een7gdr

Thanks MaidenStrat02!

What a glowing reference It is indeed a simple process, by isolating part of the FX loop circuit, you not only reduce the interference inside the IC but you are free to mount it in a much more electrically quite area of the amp.

For those who are interested, I have been performing some measurements on the FX loop with/without pedals to see whats happening at the higher volumes. This is still WIP but is on my website:

gsharp.co.uk - DSL FX Measurements

00jett

sweet, i cant wait till mine comes in

een7gdr

Yours was posted Monday, judging from MaidenStrats delivery you should get it early in the week. Of course if there are any problems, please get in touch.

00jett

so i got my mod in early this week. I was busy with work so after waiting a couple of days i finally installed. It was a very simple mod and i am very impressed with the results. my tone was back especially at the low volumes. It significantly reduced the hiss from my rack as well. Excellent job een7gdr!! Mod highly recommended for the dsl amps

carnada

Up the irons!

carnada

Its funny how the buyers of the amp need to make their own stuff to fix the amps lol Marshall should fix this problem.

solarburnDSL50

Yeah! I wanna kick Marshall in the shins.

__________________
DSL50 - FJA modded
Loaded with a Martimus Maximus Preamp Tube Stack
Power tubes 6CA7EH's

Strat HSS & Tele HH

Avatar 412 loaded with Greenbacks

Vox Night Train
Russian NOS 84's
Telefunken & RFT ECC83

carnada

so does the DSL actually have a lot of problems with the loop? I was saving to get one, but right now I dont know what to do!??

solarburnDSL50

The amp is awesome with or without the loop. I frick'n love mine. I never heard it had loop problems until here and finding as issue with mine at high volume recently. I need to check some things out. I just haven't got around to it.

een7gdr's mod is a pretty inexpensive fix if you ask me.

__________________
DSL50 - FJA modded
Loaded with a Martimus Maximus Preamp Tube Stack
Power tubes 6CA7EH's

Strat HSS & Tele HH

Avatar 412 loaded with Greenbacks

Vox Night Train
Russian NOS 84's
Telefunken & RFT ECC83

een7gdr

Thanks for the excellent reviews guys!

FWIW I love the DSL heads, ive heard mixed reports about the combos but the heads are great. Effects loops will always be a trade off in tube amps, especially when running stomp boxes through the loops. Im pretty sure theres loads of other amps out there that may well exhibit the problems ive mentioned with the DSL - unfortunatly i dont have the money/space/permission to buy them all and have a go!

If theres anyone out there that still wants one, I still have some boards left just PM me for details. For the moment Im just glad I could make the DSLs that little bit better! If anyone wants to lend me a TSL 100 ill glady try it out on that too!

carnada

do all the series of the DSL's have the loop problem? cuz some people said the new ones are better at the effects loop. Is that true?

een7gdr

Well, mines from 1997 and i had a 1998 some time ago with the same problem. Nobody has posted in this thread to say that their DSL head does not exhibit the problem. I would be interested to know if they fixed it on the newer models. AFAIK the newer models are electrically identical however there was talk about them moving to lead free solder - hence there was a period where very few DSL were being produced as the factory made the switch - however i doubt this would make any difference to the effects loop without a considerable change to the PCB layout.

Dont let this issue put you off the DSLs! The problem my mod fixes shows itself at quite low volumes but goes away as the volume increases. People are saying that the loop tends to suck a bit at higher volumes but this may be due to pedal choice as much as the amp itself - i am still trying to look into this. Does anyone know of an amp where people really rate the FX loop?

MaidenStrat02

My DSL50 is a '07 and I put in the kit as you all know. I'll also add that the DSL's are freakin awesome amps and are worth the small hassle here and there. No amp is perfect and I'm sure if you look on forums for different brands they will have their glitches too.

__________________
Gibson '07 SG
2 Customized Fender Strats
Modded DSL50 MM choke,PT&OT
Carvin 2x12 V30's
Pitchblack-LPB-1-Budda Wah-TS808. Loop= 108EQ-Modded Phase 90-Carbon Copy-George L cables-Voodoo Pedal Power 2 Plus-Pedaltrain board

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jcmjmp

Just wondering if the original poster tried two things to minimize x-talk in the RC4558 dual op amp.

1) Texas Instruments recommends the use of 0.1uf ceramic bypass caps on the power supply to reduce x-talk.
2) Install a better op amp for x-talk rejection and noise. The AD708 seems to be an excellent choice. (The RC4558 is not exactly the best op amp out there for use as a buffer)

I don't seem to have this problem on my amp so it may be due to different op amps used in production or different board versions or maybe I just don't play at low enough volumes to even notice this.

I'll check my amp out and see if I can reproduce this "issue" and try a couple of the simpler options.

een7gdr

I did try both adding capacitors direct across the +/- rails and also split from + GND - neither helped. I also tried some other pin compatible OP-AMPs some from the NE range and some from the OPA range - neither helped.

It might not be cross-talk between the circuit but actually into the signal wires and pins due to the very high impedance nature of the circuit. The mod allows the circuit to be moved to a less noisy area of the board and in fact if it is held close to some areas of the PCB it actually increases the cross-talk. This is why on my install notes i specify the best place for the install to minimise noise.

Thanks everyone for the input!

jcmjmp

Did you try an LM158? The x-talk rejection is much better in those chips - 120db vs 85db in the RC4558.

For the bypass caps to work well, they must be right on the pins of the chip (or very close). Putting the caps on the supply rails is not enough.

een7gdr

I did not try that chip however one of the chips had a similar rating. I thought the signal injection was initially due to the cross talk within the IC, however I now believe it is a simple capacitive coupling into the IC and component legs used around that area. The bypass capacitors were soldered for testing on the underside of the PCB onto the IC legs. I thought i had tried everything at the time in the hope it wouldnt require a seperate circuit mod!

While I was at it, I also tried to see if the other ICs reduced noise or sounded better but in all honesty they sounded very much alike. This mod seems to reduce hiss a little but i believe thats a result of better/closer power filtering.

MaidenStrat02

I just have to go on record again saying that this cheap mod is ABSOLUTELY worth the time to install it. Before I bought it I could always hear my guitar even when the volume was at zero on both the amp and guitar. I would strum a chord and be able to hear it through the cab. Once I put in the simple mod (one soldering point) it was all gone! Not a big deal to some maybe but to me it was just plain awesome. My thanks again to you.

__________________
Gibson '07 SG
2 Customized Fender Strats
Modded DSL50 MM choke,PT&OT
Carvin 2x12 V30's
Pitchblack-LPB-1-Budda Wah-TS808. Loop= 108EQ-Modded Phase 90-Carbon Copy-George L cables-Voodoo Pedal Power 2 Plus-Pedaltrain board

Contact for Facebook request