Express / Rocket

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

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Schmirleroo
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Joined: Fri Jul 07, 2017 3:54 am

Express / Rocket

Post by Schmirleroo »

Any thoughts on marrying a Express pre-amp section to a Rocket power section?
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didit
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Joined: Thu Sep 25, 2008 3:37 pm
Location: Canada

Re: Express / Rocket

Post by didit »

Schmirleroo wrote: ↑Thu Nov 19, 2020 5:09 am Any thoughts on marrying a Express pre-amp section to a Rocket power section?
Liverpool?

Best .. Ian
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Schmirleroo
Posts: 20
Joined: Fri Jul 07, 2017 3:54 am

Re: Express / Rocket

Post by Schmirleroo »

didit wrote: ↑Thu Nov 19, 2020 9:31 am
Schmirleroo wrote: ↑Thu Nov 19, 2020 5:09 am Any thoughts on marrying a Express pre-amp section to a Rocket power section?
Liverpool?

Best .. Ian
Yes... except the power section I'm referring to is tube rectified and cathode biased..
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didit
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Location: Canada

Re: Express / Rocket

Post by didit »

Schmirleroo wrote: ↑Thu Nov 19, 2020 10:56 am
didit wrote: ↑Thu Nov 19, 2020 9:31 am
Schmirleroo wrote: ↑Thu Nov 19, 2020 5:09 am Any thoughts on marrying a Express pre-amp section to a Rocket power section?
Liverpool?
Yes... except the power section I'm referring to is tube rectified and cathode biased..
But a Liverpool is cathode biased.
cathode bias.jpg
Significant differences between Liverpool and Rocket power amp section are in the details of ---
  • split cathode bias,
  • values of various key resistors,
  • and the choke before the screens,
  • the nominal voltages derived upstream from the power supply,
To be strict, Rocket is missing a negative feedback loop too.

Tube rectifiers are in broad strokes really no different than silicon rectifiers despite mythologies spread by certain evacuated mystics.

Best .. Ian
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Last edited by didit on Sun Dec 13, 2020 5:28 pm, edited 1 time in total.
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Schmirleroo
Posts: 20
Joined: Fri Jul 07, 2017 3:54 am

Re: Express / Rocket

Post by Schmirleroo »

didit wrote: ↑Thu Nov 19, 2020 4:48 pm
Schmirleroo wrote: ↑Thu Nov 19, 2020 10:56 am
didit wrote: ↑Thu Nov 19, 2020 9:31 am
Liverpool?
Yes... except the power section I'm referring to is tube rectified and cathode biased..
But a Liverpool is cathode biased.

cathode bias.jpg

Significant differences between Liverpool and Rocket power amp section are in the details of ---
  • split cathode bias,
  • values of various key resistors,
  • and the choke before the screens,
  • the nominal voltages derived upstream from the power supply,
To be strict, Rocket is missing a negative feedback loop too.

Tube rectifiers are in broad strokes really no different than silicon rectifiers despite mythologies spread by certain tube mystics.

Best .. Ian
Indeed it is sir... :)
R
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Mark
Posts: 2982
Joined: Sat Jan 15, 2005 8:10 am
Location: Sydney Australia

Re: Express / Rocket

Post by Mark »

There is a bit more to it than that. The Liverpool also uses 1K screen resistors in lieu of 100 ohm. The 1K offers less bass response and does make sense with the Express style preamp.

The 1K choke resistor dials in the sag for the amp as opposed to using a choke.
Yours Sincerely

Mark Abbott
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hitchcaster
Posts: 289
Joined: Thu Jun 01, 2006 12:30 am

Re: Express / Rocket

Post by hitchcaster »

why not build a liverpool with a SS rec / tube switch... bet you'll keep it on SS tho.
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