Two tips for taming 'shrillness' in Express clones

[Markusv]

Hi Mark (Abbott)

Well I was thinking a bit of presence to keep the signal cleaner especially at higher gain but then the treble cut to shave off the excess on top especially with single coils.
So I wonder what the values may be for a "set presence" I can/should probably play around with low resistor values and just keep the cap there.

BTW I have a Liverpool that I use rarely for the reasons that it's loud even with ppimv and sometimes I want a "thicker sound".

Taking out the presence altogether though may make it break up sooner/more than desirable so I really want to hear the reactions from the pros.

Markus

[Mark]

Hi Markus

what values do you have as a coupling cap and grid leak resistor to the third stage?

Do you have the high shunt mod on the plateof the second stage?

I saw this in a Dave Funk built Liverpool. It's a cap with a multi turn pot in series across the second plate resistor.

[Markusv]

Hi Mark

Standard as per the Liverpool Schem. I need to open the amp but pretty sure it is a .002 cap (.001 x 2 in parralel) and a 150K resistor.

Seems you think if I thicken up the sound there and drop some signal- I may not need the other changes?

[Markusv]

.....And no I do not have the Hi- shunt mod. That sounds interesting
What was the Multi turn pot value? I guess a regular pot would do if insulated from chassis?

Thanks as always
Markus

[Mark]

When I was experimenting with the Liverpool amp I used two 0.0022 caps in parallel and a 68K resistor. I tried a 56K resistor but it sounded too tame. The 68K sounded right to me and was in the real Liverpool I saw a picture of. I wasn't aware a Liverpool used the Express values of 0.002uF and 150K.

I'd try the cap increase before changing anything else.

https://ampgarage.com/forum/download/file.php?id=6861

[Markusv]

Thanks Mark
Appreciate your response.
YEs- I may be wrong about the 150K resistor- I did not open the amp and may have simply remembered the value from Express Schems.
Certainly when I built the amp I did not deviate too much from the original design except adding a PPIMV later.

OK- so based on your feedback I will double the Cap value first and see.
But I may do the hi-shunt across the plate resistor too while I'm at it

[Colossal]

On Miles' Liverpool, we started with 0.002 Mallory PVC in parallel with an 0.0022 ceramic and the load at 150k. 150k was really too much, but the low end beef just right. He tuned the 150k quite low for a Strat and lower for a LP. I'll let him explain, if he sees this.

[Reeltarded]

Ended at 56k which is a great place to be for any guitar. By 5 on the dial, still only insanity there and above.

[kanderson70]

I just finished up my Liverpool build and found the same to be true. The high end is a little too ear piercing for me with a strat (even with a 4x12). I did end up putting an old Brimar CV4004 in V1 and that really helped a lot, but I'm going to try putting another 0.0022 cap in parallel as you guys have done.

[Mark]

I suspect the issue is the EL-84 output valves, they don't require a lot of signal and typically forward conduct at about 13V, the AC-30 P.I.values help cool the input to the EL-84's.

[Reeltarded]

I just finished up my Liverpool build and found the same to be true. The high end is a little too ear piercing for me with a strat (even with a 4x12). I did end up putting an old Brimar CV4004 in V1 and that really helped a lot, but I'm going to try putting another 0.0022 cap in parallel as you guys have done.

Are you using the 150k after that second stage? Mr. Beasley puts a trimmer there. I bet his testing goes like this:

1. Set volume around 4

2. Turn trimmer until amp sounds like you wished it did with the volume at 4

3. Measure trimmer and replace with nearest lower value resistor.

With the big resistor, the early breakup happens with the volume barely cracked with a strat. It's hashy and ear killing. Replacing mine with 56k sounded way more open and even acoustic and piano-ish til 2, then that sound we love about the Liverpool til about 5, and then that ridiculous thing that makes you laugh about a Trainwreck til 10. The tone controls work REALLY well if they are not swamped in gain.

[kanderson70]

I just finished up my Liverpool build and found the same to be true. The high end is a little too ear piercing for me with a strat (even with a 4x12). I did end up putting an old Brimar CV4004 in V1 and that really helped a lot, but I'm going to try putting another 0.0022 cap in parallel as you guys have done.

Are you using the 150k after that second stage? Mr. Beasley puts a trimmer there. I bet his testing goes like this:

1. Set volume around 4

2. Turn trimmer until amp sounds like you wished it did with the volume at 4

3. Measure trimmer and replace with nearest lower value resistor.

With the big resistor, the early breakup happens with the volume barely cracked with a strat. It's hashy and ear killing. Replacing mine with 56k sounded way more open and even acoustic and piano-ish til 2, then that sound we love about the Liverpool til about 5, and then that ridiculous thing that makes you laugh about a Trainwreck til 10. The tone controls work REALLY well if they are not swamped in gain.

Thanks for the suggestion. I'll have to give the trimmer or a 56k a try. I currently have a 68k in there. Around 2 it's got a great clean piano-like tone but still a little too bright. I tried it with a 1×12 EV cab and seems to be a great match and tames the highs a bit. I'm going to have to install a VVR. The volume is absolutely insane for a 30 watter.

[Reeltarded]

YES it is CRAZY!

68k is where it started making me happy. I went down in the 40k range but it lost a little of it's peril for mine. Lower values take a bit of the face off and let the amp open up a lil before the rampage at 5.

[leadfootdriver]

I find RCA Long Plate 12AX7's to be full and mellow.

[Reeltarded]

50p-150p over feedback resistor or even larger with a small value trimmer.