As I’m waiting for other parts to come in for a related amplifier project, I thought I may as well upgrade/update my preamp (a308cr) and tube buffer (x10v3) while they remain unused at the moment.
There’s not much to change to this preamp aside from the bipolar caps. I don’t use the phono stage so I’ll be skipping modifying that section and the PSU caps seem to be alright as well but I’m open to any and all suggestions in changing or bypassing area’s of interest that you guys would suggest.
Things that I plan on changing so far:
Jamicon Bipolar 10uf 63v (x8) --> Nichicon 10uf 100v Bipolar (UVP2A100MPD1TA)
Jamicon 100uf 63v (x6) --> Nichicon 100uf 100v (UKZ2A101MHM1TN)
PSU caps? Jamicon 6800uf 63v (x16) --> Nichicon 6800uf 63v (LKG1J682MESCBK)
104J 250v (x12) --> Epkos 0.1uf 400v (B32521E6104J000)
Jamicon 25v 2200uf (x3) --> Nichicon 2200uf 63v (UFW1J222MHD)
Since I am not able to fit film caps in place of the bipolar electrolytics (or at least I’d prefer not to extend the leads on wire, potentially causing RF problems), would it be wise to bypass these caps? What values and what types would be best for doing so?
I have attached the full schematics for the a308cr Pre (I still can’t believe I managed to get it!)
There’s not much to change to this preamp aside from the bipolar caps. I don’t use the phono stage so I’ll be skipping modifying that section and the PSU caps seem to be alright as well but I’m open to any and all suggestions in changing or bypassing area’s of interest that you guys would suggest.
Things that I plan on changing so far:
Jamicon Bipolar 10uf 63v (x8) --> Nichicon 10uf 100v Bipolar (UVP2A100MPD1TA)
Jamicon 100uf 63v (x6) --> Nichicon 100uf 100v (UKZ2A101MHM1TN)
PSU caps? Jamicon 6800uf 63v (x16) --> Nichicon 6800uf 63v (LKG1J682MESCBK)
104J 250v (x12) --> Epkos 0.1uf 400v (B32521E6104J000)
Jamicon 25v 2200uf (x3) --> Nichicon 2200uf 63v (UFW1J222MHD)
Since I am not able to fit film caps in place of the bipolar electrolytics (or at least I’d prefer not to extend the leads on wire, potentially causing RF problems), would it be wise to bypass these caps? What values and what types would be best for doing so?
I have attached the full schematics for the a308cr Pre (I still can’t believe I managed to get it!)
For those who may come across this post in search of what they can do with their a308cr preamp, here's an update and parts list.
All specs are of same capacitance but of much higher quality and higher voltage ratings. I couldn't fit film caps unfortunately and I didn't want to go into the "boutique exotic" realm of caps but these parts should be just as good. I also skipped upgrading the phono section and related power since no record player is being used in my system
Parts list:
- replaced all 4 4amp glass fuses to Bussman ceramics
All specs are of same capacitance but of much higher quality and higher voltage ratings. I couldn't fit film caps unfortunately and I didn't want to go into the "boutique exotic" realm of caps but these parts should be just as good. I also skipped upgrading the phono section and related power since no record player is being used in my system
Parts list:
- TDK .1UF 400VDC (X6)
- Nichicon MUSE 10uf 100v (x8) Uvp2a100mpd1ta
- Nichicon MUSE 100uf 100v (x8) ukz2a101mhm1tn (these things are huge compared the old ones and spec much better)
- replaced all 4 4amp glass fuses to Bussman ceramics