edited out those amp builders names so someone reading this in the future does not get the wrong idea. Though i feel some people are really enjoying the process documentation and insight into how builders think.
Long Response
Good Morning,
Thank you so much for the detailed email as well as the link to the music list. I’ll go into the music later this afternoon. 
After considering your needs (and musical “bent”) last evening and this morning…, I’ve decided that perhaps the best output tube would actually be the 2a3 (will also accept the Psvane W.E. replica 275a). This would allow the use of the “perfect” FineMet output transformers…, bandwidth of 14Hz to 60KHz. Giving you the sparkle on top as well as the powerful, articulate bass that you need. While at the same time giving you that wonderful 300b-like bloom in the midrange. Also, having 3-ish watts on tap gives you plenty of headroom without the need to take the tube out of its operational sweet-spot to minimize the noise from excess gain.
I believe this is the reason why REDACTED uses this tube as well. However, unlike REDACTED, my topology is better…, for several reasons. Not the least of which is my choice of voltage driver. In your case I’d use my ultra-performance driver stage…, using the C3g. Which, if you do a bit of research, is the MOST linear small-signal tube ever created. No other tube on the planet provides the detail and nuance (throughout the entire frequency range) that the C3g (run as a triode) provides. It is truly special.
You mentioned filament heating in the body of your text. I’d use regulated DC filament supplies for every tube (aside from the rectifier) in the amplifier. This ensures the lowest noise-floor possible. Additionally, as mentioned in our phone conversation, your amplifier would enjoy the additional lowering of the noise-floor by the use of the 79% nickel high-impedance input isolation transformers. Another benefit to my topology is the biasing methodology that I employ…, it is achieved by means of a CCS or “current sink”. This is a type of auto-bias that doesn’t require the end user to do anything. Part of the reason this bias method is desirable is that unlike the typical “cathode bias” the sound quality does not degrade with tube ageing. Either the tube can or cannot provide the desired quiescent current necessary as defined by the CCS. Another benefit is as a result of this specific current demand, tubes do NOT have to be matched…, understanding of course that tubes “age” at varying rates and would only be “matched” when initially put into service. My topology nullifies these concerns. The C3g’s would be “grid biased” via LED’s as per my usual methodology. Again, this method nullifies the same concerns and is the best sounding by far.
The power supply for your amplifier would be built around a fully potted, N.O.S. CTC power transformer (from my personal stash). This would allow me to build your PSU as a “choke input” supply which yields the very best low end “slam”, and it allows the use of your favorite rectifier…, the GZ34.
Unfortunately all of this wonderful stuff requires space and for that reason we would have to move up to… 15.25" Wide X 13.5" Deep, I think this will still fit on your shelf? As you won’t have any binding posts for speakers on the rear of the unit, and the knobs sticking out of the front won’t need to actually be on shelf, this should work out great. The chassis would be configured much like my Line Stage in terms of layout. The entire left side of the amplifier (as you’re facing it) would be occupied by the massive power supply while leaving the entire right side of the amplifier for the circuit and output transformers…, very Japanese-like. And, ideal for keeping the AC away from the signal components.
As for the “Stereo Volume Control”, my thoughts were to actually use a stepped attenuator designed by my good friend John Broskie (TubeCAD Journal), since you told me that you are going to nearly exclusively use the volume slider on the app you control your DAC with. The huge benefit to this stepped attenuator is that although it is only 12 steps, these steps can use the finest (read: least impactful to sound) resistors available. Not just some cheap Vishay SMD’s. The main benefit of this type of application is that it allows you to decide how much gain comes from the DAC, and how much gain comes from the amplifier. It’s ideal.
Anyway, I could go on for days actually describing why my amplifier is superior. Both in terms of topology as well as parts quality, but I’m sure you get the idea.
The only thing i pushed back on here is the 12 steps on the stepped unit. Yea i would use it mostly wide open but if anything ever changes then 12 volume steps is just too little.
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what app are you using for volume control? isn’t your Lampi the dac?
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Yes, i did correct him that is isnt an app but the relay unit in the dac itself.
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I like C3G’s too, but they aren’t dramatically more linear than a 6SN7 when triode strapped.
They will last longer, you can get them NOS still if you know where to look (though you’ll likely have to order from Europe).
I’m assuming he’s doing this to decouple input ground
CCS’s aren’t common solutions for DHT power tube biasing, there is nothing wrong with it, but the primary reason it’s done is it provides a more linear response, because the load line becomes basically horizontal, the reason it’s not common in DHT amps 2A3/45/300B has more to do with the fact it doesn’t buy you as much there. They are already very linear.
Not sure I entirely buy the don’t need matched tubes argument, though it will certainly be less sensitive to matching than a resistor bias.
Your limited in what you can use in capacitance before the Choke when using a tube rectifier anyway, and a Choke input is always “safe”. I assume HV supply is not rectified. This is typical, and means you’ll see pretty dramatic shifts in amp tone from the regulator, because different rectifiers sag differently.
Agreed I’d want more, you also want to make sure the input impedance is on the higher side, your Lampizator won’t be as sensitive as mine, but I’d want 50K at least to be safe (there are good reasons he’d choose to go lower) and that’s almost certainly determined almost entirely by the selection of volume pot.
