S.I.R. 100W SuperLead Schematic pt. II

[dukeamps]

Picked up a 76 JMP 100w this week, it already had been modded before & put back to stock, i would have left that way but it has a couple of holes drilled in the front of it, so i modded my 36 mod in it, it has Mullard caps on the cathode & pres, the rest of the caps are the green type Marshall used in the 70s.

Here is a clip from it, NT then SCOM at the end of the clip, Chinese nos pre, Winged C el34s, G12M25w speaker, & sm57 mic,


http://soundclick.com/share.cfm?id=13257113

[BRMSlash]

Interesting tone you've developed there mate. Very spongy yet buzzy at the bottom end. You must have a highly developed mod to be fine tuning the B+ voltage. Respect.

Thanks. For a long time I've been running the cathode follower around 305v, which is higher than the maximum nominal 300v spec for ECC83/12ax7's, but I needed the voltage higher to increase the headroom and clarity when I was using 10k cathodes. However, now I've stopped using 10k's, there are more opportunities for fine tuning the circuit.

With my last recording, I lost a bit of clarity/headroom on the intro to My Michelle, so will probably have to adjust the cathodes slightly or bump up the voltage. This also got me thinking, that I might reconfigure the 2nd and 3rd stages to be on the same tube, so they have the same B+. This also opens up the possibility to try putting a stock (or modified) "normal" channel in parallel with the "bright" channel, which might make some interesting experiments jumpering the two together and blending tones.

[rockgod212]

sounds killer as always, man your starting to make me want to go back to el34's.

Picked up a 76 JMP 100w this week, it already had been modded before & put back to stock, i would have left that way but it has a couple of holes drilled in the front of it, so i modded my 36 mod in it, it has Mullard caps on the cathode & pres, the rest of the caps are the green type Marshall used in the 70s.

Here is a clip from it, NT then SCOM at the end of the clip, Chinese nos pre, Winged C el34s, G12M25w speaker, & sm57 mic,


http://soundclick.com/share.cfm?id=13257113

[BRMSlash]

So I bumped up the voltage to 292 at the cathode follower, moved the 2nd stage to the 2nd tube, went from 0.68u to 1u on the 3rd cathode and dropped back to a 1k on the 4th stage cathode. Also tweaked the reverb EQ a bit. Note that I had to use a sub-standard part to get the correct voltage, so there's a fair bit of buzz particularly notable in My Michelle.

http://sclk.co/s7w624

[snakepit86]

Picked up a 76 JMP 100w this week, it already had been modded before & put back to stock, i would have left that way but it has a couple of holes drilled in the front of it, so i modded my 36 mod in it, it has Mullard caps on the cathode & pres, the rest of the caps are the green type Marshall used in the 70s.

Here is a clip from it, NT then SCOM at the end of the clip, Chinese nos pre, Winged C el34s, G12M25w speaker, & sm57 mic,


http://soundclick.com/share.cfm?id=13257113

Duke, i think its the BEST sounding AFD ive heard in a while.

I was thinking about something, i would like state some rules

Use the same mic
same speakers
same position
even same riffing

only have to change the amp, settings and mods of course. Just to make a fair comparative between mods, because sometimes the recording isnt that we hear and the other persons in this forums can not hear what we do with our amps.

If we all no have the same speaker, just use the same mic and same position, that will make the recordins more easily to compare and discuss and share spects, what do you think?

[stoof]

Duke, your last clip sounds awesome !

[dukeamps]

Cheers guys, thanks for your feedback

[BRMSlash]

So I added an extra stage in parallel with the first and blended the tones together like a jumpered 4 holer. I tried a few different cathode and plate resistors, but I couldn't get any better tones than I previously had.

To my ear, there's still a certain mid range raunch that no one has reproduced. I'm just trying different ideas. It might not even be in the amp, but some external effect, speaker, or mic preamp. However, it does seem to have a tube like sound. I might explore changing the tone stack to be plate driven, rather than cathode, or maybe stick some diode clipping in to see what effects they produce.

[BRMSlash]

Here's a clip with the tone stack driven off the plate of the 4th stage (i.e. no cathode follower). I'm surprised it's not that different, just lost a little chime and a bit more buzzier I think. So it's possible for the mod to be done without adding another tube with a little sacrifice in tone quality.

http://sclk.co/s7w7je

[bennyx]

Shield trick shield trick shield trick.....i'm going mad.....

[snakepit86]

benny come once again, whats differences you ear on normal shielded cable, shield trick and cap?

I really like the nrmal shield and the 47p cap like the jubilee.

Just to be clear shielded trick is to tie the shield to the plate of the valve instead of ground right'?

[rockgod212]

has any body built the SDM xtra stage mod, how close does it come to AFD tones? I think im going to drop it in my 50watt el34 plexi, just to see how it sounds.

2203%20mod%20AJ%20Rev1.jpg

(762.79 KiB) Not downloaded yet

[budubum92]

Here's a clip with the tone stack driven off the plate of the 4th stage (i.e. no cathode follower). I'm surprised it's not that different, just lost a little chime and a bit more buzzier I think. So it's possible for the mod to be done without adding another tube with a little sacrifice in tone quality.

http://sclk.co/s7w7je

i must admit that this plate driven tone stack sounds closer to AFD than any of your previous experiments.

[BRMSlash]

I agree, but it's not due to the plate driven tone stack. I rolled back to the spec I had a few clips ago, replaced that substandard resistor I was using to adjust the B+ and adjusted the settings on the amp. Using a 39k carbon film for the first grid stopper and tone stack slope resistor helps quite a bit too. Snubbers are now 150p, 470p & 1n from 1st to 3rd stage. I'm going to reinstate the cathode follower and I also want to try bumping up the 100k plate resistors to 120k. I've tried 150k and 220k on the first stage but they compress too much, but I do like the crunch they produce.

[bennyx]

benny come once again, whats differences you ear on normal shielded cable, shield trick and cap?

I really like the nrmal shield and the 47p cap like the jubilee.

Just to be clear shielded trick is to tie the shield to the plate of the valve instead of ground right'?

After remove all old bad pond in my amp, re make all welding.....definitely the amp sound correct.....now i decided the lenght of shield ....when i finish post some samples....will a big surprise...i have re- stock the tone stack and re-put a 2n2 treble peaker on third stage......now the amp don't have too much treble, don't have hiss and have right mids.....fuck the old bad pond....without lead

So i prefer shield trick.....the lonely cap cut too gain....shield trick have more natural cut than cap....Frank advice me "use a good shield cable" so i have use good cable....don't use thin shield cable....have too parasite capacity and cut too sound, gain and freq....

Shield trick consist to simply connect shield of cable to the anode, in this way work similar like a cap.....the other cape of shield don't connect.....must be protect with isolation....don't absoltely connect with ground