OT: Show us your DIY tube amps

**mah** · May 17th, 2013, 10:02 PM

The operation of a tube with apparent plate glow seems to be tolerated by types that have suitable graphite plates and suitable construction. I don't know if this is something a tube manufacturer would support.

Eric Barbour: How Vacuum Tubes Work

Audiokarma post: Graphite and tubes... - AudioKarma.org Home Audio Stereo Discussion Forums

**RonSSS** · May 17th, 2013, 10:26 PM

I didn't say it was a good thing, just the way it is in my amp. They are self bias, so unless I make changes to the design, I get what I get.

Good story Joe on the 300B's.....I have 1 engraved base, half the filament is dead. But, great for display.

I will check out those PSVANE tubes Alan, thanks for the tip.

Ron

**analog addict** · May 18th, 2013, 10:02 AM

Originally Posted by bowtie427ss

Agreed, looks like the OPT's are the ones with end bells directly behind the 2A3's, or maybe those are the ones Alien is asking about............................

Oops. Sorry I missed this part of the thread. The OPTs are Transendars.

As far as my hot rod amp, I should clarify that my amp is a prototype that Dennis used to absolutely push the envelope as to what a 6BQ5 tube will do. IIRC, this will do about 8 WPC, while even his new high output Fire Bottle amp will only put out six. I may up the cathode resistors a little just to add a little piece of mind because as one of the other poster noted, it's hard to enjoy the music when you always have an eye on the tubes....

**wiselisle** · May 18th, 2013, 01:11 PM

nice working...............

**alancohen** · May 19th, 2013, 11:25 PM

All this tube amp talk got me itching to build another Cathode Follower. I just might end up using both to bi-amp the 604s.

I just went through the BOM and ordered everything. As usual the output transformers were the most expensive components. All tolled including shipping came to $519. That's dirt cheap for a 3W Pure Class A SE amp, let alone in a cathode follower configuration.

Here's the BOM:

I got some NOS Sylvanias for the drive tubes and I'll try the TungSol reissues for the power tubes.

The power transformer is this http://www.antekinc.com/details.php?p=673 It's more like the one that originally came with the kit and more quiet than the laminated Hammond for DIYers on the BOM...and 1/3 the price!

**Alien_Shore** · May 20th, 2013, 07:41 AM

Funny you should mention, Alan. I have a couple of Z565 OPTs here, now if I dig out that old SCA35 and see if the power trannie is any good...I could biamp my 604 as well.

**alancohen** · May 20th, 2013, 09:18 AM

Originally Posted by Alien_Shore

Funny you should mention, Alan. I have a couple of Z565 OPTs here, now if I dig out that old SCA35 and see if the power trannie is any good...I could biamp my 604 as well.

With all the crossover gyrations attempting to address the hills and valleys and driver delay in these speakers, it seems obvious that they are just begging to be bi-amped.

I'm going to finish my crossover anyway so I'll have something to compare it to, but there is likely a Marchand active crossover in their future.

**Alien_Shore** · May 20th, 2013, 02:22 PM

Originally Posted by alancohen

With all the crossover gyrations attempting to address the hills and valleys and driver delay in these speakers, it seems obvious that they are just begging to be bi-amped.

I'm going to finish my crossover anyway so I'll have something to compare it to, but there is likely a Marchand active crossover in their future.

sending you a PM

**LowOhms** · May 21st, 2013, 05:20 AM

I agree with Alan Cohen. IMHO, amps that run the tubes hard are JUNK !!! Poorly designed. If you can't get 10,000 hours out of a tube, your amp is junk. Garbage, mis-designed.

The MAIN reason people "hot rod" tubes is because they don't know how to build and properly wire an amp internally, for what "I" call maximum transfer efficiency. They use crummy ( thin ) wire, and too long of lengths ... and non-thoughtful layout choices.

To justify their mis-designs, they do an "A-B" test and guess what, the hot rodded tube sounds better on the A-B, so they think "lets push upwards" the tubes plate dissipation ( voltage times current ).

The problem occurs as such: Within 10 hours of over-dissipation, the tube is degrading, and within 200 hours, the tube is sounding crummy compared to when it was new ( and originally A-Bed ), and maybe it will last 2,000 hours before you spend the bucks to replace them. Who the heck wants to own gear that is constantly degrading ?? Not I.

Guess what, in a properly executed amp, one that is well-wired, and has good lay out and internal wiring ( optimized for a wide -band transfer efficiency ), the "hot rodded" tube will always sound WORSE than the conservatively operated tube. Why ??

This is the way it is, in many things in nature.

The "hot rodded" tube has a higher dissipation across its plate, and as such, it is running at higher internal temperatures. In a good amp, on a good hi fi system, these high temperatures are STRESSED SOUNDING as all get out. Not "relaxed and free sounding", just stressed and uptight.

You all know these things. Your lawnmower runs better at 2/3rds throttle than at full throttle, and your family sedan runs better at 62 MPH than it does at 100 MPH. In nature, we call it "The Golden Ratio", about 62 percent as I recall.

So, say a Type 45, a pristine sounding tube - ( which KILLS KT-88s if you don't know that ) - it would be a GOOD idea to run the 10 Watt rated Type 45 at 6 or 7 Watts dissipation . It WILL easily last 10,000 to 50,000 hours, and it WILL DEFINITELY sound better at that Golden Ratio dissipation, IF the amp is well wired internally, and well designed internally.

