D-style TS to Marshall TS switching

[10thTx]

I like my Tweed Overdrive amp. I was pondering the idea of how I could somewhat simulate a quasi-D-style tone stack to be switched into a quasi- Marshall style TS. (schematic attached)

This is what I came up with. Just thought I'd share the idea for the non-cloners of D-style amps. I have not built this yet but tenatively plan to try it. I find I don't use the MV very much because I use the PPIMV more. That leaves a hole for a pot to do something different.

Thought this might be an interesting way to get a significantly different sound? Hopefully something sort of Marshally sounding. You could have this relay switched and call it the Blues/Crunch switch.

With respect, 10thtx

[rogb]

As usual, you always come up with some interesting new idea!

It's guys like you who drive the Amp Garage forward. Not "look at my weird amp, here's an external pic". Total respect mate, for your hard work, and always willing to help and share too!

Right, that's enough smoke up your a.. for now

My idea, one I would really like to do is an Ultraphonix built from the ground up into a Deluxe type chassis, pair of 6V6s.

I'm gonna start a thread I think

[Structo]

Can you explain what the MOSFET is doing for you in that circuit?

Are you using it as a constant current source?

[ChrisM]

Can you explain what the MOSFET is doing for you in that circuit?

Are you using it as a constant current source?

It's a buffer. Equivalent to a triode CF.

[10thTx]

I did NOT have a dual gang pot, so I tried something different that I used successfully on a previous build I did for someone called a Double C amp.

And this one knob tone stack worked very nicely! When the PAB is switched, it somewhat disconnects the tone stack prior to V1-b & engaged the tone stack after the mosfet cathode follower.

On a scale of 1-10 (10= very dramatic), I'd say this is a "4" & a useful modest but significant tone change.

It adds a very noticeable dash of "chime" and a vowel tone which I like ALOT. It almost sounds like a wah pedal is engaged coloring with the vowel/wah type tone. I am confidant that with this PAB/chime engaged that it would help a solo cut thru the band mix more easily.

I also found that I like the clean better without the master volume. I feel like I perhaps have more headroom & the amp is actually quieter at idle. (and it was already very quiet).

Only downside for me doing this is, is that I really wish I had the PAB on a footswitchable relay but I don't.

Keep in mind that this amp is only about 23 watts, so the PPIMV works just fine for me to control volume. IF this were a 50 watt version of the TOS ......... I might still want a master volume on the clean channel, but you could still add the tone stack.

I have added the schematic and layout here:
http://www.el34world.com/Forum/index.ph ... #msg113204

With respect, 10thtx

[Structo]

Can you explain what the MOSFET is doing for you in that circuit?

Are you using it as a constant current source?

It's a buffer. Equivalent to a triode CF.

Why is a buffer needed there?

I see CF's used to drive tone stacks to keep the gain up but why would you buffer after two gain stages?

[10thTx]

Regarding why 2 CF's?:

Note that the passive effects loop is after the clean and after the OD channel.

It is my impression that if you're NOT using a d-lator in the passive effects , that the mosfet CF seems to help with a Boss digital delay.

I had built an active effects loop similar to a D'lator that I was using in the passive effects loop, but when I put the triode CF after the 5879, I found I actually liked the delay better withOUT the d-lator then with it. Just a preference thing. Someone else may not like it? However, I remember Mat talking about liking the delay without the d-lator better on his 86 Special also. I found that I wasn't using or needing the active effects loop once I had a CF.

So this allows a CF for both the clean and OD channels. I like how it's turned out.

And at this juncture, I do have a quasi tone stack there that I am calling a chime pot.

with respect, 10thtx

[Structo]

Thanks for the explanation, that makes more sense now to me.

[10thTx]

And as a side note, I found the triode after the 5879 really smoothed out the OD tone to my ears.

I had a "left over" triode and just decided to experiment with it and see what happened. Made it a smoother and somewhat less chimey OD tone.

With respect, 10thtx