Sales is a difficult line to walk… On the one hand you want to push your products strengths as you see them on the other hand you can pretty easily come across as an arrogant ass.
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This is a pic of one proposed design.
Here is more talk mostly about nailing things down, understanding each other, and the builder giving me some education on the process.
The Long Chat
The mirror image layout, no problem. The “standard” Khozmo stereo stepped attenuator, no problem.
Yes, “bent” means, in this context, preference. And your preference is for mojo throughout the frequency range, or an agnostic genre preference. This is excellent but requires a specific recipe to achieve. One that unfortunately precludes any type of “universality” to amplifier design (such as compatibility with a “45” tube…). Let me explain, I have built maybe 60 or so 2a3/45 amplifiers…, ALL of which were a compromise in terms of the operating conditions, neither perfect for the 45 or the 2a3, but compatible with both. My guess is the same holds true of the Moth Audio design. There is no way around it, the 45 is best using output transformers with a 7K primary, and the 2a3 is best with 2.5K primary. So…, use a 5K primary and both tubes will “play nice”. However, this is less than perfect. An “end-game” amplifier deserves not to be a compromise. The output transformers I have in mind are not compatible with the 45, they have a primary impedance of 2.5K which is much too low. As for the “meh” performance of the Woo…, yeah, that amp uses AC heating on the 2a3, hence the “working as intended” crapola. The 2a3 can sound really, really good.
And lastly, my biasing methodology isn’t done for “convenience”, it is simply the best sounding method. It just also happens to be convenient. and you are absolutely right! The C3g does look really cool naked.
Well, here is a pic of what I’ve got on the bench right now, a Line Stage in progress…, your amp wouldn’t be too dissimilar from this (aside from being flipped)…
Yep, nothing to hide…, I routinely post “gut shots” of these pieces. Full transparency. :)… even the indicator lamp has its own discrete regulated DC power supply… 
The tube socket mounting/isolation plates are of my own design as well. Good stuff.
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I’d be using the outstanding Soviet era ceramic/pure silver contact Loctal sockets in 1/8" Copper mounting/isolation/ventilation plates for the C3g’s, and EIZZ UX-4 and an EIZZ Octal Teflon sockets set in 1/8" Copper mounting/isolation/ventilation plates for the 2a3/275a’s and the GZ34 rectifier. These are the best there are. Unless you have a preference for the EIZZ 4-pin XLR, I’d be using the Switchcraft XLR and TRS. These are the heavy-duty Pro-Audio version that I like a lot. And they go really nice with the aluminum faceplate.
The RCA’s…, OK, I’ll use whatever you’d like, but I’ve got to say that I’m not that big a fan of the plasticy Eichmann’s or the overblown hype of the WBT’s. I really do like the Cardas, and the CMC’s. They are nice, don’t impart any weirdness to the signal, and are easy to work with. My preference is for either Rhodium or Silver plated over high purity copper for RCA’s. They’ll last forever.
I had a good, and respectful back and forth about transformers. Since a lot of this started with 300b talk, it was mostly around Monolith’s Nano offerings. Each section is the builder digging a little more and looking into documentation and, what i appreciate the most, peeling back his original strong stance and having a more open mind. In the end i still think there is preference and implementation making the decision, and all these high end irons perform greatly
Transformer Talk
Hahahaha…, I’d LOVE to see a transformer with specs from 7Hz to 135KHz…???, on what planet? That’s absurd. Who advertised these specs? I’ll call them immediately and scream liar into the phone. It just simply isn’t possible. Any Physicist will tell you so. Ok, so the James Transformers are also unobtainium now too. They went out of business about 7 or 8 years ago. Along with Tribute and I guess Bartolucci. I don’t much care though, the Noguchi’s and FineMets are better anyway.
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As for the specs stated on the Monolith website, yeah, you’ll also notice that they don’t have a frequency graph to support their bandwidth claims. Since all transformers “roll off” on both ends of the frequency extremes, those specs could be like -60dB on both ends… The specs on the FineMet transformers are ruler FLAT from 20Hz to 20KHz. This is the important spec. It means the transformers have the primary inductance necessary to amplify every note EQUALLY, from bottom to top. So you get slam AND sizzle.
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Thanks for the attachment…, so, I stand (somewhat) corrected. OK, so if we were to get into a very detailed conversation about the Monolith transformers I’d start with how BIG they are. Ya, the only way to get the kind of bandwidth they are suggesting is to wind them on literally giant cores. Not that it matters if what you actually need is the bandwidth of human hearing. And of course, how they are wound, this is the essence of the “artistry” of transformer winding. FineMet transformers have been wound since the 1960’s. I trust them implicitly…, they just “sound” right.
I will probably take a step back for a while, digest, and get more time logging with my ears and better refining my preferences and fleshing out what i actually gravitate towards listening to vs what i think I want.
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This is good attention to detail, the C3G are sensitive to sockets due to the design, and new ceramic sockets have the tendency to break the glass inside the metal shield. Some type of torque action when inserting and removing. That’s a generalized explanation, need to look up the specifics in my email if interested in the proper explanation.
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