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Author Topic: NDIYAD - New DIY Amp Day  (Read 8121 times)

Dmoney

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Re: NDIYAD - New DIY Amp Day
« Reply #15 on: September 11, 2011, 10:04:56 PM »
Ok.

This is now definitely done...
cleaned up some of the wiring... and settled on it as a 50watt JCM800 power stage with a Soldano X88r Crunch Channel as the preamp, with a couple of changes in component values.

One thing I added is a switch which puts a 47K to ground as per the little schematic I've attached.

With the 47K off ground, the amp has this warm fuzzyness (but not too fuzzy) to it which has this rounded kind of breakup. It sounds really nice. It's basically as per the first youtube clip but with a bit more gain/saturation available.

With the 47K switched to ground, some of the low end drops out and some of the fuzz quality too. To me it sounds more clear and modern.

any thoughts on this? I stole this idea and I'm not 100% sure what is going on to have the effect it's having. If anyone can explain it a little bit I'd be grateful.

HTH AMPS

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Re: NDIYAD - New DIY Amp Day
« Reply #16 on: September 11, 2011, 11:48:52 PM »

FJA's noise gate mod is exactly that. The Peavey circuit, that is. FJA only solders his into the lead channel, while I have it elsewhere in shared circuitry because I have no clean channel to be affected negatively. I lifted it from the XXX, but the JSX has the same thing except with a pot instead of a static resistor. It's a three component circuit. I can look it up later, but I'm just home for a change of clothes and I'm going back out.


so (from memory) is it just a 1M pot with back-to-back diodes ????

I'd like to see this too.


HTH AMPS

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Re: NDIYAD - New DIY Amp Day
« Reply #17 on: September 12, 2011, 12:05:51 AM »
Ok.

This is now definitely done...
cleaned up some of the wiring... and settled on it as a 50watt JCM800 power stage with a Soldano X88r Crunch Channel as the preamp, with a couple of changes in component values.

One thing I added is a switch which puts a 47K to ground as per the little schematic I've attached.

With the 47K off ground, the amp has this warm fuzzyness (but not too fuzzy) to it which has this rounded kind of breakup. It sounds really nice. It's basically as per the first youtube clip but with a bit more gain/saturation available.

With the 47K switched to ground, some of the low end drops out and some of the fuzz quality too. To me it sounds more clear and modern.

any thoughts on this? I stole this idea and I'm not 100% sure what is going on to have the effect it's having. If anyone can explain it a little bit I'd be grateful.

afaik it's just a high-pass RC filter, which is why you're getting less low end with it switched in. 



JacksonRR

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Re: NDIYAD - New DIY Amp Day
« Reply #18 on: September 12, 2011, 04:01:39 AM »

FJA's noise gate mod is exactly that. The Peavey circuit, that is. FJA only solders his into the lead channel, while I have it elsewhere in shared circuitry because I have no clean channel to be affected negatively. I lifted it from the XXX, but the JSX has the same thing except with a pot instead of a static resistor. It's a three component circuit. I can look it up later, but I'm just home for a change of clothes and I'm going back out.


so (from memory) is it just a 1M pot with back-to-back diodes ????

I'd like to see this too.



Yeah. A 1M pot or resistor and two 1N4148 diodes, all in parallel. The diodes do indeed face opposite directions. In the XXX schematic, this little circuit is located right after the coupling cap between the 3rd and 4th gain stages. I don't have the JSX scheme on hand and can't remember where it is in that pre.

I'm going to give that 47K trick a shot tomorrow as I'm off. I just can't see having more options as a bad thing if implemented correctly.
I don't have quick access to a six-position rotary switch, but I'll also experiment with some of the values in Lee Jackson's mid-boost thing. I'm gonna hit post right now, but I'll edit in a quick scheme of that once I actually do it in a couple mins. It'll look like cr@p, but you guys should be able to read it.


Just stuck it on a tone stack I got from Google as that was the easy way out, but that's it. Everything past the previous stages Co is there, your stack may differ. I wonder what the 10M resistor is for.... Maybe to keep the caps from popping?

« Last Edit: September 12, 2011, 04:26:01 AM by JacksonRR »

Dmoney

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Re: NDIYAD - New DIY Amp Day
« Reply #19 on: September 12, 2011, 08:17:38 AM »
Ok.

