Shielded cable

[Darkbluemurder]

With a decent lead dress, you should only need sheilded cable on the grids of the first two preamp tubes, ala Dumble. Four pieces in total. Use the recommended coax and make them as short as possible and you'll be fine.

For what it's worth, Dumble uses four pieces of shielded wire as described PLUS two more from the output of the LEVEL and RATIO pots to the board, for a grand total of six pieces of shielded wire all together.

Cheers,

Gil

It appears that HAD must have used very good shielded cable as there is a thick sheath of insulator between the conductor and the braid. I doubt that the one Fender used in the 80s amps is that good.

[ayan]

It appears that HAD must have used very good shielded cable as there is a thick sheath of insulator between the conductor and the braid. I doubt that the one Fender used in the 80s amps is that good.

I have seen pictures of various amps, and it seems that he used many different types of cable even "Tandy Corporation" (Radio Shack) ones. I think the analysis of capacitance done here may be an overkill, as I suspect Dumble probably used whatever he had at hand and tweaked from there.

Gil

['67_Plexi]

Right on. Absolutely agree. We can all get a little hung up on certain things.
Yeah it makes a difference, but there are so many more things that make much bigger differences.

[Darkbluemurder]

I definitely agree on that. Sometimes it's easier to make a circuit change for a broader stroke. Yet my problem with my modded Concert is that it does not have any sparkle in the OD channel with the Vol. and Drive set to low levels (up to 4). Before I go and add parallel caps in series with resistors I want to make sure that it is not a component problem.

FWIW I pulled out my capacitance meter and measured some pieces of shielded wire. One of them was a piece from the Concert which I replaced for other reasons. I found that roughly the same length of George L or Lawrence Belden wire had only half the capacitance of what is used in the Concert. This came as no surprise to me as the Concert cable's diameter is very small. I also have some leftover video antenna cable which I will check tonight for capacitance. Anyway the wiring will be my next source for tweaking as I am now quite sure that I have a component problem with this amp. I will post the results.

BTW I found the worst offenders for high capacitance to be the shielded single conductor wires used on humbucking pickups (not that I was going to use these in amps, this is just for information).

[Darkbluemurder]

OK I couldn't resist the temptation and exchanged three of the longer pieces of shielded cable to better quality shielded cable. Total improvement in capacitance pursuant to the meter: 33 pf. Not much really! Very little if any audible improvement in the high end. So the cable isn't it. If HAD used whatever he had provided it was decent quality he obviously did the right thing.