shane wrote:Thats a very nice build! and pretty much answers my original question I'd guess!
Couple of things I'd like to ask you if I may.
What value is the side pot? and is the gain pot wired backwards for any particular reason?
Oh yes and what is that huge cap on the presence control?
Bloody well done mate!
Cheers
Shane
Smokebreak wrote:I'm guessing 1M side pot, so you can get the 68K/1M little gain stage, or run it like 68K/68K Jose or anything in between. Drilling side holes in all my chassis now!
In the tweaking process, I ended up subbing out the bottom resistor to something like 220k IIRC. The 68k/68k divider works well for the Jose style circuit (e.g. brown eye, cali etc) as the low impedance in parallel with the extra stage does provide some loading effect and compression and certainly adds brightness.
But for me, that's not what this amp is all about. It's about chewy fat and a nice compression, rather than an aggressive compression if that makes sense.
So bringing up the impedance of the maximum "saturation" setting (which is what I call that dial) helped to fatten up the tone and dial back down gain, so the range is a little more usable and classic rock. It can still get gained up, but not as hairy.
I may have also increased the top resistor, I just can't remember.
In relation to how it's wired, doesn't really matter as you can instantly hear the gain increase as you turn and it's really set and forget.
That's an old school polystyrene cap. I love styros in certain spots and it was the only one I had in the right value, so it got used.shane wrote:Oh yes and what is that huge cap on the presence control?
Good question. I had an OT from Heyboer lying around that had a 2ohm tap and a 3k6 primary, so it could be mismatched for 7k2 so I could run 5881s like the original.Roe wrote:what kind of OT do you recommend for this type of amp?
That's what the switch on the back does: JTM45 (7k2) / JTM50 (3k6).
I do like the 5881s, but I keep gravitating towards the KT77s at 3k6. I really should give the 5881s more time and allow it to be what it should be.....I have my plexi for the super aggressive EL34s thing.
BTW - I should say that I've never been inside a Dirty Shirley, so this build took some design and starting point inspirations from that amp and I tweaked from there. The mystery is still that regarding the actual circuit of the original. I am as curious as everyone else.shane wrote:Thats a very nice build! and pretty much answers my original question I'd guess!