Hey lads, long time lurker first time poster...
I found a 'dumble/two-rock' schematic somewhere that was hand drawn, and was apparently the innards of a two-rock custom reverb.
The preamp section, from what I could work out (terrible diagram) was similar to the OTS, but had 100k plate resistors...
What does increasing the voltage on the plates do for the tone?
as a side note, are there any resources for learning what mods do what? I've got experience in solid state amplification, more of a hifi background, so I do kinda know what I'm doing, but these terms like 'snubber' 'bleed' etc are all new to me.
Thanks in advance.
Changing the plate resistors will change the gain and tonal characteristics of the pre-amp. Lower plates = lower gain and more harmonic distortion. I can recommend that you read up at
http://www.aikenamps.com/ or
http://www.freewebs.com/valvewizard/Sounds like you've been reading up at Ampgarage? That's where the two-rock schematic was posted and yes it was basically a Dumble #124 with built in reverb.
The term 'snubber' is not really used correctly but as installed in many Dumble derived amps it is used to describe the 2 capacitors that are attached to the base of V2. They filter out high frequencies to tame treble / smooth the overdrive sound. Increasing their value will give a less harsh overdrive (only impacts when overdrive is in use). The Two-Rock schematic in question used 470pF.
Treble bleed usually describes a capacitor that is placed across a Pot (volume control). It allows high frequencies to bypass the Pot when the POt is turned down (lower volumes) at higher volumes it has no impact. This makes for a brighter sound.
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