Diode in series w power supply

[Chadwick]

Put a diode in series with the power supply after the screen grids and before the phase inverter plates. 4007

It speeds up the attack, tightens, stiffens, more punch and faster playing. Its also great for shocking you because it will keep that voltage heavy unless you play the amp as it is powering down or discharge the preamp filter caps.

I learned it from a Torress book, a true tube amp master. I heard he was at the NAMM show this year and I missed him again. I wanted to tell him how cool he is.

[Arthur B.]

Elaborate?

Can you be clearer in your explaination? What style of amplifier are you referring to in your mod, and what do you mean in series with the power supply?

[Chadwick]

diode

This is definately a high voltage mod and nothing you want to mess around with lightly.

All tube amps have a power supply beginning with rectification and filtering [cap to ground]..

Almost all tube amps use the first filterstage to supply the centertap to the output transformer [which supplies the plates of the output tubes],

then usually a choke or a resistor and another filter cap that supplies the screen grids..

Now there is a 10k resistor and you can placde the diode here in series not to block voltage, and then a cap connected to the phase inverter or preamp.

[Rob Mercure]

Chadwick,

I'm glad you've had a good experience modifying your amp - but I believe if you seach the archives of this forum and it's predecessor you'll find other opinions about Torres being a "master." For myself one can get more info from an old ARRL handbook, an RCA tube manual, and one of the circuit "cookbooks" that have been published for years (one from the late 1950s is best) or H. Lewis York's "Amplifiers." Anyhoo, the point is to provide sound theoretical background and understanding of the circuits and not just point to "tricks" without explaining why they work. Torres, as have most other modern tube amplifier "gurus," seems to be not concerned with technical mistakes nor simple poor use of the American idiom of the English language - the technical mistakes are more in line with this forum's purpose, the language mistakes just annoy me as a lifelong reader who spots sloppy usage (it's really easy to get a friend to help edit one's writing - one thing I always did when it was important to my living).

But, anyway, enjoy your amp/work and do report your successes.

Rob

[Chadwick]

have you tried that mod?

Interesting on Torress. I only read one of his books and I got alot out of it. I certainly wouldn't look to a tube amps guru for a fine literary experience, but your right about getting any 'about to published' work proofread.

I should proophread my own posts. lol.

I love the diode thing and wouldn't doubt if somebody else did it sooner. Have you tried it?

[bob p]

... more punch and faster playing.

Damn. I feel like a friggin' IDOT for living for so many years without a diode in my PS rail!!! I've always wondered why I've never been able to play fast! Now I know!

[bob p]

... but I believe if you seach the archives of this forum and it's predecessor you'll find other opinions about Torres being a "master."

i'll disagree with Rob on this one -- i can think of at least one word that begins with "master" that describes Torres pretty well.

interesting that you mention York. I've got that book and I like it too.

[AdmiralB]

I love the diode thing and wouldn't doubt if somebody else did it sooner. Have you tried it?

The only amp I've seen (that I can think of right now) that came with one is the Komet 60. I always assumed that was because Fischer wasn't really a tube rectifier guy (I think it's really only there as a marketing point), and it was a way to somewhat 'de-sag' the circuit. The KF-50/Concorde doesn't have it.

I built a Komet clone, and it doesn't sound or feel any different with or without the diode - the power supply is plenty robust. I have used it in tube guitar rigs in bass applications (Showmen, etc.) with positive results.

[Rob Mercure]

Hey Bob, well, somehow I tend to think that your "disagreement" is more of an "agreement" but I was attempting to be "gracious" in my comments. 'Tis funny how even the best of the "amp books" tend to be filled with "lore" that really isn't true. I've generally liked KOC's books (although he did defensively post on the old Ampage in an truly AH way at times) but he repeats "rumors" that just arent' factual. Fer instance: That Ampeg switched from the 6146Bs to 6550s in the SVT due the RF oscillation cuz the 6146 was originally designed as an RF output tube. Yeah, right - and hams have used 6L6 metal tubes for years and the horizontal output tubes that some HiFi amps (and at least one Gibson) used were used in "linear" amps at RF for years, and, and, and .... foam, slather... I hope you get the idea. What about: "6550s were cheaper and more available than 6146Bs?" But this is only to pick on what are perhaps the "best" of the genre of amp mod books to demonstrate that factual and editing errors plague everyone. And, what the hay, I haven't the energy, gumption, nor "whatever" to write a book myself so it's somewhat hard to criticize Torres. Perhaps the worst have been Pitman's "Tube Amp Books" - when I got my first one around 1991 I wrote - paper that is, no e-mail then - Pitman offering to proofread the next edition for him as long as he provided it on disk (WP 5.1 was my word processor then) but never received any reply of any sorts. Now I've not seen the very latest edition but I'd be truly suprised if all the technical and language errors have been corrected!

