11-02-2021, 12:17 PM
Hi.
Having repaired umpteen Marshall amps during my years in "the trade" I have come to the conclusion that although the bands revel in them they are really not that wonderful.
OK I suspect I'll be shot down in flames, in a service engineers point of view and someone that has built many valve amplifiers they dont cut the mustard.
I'll explain why. They are well known for hum, noise and pick up. One issue is the method of wiring and component layout along with cheap materials. I've encountered those with the black tag boards, they are paper based and prone to leaks and carbonisation, for an amp that is not exactly cheap it penny pinching.
Layout is often poor, wiring can be long and loose, and the quality of build especially in the 60's sought after offerings very bad.
Looking at some of the circuits as well you often say..... why on earth do it this way, coupling caps are also low in value so LF response is poor and phase shifts high. No NFB, no UL output, small transformers in some amps.
Bands seem to like distortion and that's what these amps do (not all of them though) .
I have to say I prefer Peavey, Fender, Blackstar & VOX.
If you want to build this amp I honestly would say that seriously look at the circuit and improve it. Use good quality transformers, think about going Ultra Linear.
The ECL86's are good enough and have been used in many high quality amps, the downside now is the price and availability, The EL84 is a good valve and there are perfectly good Russian equivalents that you can use. The ECL86 triode is half an ECC83 so you can use them, admittedly that's two extra bottles but that will improve reliability somewhat, EL84's are cheaper than ECL86's unless you go for cheap ones like Lamba etc.
The addition of a pre-amp is a worthwhile inclusion and you could add in some NFB to improve stability etc.
Having repaired umpteen Marshall amps during my years in "the trade" I have come to the conclusion that although the bands revel in them they are really not that wonderful.
OK I suspect I'll be shot down in flames, in a service engineers point of view and someone that has built many valve amplifiers they dont cut the mustard.
I'll explain why. They are well known for hum, noise and pick up. One issue is the method of wiring and component layout along with cheap materials. I've encountered those with the black tag boards, they are paper based and prone to leaks and carbonisation, for an amp that is not exactly cheap it penny pinching.
Layout is often poor, wiring can be long and loose, and the quality of build especially in the 60's sought after offerings very bad.
Looking at some of the circuits as well you often say..... why on earth do it this way, coupling caps are also low in value so LF response is poor and phase shifts high. No NFB, no UL output, small transformers in some amps.
Bands seem to like distortion and that's what these amps do (not all of them though) .
I have to say I prefer Peavey, Fender, Blackstar & VOX.
If you want to build this amp I honestly would say that seriously look at the circuit and improve it. Use good quality transformers, think about going Ultra Linear.
The ECL86's are good enough and have been used in many high quality amps, the downside now is the price and availability, The EL84 is a good valve and there are perfectly good Russian equivalents that you can use. The ECL86 triode is half an ECC83 so you can use them, admittedly that's two extra bottles but that will improve reliability somewhat, EL84's are cheaper than ECL86's unless you go for cheap ones like Lamba etc.
The addition of a pre-amp is a worthwhile inclusion and you could add in some NFB to improve stability etc.
