Liverpool EL84 cathode bypass cap value

[Ledvedder5150]

In my Liverpool build, the layout that I followed uses a 50r/22uF setup on the EL84 cathodes. I see that many of the Liverpool schematics available show it as 50r/220uF. Although I've been learning a ton about amp build, and have built many amps to this point, I'm not very familiar with this area of the circuit. What would be the result of using different value bypass caps here?

[Colossal]

In my Liverpool build, the layout that I followed uses a 50r/22uF setup on the EL84 cathodes. I see that many of the Liverpool schematics available show it as 50r/220uF. Although I've been learning a ton about amp build, and have built many amps to this point, I'm not very familiar with this area of the circuit. What would be the result of using different value bypass caps here?

220uF is going to give a bit tighter bass response, and more of a fixed bias response once the cap is increased even more to 1,000-2,200uF as is done as a mod on some 18W-36W style Marshall builds. I looked at the layout you used and it is Modulus Mike's take on a Liverpool. It looks more like a Rocket-Pool (a Dirty Pool?) with some features from both amps, so this may account for the low end response you mentioned in your other thread. It may be also why Mike picked a low value like 22uF to bypass the 50R bias resistor with, instead of the 220uF caps found in the Rocket and Liverpool. A Liverpool has 130R/220uF for each pair of EL84s, the Rocket 50R/220uF for the quad.

[Ledvedder5150]

In my Liverpool build, the layout that I followed uses a 50r/22uF setup on the EL84 cathodes. I see that many of the Liverpool schematics available show it as 50r/220uF. Although I've been learning a ton about amp build, and have built many amps to this point, I'm not very familiar with this area of the circuit. What would be the result of using different value bypass caps here?

220uF is going to give a bit tighter bass response, and more of a fixed bias response once the cap is increased even more to 1,000-2,200uF as is done as a mod on some 18W-36W style Marshall builds. I looked at the layout you used and it is Modulus Mike's take on a Liverpool. It looks more like a Rocket-Pool (a Dirty Pool?) with some features from both amps, so this may account for the low end response you mentioned in your other thread. It may be also why Mike picked a low value like 22uF to bypass the 50R bias resistor with, instead of the 220uF caps found in the Rocket and Liverpool. A Liverpool has 130R/220uF for each pair of EL84s, the Rocket 50R/220uF for the quad.

What's different about this layout compared to the regular Liverpool schematic? Besides the EL84 cathodes, it seems close to me.

[Colossal]

Mike's layout shows the second preamp stage cathode bias at 1k5/22uF where in the Liverpool and Express, it is 2k7/22uF. The RC low pass after the second stage in a Liverpool is typically 1-2n2/68k, not 150k. And as mentioned, the power tubes are biased as 130R/220uF per pair of EL84s.

[Ledvedder5150]

Mike's layout shows the second preamp stage cathode bias at 1k5/22uF where in the Liverpool and Express, it is 2k7/22uF. The RC low pass after the second stage in a Liverpool is typically 1-2n2/68k, not 150k. And as mentioned, the power tubes are biased as 130R/220uF per pair of EL84s.

Ahh yes! Luckily, I was one of the first customers to build Mike's layout. Throughout the build, we exchanged our findings and changed some things, which aren't noted in the layout. The 2nd stage is 2k7/22uF, and it is also 2n2/68k after the 2nd stage. We also adjusted some of the dropping resistors to get correct voltages at different points.

[Littlewyan]

Mike's layout shows the second preamp stage cathode bias at 1k5/22uF where in the Liverpool and Express, it is 2k7/22uF. The RC low pass after the second stage in a Liverpool is typically 1-2n2/68k, not 150k. And as mentioned, the power tubes are biased as 130R/220uF per pair of EL84s.

What about that letter that Glen received from Ken? Ken gave Glen another .0022uF cap to put in parallel with the existing and said all Liverpools now have this. Have we seen any real Liverpools with this? I tried doing a quick search the other day but couldn't find any original Liverpool threads where a deep dive was done.

[Reeltarded]

I understand less each time I consider what is the intention of a Liverpool.

Weird amp!

[Ledvedder5150]

I understand less each time I consider what is the intention of a Liverpool.

Weird amp!

What do you mean? Don't you have one?

[Reeltarded]

Yeah, and it is swamped with gain.

[Reeltarded]

v2 input is the problem with these amps. It flattens the output if you are at 68k and it never gets cooly insane @56k. That is a narrow place to play with. If you mess with the previous stages the amp loses it's identity. Losing it's identity makes it useful with a much wider range of pickups for several useful settings across the tone control ranges.

Hmm.. still not an el84 guy. They just shit when you look them so hard.