Question About Capacitor Upgrade in Tube Amp

Does anyone know how the power supply bypass capacitor effects high end frequency response?

For example the Willsenton R300 amp uses a .33uF and is a slightly rolled off sounding amplifier while Muzishare amps are using .47uF on the filter cap and are brighter sounding amplifiers. PS audio apparently uses a .1uF

Is this power supply bypass cap impacting high frequency response? Or are the bass and treble response all in the various coupling caps and cathode caps etc in the preamp stage?

Thanks.

@calieng - the primary purpose of the bypass cap on the power supply electrolytic is to shunt high frequency noise on the B+ rail. I doubt it will have any affect on the high frequency response of the amp. The value of the cap is really not that significant as long as it is a good quality film cap. 

The biggest influence on the high frequency response will be from the output transformer and possibly from the feedback network. I wouldn't recommend changing these parts without a solid understanding of how the amp works as well as having adequate test equipment to make sure the amp is stable after the changes.

Using a higher quality coupling cap also might give you a small improvement in high frequency response if the one that is in there now is not of very good quality.  

@jaytor - Thanks for the reply!

Based on the good results with the Willsenton R300 I went ahead and upgraded the Muzishare X7 KT88 amp. It required four 0.22uF coupling caps and one 0.47uF filter cap bypass film cap.

I used the Mundorf SilverGold Oil 1000VDC again.

Similar results. Most noticeable change - the depth of the soundstage significantly increased and more holographic image. Slight increase in soundstage width. Better treble crispness and rounder fuller bass with better instrument separation.

Upgrade cost approx $200.

I am using Gold Lion KT88 and 5AR4 tubes with Mullard reissue 12AX7 and 12AU7s in the Muzishare.

Between the two upgraded amps, the Willsenton R300 has the edge in vocals and holographic sound. The Muzishare X7 has the edge in treble response and bass punch. Both are wonderful amps with the upgrade.

And if there was any doubt - after doing this for a second time, good coupling caps make a significant improvement in sound over the factory cheap caps.

I peeled the labels off both the factory branded Willsenton and Muzishare coupling caps and there is no label underneath. So the source of the factory caps is unknown. Although the Muzishare factory caps were much larger than the Willsenton with what looks like a better construction.

And once again the Willsenton R300 comes from the PrimaLuna/Cayin factory (Zhuhai Spark Electronic Equipment Co, LTD) and the Muzishare from the Line Magnetic factory (Zheng brothers Zhuhai factory) so other components in the amps do appear to be decent and not requiring an upgrade (Nichicon electrolytic, Alps potentiometer etc.)

Hi @calieng ,

You did right thing to chose relatively affordable Mundorf capacitors for your Willsenton R300 amplifier.

Duelunds and V-Cap CuTf are very good but they are overkill for such not expansive amplifier. With all respect coupling and power supply bypass capacitors shouldn't be the most expansive part in any amplifier.

Regards,

Alex.