[baronbeehive]

Ok, so on first page, according to Ridge78, half the current of the WCF push/pull design, comes from the cathode caps(!).

So now, what about the WCF cap between the triods? Have we been overlooking these?

This could be why we need those large cathode caps when the graph doesn't show them to be necessary above, say 100uF... blasted WCF circuitry

... then if we need large cathode caps... then... we also need large WCF caps to help the output , unless I'm totally wrong.. again

 

[baronbeehive]

I'm guessing a test with a paralleled electrolytic here would find out...

You mean to try different capacitances from the paralleled cap, and then when we have found that out, replace with equivalent high capacity film cap?

 

[baronbeehive]

So really we have been treating the WCF cap mod as the coupling caps little sister when it's more important than that and the paltry .33uF should read more like 330uF?

It's an output cap, not a coupling cap.

 

[Maxx134]

You mean to try different capacitances from the paralleled cap, and then when we have found that out, replace with equivalent high capacity film cap?

No...
Just need to find out the circuit behavior with increased capacitance in the WCF position.
Audio quality should not be affected much because of the .33uf film that's already there. Just need to see if an increased (paralleled) capacitance there would increase the output potential.

 

[Maxx134]

It's an output cap, not a coupling cap

Well yes it is coupling the two triodes, but we want to see if any "output cap" capabilities can be had here.

 

[Maxx134]

I must have had a brain fart. The cathode caps are part of the WCF circuit, so I need to look at the schematics again

 

[coinmaster]

The cathode caps are always going to reduce the sound quality. Which is part of the reason I got rid of them in my mod that solved every issue the MK6 has.
Hindsight, I probably should have just made a perfected version of the mk6 and sold it to members here to fuel my other research instead of going crazy and making an over the top version with 4P1Ls and 6c33cs.
Oh well.

In any case if you want to play with the cathode caps, bigger is better, and higher quality is better. Bypassing smaller higher quality caps with larger less but still good quality caps is the way to go.
The huge industrial film caps I used in my initial mk6 mod somewhere around the first pages were pretty amazing in this regard. I also used the stupidly expensive mundorf pure copper caps or whatever they were. Needed a wood box to fit it all though.

 

[baronbeehive]

I must have had a brain fart. The cathode caps are part of the WCF circuit, so I need to look at the schematics again

x2 . This is what I wasn't sure about, but they must be as they are involved in processing output from driver stage which obviously includes both triodes, first and second in WCF. That means that the cathode bypass is involved in frequency cut off for both as well. So we can't increase capacitance willy nilly without taking this into account.

I will go back and look at page 1 if I can remember where it is.

The schematic is Sonic's here: https://www.head-fi.org/threads/lit...se-owners-unite.522099/page-171#post-14709323

@coinmaster I couldn't find your schematic any more, most of the picture links are broken here.

 

[baronbeehive]

The cathode caps are always going to reduce the sound quality. Which is part of the reason I got rid of them in my mod that solved every issue the MK6 has.
Hindsight, I probably should have just made a perfected version of the mk6 and sold it to members here to fuel my other research instead of going crazy and making an over the top version with 4P1Ls and 6c33cs.
Oh well.

Yes.. .

... but it was great entertainment for the rest of us

 

[baronbeehive]

Stock LD without a cathode bypass cap, ie 0uF.

Gain is much reduced, obviously.

 

[Maxx134]

I do not believe cathode cap decrease sound quality at all. The interaction between the cathode cap and tube creates more gain, and more tube harmonics. This is added onto the sound, so doesn't take anything away. But it has to be done lightly, as if you sprinkled salt on food, not overdone.

Issues arise with using electrolytics which we have already noted and helped with film caps.

The schematic is Sonic's here: https://www.head-fi.org/threads/lit...se-owners-unite.522099/page-171#post-14709323

@coinmaster I couldn't find your schematic any more, most of the picture links are broken here

That link is a schematic from coinmaster's work.
Anyways, I have stumbled onto some better schematic diagrams from an asian website.
Amp:

That is one channel, not whole amp.

PSU:

Driver stage PSU:

So we have a better look at what's going on.
I see that we haven't even touched the driver stage cathode area, but since you replaced the cathode resistor with
a CCS, you can't place a cathode cap there.

 

[Whitigir]

I do not believe cathode cap decrease sound quality at all. The interaction between the cathode cap and tube creates more gain, and more tube harmonics. This is added onto the sound, so doesn't take anything away. But it has to be done lightly, as if you sprinkled salt on food, not overdone.

Issues arise with using electrolytics which we have already noted and helped with film caps.


That link is a schematic from coinmaster's work.
Anyways, I have stumbled onto some better schematic diagrams from an asian website.
Amp:

That is one channel, not whole amp.

PSU:


Driver stage PSU:


So we have a better look at what's going on.
I see that we haven't even touched the driver stage cathode area, but since you replaced the cathode resistor with
a CCS, you can't place a cathode cap there.

What is that OPAMP chip ? Would swapping it For another kind (discrete) be an upgrade ? Cathode caps are in series ? Interesting

 

[Maxx134]

What is that OPAMP chip ? Would swapping it For another kind (discrete) be an upgrade ? Cathode caps are in series ? Interesting

That chip is there to control the DC offset between the the 2 tubes (for each channel). Because the 2 tubes at rest (each tube representing the "*" or "-" of the signal) must equal to zero DC at output of the headphones jack.
The op-amp control this.

If you hear a pop, in any amp (tune or solid state, especially solid state) as you are plugging your headphones in, that is DC offset. It usually equalizes after headphones plugged in and circuit sets, but if you always have a tiny pop/click, then that's DC.

In this amp, there are very high value resistors across the output load, to have the op-amp equalize the DC offset.
But there is also an adjustment pot which is not easy to do, which was covered long ago in this thread.
I did mine for perfect reduction, as there may always be an adjustment necessary if you change your resistors and parts.

 

[Maxx134]

Ugh ugh ugh..
With help of @Whitigir , I am seeing multiple weaknesses that need to be addressed.

 

[Whitigir]

Ugh ugh ugh..
With help of @Whitigir , I am seeing multiple weaknesses that need to be addressed.

Cheers!! I look forward to your results