Thoughts on my Jose 2204

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I was gonna say that increasing the resistor to ground will loosen the bass as well as increase gain but you said similar above (that the 82k reduces gain and stiffens the response). I'm sure V2a can explain it but that resistance seems to be a somewhat delicate part of the amp when it comes to tightness. Like you said, 82k is almost too much (depending on other things like the plate resistor). I think it has to do with the loading on the previous stage which as V2a said above, all that stuff is in parallel with the plate resistor (and also the internal plate resistance of the tube). It's almost like the dynamics are too much when loading is low (higher resistance to gnd) but when you increase the loading (lower the resistance to gnd) the dynamics are softened so it doesn't get loose.

IIRC, Micheal R/Ts OWM has the 2 68ks in parallel for 34k to ground with the dummy plug out and then 68k with the dummy plug in (gnd connection to one of the 68k is severed). You can hear in his videos when he uses the dummy plug it gets a little more loose with the dummy plug in.
 
SpiderWars":19zs24dm said:
I was gonna say that increasing the resistor to ground will loosen the bass as well as increase gain but you said similar above (that the 82k reduces gain and stiffens the response). I'm sure V2a can explain it but that resistance seems to be a somewhat delicate part of the amp when it comes to tightness. Like you said, 82k is almost too much (depending on other things like the plate resistor). I think it has to do with the loading on the previous stage which as V2a said above, all that stuff is in parallel with the plate resistor (and also the internal plate resistance of the tube). It's almost like the dynamics are too much when loading is low (higher resistance to gnd) but when you increase the loading (lower the resistance to gnd) the dynamics are softened so it doesn't get loose.

IIRC, Micheal R/Ts OWM has the 2 68ks in parallel for 34k to ground with the dummy plug out and then 68k with the dummy plug in (gnd connection to one of the 68k is severed). You can hear in his videos when he uses the dummy plug it gets a little more loose with the dummy plug in.
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Yes, pretty much. The stock Chupa has that resistor on a push/pull. So gain pot pushed = no resistor/no ground = full gain and bass. Pull gain 1 out and it engages that 82K, reducing gain a bit, tightening up the feel/response. What I do is engage that thing and then push the gain up higher to compensate. So it's as heavy sounding, but tighter response and brings in a bit of this pinch-harmonic type of pissed off snarl.

Some other Jose amps on the market recently use 68K as well. I think I prefer the 82K over 68K. I will try higher values as V2a suggests. I like the 150K V1b input grid to kill some additional highs. These amps are super bright to begin with.

I think the stock Chupacabra is a great voicing. Only thing that circuit really needs (depending on your taste) is dropping V1a plate load to 320K (or even 300K), changing slope resistor to 33K/36K/39K, upping B+ from 450v to 475 or so, and then adding in the missing 10K dropper from PI to CF. Those simple changes make the stock Chupa tighter and more of a throaty growl, while retaining the pissed off character. Plenty of other things you could mess with, but I think these are the most simple changes one could make.
 
The gain1 pot and any parallel resistance (like the 82k shunt resistor) work with the preceding coupling cap to roll off low end. The -3dB "cutoff" moves up (to higher frequencies) as the load resistance is reduced. Hence tighter bass...
 
Where do you guys learn all this stuff ? I need more books and other materials...seriously.
 
Reading and doing. Lots of books out there now. Check out Kevin O'Connor's TUT series and get TUT1 and TUT3 for starters. Available at London power website
 
I'll second that... I learned a lot from the TUT series. For me, it was a great place to start, as was Gerald Weber's series of books.
 
I have the Weber books, and the Torres Engineering book, as well as Aspen Pitman’s books. Books on tube amps or even tube electronics are hard to come by.
 
I'll third the TUT books. Randall Aiken's site has lots of cool info too.
 
