Matchless spitfire el84 dissipation

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#3
The current through the common cathode resistor is I=11.2/120 or 93.3 ma, devided by two is 46.7 ma per tube. I think thats not so bad. If p=.046 X 348 then each tube is disapating 16.0 W ---- I would like to hear from other on this because I have thoughts of trying a EL84 guitar amp.
 
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#4
I smiled reading that old post, I was a noob back then. Well, Firechief - what do you want to know? I didn't finish that amp, my friend didn't have a good finish - toxic ways. Spitfire is sort of a Vox clone, not much gain in front though . I love PP el84's amps- hifi and guitar amps. There's the Vox and the Marshall 18 watt.

http://www.ampwares.com/schematics/marshall/marshall_18watt_schem.pdf

Both would be good choices, I like the Vox 15.

I don't think there's much difference in sound with a colder bias, my cathode resistor is 150 Ohms.
 
#5
Cassiel- I honestly didtent read the date on that first post😕 That just goes to show not much has changed. Here is my latest project. Quad El84 amp. Let your friend's story be a lesson to us all.
 

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#6
Having several Matchless amps, the trick of the trade is to know how to run the amp (with high bias). It has to sweat - but never to be leaved with no signal and plate on for longer than ten minutes. Unless you use unarticulate speakers it's clear to hear loss of the typical "shimmer" when you dial down the bias. The nearest comparison-device is a Celestion Gold.

Peter
 
#8
firechief said:
note taken
Click to expand...

It wasn't to sound rude FC, but there's so much hype around these amps. They call them "Class-A" - and all they are is high-bias'ed AB's.
Around tube choice, go for the Winged-C Svetlanas or the JJ's that Phil stick in before they leave for customers.
They will last some 200-300 hours before they need a switch, but that is the downforce of running hot.
Of utmost importance for that "sound" is the input-tube! A NOS Mullard will maybe empty your pocket but will last nearly forever.

Peter
 
#10
firechief said:
Not rude at all. I know that class A guitar amps is are a myth. Why would you even want a super clean, distornless amp anyway? Here is a link to my earlier efforts
http://www.diyaudio.com/forums/musical-instruments/164358-one-off-guitar-amp.html
and thanks for posting . Tube coice is kinda limited, I need to stick with current production output devices, So for now JJ's are my tube of choice.
Bob
Click to expand...

Hey Bob,

The guitar-amp scenario are as complicated as the hi-fi ditto. Do you want the British Brown-Sound or the American Fender Surf! 6L6's, EL34/EL84? Open back or semi-vented, one/two/four speakers... And what kind of music do you play, single-coil or humbuckers, miked cabs on the scene or "direct-in-your-face" stacks?.

And then comes the fairy with another problem: effects! Currently I'm running a Matchless Phoenix with EL34's and am trying to implement a stage-mounted effects-unit in the loop. Six isolation-transformers needed to get grip of ground-level hum.

There's no free lunches...

An externally hosted image should be here but it was not working when we last tested it.
 
#11
Verry cool Peter! The real truth is that I am not a gutar player myself, but I do this for my friends. Im just the tech guy. So this amp is sitting here in my condo where I cant make noise even if I was a musician. No I just build what they tell me to, and then there is a big party where we all sit around and pick the thing apart and try to understand gitar amps. Between the two of my musician friends they have a ton of choices for insturments so when we get together Im the guy in the back drinking the beer and watching 🙂
 
#12
They're all class A - up to a point. 😀

About the shimmer- I was seeing the local guitar shop cash register's shimmer far too often so I rebiased my amp. IMO it still sounds great.

Another tip for builders - If the tubes are upside down they have a tendency to fall off, so use a tube holder. The extreme heat loosens the contact pins.

Firechief- Good amps.
 
#13
firechief said:
Not rude at all. I know that class A guitar amps is are a myth. Why would you even want a super clean, distornless amp anyway? Here is a link to my earlier efforts
http://www.diyaudio.com/forums/musical-instruments/164358-one-off-guitar-amp.html
and thanks for posting . Tube coice is kinda limited, I need to stick with current production output devices, So for now JJ's are my tube of choice.
Bob
Click to expand...

Actually, real Class-A guitar amps are being very popular among jazz-guitarists with carved-top acoustic/electrics.
Peter
 
#16
Cassiel said:
They're all class A - up to a point. 😀

About the shimmer- I was seeing the local guitar shop cash register's shimmer far too often so I rebiased my amp. IMO it still sounds great.

Another tip for builders - If the tubes are upside down they have a tendency to fall off, so use a tube holder. The extreme heat loosens the contact pins.

Firechief- Good amps.
Click to expand...

Actually, none of my Matchless amps uses base-clamps. On the opposite, you very often have to use force to extract the tube and apply DeOxit before the new tube is inserted.
It's just a matter of the quality of the socket...

Peter
 
#17
The topic here would be the question of proper guitar-amp design. The Vox DC-30 was a very weak desing when it came to durability on stage long-term. The inventor of Matchless, Mark Sampson started as a "tech" for the renowned guitarist John Jorgenson, who sweared to the Vox. But it broke down nearly every two gigs - so Mark was on the phone late hours with John in his hotel-room after gigs, dictating which faulty joint to solder to get the bastard running.
After that, Mark founded Matchless - with top-components, nearly the same curcuits - and a mil-spec point-to-point wiring that even included laquer over every solder-joint to keep intruding oxygation out of the equation. And then came the famous Matchless "John Jorgensom Signature" - now extinct but one of the costliest amps when it appears on eBay (along with a vintage Dumble).
Today Phil Jamison has taken over, with less "mil-spec" but with attention to every component and longevity.
 
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#18
Actually, real Class-A guitar amps are being very popular among jazz-guitarists
Click to expand...

I'm curious because I don't know any full power class A guitar amp. Could you tell me who makes them?

Also, I agree that the hotter the bias the more spectacular it sounds but I can live without that extra. What tube sockets are you using? Are we talking about el84's?
 
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