Interesting. I'm not a huge fan of JJ pre's except for in Marshall's. 803 in the pi huh? I have a couple and will try it. I don't want to cut gain really. I want the od channel to have more mids and less top end fizz. I'm thinking lowering the nfb r54 from 100k to 47k-75k should do the trick. That's easy enough to do first
DSL20hr clean channel?
- Thread starter Parkerx02
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So I put put a Tung Sol in v1, JJ ecc83 gold pin in v2 and JJ 803 gold pin and the amp def sounds better. I usually favor Chinese 12ax7's and don't favor Tung Sol's or the JJ 803 that I've had forever. I think i finally found a home for them
So R52 control mids and bass? What about R45 and R53?
"If you want to increase mids, increase R52. If you want to reduce bass, reduce R52."
Oops. I said above that that R53 controls the bass, then goofed on the sentence you quoted. Reduce R53 to reduce bass.
The clean channel sounds great with the volume way up and the gain way down since the 1000p treble cap is filtering out bass. I'm thinking dropping c29 to 2n2 from 22n should help cut bass and also the 27k slope seems really low and bassy. The dsl40 has a 100k slope resistor so i bet changing r44 from 27k to 47k-100k would cut bass and some mids. What you think?
My very favorite DSL20 mod, which I've also done on my DSL1, is to remove R97 ( R75 on the DSL1 ). That turns the tone shift button into simply a treble cap selector switch. I also changed the treble caps to 470pf and 560pf so that the tone shift switches between 470pf and 255pf (the tone shift puts the two caps in series when pushed in ). I went from never using the tone shift to using it all the time. I see I'm currently playing them with the button pushed in which would be the 255pf treble cap. I've modded the rest of the tone stack too but that's my favorite mod. So far as the clean channel, I never use it so I haven't modded mine. But for me I would start by lifting a leg of R44, C28 and C29 and jumpering across the whole thing straight to the clean gain pot. Bypass that whole mess and see if I can get my tone thru the downstream tone stack. I'd start there first.
That's exactly what my plan is, remove r97 change the treble caps to 470p and 560p. I also want to remove r92 over the treble pot to bring the pot value back up to the 250k. The mid pot is only 10k for some reason. I am running my mids on 10, so I've ordered a 20k mid pot to install like the big DSL and most other amps have. Weird how the tone shift button doesn't affect the slope resistor like on the big DSL. On my TSL100, I modded the tone stack to not affect the treble or mids, only to bring the slope resistor from 33k to 47k. It's a great mod and makes the tone shift much more usable. I would like to do that with the 20hr, but would have to get crafty a lil and these boards are so fragile and hard to work on. Even my TSL100's board sucks. I'm pretty decent at modding and always end up putting new components back in point to point because the solder pads or traces get crappy. And with the clean channel... the slope resistor at 27k sounds really fat and would think a 100k like on the DSL40 would be better. I'm also thinking about scrapping the whole clean tone stack and wiring in the typical 22n to 470k/470p combo. I bet that would sound great. Should clean up good since clean only has 2 gain stages and should get a lil crunch with the gain up. Thanks for the reply!
@Parkerx02 yes I also removed R92. It's a lot easier to find your tone when the treble pot works normally. I also changed C24 and C33 to 22n each. I experimented with the tone slope resistor (R16) but in the end reverted back to the 39K it came with. That's a matter of taste as is all of this. I experimented with so many mods on my DSL20 that I got to where I could go from it being all put together in the cabinet to having the main board out in less than 15 minutes. I found youtube vids on repairing traces and pads....because I had to. I absolutely love the red channel on my DSL20HR now.
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My r16 slope resistor is stock and 33k, yet the schematic says 39k. What all mods have you done? Once i get the 20k mid pot, I'm going to tear into mine.
@Parkerx02 looking back at my notes my R16 was also 33K which is what I put it back to. What else did I do? I changed R8 to 470K, put a .68u cap in C20, changed R28 to 18K, changed R29 to 470K, removed C21 and my C95 was 470pf which I changed to 220pf. Overall that increased red channel gain and brightened it up though it doesn't hit the 4th stage as hard. Then I reduced the treble sizzle by redoing TR3's circuit. I simplified it to like how it's done in the DSL1 and used a 130pf cap for the miller cap. All that was a lot of experimenting but now it's almost as rocking as my EVH LBX. But not as noisy. It's my favorite amp.
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Nice! I got the 20k mid pot in the mail so now i just need time to dig into it. How did u mod tr3's circuit? What 130p Miller cap? I've heard of grid block resistors being used to knock treble down from the Miller effect, but haven't heard of a Miller cap
@Parkerx02 take a look at a DSL1 schematic. It has the same MPSA44 transistor amp after the DFX IC but without the buffer in front of it that the DSL20 has. In the DSL1 circuit C99 at 68pf is the Miller Cap and sets it's highs. The bigger the cap the less highs. The DSL20 does a more complicated circuit. I simplified mine to the same as the DSL1 circuit to make it easy to experiment with the Miller cap and settled on 130pf, which after brightening up the pre amp was perfect for me.
