I’ll jump in with a further question as I’m building a SEP with 12at7 and el84’s and was thinking about this the other day.
How do different values affect the sound if the bypass is done in the pre rather than the power stage?
I’m following a slightly adapted version of the RH84 and looked at other similar designs, and some don’t have a bypass cap in the preamp tube.
How do different values affect the sound if the bypass is done in the pre rather than the power stage?
I’m following a slightly adapted version of the RH84 and looked at other similar designs, and some don’t have a bypass cap in the preamp tube.
Hi noisyneighbour,
Please don't ask about the sound of capacitors. That will degenerate this thread into chaos.
Please don't ask about the sound of capacitors. That will degenerate this thread into chaos.
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@anatech sorry I didn’t mean snake oil subjective sound but rather bypass capacitor value related to the frequency response. And how does bypassing the power tube sound differently than doing it on the preamp tube.
Didn’t mean to interfere with the topic🫣
Didn’t mean to interfere with the topic🫣
An unbypassed cathode resistor provides local negative feedback which would reduce gain and distortion. Depending on the amplification factors of your preamp and power tubes, you can tailor the overall gain and/or distortion by choosing the stage where you place the bypass capacitor.
If your circuit includes global negative feedback, then that is another factor to consider.
If your circuit includes global negative feedback, then that is another factor to consider.
The preamp stage in the RH 84 should have an unbypassed cathode resistor. The unbypassed resistor increases the output impedance of the stage, making the feedback from the output stage plate more effective. The output stage should be bypassed to increase its gain (which being in the feedback loop, decreases distortion) and lower the output impedance, which improves damping factor. Most speakers provide a flatter frequency response with higher damping factor.
In regards to the sound off bypassing of cathode v non bypassing just try it and listen to your ears.nobody is going to tell you how it sounds and wether you prefer one topolgy over another.diy is about expriementing and building the circuit to your sonic preferences.