And the York book is truly great if you can find a copy. While there are numerous tomes that describe audio amplifiers York's is the clearest and most concise and I truly honor anyone that can define complex issues in fast and simple terms that don't have you wondering "what in the hell did I read" for hours afterward - I only wish I had the book when I was 16 and first into tube electronics (this is where the ARRL Handbook and the RCA tube manual provided my "teething").

Chadwick: As far as the diode trick - my playing style probably wouldn't benefit from the mod but I've been aware of it for quite a few years - from the old Ampage board actually. My main amp is a 1967 Vibrolux Reverb - slightly modded by me - that is never played on stage at sufficient volume to worry about "sag." But perhaps I'll get back to my "mini-Deluxe" project and incorporate it in that design (an old Crate SS chassis and cabinet that barely accomodates a 10" speaker - had to route out some of the cabinet as it was originally an 8" - to provide an amp that is so small that it can sit behind the seat of my truck at all times "in case I need it" - did most of the work last summer but somehow haven't returned to the project.).

Cheers

Rob

[bob p]

yes, setting the snearing sarcasm aside for a minute, i think we have similar thoughts about some of the self-professed tube amp gurus and bookwriters. i remember more than one of them pimping his books at the old site, making claims that defied the laws of physics.

one of my favorite lores of yore is how the SF amps get hammered because "their poor lead dress causes oscillation." nevermind the concepts of OT design and phase correction, people blamed lead dress because it was something that every armchair amp guy could easily visualize -- and the lore has stuck to the point that fiction has become widely considered as fact. sigh.

[Chadwick]

Tube amp lore, Torres.

nice. my wires are coated with cloth from the future making it sound awesome. lol. Not to mention I feed my flux capaciter baby crickets for extra tone.

Anyway just out of curiosity on Torres, what is an example of his mistakes or 'lore'. A link to another thread would suffice. If I remember he published pages and pages of bias charts, seems like an easy place to screw up since each tube is different anyway.

[Rick Erickson]

"their poor lead dress causes oscillation."

It certainly CAN, but it 's not the reason I dislike the crappy white plastic coated wire. That wire seems to have a near perfect combination of flexibity and brittleness that makes it not stay where where you put it, and frays or breaks at the solder joints. It seems backwards, but the solid wire Fender used was more reliable than any of the "flex" hookup wire they have used, including the stuff in their latest PC board amps. Another annoying problem with the silverface amps from about 1970 on is the conductive eyelet board that gets more and more conductive as the amp heats up. The only cure I know of is to replace the board, and while you're at it - you may as well replace the harnessing wire with the cloth covered solid stuff. Sorry if I sound jaded here - I just got done fighting with one of these beasts.

RE

[Enzo]

I have had success on conductive eyelet boards using a heat gun. sTarting at one end, heat it up in small areas at a time. You can see the waxy look of the board turn to looking "dry" as you move along. The contaminated waxy surface coating is evaporating away. Keep going like you were cleaning the debris off your driveway with a garden hose. I also then cleaned the board with Blue SHower - an excellent product they can no longer make with the CFC ban. Contact cleaners in general should help though.

[Steve Conner]

The idea is to stop the preamp and PI supplies getting sucked back into the screen and plate nodes when the output stage is wailing and dragging those voltages down, I guess. With the diodes in, the preamp and PI voltages should be higher during loud playing. You will get less of the compression, pumping and breathing effect that comes from the preamp rail bouncing up and down.

I figure this because I built an amp with all its B+ rails regulated and it does indeed sound pretty "tight" and "stiff". It's great for heavy riffing, or bass, but I found that I like an ordinary amp more for most things.

As for fast playing, I guess Joe Satriani has 10 diodes there