rant: volume, wattage, and tone

[EtherealWidow]

I mean, an imbalanced tube in an imbalanced circuit can actually create more balance.

Or it can actually create perfect balance! Haha.

[gingertube]

I believe that you do get better sound by letting components work at reasonable levels of voltage and current. Thats why I view "with a grain of salt" those posts I see here claiming that some thing sound best with everything "dimed".

My absolute favourite EL34 amp is cathode biased with a B+ of 380V for a maximum of 32 Watts (continuous sine wave at the edge of clipping). A JTM45 Output Tranny was used, output tubes are actually NOS Philips 6CA7.

I'll stack that against any Marshall or anything else for that matter with EL34 working a 450 to 480V to squeeze out 55 Watts.

Stressing amps to the max. in persuit of that last watt often leaves them sounding like a haemorrhoidal bear trying to pass a pine cone. It definitely leaves them with a habit of blowing up at inconvenient times.

Is there a single design issue we can point at which 99% of amps do badly - yes there is, inadequate control of output tube grid1, that is, Rg1 values too high and drive impedance too high.

Well thats my vent of the spleen for today - I feel better already.

Cheers,
Ian

[matt h]

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[Jana]

Ian,
That's what I've been saying for a long time--380 volts for a pair of EL 34 in a Marshall is the tone zone. That is my all time favorite amp. I use 100K for the grid 1 / bias feed resistors.

[Jana]

Ampfab, I used to like playing loud too--150 watts loud. Now I have hearing loss and perpetual tinnitus. If you can't hear yourself over the rest of the band with a 20 to 30 watt amp, it's time to find a different band. And, with the PA systems that are available these days, if the 30 watt amp isn't enough for a venue, mic it. Save your ears. I wish I had.

[Leo_Gnardo]

Stressing amps to the max. in persuit of that last watt often leaves them sounding like a haemorrhoidal bear trying to pass a pine cone.

Bosh & balderdash, you don't have such bears in Australia!

But your review on tone is spot on. My favorite 50W Marshalls (which I foolishly sold) ran 380-400 B+. Some day I'll start on a JTM45 series, aiming for that B+ zone.

As for the pine cone tone zone, there are some performers & bands that try for it ... cookie monster voice is popular going on for decades with guitars to match.

[gingertube]

Ian,
Thank you for venting! This is precisely the sort of thing I'm talking about. The 32Watter is certainly in the same class as the exploding 55Watter.

Just to be clear, are you saying the grid stoppers are too large? Or the grid leaks?

Grid Leaks too large - that makes the output tube bias point unstable AND introduces noise. The voltage generated across the grid leak from grid current opposes the bias and it is statistical in nature, that is there is an AC noise component generated along with the DC bias shift.

I run an own design 6V6G PP for the HiFi. In that I use mosfet source followers with current source loads to drive the 6V6 grids. It is absolutely dead quiet background, no his or hum at all.

Grid Stops can be made quite large BUT remember that when you look at a max Rg1 value on a datasheet, that is the max resistance from grid to 0V, that is it is a maximum value for Grid Stop + Grid Leak.

Cheers,
Ian

[matt h]

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[gingertube]

I've experimented with neo speakers and thinner cabs, but the innovation I'd love to see is to get rid of those heavy transformers

Well the Output Transformer is part of the valve amp sound so we are not going to ger rid of that in a hurry.

The power supply however is another story. I've been waiting for these things to come down in price.
http://www.martekpower.com/files/pdf/361.pdf

An Isolated Power Supply Front End to give 380V DC intended to run DC to DC Converter Modules. Universal Voltage Input, Power Factor Correction and Harmonic Attenuator Filter all in one package. Use it's 380V DC which is ISOLATED from mains for the B+ and hang a 380V to 6V DC to DC Converter on it for heaters. So why aren't we all doing that - its too bloody expensive. There is a 1000W rated version too.
Many manufacturers of suitable 380V to 6V DC to DC Converters - VICOR for one http://www.vicorpower.com/dc-dc-convert ... c-converte.

I do do it in the day job, for a laser power supply for airborne equipment where weight is more important than cost.

Cheers,
Ian

[Ken Moon]

Cool stuff.

In my previous life, I worked with a group of engineers who were designing automated test programs for the AN/ASQ-228 ATFLIR system on the Navy's CASS Electro-Optics test system.

I never got deeply into the laser power supply technology used in that system, but it may have used modules similar to the ones you referenced.

Since the PT is usually the heavier of the trannies, this would indeed be a nice amp innovation, if the cost could come way down.

[Firestorm]

Wandering back toward the original post, I think we should start rating combo amps in terms of SPL (heads too for that matter, we all know what speakers we'd recommend); I'd love to see gearpage posts like "it does .375 pascals"..." well oh yeah, mine is rated for .392. "

Tone, though: what exactly is it (a Zen question)? If you listen to recordings of tweed amps on "12, " they get this wonderful "warbly" tone happening.

Which components in the chain are going silly to make that happen?

And Marshalls: you start with one basic circuit and get nineteen different sounds depending on what year it was made.

[matt h]

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[ampfab]

The reason I would ask "how many watts?" Is simple, and probably why most poeple would ask the question. I wanna know if the amp will "cut the mustard". When I play out I like to have fun, most places I play I can not mic the amp. I've found that a 15 watt amp won't cut it, not fun!
I've found I need a 30-50 watt amp to be able to hear myself and have some versatility in my tone. I don't want to be the guy telling every one else that they should turn down.
I tend to favor cathode bias power amps, certainly not the most efficient. If its a 15 watt cathode bias amp, it may sound great, but it will piss me off when playing with a group of guys, But a 30 watter will "cut the mustard".
when I build an amp for myself, I don't build anything under 25-30watts, because I use amps on stage without a mic.
if I used my amps for recording, I would probably build 15watt amps, but I don't record much.
you guys will probably want to lynch me, but I have a small modeling amp that I use as a bedroom amp. I find that the best type amp for that situation because I can get a lot of different tones (although not the best tones) at low volumes. if i'm playing in my bedroom i'm not terribly worried that I have the best tone or am I interested in the wattage of that amp.
I think higher wattage amps provide versatility.
amps need to be designed to meet the needs of the guy who's going to be using it. if it doesn't meet his needs, tone doesn't matter, he won't be using your amp.

[JoeCon]

People,

I'm the one who started all this on another post. But one thing I was wondering about was integrity. Sure they saw my twin tube Rocket and figured it wasn't a 50 watter, but the KT66 Rockster sure looks different. If I had said..."sure it's 50 watts easy" they might have been more interested but I said it's a 30 watter erring on the less power side. With that they were not interested as ampfab said because they felt it wouldn't "cut the mustard." But they didn't even want to try it.

Guess what I'm getting at is how would they know if it's 50 watts or 30 and why would it matter if it could do the job? How many Marshall 50's were actually 50??

I was hopping to get a couple of amp builds but wanted to be honest as well...

[ampfab]

People,

I'm the one who started all this on another post. But one thing I was wondering about was integrity. Sure they saw my twin tube Rocket and figured it wasn't a 50 watter, but the KT66 Rockster sure looks different. If I had said..."sure it's 50 watts easy" they might have been more interested but I said it's a 30 watter erring on the less power side. With that they were not interested as ampfab said because they felt it wouldn't "cut the mustard." But they didn't even want to try it.

Guess what I'm getting at is how would they know if it's 50 watts or 30 and why would it matter if it could do the job? How many Marshall 50's were actually 50??

I was hopping to get a couple of amp builds but wanted to be honest as well...

I would suggest loaning it to him for a few days if you think it would "cut the mustard".