The dsl joey mod thread

[Jason77]

Well this is interesting. My schem says 220k for r38. I'll have to take a look inside the amp tomorrow and see what's actually there.

 

[rockgod212]

look on the mainbord for links 4 and 5, they should be by the phase inverter circuitry........see if you have them and let me know what R38 is......

Well this is interesting. My schem says 220k for r38. I'll have to take a look inside the amp tomorrow and see what's actually there.

 

[Jason77]

I'm looking inside the amp now and this is what I've got:

r38 = 470k

r4 and r5 = links

 

[rockgod212]

cool thanx for the info......

i ended up leaving r38=470k stock, but i added a on/off/on switch to add another 470k or 1m over it.....adds a bit more volume, slightly different tonal texture to it...i like it.....

 

[rockgod212]

here something i understand.......on the potboard.....
why did marshall use a 220n from the mid pot to ground?
i just jumped it with a wire and oh my god did it open up the tone stack, it gave the amp its growl back......try it and let me know what you think of it...

 

[Jason77]

Wow, I never really noticed that. I'll definitely try jumping it and see what it sounds like.

 

[rockgod212]

its c24 on the pot board......i couldnt believe it.......all the classic marshall mids came back......its those mids that make the marshall growl famous....

 

[Jason77]

For the hell of it, I looked at the TSL schematic (since they're related) to compare, but that cap doesn't exist in the TSL. Odd.

 

[mickeydg5]

As for that R38 470K on the main PCB, I tinkered with that myself quite some time ago. I found that lowering the value made my already too loud DSL even louder and harder to get into that "sweet spot" at a decent lower volume. And it made the amp become unstable. I think that is the reason it is there...

I was thinking about putting a pot there to act as an overall master volume. But I do not really feel like drilling any holes in my chassis at this time.

That is what I was waiting to hear. It is overkill and Marshall most likely settled at 470k being the best for all worlds (settings) for the loop and downstream stages.

 

[mickeydg5]

here something i understand.......on the potboard.....
why did marshall use a 220n from the mid pot to ground?
i just jumped it with a wire and oh my god did it open up the tone stack, it gave the amp its growl back......try it and let me know what you think of it...

I was wondering if someone was going to pick up on this component.
The thing is can you get the same tone by tweaking controls?
And, did you loose any bottom end control by bypassing the 220nF (C24)?

 

[RickyLee]

I was wondering if someone was going to pick up on this component.
The thing is can you get the same tone by tweaking controls?
And, did you loose any bottom end control by bypassing the 220nF (C24)?

Yeah, that C24 is breaking the usual tonestack to Ground/Negative connection and bleeding/passing frequencies to Ground.

I put a 100K midrange pot in my DSL which gave me all the mids I would ever want LOL. But I would rather have a 50K pot which they do not make in those Korg style pots.

My DSL has too much bottom end with that 100K mid pot. Well, actually I should say I lost some of the Bass pot ability to turn the Bass down. That is more of a correct observation.

I guess I could try putting my stock mid pot back in and put a small 20K trim pot in place of that C24.

EDIT: Or you could put a switch in place of C24 for a Boost function of lifting the tonestack Ground. BUT that might not work in this circuit as there's already quite a bit of AC signal gain going through this circuit.

 

[mickeydg5]

Yes, too large of a midrange pot will affect the bass control.

The 220nF C4 is there to aid in preserving bass frequency and control. It is a low pass filter component and sets the cutoff for low frequency attenuation.

 

[Jason77]

(nevermind this post. just saw Mickey's post, which answered my question)

 

[rockgod212]

my amp is anything but stock, so i prefer c24 bypassed- i didnt lose any lowend or nothing like that....in fact it improved the tonal response for my amp......so for me it works.....the only part of my amp that is solid state is the deep switch which sounds better now that i put a 4n7 in line with
the 47k nfb.....

 

[mickeydg5]

I told Ricky this earlier. I think it applies here too as well as lots of other places.

The thing with a lot of design and tinkering is that there is give and take. As long as you are happy with the results and it all works well together, what more can you ask for?
Do not answer that.

 

[rockgod212]

 

[Jason77]

OK, I jumped c24 and i do like it better that way. Its subtle, but it does have a little more bark.

While i was in there on the pot board, I also changed r12 to 100k to get a little more out of the crunch mode and changed r2 to 33k to bring back some mids to the clean.

 

[rockgod212]

i thought those who tried it would like it.........i feel it makes the tone controls much more responsive and interactive......

next up is to replace all the pots with regular mini pots using fly leads.....ill leave the reverb pots to hold the board up, but when i did the red gain pot the old one measured 800k, so out of spec they are.....they get stuck, so time to replace them with correct value pots....

OK, I jumped c24 and i do like it better that way. Its subtle, but it does have a little more bark.

While i was in there on the pot board, I also changed r12 to 100k to get a little more out of the crunch mode and changed r2 to 33k to bring back some mids to the clean.

 

[RickyLee]

I have my DSL opened up again. It was not sounding like I thought it should last time I played it. Probably due to me playing through that Bandmaster I have been tinkering on.



I just took some measurements, and I am getting continuity to the metal chassis on both ends of that C24.



I replaced a couple of preamp valves and it is sounding a bit better now. I was hearing some extreme spikey treble coming through on all channels, which is odd. This thing has been more bottom end heavy than all my other amps.

I am thinking about either putting the stock mid pot back in as I have a 100K in there now. Or I am going to see if I can put a resistor on one leg of this 100K mid pot to make it react like a 50K pot.

Figuring I will try a 50K resistor from the wiper to Ground. As the way I am seeing this tonestack, whatever value mid pot is used, keeps that value between the tonestack and Ground at all times regardless of the mid pot setting. Where a Fender type tonestack is set up to put the tonestack entire mid pot value to Ground when its mid pot is at 0.

If I am incorrect here, someone let me know please.

 

[RickyLee]

I have my DSL opened up again. It was not sounding like I thought it should last time I played it. Probably due to me playing through that Bandmaster I have been tinkering on.



I just took some measurements, and I am getting continuity to the metal chassis on both ends of that C24.



I replaced a couple of preamp valves and it is sounding a bit better now. I was hearing some extreme spikey treble coming through on all channels, which is odd. This thing has been more bottom end heavy than all my other amps.

I am thinking about either putting the stock mid pot back in as I have a 100K in there now. Or I am going to see if I can put a resistor on one leg of this 100K mid pot to make it react like a 50K pot.

Figuring I will try a 50K resistor from the wiper to Ground. As the way I am seeing this tonestack, whatever value mid pot is used, keeps that value between the tonestack and Ground at all times regardless of the mid pot setting. Where a Fender type tonestack is set up to put the tonestack entire mid pot value to Ground when its mid pot is at 0.

If I am incorrect here, someone let me know please.

Strange. Jumpering C24 makes no change in my amp, so I was reading it correctly - seeing Ground continuity on both ends of that cap. I guess I should lift my PCB to see if it was jumpered already.

And the tinkering with a resistor to lower my mid pot value from 100K only allows me to get an absolute zero Bass setting. Having the mid pot at 100K just makes the lower range of the Bass control inoperative.