You know another thing that i just learnt and supports the idea that ed's amp was modded by josé too ?
Many people say that the SV20h sounds very van halesque. Did you know that the SV20h uses DC heaters for the preamp section and that no stock marshall uses them ? This move was probably made intentionnally by marshall. Why is that important because those who popularised DC heaters were josé arredondo and jackson lee, they used them on their high gain modded amps to reduce noise. But if you go for DC heaters on a stock regular marshall the tone and the feeling are completely changed. The tone gets a little bit hotter and dirtier.
José used to add small transformers inside guitar amps for this purpose :
when you use AC heaters you usually use 6.3v on pin 4-5 and 9 of the tube with DC heaters you use 12 on pin 4 and 5 only.
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