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So f*n cool, mate! Nice to hear it played by someone else than me :) I also tend to get whining from the breadboard withthis kind of circuits, I usually rejig some of the gain stages further apart til it stops. the resistor + cap after the Hi cut control is there to counter the treble bump from...

Sure, temol ;) At drain of last gain stage: After hi cut control: Nothing too outrageous, kinda standard-ish JCM but with more gain. Trying to ape 90's King Diamond type of tone, a bit more modern than 90's standard HM, but not quite modern sounding by today's standards, not scooped nor...

I did some sims just to compare side to side, here's some observations. We have those three circuits, left to right: - First one is a fairly standard jfet gain stage, with "cathode follower". - Second one is the same, but with a follower nicked from AMT L2 pedals (those that have it, e.g. S2...

Do you mean the whole bootstrapped follower thing? I have never seen it in any pedal design, personally. There is an old thread on DIYSB about a similar idea using bjt, but I don't recall seeing it in any "complete" circuit. I've ltspiced it with fets, it does increase gain and it does exhibit a...

I'm not knowledgeable enough on mosfets, but the ubiquitous RG Keen certainly is: http://www.geofex.com/article_folders/mosboost/mosboost.htm

Cool design!! This amp has an intereating topology. Kinda like the non-interactiveness of the treble control, although the mids don't seem to do heaps. I wonder which stage clips first, 6AN8, cathodyne PI or power stage, and which one is responsible for the sound characteristics?

I tend to use jfets with tight specs (SMD J201, 2N5484, J113, 2SK208R, and the dmos LND150), and rarely bother checking their Vp or IDSS. By simulating on Ltspice, you can start with drain and source values that are in the ballpark, then check with the multimeter and do some small adjustments to...

Personally, for jfet stages, I focus on 3 things: - Bias point (asymmetry) - Clipping point (gain) - Source capacitor if present (freq response) When converting from 9 to 18v (or more), leaving all source components the same and just changing the drain resistor to bias the jfet will get you in...

Never tried higher voltages, too much faff. As drew points out, 18-24v sounds great :) And yes, 9v was initially done to keep the same "standard voltages" for 99.9% of pedals. Incidentally, J201s are one of the few jfets that sound great at 9v. 2SK208 (as seen in AMT circuits) also sound really...

I've breadboarded quite a few jfet circuits at 18v and 24v. JFet, BJT and Depletion Mosfet will all exhibit cathode follower compression/distortion, with some difference in regards to the tone/timbre. I found LND150 to sound a bit darker (or less harsh) than Jfet, with BJT being a nice middle...

There goes. I find that biasing LND150 with a diode gives a bit more snarl than resistor+cap, but ever so slightly lower gain. I didn't emulate the feedback around the valve stage because it would have defeated the mosfet grind I was getting :D "cathode follower" can be anything you fancy, bjt...

Note that, in the Sabbra snipped you posted, you can replace the fixed tonestack with actual pots for more versatility ;)

The original Laney presence control relies on modifying the frequency response around the feedback loop between the phase inverter and the power amp stage (essentially allowing more/less high frequencies to feedback). In your schem, and the EffectsLayouts project, the phase inverter is...

Funny, I breadboarded that channel two weeks ago, with LND150 in lieu of tubes, and the (heavily modified) diode section of the Ethos twe-1 instead of leds. Quite nice sounding actually, I can post a schem if interested. I used TL062 for opamps (a tad less harsh than 72s or 4558s), ran the whole...

Not the best practice IIRC, but depending on the circuit you might get away with it. Would that be the Randall X2-G3 or similar?

Q5-Q6 simulate the phase inverter of the amp. As it is, I am not sure it will work, since both sides are hard-connected via the output capacitors. I'd be inclined to use a couple of mixing resistors (say, 33k for example) between the caps and the master volume. As stated above, presence will...

The way I understand it (someone correct me if I'm wrong), J177 (or BAT diodes gate-to-ground on the Series 1) are there to simulate valve cutoff and subsequent dynamic shifts. What puzzles me a bit is that some jfets already exhibit gate cutoff even at 9v, so, unsure about the need for added...

Here are a couple of examples using BJT (a tad... Old): https://www.drtube.com/schematics/marshall/2099u.gif http://www.lynx.net/~jc/SchematicMonoBlock-II.pdf For Jfets run on bipolar supplies, Gallien-Krueger amps from 1980 to late 90s feature them in several very interesting topologies :)

Replace the tonestack with the circuit on the right and you'll get roughly the same freq response, with a little extra volume on tap. Scaled down for less noise, 100k volume pot instead of 1Meg. Doesn't match 100% but reality doesn't either, due to pot tolerance ;)

FWIW the pre-dist voicing on the MT-2 is almost identical to the Ampeg VH140 (albeit using different circuits - gyrator vs. feedback loop hacks). Where the difference becomes noticeable is in the post-dist controls and voicing (big presence and resonance bumps + different tonestack). OK...