I will be looking into all the suggested material, thanks to all. Keep it coming if there’s anything else...
 
paulyc":28p56cke said:
I will be looking into all the suggested material, thanks to all. Keep it coming if there’s anything else...
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FWIW paulyc, (and I may get flamed for this but wtf) I don't see everyone clamoring for the amps made by a lot of these gurus. Although I appreciate their knowledge and sharing it. Yet there is top dollar paid for Camerons...despite the rep. I haven't heard any of these gurus PLAY guitar except MC, and he fucking rips.

Here's an analogy: I don't play tennis. You could hand me a shitty tennis racket and a great one and I wouldn't know the difference. But Serena Williams would, because she's an expert at PLAYING tennis even though she doesn't build tennis rackets. You can know all the theory but if you can't tell when a tweek sounds/feels better than it did before then achieving stellar tone will be difficult. Guitar amps with great distortion break a lot of the 'old school' rules. Knowing the theory surely doesn't hurt (and I have no idea how much theory MC or any of the other highly sought after builders do) but imo just knowing old school theory doesn't = awesome tone. For years I read how higher plate loads was bad, bad, bad but here we are with 330k+ plate loads sounding just dandy. Just something to keep in mind and all just my stinkin opinion. :)
 
Rob Robinette's website is a good resource too. Also, I just pick people's brains a lot. I've also built a bunch of amps and play around/experiment with them until I find something that works. I do need to learn more about the theory and circuit design though. It's just so tedious sometimes.
 
SpiderWars":1zll4bu2 said:
paulyc":1zll4bu2 said:
I will be looking into all the suggested material, thanks to all. Keep it coming if there’s anything else...
Click to expand...
FWIW paulyc, (and I may get flamed for this but wtf) I don't see everyone clamoring for the amps made by a lot of these gurus. Although I appreciate their knowledge and sharing it. Yet there is top dollar paid for Camerons...despite the rep. I haven't heard any of these gurus PLAY guitar except MC, and he fucking rips.

Here's an analogy: I don't play tennis. You could hand me a shitty tennis racket and a great one and I wouldn't know the difference. But Serena Williams would, because she's an expert at PLAYING tennis even though she doesn't build tennis rackets. You can know all the theory but if you can't tell when a tweek sounds/feels better than it did before then achieving stellar tone will be difficult. Guitar amps with great distortion break a lot of the 'old school' rules. Knowing the theory surely doesn't hurt (and I have no idea how much theory MC or any of the other highly sought after builders do) but imo just knowing old school theory doesn't = awesome tone. For years I read how higher plate loads was bad, bad, bad but here we are with 330k+ plate loads sounding just dandy. Just something to keep in mind and all just my stinkin opinion. :)
Click to expand...

My view is that you should know the rules before you start breaking the rules. A basic understanding of electronics is essential to go beyond building clones.

MC rips on the guitar and his amps also rip from what I can tell. But that shouldn't stop anyone from gathering info from the available sources.

BTW - Bruce Egnater is a guru who makes killer amps (including all of the Synergy modules, regardless of the name on them). But does he rip on the guitar? Dunno.
 
V2a":size7pa0 said:
My view is that you should know the rules before you start breaking the rules.
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Took the words out of my mouth. :lol: :LOL: I don't remember where I heard this, but... you've got to know the rules so you know which rules to break. Pretty sure that it was in relation to music theory when I heard that, but I think it applies to many things.
 
V2a":17hm5fiw said:
SpiderWars":17hm5fiw said:
paulyc":17hm5fiw said:
I will be looking into all the suggested material, thanks to all. Keep it coming if there’s anything else...
Click to expand...
FWIW paulyc, (and I may get flamed for this but wtf) I don't see everyone clamoring for the amps made by a lot of these gurus. Although I appreciate their knowledge and sharing it. Yet there is top dollar paid for Camerons...despite the rep. I haven't heard any of these gurus PLAY guitar except MC, and he fucking rips.

