OT: Show us your DIY tube amps

[LowOhms]

Hi alancohen,

What that amp's schematic you have posted herein will NEVER do is be as "transparent" as possible. Nor will it be able to possibly convey the intent of the musicians as they played the music.

It is taking FIVE audio stages and two series cap couples, to amplify a signal. Heads up !! Every unnecessary stage you go through is a opportunity to LOSE information, because there are NO perfect amplifying devices.

In contrast, the topology I espoused has only two stages - direct coupled.

Far less "messing " with the signal. No unnecessary stages. No sorry-sounding cap couples. KISS rules in audio design. My point to you all : The audio path needs to be as simple as possible to get the job done, and NO more complex than that.

Next point, generally speaking, most of the greatest audio designers have found that a circuit usually sounds better when you have no cathode followers. *

* I should exclude Finals stages, I don't know about that in the "right" design ( there is only ONE that I know of that may be OK, and it isn't the one you showed us ) ......so please lets just apply my above cathode followers comments to preamps and an amp's preliminary stages.

Final point, Cathode Follower output stages you have read about simply trade off gain for low Z. However, the power supply design and filters in conventional tube amp designs ( such as the ones you show us herein ), can not EVER begin to properly feed that Low Z. It ends up sounding like someone threw a wool blanket over your horns, versus an ideal, more modern power supply implementation.

There is no free lunch, and its not just science, but an art form also. Lotsa fun.

LowOhms

[alancohen]

I'm not sure why the schematic is draw that way, but there are only 3 tubes per channel, not the 5 that appears on the drawing. There's a 12AX7 into a 12BH7 into the 6550. So that would be 3 stages?

And you're trading gain for high Z, but that high Z gives you slam in the bass response that SE triode amps are notoriously void of. Beautiful mids and highs, but weak below 100Hz. This amps measure 1dB down at 30Hz and 3dB down at 20. That's what a CF output stage gives you.

The power supply toroid for this amp is only 300V so not too unconventional.

If transparency is the goal, get rid of the output transformer. My new 300Bs monoblocks will have the cathode of that tube connected directly to the speaker Can't get much more transparent than that. But transparency is not the main goal for tube amp lovers. It's something about the way the vocals sound. The harmonics of the tubes have a naturally pleasing sound to the human ear. It's hard to explain, but its almost like why we like hearing vocalists sing harmonies. There's something in the blending that appeals. No, it's not the most transparent, it just sounds nice.

And I'm a huge fan of KISS, but for me it must be KISS...and reasonable. I've perused Dennis' site and for me personally, I would never be able to enjoy listening to a system where the volume knob cost $3150. I'm not sure how much his amps are, but if they are that simple, they shouldn't cost that much...right? If the silver hookup wires are so short, you can't be using to much of it. And I can't imagine replacing a 3" copper wire with silver one would ever make a difference I could hear. Just sayin'.

With this amp you spend $500 on parts, a weekend putting it together, another $500 on a tube preamp kit and hook it all up to a pair of A7s and you're 99.7% of the way there. That's what I find enjoyable. But that's just me.

[analog addict]

And I'm a huge fan of KISS, but for me it must be KISS...and reasonable. I've perused Dennis' site and for me personally, I would never be able to enjoy listening to a system where the volume knob cost $3150. I'm not sure how much his amps are, but if they are that simple, they shouldn't cost that much...right? If the silver hookup wires are so short, you can't be using to much of it. And I can't imagine replacing a 3" copper wire with silver one would ever make a difference I could hear. Just sayin'.
.

Actually he sold of the majority of his interest in Cary Audio several years ago, and works out of a 700 sq ft shop very near where he originally started Cary many years ago. He only sells his current amps on E-bay under the ID "radioman731"

Here is an example of his current offering....

Inspire Stereo Tube Amplifier by Dennis Had 807 Tube McIntosh Amp Inspired | eBay

You can read all about it in his own words. And for $1200 where are you going to find an amp hand built by someone with his talent and experience?

And yeah, I'm that audio buddy he mentions in the ad....

[zelgall]

AA, you're referring to Dennis Had but LowOhm and Alan were talking about Dennis Fraker of Simply Stereo. DF makes 2a3 amps only. Please don't taunt LowOhm, he's like a Mormon missionary with an Amway franchise.

[alancohen]

AA, you're referring to Dennis Had but LowOhm and Alan were talking about Dennis Fraker of Simply Stereo. DF makes 2a3 amps only. Please don't taunt LowOhm, he's like a Mormon missionary with an Amway franchise.

