Brand of filter caps - Page 8

Creighton · #**106** 03-27-2012, 12:04 PM

I haven't gotten the correct Vishay caps for this amp installed yet, so I don't have a report yet but I will say, whether it's the spec or brand of cap or whatever, the Nichicons have made the amp sound like absolute piss.

neteraser · #**107** 03-27-2012, 12:30 PM

jetlag · #**108** 03-27-2012, 01:01 PM

I've experienced this situation before when I replaced all the original electrolytic caps in the power supply of my 1960 tweed bassman. I used the blue spragues as replacements, and also, since I didn't have 600V rated caps, copied the filter network you see in super reverbs. Thus, capacitance was raised over the stock value a bit. The result was an amp that sounded closer to a reissue bassman than an old one. I ended up substituting a 5R4GA rectifier for the GZ34 to bring B+ down, rebiased, and the amp sounded much closer to what it used to sound like. I left it like that for about 6 months. Then went back to the GZ34, and again rebiased the amp. By then, it sounded good. I'm not positive but suspect your amp doesn't have a tube rectifier, so I realize that approach is not an option. However, if you had a buck-box type of unit you could drop line voltage a bit (being careful not to starve the heaters), rebias, and see if you like the sound of the amp. If so, leave it like that for a while. Every once in a while switch back and see if things have settled in enough to where you can ditch the buck-box. Another option is to buy some higher rated tubes like 7581As and bias to increase plate watt dissipation. This will drop B+ and might brown the amp out enough to where you like the resultant sound.

Creighton · #**109** 04-18-2012, 09:55 PM

Still waiting on the Vishay's but with more playing the amp sounds a bit better. Still not where I want it to be but it does seem that maybe new caps have a break in/smooth out period like a speaker.?