Most tube audio designers, ( or should I say the undersides of their amps - when I see them), are totally ignorant of these things I've discussed herein, or, to say it nicer, are simply unconscious of this. These amp designers are all nice fellows. I am sure Dennis Had is a good guy, but they are lacking in the mastery of the task at hand. Running tubes hard is dumb and unjustifiable, once you understand there IS a better way to execute a tube amp.

LowOhms

- - - Updated - - -

Here is a DIY amp design and build of mine from 28 months ago. This was when I was just starting on my journey of "high transfer efficiency" and it is filled with my learning errors.

http://db.audioasylum.com/mhtml/m.ht...ers%3Dspeakers

(1) The chassis is too large ( the amp was a stereo amp, a poor decision which created FAR too many wire length compromises. (2) I should have done the 2A3s as monoblocks. (3) More recent builds have used more wire in parallel and shorter lengths, to get better overall results.

Dig that chassis, 12 gauge steel, laser cut, welded corners, and powder coated midnight blue wrinkle, one of my favorite finishes. Bare chassis by itself weighs 33 pounds, power transformer weighs another 18 pounds.

My newer 2013 amp is improved IMHO - as I learned more. The newest 2013 amplifier is also a two stage direct coupled circuit, ( for maximum possible transparency ), and designed with the Altec A7s in mind. Fun to hear on efficient speakers, almost a revelation.

LowOhms

**analog addict** · May 21st, 2013, 10:32 AM

Originally Posted by LowOhms

I agree with Alan Cohen. IMHO, amps that run the tubes hard are JUNK !!! Poorly designed. If you can't get 10,000 hours out of a tube, your amp is junk. Garbage, mis-designed.

The MAIN reason people "hot rod" tubes is because they don't know how to build and properly wire an amp internally, for what "I" call maximum transfer efficiency. They use crummy ( thin ) wire, and too long of lengths ... and non-thoughtful layout choices.

To justify their mis-designs, they do an "A-B" test and guess what, the hot rodded tube sounds better on the A-B, so they think "lets push upwards" the tubes plate dissipation ( voltage times current ).

The problem occurs as such: Within 10 hours of over-dissipation, the tube is degrading, and within 200 hours, the tube is sounding crummy compared to when it was new ( and originally A-Bed ), and maybe it will last 2,000 hours before you spend the bucks to replace them. Who the heck wants to own gear that is constantly degrading ?? Not I.

Guess what, in a properly executed amp, one that is well-wired, and has good lay out and internal wiring ( optimized for a wide -band transfer efficiency ), the "hot rodded" tube will always sound WORSE than the conservatively operated tube. Why ??

This is the way it is, in many things in nature.

The "hot rodded" tube has a higher dissipation across its plate, and as such, it is running at higher internal temperatures. In a good amp, on a good hi fi system, these high temperatures are STRESSED SOUNDING as all get out. Not "relaxed and free sounding", just stressed and uptight.

You all know these things. Your lawnmower runs better at 2/3rds throttle than at full throttle, and your family sedan runs better at 62 MPH than it does at 100 MPH. In nature, we call it "The Golden Ratio", about 62 percent as I recall.

So, say a Type 45, a pristine sounding tube - ( which KILLS KT-88s if you don't know that ) - it would be a GOOD idea to run the 10 Watt rated Type 45 at 6 or 7 Watts dissipation . It WILL easily last 10,000 to 50,000 hours, and it WILL DEFINITELY sound better at that Golden Ratio dissipation, IF the amp is well wired internally, and well designed internally.

Most tube audio designers, ( or should I say the undersides of their amps - when I see them), are totally ignorant of these things I've discussed herein, or, to say it nicer, are simply unconscious of this. These amp designers are all nice fellows. I am sure Dennis Had is a good guy, but they are lacking in the mastery of the task at hand. Running tubes hard is dumb and unjustifiable, once you understand there IS a better way to execute a tube amp.

LowOhms

- - - Updated - - -

Here is a DIY amp design and build of mine from 28 months ago. This was when I was just starting on my journey of "high transfer efficiency" and it is filled with my learning errors.

Its FUN to build a 2A3 amplifier.... - drlowmu - Tube DIY Asylum

(1) The chassis is too large ( the amp was a stereo amp, a poor decision which created FAR too many wire length compromises. (2) I should have done the 2A3s as monoblocks. (3) More recent builds have used more wire in parallel and shorter lengths, to get better overall results.

Dig that chassis, 12 gauge steel, laser cut, welded corners, and powder coated midnight blue wrinkle, one of my favorite finishes. Bare chassis by itself weighs 33 pounds, power transformer weighs another 18 pounds.

My newer 2013 amp is improved IMHO - as I learned more. The newest 2013 amplifier is also a two stage direct coupled circuit, ( for maximum possible transparency ), and designed with the Altec A7s in mind. Fun to hear on efficient speakers, almost a revelation.

LowOhms

Strong language and strong opinions. The proof is in the pudding, isn't it?

His:

Yours:

His distortion results:

At least -40db at the 2nd harmonic with the 3rd harmonic -50 db.

Yours? You seem awfully sure of yourself.

How long have you been building tube amps, and how many electronics businesses have you founded, and then sold for a profit?

I'm sure Dennis could care less what you or anyone thinks, but you're putting me in the position of defending him, so I feel obligated to respond.