Upgrade capacitors in tube amplifier?

I have upgraded crossovers with very good results.  I now have a "very good" IMO chinese tube amplifier that can probably be improved with a couple of capacitor upgrades.  

I don't have a schematic, but I have a picture and I expect some of you knowledgeable folks can point me to/confirm the ones to change.  My thought is to change the two large silver ones first and then maybe the four smaller silver ones (on the circuit boards). 

Would probably replace with something like Jantzen Superior Z-Cap or comparable and go with a higher voltage if space permits.  




Showing 5 responses by chinook9

The biggest upgrade you can do is buy the R-300B model. It is amazing! I also have the R8 with KT88 tubes and the R-300B is significantly more organic sounding.

calieng3, thank you for this information. Yong Lee recommended the R300B as an upgrade and I have been looking for anything on the comparison of the other Willsenton amplifiers and the R-300B.

I am playing with the R-35i now, but I know, with Covid19 limiting my other hobbies, I will be trying to improve upon it before too long.

My hobby, at this time, is to work at getting the best possible sound (IMO) for the least possible cost. 
The amp is a Willsenton 35i.  Around $88o including air shipping from china hi-fi.  I'm really impressed by it.
If you do upgrade just do the coupling caps connected to the tube sockets and realize a speaker crossover environment is very different from a tube amp.
1extreme119, I realize the circuitry is very different. Generally, do you think there is less potential for a coupling cap upgrade to be as effective as a crossover cap upgrade?
So if you haven’t already done so I would recommend two matched pairs of Tung Sol EL34’s and also upgrade the 12AX7 and 12AU7 vacuum tubes.

I have another thread on the tube angle. Have replaced the 12AU7 and have 12AX7 on order. I’ll study the EL34....these can get into real money.  Edit:  check reveals the Tung-Sol EL-34 are not too bad......but I'll still study the possibilities.
Thank you all for your input. 

I will do as recommended by many of you: roll tubes first and then consider the caps.  I took the bottom off the amp and found that the caps mentioned by most are two large 0.33UFD 5% 630VDC and four 0.022UF 5% 630VDC.  I realize you can't tell much by looks but they did look pretty good.  They are oval.

I have some ECC82 (Tung-Sol black glass) and 5751 (GE black plate) on the way and now I'm trying to decide on the EL34/6CA7.

Thanks again.