Cleaning up an Express' act

Express, Liverpool, Rocket, Dirty Little Monster, etc.

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monkeymagic
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Cleaning up an Express' act

Post by monkeymagic »

I love my Express clone!

..but, I want a bluesy, compressed, edge of breakup sound for my Tele, too. Sold on the Wreck philosophy and only Express-like touch sensitivity and dynamics will do (but with less gain, so it will properly clean up when heavily attenuated.

I've not played a Rocket (none available in the UK and no YouTube clips floating my boat) and I'm wary of El84s from experiences with raspy Cornfords

Im also concerned that less 'gainroom' might equal less touch sensitivity - pls tell me if you know different?

I'm thinking of trying a 12au7 in P1 and possibly P2 and 12at7 in the PI. If it works, then a second Express is in the offing

I wondered if anyone had tried any of the above and what they thought?

BP
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Colossal
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Re: Cleaning up an Express' act

Post by Colossal »

You can change the input tube to a lower gain tube as desired and tone preference dictates. Also, you can target the coupling cap and grid leak resistor at the entrance to the 10k stage to lower gain.
monkeymagic
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Re: Cleaning up an Express' act

Post by monkeymagic »

Thanks Colossal,

I'm still learning my way around the board, so you'll have to forgive my ignorance - I'm assuming the '10k 'stage is one of the 3 preamp stages, but I don't know which? ..assume the 3rd?

best

BP
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Colossal
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Re: Cleaning up an Express' act

Post by Colossal »

monkeymagic wrote:Thanks Colossal,

I'm still learning my way around the board, so you'll have to forgive my ignorance - I'm assuming the '10k 'stage is one of the 3 preamp stages, but I don't know which? ..assume the 3rd?

best

BP
Yes, sorry, the 10k is the sole cathode resistor (unbypassed) on the third stage. The grid leak resistor at the entrance to the third stage is the one to adjust and lowering that value (stock is 150k) will lower the gain. 56-68k are common choices there.
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monkeymagic
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Re: Cleaning up an Express' act

Post by monkeymagic »

Fantastic - thanks!

I'll try running a 100k resistor across there in parallel as a reversible test

BP
Zippy
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Re: Cleaning up an Express' act

Post by Zippy »

monkeymagic wrote:I love my Express clone!

..but, I want a bluesy, compressed, edge of breakup sound for my Tele, too. Sold on the Wreck philosophy and only Express-like touch sensitivity and dynamics will do (but with less gain, so it will properly clean up when heavily attenuated.

I've not played a Rocket (none available in the UK and no YouTube clips floating my boat) and I'm wary of El84s from experiences with raspy Cornfords.
FWIW, the Liverpool is the EL84 version of the Express, and the "Rockster 66" is an Ampgarage version of the Rocket that uses KT66, or similar, output tubes.

Bottom line: You can have a Rocket topology, and NOT have to use EL84s.
kwijabo
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Re: Cleaning up an Express' act

Post by kwijabo »

i second the idea of the rockster 66. i built mine with a bit higher voltage, using a 300-0-300, diode rectifier, and a choke. i think its great for what you're describing.
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sliberty
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Re: Cleaning up an Express' act

Post by sliberty »

Zippy wrote:
monkeymagic wrote:I love my Express clone!

..but, I want a bluesy, compressed, edge of breakup sound for my Tele, too. Sold on the Wreck philosophy and only Express-like touch sensitivity and dynamics will do (but with less gain, so it will properly clean up when heavily attenuated.

I've not played a Rocket (none available in the UK and no YouTube clips floating my boat) and I'm wary of El84s from experiences with raspy Cornfords.
FWIW, the Liverpool is the EL84 version of the Express, and the "Rockster 66" is an Ampgarage version of the Rocket that uses KT66, or similar, output tubes.

Bottom line: You can have a Rocket topology, and NOT have to use EL84s.
Having said that, though, Rockets are glorious sounding amps. They run the EL84s very hot, and the results are marvelous.
monkeymagic
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Re: Cleaning up an Express' act

Post by monkeymagic »

Thanks all for the replies!

I'll do some digging
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M Fowler
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Re: Cleaning up an Express' act

Post by M Fowler »

I've built several Reverb Rockets 6L6GC with 355-0-355 MC iron makes a great amp.
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Jackie Treehorn
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Re: Cleaning up an Express' act

Post by Jackie Treehorn »

monkeymagic wrote:I love my Express clone!

..but, I want a bluesy, compressed, edge of breakup sound for my Tele, too. Sold on the Wreck philosophy and only Express-like touch sensitivity and dynamics will do (but with less gain, so it will properly clean up when heavily attenuated.