.........

[LowOhms]

Hi alancohen,

Your interpretation is incorrect.

The schematic is certainly correct, notice the 12AX7 and 12 BH7 are dual triodes.

Even though its "one" tube, in your posted schematic the first triode section is employed as a gain stage, and the second triode section is employed as a cathode follower stage. There are the attendant losses in two stages, for each triode section. Add five such stages in series and you have screwed the pooch so to speak.

For your information, an optimally designed two stage SE tube amp will always sound better than a well designed three stage amp. ( That is why I build and use them. ) The two stage will be heard as "more transparent" and that is a VERY nice listening experience !!

In the case of the amp you are suggesting, we are not comparing a two stage to a three stage, but rather, a two stage amp to a five stage amp. It will be slightly worse sounding than an optimally designed three stage amp with no cathode followers. And yours ALSO has two series cap couples in the circuit path...ugh. Less is more !!

The real virtue of owning an Altec A7 type speaker is that you can effectively use a two stage direct coupled tube amp on them, which is simply the highest performing tube amplifier topology possible in today's world.

You have wildly missed the build costs associated with the amps you looked at. $500 will perhaps get you the Cryoed AC cord wire for the pair, but that is all!!

Ever price Siltech wire alancohen? Its multiple dollars per inch. You just need to hear this, then you would understand !!

LowOhms

[alancohen]

Actually he sold of the majority of his interest in Cary Audio several years ago, and works out of a 700 sq ft shop very near where he originally started Cary many years ago. He only sells his current amps on E-bay under the ID "radioman731"

Here is an example of his current offering....

Inspire Stereo Tube Amplifier by Dennis Had 807 Tube McIntosh Amp Inspired | eBay

You can read all about it in his own words. And for $1200 where are you going to find an amp hand built by someone with his talent and experience?

And yeah, I'm that audio buddy he mentions in the ad....

zelgall is right, AA, I was talking about the other Dennis.

And $1200 is an excellent price for the Inspire. I'd be all over that if I wasn't building from kits. I love supporting cottage businesses when they're reasonable. I have TS amps, a John Kenny DAC and GPA components in my speakers. I have no issue paying for someone's clever, hard work. I just won't pay $5000-$10,000 for a box of electrical components that cost $500-$1000 and 20 hours to assemble. No design is that good.

Bruce's philosophy with his amp designs is that once he sells one, it wouldn't take a rocket scientist to reverse engineer it and build their own. So he gives his designs away for the price of a book and then sells kits. Pretty clever actually.

- - - Updated - - -

The schematic is certainly correct, notice the 12AX7 and 12 BH7 are dual triodes.

$500 will perhaps get you the Cryoed AC cord wire for the pair, but that is all!!

Ever price Siltech wire alancohen? Its multiple dollars per inch. You just need to hear this, then you would understand !!

Yep, I just realized that. Each tube a two triodes in it.

And I am in no danger of paying $500 for a cryoed AC cord. There is just no way I would be able to tell the difference. It's intriquing to me how much people will spend on audio equipment, only discover it still sounds like crap because the room it's in is acoustically barren.

Nowhere are the laws of diminishing returns demonstrated more clearly than in over-hyped audio products. My little cathode follower sounds amazing for a $500 investment. Let's be fair and call it $1200 assembled. Now is a $5000 amp 4X better? Of course not. It's maybe 2% better on the audio quality continuum. That's just not worth it to me.

That said, I'm sure their are people out there that like to discuss their cryoed AC cords and Siltech wire at dinner parties; I'm just not one of them.

[alancohen]

With all this DIY talk here and on the crossover threads I thought I'd look into getting a scope. I asked around at what to get, old school analog or newer digital storage scope. I was surprised to get this recommendation from a respected source:

Velleman SA Three-in-One Lab Unit with Scope, Function Generator and Power Supply | LAB2U | Velleman SA

Then I saw it on Amazon for half the cost.

Amazon.com: VELLEMAN LAB2U THREE-IN-ONE LAB UNIT (Scope, Function generator and Power supply): Everything Else

Rumor has it it will do more than I will ever need. Hard to pass up for $126.

I'm looking forward to a few fun projects and learning and learning.

[alancohen]

My latest DIY tube amp...some of it anyway.

[gortnipper]

My latest DIY tube amp...some of it anyway.

Oooh...it even has a remote!