Have had my Clone for a couple of months and have been very happy. Pretty much followed every piece of advice except one, the chassis cover.
Well today I got a piece of adhesive aluminium sheet from a trophy shop (good idea Richie). After I got it back together and fired her up, the hiss has increased quite a bit.
Is there any secret to the chassis cover? Anything perhap I hould be wary of.
Cheers Guys
Mick
Did you perhaps unintentionally disturb some of the lead dress?
With these amps as you know, a 1/4 inch can make a difference
My liverpool is more quiet when in its wooden cab, with or without a chassis cover- go figure
Have had my Clone for a couple of months and have been very happy. Pretty much followed every piece of advice except one, the chassis cover.
Well today I got a piece of adhesive aluminium sheet from a trophy shop (good idea Richie). After I got it back together and fired her up, the hiss has increased quite a bit.
Is there any secret to the chassis cover? Anything perhap I hould be wary of.
Cheers Guys
Mick
What we refer to as hiss is generally not externally induced. All tubes have hiss (thermionic emission, aka shot noise) and the more treble-voiced and high gain the circuit the more the hiss from the first tube is amplified by the following circuit(s). A split cathode Marshall JTM50 has more hiss on the Lead channel than the Norm, yet the V1 gain for both channels is the same at the higher 'hiss' frequencies and the only difference between the two are the Rk/Ck values, which attenuates lows on the Lead channel, and the 500p mixer bypass which allows more highs, i.e., hiss, to reach the V2a grid and also attenuates those highs on the Norm channel. I'd look elsewhere besides the shielding for your source of hiss.
I checked the lead dress doesn't seem to have changed. I changed the V1 tube no real difference. Took the chassis cover out all to gether and bingo, the hiss dropped back to what it was. Got me confused, I'll try a different piece to see if that helps.
Cheers