Here's an analogy: I don't play tennis. You could hand me a shitty tennis racket and a great one and I wouldn't know the difference. But Serena Williams would, because she's an expert at PLAYING tennis even though she doesn't build tennis rackets. You can know all the theory but if you can't tell when a tweek sounds/feels better than it did before then achieving stellar tone will be difficult. Guitar amps with great distortion break a lot of the 'old school' rules. Knowing the theory surely doesn't hurt (and I have no idea how much theory MC or any of the other highly sought after builders do) but imo just knowing old school theory doesn't = awesome tone. For years I read how higher plate loads was bad, bad, bad but here we are with 330k+ plate loads sounding just dandy. Just something to keep in mind and all just my stinkin opinion. :)
Click to expand...

My view is that you should know the rules before you start breaking the rules. A basic understanding of electronics is essential to go beyond building clones.

MC rips on the guitar and his amps also rip from what I can tell. But that shouldn't stop anyone from gathering info from the available sources.

BTW - Bruce Egnater is a guru who makes killer amps (including all of the Synergy modules, regardless of the name on them). But does he rip on the guitar? Dunno.
Click to expand...

Bruce makes some cool stuff and he definitely knows his stuff, but I’ve never played an egnator or module that feels like a Cameron amp. ;)
 
Ok I hooked up a 250K pot (all I have at the moment) from Gain 1 wiper to ground. I guess this is the "Feel" control you see in Fortin Cali mods. It's an interesting effect. But I don't understand how it's any different from just turning the gain control down? You're basically just shunting signal to ground, right? Seems to sound the same if I just turn the gain down a bit. Sort of. Close, but not exactly the same I guess.

Lower values = less signal. Less distortion. Tighter response. Less saturation. Less bass.
Higher values = more signal. More distortion. Looser response. More saturation. More bass.

I can get the amp to sound pretty angry with about 82K - 200K. Lower than 82K (like Fortin's use of 68K) and the amp is too stiff and you lose a lot of saturation. Compensating by switching in 5v transistors (like Fortin does) brings back the compression and saturation. Then push the volume up a bit and presto: You've got yourself some Swedish Death Metal. I don't play 8 strings tuned to Drop Z, though. But I can tell the use of 68K here really keeps things bright and tight.

The Chupa's stock 82K is a good value. But upping it to 150K or even 250K brings back the thickness and bass response for standard or Drop D tuning. I haven't tried higher than 250K because that's the pot I used. I can hook up a 1M pot another time and give it a try.

But at what point does the resistance get so high that it has no effect? Eventually it will be higher than the resistance of the stage it's feeding and the signal will ignore the pot completely. I guess that would take into account the grid resistor. In this particular amp, it's 150K. How can I determine the threshold value?
 
The answer depends in part on the setting of Gain 1, because the resistor is in series with the shunt portion of that pot. So when Gain 1 is at max, you have 1M to ground in parallel with the additional resistor. If that R was 1M, then you have 500k to ground. That seems like a big drop, but it doesn't coincide with a 50% reduction in perceived volume. When the additional R is only 82k, the total shunt R is about 76k, which makes a big difference in volume and in the corner frequency of the high-pass filter formed by the coupling cap and the resistive load.
 
It simply changes the impedance of the pot. I personally don’t like this since it makes the tone weird. I read the technical posts on SLO forum... ;)
 
psychodave":1w2jk8cc said:
It simply changes the impedance of the pot. I personally don’t like this since it makes the tone weird. I read the technical posts on SLO forum... ;)
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Eh?

I like it. Tightens up the amp. Brings out the snarl. 68K is too low for standard/drop d though.
 
FourT6and2":1qeksvuc said:
psychodave":1qeksvuc said:
It simply changes the impedance of the pot. I personally don’t like this since it makes the tone weird. I read the technical posts on SLO forum... ;)
Click to expand...

Eh?

I like it. Tightens up the amp. Brings out the snarl. 68K is too low for standard/drop d though.
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Years ago Mike and I were chatting about this and I ended up putting it on my BE clone. It definitely makes the amp tighter. I know people also throw a resistor across the gain lots on stock JCM800’s to change the pots impedance and tighten up the amp. I remember talking to Cameron about this and we both agreed it chokes the amp in a way I never care for. I’ll try find a video I made of that amp. I seem to remember turning that “feel” pot I had added.
 
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