OT: Show us your DIY tube amps

[alancohen]

This is a fun thread.

The biggest pitfall of the 300B (I know because I've been listening to my PP 300B amps for years) is that they are terribly microphonic. I suspest that is what gives them their sound.
I personally believe it is due to the long grid and filament strusture.

I can hit the pause button on the CD when I have it up pretty loud, and you can literaly hear them ring and decay.

So far I haven't experienced microphonics. Here's a couple of clips. On this one I just tapped on the tubes and cab.

DSCF4114 | Flickr - Photo Sharing!

This one I clicked the pause button on and off a few times. I can't hear anything. And this amp is dead quiet. There is a blackness behind the signal that I haven't heard before.

DSCF4115 | Flickr - Photo Sharing!

[RonSSS]

That's cool. Thanks.
My amps have no global feedback, perhaps the reason? And, I have the Svetlana "sparkler" tubes, maybe also part of the problem.

How hard do your amps run the 300B? Plate volts and current? Or simpler, plate dissipation?

I just might pick up a quad of those tubes.

BTW...I really like Lyle Lovett's Large Band CD. Very nicely done to boot!

Ron

[alancohen]

Plate dissipation in this circuit is 20W, or 50% below maximum rating.

[RonSSS]

The B's will last forever.

[alancohen]

The B's will last forever.

Forever is good. It puts out 1.5W SS into 8 Ohms. Into my 604s which are 16 Ohms I'm getting about 50% more. Of course, more would be nice, but that's not what this system is for. I'll have my 15W amp and A7s when I want to rock the casbah. But even at 2+W, into a 99dB speaker you can get pretty loud.

[alancohen]

After a day and a half of trying to track down why one amp wasn't working, with Bruce's help I found out I had a bad preamp capacitor that was basically shorting Pin 1 to Pin 7. The eerie thing is I replaced it last night with another one and the 2nd one was bad too!!! What are the odds.

Well they are burning in nicely. The sound is intoxicating. These amps do for music what salt does for a recipe. All the flavors are there already, it just brings them out so we can taste them. Yum.

[mah]

SE doesn't have to be wimpy.

http://www.pentalabs.com/pdfs/833d.pdf

[alancohen]

SE doesn't have to be wimpy.

Use one of these: http://www.pentalabs.com/pdfs/833d.pdf

Now that's what I'm talking about. A little research revealed that the Lumley Metropolis monoblocks actually used this tube...but it dissipated 1800W in just heat. You would have to run your A/C in the dead of winter.

[LowOhms]

SE doesn't have to be wimpy.

http://www.pentalabs.com/pdfs/833d.pdf

Hello,

You certainly don't need a "big" tube to have a non-whimpy amp. What is needed is a proper power supply, and a small tube can easily rock on a Altec system. In the end, we all listen to a modulated power supply. How good is that power supply?

Most audio power supplies are very-much inadequate, so people compensate for that by using bigger tubes, to make up for their poorly designed, poorly wired, poorly power supplied tube amps. However, if you do it right, it can be done with a single 2A3 or maybe even a single 6AQ5, triode connected. Little tubes can and do often sound better than bigger tubes, and the DHT Type 71A and Type 45 come to my mind.

Little tubes, well implemented, are NOT whimpy at all and can have fantastic bass, PRAT, etc. I have such a DIY amp sitting in my living room powering EV12-TRXBs right now, 1.4 Watts output with a 18 pound purpose-designed power transformer. Wimpy power supplies are whimpy. Poor executions are whimpy. And all such amps are musically uninvolving to hear.

LowOhms

[Alien_Shore]

I have such a DIY amp sitting in my living room powering EV12-TRXBs right now, 1.4 Watts output with a 18 pound purpose-designed power transformer.

Since this is the "show me" thread....would you be willing to post a picture and schematic of your amp?