OT: Show us your DIY tube amps

[alancohen]

Here is a very recent ( finished last week ) DIY triode amp, made by a long-time Altec 604 user from Saint Louis, Drummerwill :



The LP 845 amp: It took 4 months of planning..... - drummerwill - Tube DIY Asylum

But it has a buzz...that's not acceptable, is it?

Next I plan to improve the 10.0 volt output tube filament supply. Right now they are very quite, but a slight buzz on my 604's...


In my world, Mission 1 is rock solid reliability, mission 2 is dead quiet, both mechanically void of transformer buzz as well as electronically void of any speaker hum.

Without those features, it doesn't matter what the amp sounds like.

[LowOhms]

But it has a buzz...that's not acceptable, is it?

Next I plan to improve the 10.0 volt output tube filament supply. Right now they are very quite, but a slight buzz on my 604's...


In my world, Mission 1 is rock solid reliability, mission 2 is dead quiet, both mechanically void of transformer buzz as well as electronically void of any speaker hum.

Without those features, it doesn't matter what the amp sounds like.

Q. "But it has a buzz...that's not acceptable, is it?"


A. Of course it is acceptable to have a buzz or humm in a tube amp, every experienced person knows that !


READ as to what Willie went on to say, on his own :


Audio Asylum Thread Printer




Your statement 2 :

"In my world, Mission 1 is rock solid reliability, mission 2 is dead quiet,"

Agree 100% on Mission 1, disagree 100% on Mission 2.

You make the same novice mistake that Analog Addict made ....seeking an amp with low ripple. The good reasons WHY you are wrong ( about an amp being "dead quiet" ) have been shown earlier by me in this thread !

BTW, is your new 300B amp dead quiet ?? :-) Hypocrite.

An amp that is dead quiet is always a dead sounding amp, and always out-of-time in relationship to the music. It misses information and on-time information is lacking...always.


Willies amp is possibly the best sounding 845 SE amp ever made to date. It has a well thought out modern power supply that has not ever been applied this way, to any 845 amp. His supply is superior to all others extant.

Transformer buzzing you mentioned ?? Ha!! I personally designated all the specs to that transformer.

(1) It weighs 18 pounds, wound with 900 mA. capable wire, even though the load is 180 mA. in stereo.

(2) It has a DCR of under 9 Ohms from either end of the high voltage winding to center tap, just the DCR it takes for what I like to call ultra-high fidelity. Measure other power transformers as to DCR !! " Takes 10 Ohms or less - to boogie the best. "

(3) It has multiple TCSS lead outs, applied at the time of manufacture, which is totally unique AFAICT, so it is specifically optimized for SE audio performance.

The power supply is IN the audio circuit in SE, and it all needs to be worthy. Why do you think people say "that SE amps are whimpy, can't boogie" ........because they ARE that way .......when mis-designed.

Willie's, and mine, isn't !

How it sounds, after reliability, is ALL that matters in an amp.... the ability to perform is everything.

LowOhms

[alancohen]

But you designed a wonderful transformer...that buzzes. Keep it. He says that he can't hear the buzz at 88dBs. That tells me he can hear it at 87dBs. Nothing would fatigue me more than listening to that.

And BTW, I can read. You don't need to use annoying red lettering and oddly placed bold print for emphasis. It only makes it look like you're trying to establish a point that you can't back up otherwise. Like "an amp that it dead quiet is a dead sounding amp". Hogwash.

And yes, this 300B system is virtually dead quiet. When you first turn them on there is a slight hum. After they start heating up, within about 2-3 seconds, it shuts off and becomes a black hole of non-sound. It's so quiet that I habitually reach for the volume knob thinking it is either very low or off, only to find it is where I left it at about 12 o'clock, which at that level will produce 99dB in my living room.

The amazing thing about that statement is that these are OTL 300Bs. As you know in an OTL the cathode is connected directly to the speaker. In a 300B triode, the filament is the cathode. It took quite a bit of clever engineering to make that work. I know you won't bother, because you know everything, but anyone else who's less endowed can read about how it was accomplished here...Tubes and Circuits by Bruce Rozenblit. It's a great read for tube heads.

As far as I know, this 300B system is a unique 3 box configuration. The PSU is the bottom box. It converts 60 cycle AC to 25 cycle AC before supplying the filaments. That effectively lowers what little hum there might be to beyond the ability of most speaker systems to reproduce it or humans to hear it.



The amps themselves are the epitome of uncluttered simplicity:





And FWIW, they sound anything but dead. My listening area is 21' x 60' and at 12 o'clock on the volume knob they fill the house with glorious sound. Rated at 1.5W into 8 Ohms, I can get 100dB at my listening chair with my 604s. They have thunderous bass and etherial mids & highs...and no buzzing for Pete's sake. The whole package was only $1699 (sans tubes) and 3 days of soldering, not $15,000 and 4 months to build.

