DSL40C Tone Bleeding between Channels

Henry Sabbath

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Hi everyone.. Thanks for having me in this community....

I´ve come across an issue with the Dsl40C that will like to know if anyone has experienced same issue as me...

I have a DSl40C from 2015 from a trade a little longer than 1 year an a half ago. Long story short, it needed a new power transformer as it was made for the american market with a 110-120 v tranny. As I´m from Spain, got a new original Marshall replacement PT from Tube amp Doctor in Germany that I pressume belongs to the latest DSL40C HR version as direct replacement. Nothing to worry about, just getting u into context.

Replace all tubes/valves as they where quite wasted and had inner rattling issues within power tubes and a blown preamp tube from the cathode follower... So I got some TAD el34bstr on the power section, V1 7025 TAD, V2 and V3 run of the mill chinesse shuaguang 12ax7 and on V4 an EHX 12ax7 lps... adjusted Bias settings on 36 Ma per tube...

Did perform C19 mod, which for me it´s a "Must do" situation, as I play Low tuned Sabbath- Hard Rock and Thrash styles... suits better to my ears and it´s a long debated mod...

Did convert the combo into a head and cabinet configuration and I´m quite happy with the amp for rehersals and small club gigs...

I´m quite picky about tone coloration and can tell the difference between minimal setting diferrences in amps, pedals and whatnot... So I have come across an issue between channels...
To begin with any switch on the front panel interacts between the channel not being used.. let me explain... if you are on the ultra channel and engage the clean/crunch switch from the classic gain channel, you will get a quite subtle increase in gain on your ultra channel, like having 1 more half gain stage of some sort...
also if you have your footswitch connected and engage the front panel channel switch you will notice another subtle increase of gain structure... so as it is one channel amp with different modes..it does bleed gain and cloration in more or less amount to your ultra channel...
And Again, if you have a patch cable in your loop effects engage or not, you will notice gain increase and tone coloration in a good way...

Now, this is more or less normal in many models and manufacturers as I have come across this issue through the years (I worked as a Music Merchant for 15 years and been at Namm and factory tours from various big brands)..

But the Issue here is that whenever you switch channels between classic and Ultra channel is that the tone gets some how shaped and losses low end on the ultra channel, but if you engage back to clean channel and straight back to ultra channel, the tone gets restored and gets back that low end and slight gain increase... So it happens on the follwing pattern:

1- fire up your amp on classic channel..
2- switch to ultra channel.. and will sound thick, tight and rich harmonics (good tone)
3- switch to classic channel back again
4- switch again back to ultra channel and you will notice that the tone has decrease in gain, low end ,thicknes..and a bit nasal sounding with shaped mids.. (bad tone)
5- switch back to classic quickly.. and..
6- switch into ultra channel and you get back to number 2 (good tone), restored gain, tone and harmonics... and so forth if you keep doing the operation as described..

So there is some bleeding tone issues between channels so it does not return to the same tone characteristics when you switch between channels, like some relay or transistor getting funny and not letting pass through the signal with the same properties.. or some sort of signal trace loss somewhere in the circuit..

Has anyone come across this issue or check it if does behave like mine????

thanks for your time and Crank up your DSL!!!
 
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Henry Sabbath

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Have in mind that a Boss SD-1 is engaged always when I say "tight, thick and rich harmonics"... We all Know that Ultra channel is muddy and loose without overdrive pedals slamming the front end....

cheers..
 
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tallcoolone

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Damn, sounds like that amp has been used hard and put away wet lol. Transformer replacement, board alterations AND a combo to head conversion? That’s an import/low end amp, at this point I’d dump it and start fresh with a non combo DSL.
 

tallcoolone

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Have in mind that a Boss SD-1 is engaged always when I say "tight, thick and rich harmonics"... We all Know that Ultra channel is muddy and loose without overdrive pedals slamming the front end....

cheers..
Depends on how you are setting your OD too—no gain, tone and levels up
 

Henry Sabbath

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Damn, sounds like that amp has been used hard and put away wet lol. Transformer replacement, board alterations AND a combo to head conversion? That’s an import/low end amp, at this point I’d dump it and start fresh with a non combo DSL.

It hasn´t been used hard, just had a trade with an American Buddy living in southern Spain and its a DSL40C made in vietnam for American market, and instead of running the amp through a variac, I decided to swap the power transformer for 240 V for European countries. Easier and safer... drop in replacement..Got the amp from a really cheap trade as the man who traded was leaving Spain and didnt want to take it back to the states with him... So Did spend less than 100 dollars on the Tranny, so it hasn´t been a waste of time/money or anything like that... Got a fairly nice Marshall for little money, as what was traded in, was a guitar with no use or significant value at all...

There are no board alterations except for clipping the C19 bright cap out of the pcb... very well known mod across all Marshall line of amps... No burnt traces or any stress being given to the amp...

It is made in Vietnam, don´t mind as it is well made... All current DSL family is made in Vietnam from quite some years ago already...

