[Pontious Rednose]

Hi, can anyone give me advice on upgrades for my 708b, as it sounds awful at the moment. thanks, Pontious.

 

[Postal_Blue]

These should get you started....
http://www.head-fi.org/forums/f5/mod...8b-56k-221733/

http://www.head-fi.org/forums/f5/xia...ht=xiang+sheng



Quick answer for valves:

Driver Tube (front of the three inline on right hand board):
6n3p-eb Russian military // Nos GE 5670

Output Tubes (two behind driver):
Nos RCA 6DJ8 // Amperex 6922

 

[Postal_Blue]

Also, one of, if not the most important mod is replacing the terrible volume pot. Mine actually had a 50k pot, so not only was it a cheap carbon pot with terrible tracking, it was not the proper rating. Check that immediately.

 

[Nugget]

I can vouch for the Russian 6N3P-EB as a driver tube. The only output tubes I've used (other than the godawful stock tubes) are NOS Russian 6N23P-EBs.

I was disappointed by the 708B when it first arrived as well. Lots of background noise, no bite at all. I figured I'd try some new tubes before giving up on it, and I'm damned glad I did -- it's amazing how much difference $30 in tubes made. Still lacks a bit of separation in orchestra pieces, though that may be my crappy source, but the liquid tone on a jazz album is very, very nice; nice punch on rock; all around a fun amp.

 

[Pontious Rednose]

Thanks Postal Blue and Nugget, you have made a depressing purchase into a potentially positive one! Again, many thanks. Pontious.

 

[Nugget]

Let us know how it goes!