Rocket Preamp in DC30... simple process...

[bcmatt]

Hi, I've only built an Express and a Liverpool; the Liverpool being my main amp. However, I am very curious about the Rocket and am unfortunately quite a broke musician. However, I also have a DC30 clone that I often will use exclusively for the EF86 channel. I never bonded much with the "top-boost" channel. I've been looking at the schematics and notice how very similar the Rocket and DC30 top-boost channel preamps are... like exactly the same values and structure.... if I only were to detach the parallel gain stages on V1 (and that additional .1 cathode cap) and change the input grid resister from 68k to 33k (this one may not matter).

So, I know this is not breakthrough news, but I am wondering how much of the rocket tone is due to that particular preamp... since I see so many people here building different versions of the Rocket with altered power sections or adding reverb, etc.
So, before I go ahead and start snipping, I'm wondering people's thoughts on this and whether I should go messing around in there... Will I be able to get a good taste of the Rocket Magic this way?

[matt h]

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[bcmatt]

Heretical advice: don't "de-parallel" your input triode. Just tack/clip/solder in identical values for plate and cathode resistors in parallel, and fit the adjusted value caps in (or add in identical valued ones in series to the current ones).

For a single triode, 220k plate resistor is equivalent to 110k on a paralleled triode.

For a single triode, 1.5k Rk= 750ohm for a shared one (most people will use 820ohm resistors as they're more common).


Keep your paralleled input, enjoy your lower noise floor and keep the bulk of the wiring in the amp untouched.

Just my two cents.

Interesting advice, Matt. Thanks. So, you are saying that by changing the values of the plate and cathode resisters to half that of Rocket's single triode, I should get a similar flavour in my parallel triodes? The cathode bypass cap would remain the same (25uF) in this circumstance?
With the the unused triode in the Rocket, I wonder why Ken Fischer didn't parallel, if it is superior...
Was Paralleling those triodes Mark Sampson's (Matchless) idea, or was straight from Vox?

[matt h]

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