The main reason for converting it into a head format and sealing the remaining cabinet for a closed back configuration, is for avoiding tube heat induced into the chasis and board as by design tubes where facing upsidedown, and avoid vibrations induced from the speaker as well, as we all know that the major maintenace problem in a long turn for a combo format, is heat and vibration causing the board to break its solder joints across the board.. Apart from tonal benefits as it sounds way better with a closed back cabinet... and looks way better as a head.... It´s a mini stack without being a lunchbox format...

Made the head shell from cheap laminated wood like a JCM format head-shell, so front panel layout is upsidedown right now, but who cares... instead of reading DSL40C it says LSD40C and everything printed at the front reads upsidedown... but I rather have it like that as many others out there, than baking the chassis and board + components in the long turn, cause as a combo it dissipates hell on the chassis and board.... EL34 run quite hot and you could fry an egg on that chassis after an hour of playing... had some left scrap pieces of fender tweed tolex laying around as spare tubes from a different project... so everything lined up for the project... did sprayed the tolex with matte black and seal the cabinet with the spare left pieces from the cheap wood blank used for the headshell...

So u can Dump the thing, and buy a new amp as you said, but for DIY nerdy people as me and with love for electronics, tubes and tone... we give second chances to a "overseas low end budget" amps that sounds way better than many other "hyped" brands....it reaps your head-off when plugged into a 4x12 Mesa boogie loaded with EV12" Speakers... With Different Consumer habits and nerdy-tweaking DIY fellas like me, as we hate obsolescence, love to give new life cycles to music devices and instruments... whatever floats anyones boat, good enough...
 
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tallcoolone

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While I can appreciate hating obsolescence your amp has already been this for years:

The main reason for converting it into a head format and sealing the remaining cabinet for a closed back configuration, is for avoiding tube heat induced into the chasis and board as by design tubes where facing upsidedown, and avoid vibrations induced from the speaker as well, as we all know that the major maintenace problem in a long turn for a combo format, is heat and vibration causing the board to break its solder joints across the board.. Apart from tonal benefits as it sounds way better with a closed back cabinet...

So while you getting it out of that (terrible IMO) combo format is prob long term good for the amp, all those aforementioned vibrations and heat have already taken a toll it sounds like. Not sure what things are like in Spain but here in the states I would just look to replace that with a $6-700 used DSL head.
 

Henry Sabbath

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While I can appreciate hating obsolescence your amp has already been this for years:



So while you getting it out of that (terrible IMO) combo format is prob long term good for the amp, all those aforementioned vibrations and heat have already taken a toll it sounds like. Not sure what things are like in Spain but here in the states I would just look to replace that with a $6-700 used DSL head.

Obsolescence comes with SMT technology for example, THD methods of manufacturing with thick modern pcb are long enduring and good to last many years, and replacement of a resistors, for example, and the rest of regular sized components will be always available.... and always reparable in some way or other at worst scenarios...

It´s been through the same toll as any combo out there being played at bedroom levels for 5 years at home very few hours per month.... So not a big deal, that does not mean its baked at all.... it needed a new set of tubes, like it could need any 5 year old tube amp, and the amp was mint new.... The tube failures where probably due to transport between the states and Spain, Europe, in US Army Vessels or Aeroplanes... same stress that any of your amps may have been through from any overseas or inland factory to your hands or whatever...

Just needed to trade in a cheap Spanish guitar with no use at all and no cost for me... plus the 110 dollars/Euros added on tranny and woodblank, I have a fairly nice Marshall amp for the collection, plus being experienced on electronics, woodwork, qualified sound tech, and nerdy DIY freak, do enjoy wasting time and money I guess..

I was just trying to share an issue with tone bleeding between channels... anyone out there?... Cheers..
 

Mitchell Pearrow

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Obsolescence comes with SMT technology for example, THD methods of manufacturing with thick modern pcb are long enduring and good to last many years, and replacement of a resistors, for example, and the rest of regular sized components will be always available.... and always reparable in some way or other at worst scenarios...

It´s been through the same toll as any combo out there being played at bedroom levels for 5 years at home very few hours per month.... So not a big deal, that does not mean its baked at all.... it needed a new set of tubes, like it could need any 5 year old tube amp, and the amp was mint new.... The tube failures where probably due to transport between the states and Spain, Europe, in US Army Vessels or Aeroplanes... same stress that any of your amps may have been through from any overseas or inland factory to your hands or whatever...

Just needed to trade in a cheap Spanish guitar with no use at all and no cost for me... plus the 110 dollars/Euros added on tranny and woodblank, I have a fairly nice Marshall amp for the collection, plus being experienced on electronics, woodwork, qualified sound tech, and nerdy DIY freak, do enjoy wasting time and money I guess..

I was just trying to share an issue with tone bleeding between channels... anyone out there?... Cheers..
I have a pair of Dsl40c’s, but they are not exhibiting the problems , of channel bleed.
I did try your experiment from your first post, but I am still not having any issues.
Cheers
Mitch
 

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