I turn them on the minute I wake up, they run all day and I hate turning them off to go to sleep. I'm a very happy camper.

[LowOhms]

Correction . The transformer I designed does not buzz at all. You got that wrong.

There was posted speculation that it may be a filament or a filament transformer that is the cause.

My power transformer design was for Willie's amp's B+ supply.

Well, I am glad you are happy. What looks on the surface to be good is the frequency conversion for DHT heating. The fact that you run a single tube front end can also be good. It is a far simpler circuit than the cathode follower amps you posted previously.

Listen on and enjoy yourself !!

LowOhms.

[alancohen]

Correction . The transformer I designed does not buzz at all. You got that wrong, it loafs.

There was posted speculation that it may be a filament or a filament transformer that is the cause. My power transformer design was for Willie's amp's B+ supply.

Well, I am glad you are happy. Listen on and enjoy!!

LowOhms.

Likewise...

[mah]

It is usual design practise to have any resonance in the power supply occur at a frequency well below the lowest frequency of the amplifier's bandwidth.

Lowohms, your posted schematic shows C1=0.47uF, L1=72mH & C2=20uF forming a high Q series resonant circuit with f(res)=131Hz. This is within the audio band width of the amplifier and considering component tolerances and inductance variation under dc loading, resonance may well be excited by the 120Hz ripple in the circuit.

[alancohen]

It is usual design practise to have any resonance in the power supply occur at a frequency well below the lowest frequency of the amplifier's bandwidth.

I have no idea what that means, but I'm not talking about resonant frequently. I'm talking about changing the 60Hz AC frequency to 25Hz for AC heated filaments.

[LowOhms]

It is usual design practise to have any resonance in the power supply occur at a frequency well below the lowest frequency of the amplifier's bandwidth.

Lowohms, your posted schematic shows C1=0.47uF, L1=72mH & C2=20uF forming a high Q series resonant circuit with f(res)=131Hz. This is within the audio band width of the amplifier and considering component tolerances and inductance variation under dc loading, resonance may well be excited by the 120Hz ripple in the circuit.

Correct on your computations. But my circuit is not at all "usual" design practice, which I have found to be inadequate.

The thing you have not thought about is that the small c/L1/C1 combo cited does not power the audio circuit Finals at all, but it is part of a two stage filter to the finals, consisting of small c/L1/C1/L2/C2. L2/C2 is what feeds the Finals.

small c, ( 0.47 uF ) is not always necessary, but L1/C1/L2/C2 most certainly are.

This new filter design has serious advantages and works much better than anything I have heard in over thirty years of designing and building DHT zero-feedback-loop amplifiers. Write to me mah with your email address and I will send you ( or anyone else ) the EE compilations ( John Swenson and John L. Hasquin ) on the design.

I am drlowmu at gee male dot commie.

Best wishes,

LowOhms

[LowOhms]

To my ears, assuming a good schematic and build, a 45 will always sound better than a 2A3 on Altecs. And most importantly, more musical. Of the amps I own, my Loftin-White 2A3 is about 4th on the list.

A Type 45 is a lovely lovely pristine tube. You are also running less current through it, about half of what a 2A3 will run, so it makes less demands upon the typical power supply to perform.

Once you make quantum leaps in power supplies, all bets are off on what sounds best. Hell, I have a triode connected $2.00 6AQ5 at home now that will boggie with any Type 45 conventional amp . Lets swap schematics one day. Fun to do.

LowOhms

[zelgall]

Jeff, my amps don't boggie. Nor have any of the amps I've ever made. I was in a swamp that was a bit boggie, but not recently.
I feel that your insistence that only your way of making a good amp is not realistic and not open minded at all. You believe that people should take your word for what works best as gospel but you present nothing other than a "my opinion is right and yours is wrong" attitude. You have been proved wrong in other forums where the high tech folks reside and you come here to try to convert the unaware. I'll take a pass on your ideas, not because I haven't tried them but because they're noisy and band width limited. I don't sell or try to sell my friends/associates amps, I've been making my own with my own concepts (right or wrong) for as long as you have and your stuff reaks of BS and dogma.
I've now got a drawer full of Triad trannies and low ohm Hammond power trannies that were expensive but instructional and will use them in traditional supplies and amps as required. The shills that you line up for the I'm right parade can keep the crap you espouse, I'm keeping my excellent sounding amps at all costs.
I think you're over your head in technical discussions as you've admitted and you should stick to expressing opinions rather than facts you can't back up with anything other than a remote subjective thought.
Just my opinion and you're entitled to disagree.