2204 & BE style pre amp in same head

[dailey]

Just sharing what I use. Because I play a lot of 80's metal & neoclassical, I was using 2 setup's to get close to the right sound. A modded 2204 { treble peaker's removed } with a DOD 250 & HS3's in a strat. And the other setup was a Friedman style modded plexi for the humbucker guitar's. A couple of years ago I decided to put both preamp's in the same amp. It's an easy mod if you don't mind adding tube's, relay's etc. I drew a schematic of the preamp if anyone would like to see if it works for them too. Again, this is just what I use and it works for me. I get ask a lot by other guitarist what has been done to my amps, so if it helps anyone else who plays what I do then here it is. You can hear the amps on youtube at https://www.youtube.com/channel/UC8tSqB ... VbDnUy_OMA

Please be kind, just sharing!!

[coldengray]

I did something similar to my 2204 build, with a "Modern" vs "Vintage" mode switching between 2204 and hot-rodded. Looks like we used a similar approach to V1.

[RockinRocket]

That's a cool amp. Ive been working with similar ideas once I decide to learn relays. Do you have gut shots? Handwired? Unexpected noise?

I did notice the 2204 circuit is always hot-rodded with the bypass cap on the 3rd stage. If the brown eye channel is to much for you, you can always Laney it up by doubling up the first 2k7 .68 stage cascaded into the next 2k7 .68 then finish it off 2204.

Are you planning to make the boost valve foot switchable?

[dailey]

the bypass caps on the CF only see ground by relay #2 when in BE mode. same for negative feedback resistor's on relay #3. the amp won't feel like a stock Marshall in 2204 mode without switching these components out of the circuit.

[RockinRocket]

Cool I missed that!

Hows the volume jump when switching channels with the different feedback levels? And does it add noise in that part of the circuit,

I wanted to implement a clean channel in a marshall build and the feedback would have to be low like a 27k 16 ohm tap while the rest of the channels would run of off 100k 4 ohm. I really don't know what to expect in terms of volume jump of if that would allow the clean to have the same vol as the dirty channel.

Post some guts Im loving this build of yours

[Haze13]

feedback works only in the PA section, means that a PI will need more voltage to be on the same level as without. So, if you want to make a clean, I suppose you do not need to attenuate the signal.
Most of the time, you have more voltage driving Pi then it needs and the result is a distortion (blocking distortion). The grid goes positive (tries to) and the result is that input impedance of a tube no longer High, but 1k or lower. 22nf in series with this "resistor". This happens way after the grid of the power tube goes positive and same thing happens.
So if you can make that a signal of a Clean channel will be the same as a of a Dirty, you won't not have to mess with a feedback. When you reach the clipping the signal remains of the same loudness, but clipped.
Since the your signals are sharing same tone stack, the best thing will be to bypass it, and make another one for a Clean channel. As far as I know, I like different settings fro cleans and others, I suppose too. Mix 2 signals at the PI and that's it.

[RockinRocket]

Thanks for the tip Haze.. and sorry Daily for the slight derail.

Say a fender clean, half triode into ToneStack, into recovery triode to LTPI then power amp. IDk but maybe not bypassing the triodes cathode after the tone stack would keep the power amp cleaner with the 100k 4ohm FB? It proabably wont be able to drive the PI fully or keep the same vol as the dirt channels. Probably a reason I don't see this configuration in Laynes or Marshalls "fender clean" type circuits.

Daily have you experimented ith a clean channel in this build?

[dailey]

I don't use the amp like a clean ch dirty ch. It's more like 2 amp's in one. That's why the negative feed back changes with the rest of the pre-amp. For the Yngwie songs it's 2204 mode [ https://www.youtube.com/watch?v=9QP3vG8kdMA ] and for the humbucker guitar tone's it's BE mode [ https://www.youtube.com/watch?v=Pw0Ypk3jzeo ]. When I change guitar's I change mode's on the amp because the BE mode doesn't sound good for the Yngwie songs and the BE mode sounds better than the 2204 mode for the humbucker song's like EVH, Dokken, Ratt, Ozzy etc. Adding a clean ch is an easy mod and if you like I would be happy to draw one up that doesn't have shared EQ. I personally foot switch to a different amp for clean tones because I use different effects for clean than dirty.

[RagnarMarGunn]

Dailey, thanks a lot for this schematic, I've been thinking about the same mod for a long time now since I have the exact setup ... one Metro modded to BE and another 2204 with some #36 AFD features. I have an unused JCM 800 that's hacked and could benefit hugely from this mod. Well done and nice sounding clips, I play similar music at big gigs few times a year

[rgorke]

Very cool!!! I have begun doing a very similar thing....having a BE and Plexi (rather than 2204) and clean channel. I need to add a tube to make it work. Extra tube will be for BE and clean with share tube with Plexi.

What we (I) need is a relay wiring discussion.

[patricef]

Nicely done and very good playing !