Ok, thanks. I will try to find a dsl1 schematic. I get all the things you changed and the effect. What made you change r28? 10k is the typical Marshall value. 18k is halfway to Soldano value. I bet 18k is great there. I have a Jet City 50h that I modded more to Marshall specs yet I took the 39k cold clipper to 22k, not far from your value.
@Parkerx02 I wanted to drop the gain there. It was sounding a little harsh with the gain dimed. An online gain calculator shows a gain of about 10db with the 8.2k resistor, about 5db with 18k. Cutting the gain in that stage about in half. And making it more asymmetric at the same time. It really helps to my ear. Sounds great.
The schematic says 8.2k, but mine actually has a 10k cold clipper. Urs was 8.2k tho huh? The 10k cold clipper definitely can be harsh
Holy shit! I made this lil beast way better. The tone stack got R92 and R97 removed, 10k mid pot got replaced with a 20k pot, C12 to 470p, C15 to 560p and C33 to 22n. Gain channel got R8 to 470k. Clean channel got R44 to 100k, C36 to 22n, R52 to 10k and C30 got snipped out. This thing has a bunch more mids now, the tone shift button only effects the treble, goes from 470p with the switch out to 250p with switch in. The switch is super useable now. The big thing is how the clean channel is. Before, the only way that wasn't mud city was to have the volume on max and gain super low. The big 1000p treble cap was saving it at that point. The 27k tone stack resistor was way too much bass and mids and R52 and C36 made it worse. Fender and even the dsl40 I believe use a 100k tone stack resistor, so why did the 20hr get a 27k?? Anyway... clean channel now is usable at any volume and any gain setting. I had the volume on 1 and then 2 and with the gain on low, its stupid clean, halfway up, its still really clean, but has a lil grit, gain full up has some grit but not a ton due to only having 2 gain stages. I just got it together so haven't messed with it a ton, but bet the clean channel will take od's or distortion pedals as well as chorus and delay like a champ. The clean channel was terrible to my ears before, and now its pretty great for sure.
imperialpint
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Newbie here. 
I've done bypass cap mods and other simple tweaks on older Marshalls.
What about modding the DSL20 Clean channel to have more gain? Like the Crunch mode on the Clean channel on the DSL40C.
Is there a place in that pseudo tone stack before the Clean Gain pot on the DSL20 where adding something could increase the gain?
(Schematic clip attached; it's the same schematic from earlier in this thread, that says DSL15mkII at the bottom.)
Thanks for any ideas!
I've done bypass cap mods and other simple tweaks on older Marshalls.What about modding the DSL20 Clean channel to have more gain? Like the Crunch mode on the Clean channel on the DSL40C.
Is there a place in that pseudo tone stack before the Clean Gain pot on the DSL20 where adding something could increase the gain?
(Schematic clip attached; it's the same schematic from earlier in this thread, that says DSL15mkII at the bottom.)
Thanks for any ideas!
Attachments
Do you have any further impressions on the final result?
Do the gain characteristics you describe above hold up as the volume increases?
Are you able to share any sound clips?
I am similarly unimpressed with the clean channel on my dsl20, and the change in breakup as you increase the gain level as you describe above is spot on what I'd be looking for.
I agree, and will work on that later. I'm thinking a switch bypass the pseudo tone stack and in its place install the classic 470k/470p combo. It still wont have much gain since the clean channel doesn't have many gain stages, but should be more gain at least. I am for sure going to install pots in r45 and 53's locations to make the clean channel have adjustable bass and treble. I'm chipping away at this thing bit by bitNewbie here.
What about modding the DSL20 Clean channel to have more gain? Like the Crunch mode on the Clean channel on the DSL40C.
Is there a place in that pseudo tone stack before the Clean Gain pot on the DSL20 where adding something could increase the gain?
(Schematic clip attached; it's the same schematic from earlier in this thread, that says DSL15mkII at the bottom.)
Thanks for any ideas!
Ya, it holds up really well at volume. I'm still tweaking on the gain channel and as it sits, one tone setting is great for both channels(I hate when you have to readjust tone knobs when switching channels). If anything, the clean channel could use a tad more bass, and a tad less treble, but thats just me being anal. I am eventually going to install pots instead of r45 and r53 so the clean channel will have adjustable bass and treble and I'm going to try to add a switch to add more gain to the clean channel. Overall, this amp, especially the clean channel is night and day better than stock. I'm super happy with the clean and still working on the lead. I recently ditched the stock resonance gyrator for a conventional 1m pot/.0047. The amp doesn't have the swooshing noise in the background anymore
