Grapevine Query

[raulduke]

I love the DLS and would like to get a better insight into its workings.

Concerning the Rock and Rawk modes, looking at the schematic am I right in thinking:

C2 (4.7u) + C6,7,8 etc in circuit = Rawk mode?

And C5 (22n) and just C4 (220n) = Rock mode?

This would make sense as adding the 4.7u cap will increase gain.

I've simulated the freq response of the first stage in spice  and it seems to match up, ie. C6,7,8 and R7 and R8 in circuit gives a more midscooped and trebly response which i would relate to a JCM800, as opposed to just C4 which gives a 'flatter' response more in keeping with early Marshalls.

I've attached the image as its kind of interesting (well to geeks like me anyway!)

Red is what the C6,7 etc filter network in circuit, Green is C4 in circuit (220n), Blue is the input signal.

The dotted lines are the phase response.

[jkokura]

Looking at the schem I thought it would connect like this:

Rock = C2 and C5 (no C6-C8 and R7-R8)
Rawk = C6-C8 and R7-R8 (no C2 and C5)

However, looking at the Wiring diagram it seems like it's:

Rock = C5 (no C2, C6-C8 and R7-R8)
Rawk = C2, C6-C8 and R7-R8 (no C5)

Is that all you're wondering? I didn't really see a question in there.

Jacob

[raulduke]

Yeah that is what I was querying; C2, C6-C8 and R7-R8 connected when in Rawk.

There were two questions at the start of my post but maybe they weren't very clear !

It makes sense for C2 to connect when in Rawk mode as it will boost the gain of the first Mu-Amp stage.

On my Catalinbread DLS the gain is boosted in Rawk.

I found the freq response of C6-C8 and R7-R8 interesting as well. Its a cool way to get that 'mid scooped sound'.

[jkokura]

Yeah, I think the DLS is supposed to be very Marshall like in it's tone structure. So that scoop makes sense.

One thing though, C4 is always in the circuit. What's happening in rawk mode is that C4 is added in parallel with C4. This adds the two together, so you get approximately 4.92uF when it's added in, and only 220nF when it's out.

Jacob

[raulduke]

Yeah mate I sussed that one but thanks for pointing it out anyhow.

I'm going to get a PCB made and play with different values on the circuit to 'tune' it to what I want to hear.

I'm more keen on 'Rock' mode so I am going to omitt the mid scoop filter network on the PCB, and then maybe mod the circuit for more gain.

Hence all the questions/ramblings!