I couldn’t resist…

[fusedbrain]

Take a jcm800 unmodified, add a 330k/680k, 2.7k/220k unbypassed, shove it through a normal cf. It’s a Iommi signature amp so in the divider there’s a bit of personal tone shaping going on to take off some harshness with a bleeder cap which is common for any Marshall mods, even mine. Stupid simple and it just works. I haven’t touched the circuit, doesn’t even need a boost pedal. I’ve boosted it before with an SD-1 and the gain is useless above 4-5.

Sorry, a little OT, but thanks for the heads-up on the Laney.
I was not familiar with that amp, so searched and downloaded the schematic.
Interesting power supply rail and filtering arrangement.
Schematics with the voltages listed for the nodes is always very instructive as well.

 

[glpg80]

No problem!

You’re probably wondering why I bothered with a first year GH100S. The first year is the only year that got stand up chassis mounted Daly filter cap cans like Marshall’s. When they went to the TI series in 1995, they were converted to Laydown axial caps. Allows me to recap it with ARS in the future. That can’t be done as easily on the TI series.

These amps are built like tanks and grossly underrated on this forum. I’m surprised more people don’t talk about the S/TI series.

 

[RedPlated]

I prefer the stand up cans. Maybe because I’ve had great success with the radial ARS 50/50 cans. Never had one fail, ever.

I also prefer the look of the standup cans. Has that classic vintage aesthetic.

 

[RedPlated]

Man, I learned Replate, it doesn't matter if it
were perfect on all levels.
... there's a lot going on...
The guitar, electronics, humidity, wall whatever voltages, cables, human health, any component inside the amp working a bit harder then the others, speaker wire on the speakers, the speaker frames on the baffles and...the ole "STE''s..
WTH are STE's??
That's a condition amp builder's, musician's, etc's,
slowly begin to suffer from..Spent Top End.
Amps get brighter cuz we hear darker.
Some dude's suffer hardcore in the end
from them STE's and throw in the towel.

Great post. Good points!

 

[RedPlated]

Finally got some time to really dial in the 4th stage. I will say it sounds much better than with 3 stages. My theory is that the 3 stages were pushed too close to maximum to get the amount of gain I wanted in the higher gain settings. I’ve learned that with this circuit, 4 cooler stages sounds better and cleaner and they aren’t individually pushed to being overly hot. And the total amount of gain is actually noticeably increased.

With 4 stages, I ended up scaling back each stage until I attained the desired gain level and frequency responses. Getting the low end flub out takes work. Not even sure I’d call it flub but it’s the big, but not so great sounding deep bass. You can’t just scale the gain back in one spot. You have to find out where to dump signal and where it affects the frequencies in the best way. I’m leaving it 4 stages all the time. No 3 stage switching. It’s working really well this way.

 

[SpiderWars]

@RedPlated, don't know if you've experimented with it but here's one data point on this. I added a tube to a 2204. I decided to add another PS node for it and at first I tapped off the screen supply. I thought it sounded good but in talking with another modder they convinced me I 'should' take power from the last preamp node. So I did that and adjusted the dropping resistor to get the same voltage. It sounded noticeably clearer/less muddy using the screen supply to tap from. No idea why but that's what I heard.

And fwiw, I added the PS node because I had read that earlier Langner mods did not add the node but later ones did. I took that to mean he thought it was a worthwhile improvement.

 

[RedPlated]

@RedPlated, don't know if you've experimented with it but here's one data point on this. I added a tube to a 2204. I decided to add another PS node for it and at first I tapped off the screen supply. I thought it sounded good but in talking with another modder they convinced me I 'should' take power from the last preamp node. So I did that and adjusted the dropping resistor to get the same voltage. It sounded noticeably clearer/less muddy using the screen supply to tap from. No idea why but that's what I heard.

And fwiw, I added the PS node because I had read that earlier Langner mods did not add the node but later ones did. I took that to mean he thought it was a worthwhile improvement.

That’s cool info, thanks. I haven’t tried this but it’s interesting. I’m assuming you were getting more filtering with your final circuit.

When I added the 4th stage it did get muddy and undefined. Just too much for the preamp filter can to handle most likely. I actually added a filter to the preamp and it cleared everything up really well. Super tight lows. I was afraid it would get too stiff but it didn’t. With the added gain and compression it evened it out. I used a 47uf/450v cap but I have 33uf and 22uf en route to test as well.

 

[RedPlated]

Couple of updates…

I called Heyboer and looks like transformers may be available in next couple weeks. And since I will buy in quantity, I can go direct through them. This is great news.

I am still tweaking the 4th gain stage. Almost there.

I made the amp switchable between 3 and 4 stages. I will add a mini toggle switch to front panel. So you get both options.

The 4th stage adds some serious gain, compression and stupid good lead tones. I also tweaked the PI coupling caps a bit.

 

[Tone Junkie]

Hell yeah. ?

 

[LP Freak]

Making the options footswitchable will make the amp more appealing

 

[bugsy5150]

?