This is now definitely done...
cleaned up some of the wiring... and settled on it as a 50watt JCM800 power stage with a Soldano X88r Crunch Channel as the preamp, with a couple of changes in component values.

One thing I added is a switch which puts a 47K to ground as per the little schematic I've attached.

With the 47K off ground, the amp has this warm fuzzyness (but not too fuzzy) to it which has this rounded kind of breakup. It sounds really nice. It's basically as per the first youtube clip but with a bit more gain/saturation available.

With the 47K switched to ground, some of the low end drops out and some of the fuzz quality too. To me it sounds more clear and modern.

any thoughts on this? I stole this idea and I'm not 100% sure what is going on to have the effect it's having. If anyone can explain it a little bit I'd be grateful.

afaik it's just a high-pass RC filter, which is why you're getting less low end with it switched in. 




ah ah! That confirms my suspicions. I think after I got into bed I thought it might be something simple like that and that I was over thinking it. So I guess the change in how the distortion feels is down to having less low end frequencies being distorted at all, since they are getting filtered off right after the first stage, and this is making the rest of the signal come out clearer.

cheers for the info Jackson, I'll check out the xxx/jsx stuff too!


HTH AMPS

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Re: NDIYAD - New DIY Amp Day
« Reply #20 on: September 12, 2011, 10:31:14 AM »

FJA's noise gate mod is exactly that. The Peavey circuit, that is. FJA only solders his into the lead channel, while I have it elsewhere in shared circuitry because I have no clean channel to be affected negatively. I lifted it from the XXX, but the JSX has the same thing except with a pot instead of a static resistor. It's a three component circuit. I can look it up later, but I'm just home for a change of clothes and I'm going back out.


so (from memory) is it just a 1M pot with back-to-back diodes ????

I'd like to see this too.



Yeah. A 1M pot or resistor and two 1N4148 diodes, all in parallel. The diodes do indeed face opposite directions. In the XXX schematic, this little circuit is located right after the coupling cap between the 3rd and 4th gain stages. I don't have the JSX scheme on hand and can't remember where it is in that pre.

I'm going to give that 47K trick a shot tomorrow as I'm off. I just can't see having more options as a bad thing if implemented correctly.
I don't have quick access to a six-position rotary switch, but I'll also experiment with some of the values in Lee Jackson's mid-boost thing. I'm gonna hit post right now, but I'll edit in a quick scheme of that once I actually do it in a couple mins. It'll look like cr@p, but you guys should be able to read it.


Just stuck it on a tone stack I got from Google as that was the easy way out, but that's it. Everything past the previous stages Co is there, your stack may differ. I wonder what the 10M resistor is for.... Maybe to keep the caps from popping?



yep, the 10M resistor IS just to stop the caps popping, but I'd have it on the switch side of the cap.


JacksonRR

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Re: NDIYAD - New DIY Amp Day
« Reply #21 on: September 12, 2011, 04:41:21 PM »
Cheers HTH! Every once in a while I actually think correctly, sort of.

JacksonRR

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Re: NDIYAD - New DIY Amp Day
« Reply #22 on: September 12, 2011, 11:27:24 PM »
Well Dmoney's mod up there is going to stay in my 2nd lead/crunch channel. I purposefully left that channel bassier and looser than the original lead for some contrast and now I have something even better..... I CAN GO TIGHTER THAN THE ORIGINAL LEAD!! Oh man.... it's a good day. 3 high gain sounds/responses and they are all usable and different. One's sorta loose with a chewy midrange, one's real djenty/mechanical and the original lead is a souped up 5150 sound with some ENGL tricks mixed in.

The Lee Jackson mid-boost is a near success. I only tried a 0.0047uF and a 0.001uF and each did basically the same thing with different frequencies boosted made it go from modern to nothin but 80's and with more volume. I had to take it down 2 notches to get the level the same. I'm thinking if I can get it to switch on with the second lead, we'll be in solo heaven. I do have an unused part of a relay in there so it's totally doable if I move some things around.


You guys think it's worth the hassle to install an SS loop and use that tube for a clean channel?

Dmoney

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Re: NDIYAD - New DIY Amp Day
« Reply #23 on: October 09, 2011, 05:43:42 AM »
Jackson RR
I was just wondering how the lee jackson stack works along side the depth control in the 5150? does it ever get super super bright and unstable or way too bassy?