Particle Accelerator - Alembic F-2B clone
- Thread starter vigilante398
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vigilante398
Authorized Vendor
The output impedance of the circuit is about 38k if you're using a 12AX7.
vigilante398
Authorized Vendor
I'm not
a 12A*7 family tube can run the heaters in parallel at 6V or in series at 12V. This circuit puts the heaters in sseries, but you can still get away with running them at 9V instead of 12. I've run 12AX7 heaters down to 8V before I started hearing a difference.kweefthief
Active member
Im waiting for my tayda order to come in tmr so i can make this thing mwahaah. I do have a question about the circuit. From my understanding its based off a showman preamp but what besides the tone stack makes it so? Otherwise its just the same as any other AB763 correct? Does it have to do with plate voltages? I'm not really knowledgeable about circuits and stuff just curious!
vigilante398
Authorized Vendor
Pretty much just the tone stack and the voicing of the gainstages, that's pretty well what makes any preamp what it is.
Mike McLane
Active member
@vigilante398 says the Space Heater diy is being discontinued. I worked on a mod to convert the Particle Accelerator to a SH by bypassing the tone stack, but also toyed with Duncan Tone Stack Calc to make an equivalent that has a flat EQ curve like the SH, but allows some adjustment to the Treble & Bass. I came up with the following and would appreciate any feedback before I try it out. It would be a fixed Mid resistor of 33K.
Mike McLane
Active member
Oops, sorry. . . the Bass cap needs to be .22u and the Mid cap needs to be .0022u.
I finished my build on the Particle Accelerator yesterday. No surprise that I really like it a lot, right up there with my Space Heater. The tone controls are surprisingly robust. : ^ )
Nathan -- are you planning to do an updated Space Heater layout using the 90 degree pins for the tube socket board? Or just letting that one go idle?
Nathan -- are you planning to do an updated Space Heater layout using the 90 degree pins for the tube socket board? Or just letting that one go idle?
vigilante398
Authorized Vendor
I'm getting rid of Space Heater. Particle Accelerator is just Space Heater with a tonestack, and I'm trying to keep the number of boards I offer to a minimum so it doesn't overwhelm the other side of my business.
That makes sense, and the tonestack brings a lot to the table. Impressive low end for sure.
Mike McLane
Active member
Nathan, did I understand you correctly that the 220K resistor just before the Master Vol is to pad the output somewhat for better use into SS amps/mixers, etc. desiring a line level signal input?
vigilante398
Authorized Vendor
You're correct that it is to pad the output, but not specifically for use with SS devices, just to make the master volume more useful. Without that resistor, unity gain is reached with the master volume at like 8 o'clock. Even running into the front of a tube amp, if you jumper that resistor you're going to get a LOUD signal. Reasonable idea if you want to run straight into a power amp, I recommend leaving the 220k in for literally everything else.
Mike McLane
Active member
I still come back to my love of the 5F6 Bassman so I applied my layman's eyes to the schematic diff's btw the 5F6 and Particle Accelerator (a blackface circuit). Seems most values are identical to the PA (tone stack has some variances depending on the schematic you look at) so the primary diff is 1) the tone stack is AFTER 2nd gain stage/cathode follower and a presence control (NFB). Didn't you place a BF-like tone stack after the 2nd gain stage in the London Underground (?) and the main diff was primarily limited to the aggressiveness of the circuit's output?
vigilante398
Authorized Vendor
Correct. London Underground is the preamp from the Orange AD200B, which has some voicing differences as well. Eventually I kept the AD200B (London Underground) layout and the Alembic (Particle Accelerator) values and smashed them together to create the Underground Accelerator, which I still sell today. Sort of a best-of-both-worlds thing in my opinion.
Mike McLane
Active member
What's your take on the addition of the cathode follower to the 5F6A/JTM45 circuit. Why'd they put that in?? I understand it lowers impedance (from 38K to ?), but how does that help and what other "benefits" does a CF ostensibly provide?
UPDATE: Never underestimate the power of Google. My query yielded the following:
Do we have a "frequency dependent load that demands a lot of current"? I'm guessing "yes" on frequency dependency and "no" on current requirements.
UPDATE: Never underestimate the power of Google. My query yielded the following:
Do we have a "frequency dependent load that demands a lot of current"? I'm guessing "yes" on frequency dependency and "no" on current requirements.
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vigilante398
Authorized Vendor
It's common to use a cathode follower as a driver before a tonestack or FX loop, both of which are considered a load. Using a cathode follower before a tonestack is also useful as the cathode will have lower voltage than the anode so you can get away with lower voltage capacitors in your tonestack, which can save you a couple bucks.
Mike McLane
Active member
I note that cathode follower questions really fall under discussions about the 5F6-A/JTM45. I have a follow up on tone stack caps voltages which I will bring up there. Sorry for the crossover.
