Express-voiced Liverpool !?

[ODwan]

Hello, there!

I've come across several mentiones of an Express-voiced Liverpool. After building both Express and Liverpool I was curious how that one would sound. So I just hooked up the preamp of my Express into the PI of my Liverpool. I don't know this is just the deal with the original amp, but the results were awesome. Thick smooth overdrive with more bottom than the Liverpool but not as gritty as the Express. Somehow reminded me of a cross between an AC30 and a JTM45, but with more gain. The low gain sounds where really nice, too. I actually like it so much I'm cosidering building such an amp (damn, and I thought I was done...!)
I reoommend and ask all builders of both clones to try the same and report what you found.

Timo

[UR12]

There are only a couple of differences between the Express and Pool preamps. Basically they are the same circuit with a couple of changes. It would seem to me that you should be able to change the 68k resistor to a 150k and that's about it except for the different resistors in the PI. Since you injected the Express preamp into the Pool PI then there will be no changes needed in the PI section.

[ODwan]

Dana,

the biggest difference is actually the tonestack.
(Kelly)Express: Liverpool:
Treble cap: 500p 50p
Bass pot: 1MegA 250kA
All other values are the same.
If you type this values into Duncans TSC you find that the 'pool has an almost flat response with a slight dip at 1k5Hz, whereas the Express has a hump in the bass at 70-80Hz. Together with the lower corner freq of the HPF between 2nd and 3rd stage, the Express preamp has much more low freq content. The PI values are part of the sound eqation, too. So maybe I will try to run the Express PI into the 'pool PA.
Remember, this was just an experiment.

Timo

[Jackie Treehorn]

Well, I've been using the Liverpool phase inverter in my Express clone since November 2003. It sounds far better to me!

[ODwan]

Well, I've been using the Liverpool phase inverter in my Express clone since November 2003. It sounds far better to me!

The Liverpool PI is a bit lesser gain and more asymetrically clipping, thus skewing the spectral ballance toward even order harmonics which sounds subjectively warmer. As I recall you are using OD caps in your clone and mentioned you did some things to warm the sound, like using a polystyrene treble cap. Is this another one?
Myself, I have no problem with my Express clone being too bright, but with the low end being mushy. I fixed this to a degree by uping the PI decoupling cap to 70µF.

Timo

[Elcabong]

Well, I've been using the Liverpool phase inverter in my Express clone since November 2003. It sounds far better to me!

I have recently modified my Express clone PI to values you recommended in another thread; 47k tail and 1.2k cathode resistor. I ended up with a more usable amp to my liking: more headroom and less gain. Before the change, I found it was too harsh.

[Jackie Treehorn]

Well, I've been using the Liverpool phase inverter in my Express clone since November 2003. It sounds far better to me!

The Liverpool PI is a bit lesser gain and more asymetrically clipping, thus skewing the spectral ballance toward even order harmonics which sounds subjectively warmer. As I recall you are using OD caps in your clone and mentioned you did some things to warm the sound, like using a polystyrene treble cap. Is this another one?
Myself, I have no problem with my Express clone being too bright, but with the low end being mushy. I fixed this to a degree by uping the PI decoupling cap to 70µF.

Timo

I think the big tail resistor increases symmetry in the phase inverter. While, it is less gain from the phase inverter, it's also increased headroom. Looking at the second gain stage on the scope, things don't get interesting until you've got the volume up around 12 o'clock. With the stock express PI at 9 o'clock or 10 o'clock on the volume you're already into full overdrive before you can get the second gain stage into the sweet spot. With the bigger values in the phase inverter, you can get a more usable range on the volume control, so you've still got a tremendous amount of gain, it's just coming from a different ratio of locations. Also, I use the 5200 output transformer which is going to have more odd order harmonics than the 6600. So, perhaps I can sacrifice some odd order harmonics from the phase inverter. The other aspect is that I just don't like the sound of stock express PI distorting. It kind of adds this thin unmusical, JCM800ish white noise to the distortion. The bigger phase inverter values give a more musical overdrive to my ears. You also get far better, chimier clean tones, headroom, way more bass. I was convinced that there was no way the schematics with the 10k/470 combo could be correct! Seems I was wrong!

Yes, I've got 716P's and a polystyrene treble cap. The 716p's let a lot more top through, so I try to shape it as best I can. I think the polystyrene treble cap gives a nicer top...a bit less clangy than a silver mica. Also, running the wires to get a touch of local negative feedback can make the extra top work for you...I like to parallel the wires from the cathode and plate especially on the second gain stage to warm up the top a bit.

Elcabong...very cool that you found something you liked! I think the greatest aspect of making your own wreck is fine tuning it to the player...not neccessarily doing it the "authentic" Ken way!

[ODwan]

I think the big tail resistor increases symmetry in the phase inverter. While, it is less gain from the phase inverter, it's also increased headroom. Looking at the second gain stage on the scope, things don't get interesting until you've got the volume up around 12 o'clock. With the stock express PI at 9 o'clock or 10 o'clock on the volume you're already into full overdrive before you can get the second gain stage into the sweet spot. With the bigger values in the phase inverter, you can get a more usable range on the volume control, so you've still got a tremendous amount of gain, it's just coming from a different ratio of locations. Also, I use the 5200 output transformer which is going to have more odd order harmonics than the 6600. So, perhaps I can sacrifice some odd order harmonics from the phase inverter. The other aspect is that I just don't like the sound of stock express PI distorting. It kind of adds this thin unmusical, JCM800ish white noise to the distortion. The bigger phase inverter values give a more musical overdrive to my ears. You also get far better, chimier clean tones, headroom, way more bass. I was convinced that there was no way the schematics with the 10k/470 combo could be correct! Seems I was wrong!

Yes, I've got 716P's and a polystyrene treble cap. The 716p's let a lot more top through, so I try to shape it as best I can. I think the polystyrene treble cap gives a nicer top...a bit less clangy than a silver mica. Also, running the wires to get a touch of local negative feedback can make the extra top work for you...I like to parallel the wires from the cathode and plate especially on the second gain stage to warm up the top a bit.

Elcabong...very cool that you found something you liked! I think the greatest aspect of making your own wreck is fine tuning it to the player...not neccessarily doing it the "authentic" Ken way!

Hey, Jackie!
I can only second your findings. Today I swapped in the Liverpool PI values (1k / 39k) into my Express and was very pleased wit nthe results.
Overdrive was more musical/warmer, touch response was improved (didn't thought that possible) and the low end was full and tight. I changed the PI decoupling back to 22µ and the tone got even warmer without gettin muddy. All the while harmonic feedback increased! Wonderfull! I definately gonna leave it that way!
Could beat myself that I did not play with PI values sooner.
BTW I think that by fine tuning it to the player, the tubes, speakers etc. is actually doing it the authentic Ken way. What we got for the express circuit is just Kelly and Franchesca. Geetarpicker offered that Li'l Orphan Anny is NEARLY identical. Somewhere there is a schem of Trudy who is done quite a different way. My opinion is that Ken had a generic circuit he build and if it did not fit he just tweaked away. The art here is to know where what and how.
So long,

Timo

[Richie]

The PI changes are very close to the vox values. you might also look at the marshall 18 PI values.. both a little different.

Richie