First off, thanks WALL-E for the detailed PM discussions, its been very educational.
I want to upgrade the output capacitance on my darkvoice 337 to improve bass response with my lower Z phones. OEM cap and layout is shown below.
Ignoring the math and first order high-pass filter calculations for just a moment, subjectively the amp sounds surprisingly good for such under-valued capacitance. Its just missing that last little sub-octave below~60Hz, well its probably missing more than that really. Its NOT a bass shy amp at all, plenty of impact and clean dynamics... its just that bottom "BLOOM" area of the spectrum is lacking. The OEM capacitors are MKP, 400V, 51uf.
By my calcs I need about 250-300uf to really open up the TS-5998 tubes.
The problem I have is one of space. If I remove the two chassis standoffs at the corner of each cap I will have a volume of about 85x77x51 mm to work in. So I need to cram 250uf into that volume.
With MKP and other film caps Its like trying to cram a can of cambells chunky soup into my jeans... I dont think its going to work.
-Do I really need a 400V cap?
-Plate voltage in the TS-5998 is 275V, is the cathode output voltage really up to 400V? Was that value chosen by the manufatcturer more for design safety factor, low-ESR, sonic fidelity... or something else?
-How would I go about safely measuring cathode output voltage? For obvious reasons I am a little hesitant to probe my fluke around inside a hot circuit.
-What are your thoughts on using low-ESR electrolytic caps for this application? They are MUCH smaller. I can very easily fit a 300-400uf - 400V electrolytic reservoir in this space, and room to spare for a smaller bypass cap of film or paper in oil.
I modded the chassis bottom cover with 5V cooling fans under the power resistors so heat really is not a concern, so long as the caps don't physically touch the resistors.
Edited by kramer5150 - 2/23/13 at 9:41am