I've not played a Rocket (none available in the UK and no YouTube clips floating my boat) and I'm wary of El84s from experiences with raspy Cornfords

Im also concerned that less 'gainroom' might equal less touch sensitivity - pls tell me if you know different?

I'm thinking of trying a 12au7 in P1 and possibly P2 and 12at7 in the PI. If it works, then a second Express is in the offing

I wondered if anyone had tried any of the above and what they thought?

BP
I recommend switching the 10k tail/470r bias resistor in the phase inverter to 39k/1k respectively. That will give you a lot more lows/low mids and a more usable range on the amp's volume knob. The amp won't really go into full on compression/mush until the last 5-10% of the rotation and you don't really lose any gain. I also think the cleans get a lot fuller. Maybe reduce the 100k feedback resistor, if you like.

A telecaster into a jtm45 is pretty magical, too.
Mark
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Re: Cleaning up an Express' act

Post by Mark »

Hi Jackie

Do you have any before and after clips?

That PI circuit is favoured by Ken Fischer and HAD, I tried it in my Boogie SOB and it does sound pretty good. What were the tonal changes of using the 1K cathode resistor and the 39K tail resistor?
Yours Sincerely

Mark Abbott
Jackie Treehorn
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Re: Cleaning up an Express' act

Post by Jackie Treehorn »

Mark wrote:Hi Jackie

Do you have any before and after clips?

That PI circuit is favoured by Ken Fischer and HAD, I tried it in my Boogie SOB and it does sound pretty good. What were the tonal changes of using the 1K cathode resistor and the 39K tail resistor?
That's really interesting. I did not know HAD set up a PI that way. Which amp was that?

I started using those values way back, pre amp garage, because I had trim pots in the phase inverter to be able to try some variations from the blue guitar schematics we worked from then. 39k/1k just sounded the best and seemed to be consistent with the tones from Glen's sundown clip. I did not know at the time they were the Liverpool values, since that was still a secret then.

What is interesting, though, is that if you look at the scope traces

http://ampgarage.com/forum/viewtopic.ph ... 052#179052

You get a different result in the full clip. Biased at -31.5, there's very little crossover distortion.

I don't have any before clips, everything I've posted has always been with the bigger resistors. My memory of the stock values was that it was thinner, crunchier, and had more of a white noise character to he distortion. It was very Van Halen 1 ish. I think the bigger values are more vox ish, and focused. I think next time I'll do a switch and call it plexi/vox!
monkeymagic
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Re: Cleaning up an Express' act

Post by monkeymagic »

Just to come back on this thread having done some experimentation.

I've not changed any component values, but I've go though a number of valves and valve types in different positions

I've actually got to a very playable Tele sound, with more headroom and still retaining the dynamics I love, so I thought I'd feedback my findings for prosperity and to see if anyone could shed some light on this? ..I'm always keen to learn more..

Guitar: Suhr Classic Antique Tele
Amp: Fuchs Train 45 (single channel, non MV) running new JJ 6v6s into a Rivera Rock Crusher
Speakers: G12 H30s in a closed back 2x12

Valves
58' Philips branded F91 type (Long plate) 12AX7
63' Miniwatt branded I61 with Blackburn codes (short plate) 12AX7
NOS Tsung Sol 12AX7 of unknown vintage
New Tsung Sol 12AU7
New JJ 12AT7

With the 12AU7 in V1, either of the12AX7s in V2 and the 12AT7 in the PI, the amp only began to break up at about 75% on the gain - sounded pretty OK still, but lost some dynamics

I tried a bunch of combinations, but what I've settled on makes little sense based on my limited knowledge of these things, maybe someone can shed some light on why this seems to work for me?:

V1 = F92
V2 = 12AT7
V3 = Tsung Sol X7 NOS

I found the 12AX7 in the PI gave a much more lively sound than either of the other two, which I wasn't expecting - my understanding was that the 12AU7 would not distort so much and would push the power tubes more?..I'm stretching here, but I thought maybe distortion in the PI might produce variances across the power tubes and more complex harmonics?

Conversely, the JJ 12AT7 sounds much more lively that the Tsung Sol 12AU7 in V2 - again, my understanding was that the higher output of the 'U7 would add 'more' to the sound and to my ears it didn't? (maybe this is a big thumbs up for new JJs vs new Tsung Sols?)

Anyway, guess I'll be playing that that for a while and might invest in a nicer 12AT7 if it's going to stay that way

BP
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rooster
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Re: Cleaning up an Express' act

Post by rooster »

The amplification factor of the AU7 is less than the AT7.
Most people stall out when fixing a mistake that they've made. Why?
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