upgrading a DSL 401?

John Phillips

Member
Messages
13,040
Speaker: Vintage 30

The stock one is quite weak-sounding and low-sensitivity, and the amp has a sort of 'hollow' midrange tone to it anyway. The V30 will cure both. You may be surprised how much bigger and more powerful it sounds with one.

Tubes: JJs. Their 12AX7s are very dark and midrangy, which is a good thing in that amp for the same reason as above. Their EL84s are robust and solid-sounding... also a good thing. Be careful though, some of the early 401s had chassis cut-outs for the power tubes which are too small to accept wide-bottle EL84s... DOH! :rolleyes:. If you don't want to open them out (which is tricky), you're probably best with EIs, which were fitted as stock I think. Hopefully yours is not one of these...

The other thing you should do is heatsink the bridge rectifier on the PCB. These have a habit of overheating and desoldering themselves... luckily it's easy to fix. You need to drill through the PCB (there's space between the traces) and fit a standard bolt-down heatsink onto it, making sure the rectifier is tight down against the PCB first. The often-recommended fix of fan cooling the chassis from the outside does almost nothing BTW, since the rectifier is thermally isolated from the chassis.
 

rockinlespaul

Member
Messages
3,854
Originally posted by John Phillips
Speaker: Vintage 30

The stock one is quite weak-sounding and low-sensitivity, and the amp has a sort of 'hollow' midrange tone to it anyway. The V30 will cure both. You may be surprised how much bigger and more powerful it sounds with one.

Tubes: JJs. Their 12AX7s are very dark and midrangy, which is a good thing in that amp for the same reason as above. Their EL84s are robust and solid-sounding... also a good thing. Be careful though, some of the early 401s had chassis cut-outs for the power tubes which are too small to accept wide-bottle EL84s... DOH! :rolleyes:. If you don't want to open them out (which is tricky), you're probably best with EIs, which were fitted as stock I think. Hopefully yours is not one of these...

The other thing you should do is heatsink the bridge rectifier on the PCB. These have a habit of overheating and desoldering themselves... luckily it's easy to fix. You need to drill through the PCB (there's space between the traces) and fit a standard bolt-down heatsink onto it, making sure the rectifier is tight down against the PCB first. The often-recommended fix of fan cooling the chassis from the outside does almost nothing BTW, since the rectifier is thermally isolated from the chassis.
Thank you for your reply! I've heard the EH tubes are good for these. Any thoughts? Also...this is a 2004 model. I'm hoping most of the bugs I hear about with these have been fixed by now.
Also...I understand this is a fixed bias? So no need to rebias after the new tubes? Is this true?
 

John Phillips

Member
Messages
13,040
I don't actually like EH tubes... seen too many bad ones, both pre and power. Some people like them though, so it just depends.

If it's a recent model the power tube cut-outs should be large enough. I'm not sure if they've cured the rectifier problem or not. I haven't seen inside a recent one though... so maybe they have (although the problem takes a while to develop anyway usually). I don't get to see too many very new Marshalls since they give a 3-year transferable warranty, and the shop I work for is not a Marshall dealer, so I tend not to see ones less than three years old.

It's a fixed-bias amp, yes - but this doen't mean it's not adjustable... major source of confusion. Fixed-bias amps are the ones that can be adjusted, if they're fitted with a trimmer to do it. I'm pretty sure it has a test point to make this easier.

('Fixed bias' means that the bias voltage is fixed by a separate circuit. 'Cathode bias' or 'self bias' means that it's set by the cathode current itself passing through a resistor - these are generally not adjustable.)
 

rockinlespaul

Member
Messages
3,854
Originally posted by John Phillips
I don't actually like EH tubes... seen too many bad ones, both pre and power. Some people like them though, so it just depends.

If it's a recent model the power tube cut-outs should be large enough. I'm not sure if they've cured the rectifier problem or not. I haven't seen inside a recent one though... so maybe they have (although the problem takes a while to develop anyway usually). I don't get to see too many very new Marshalls since they give a 3-year transferable warranty, and the shop I work for is not a Marshall dealer, so I tend not to see ones less than three years old.

It's a fixed-bias amp, yes - but this doen't mean it's not adjustable... major source of confusion. Fixed-bias amps are the ones that can be adjusted, if they're fitted with a trimmer to do it. I'm pretty sure it has a test point to make this easier.

('Fixed bias' means that the bias voltage is fixed by a separate circuit. 'Cathode bias' or 'self bias' means that it's set by the cathode current itself passing through a resistor - these are generally not adjustable.)
Again...thanks for the advice! BTW...it's a 5 year transferable warranty now! One more question if I may. I'm going to build a extension cab for this(had one for a JCM601 and it sounded way better IMHO)and was wondering about speakers...if I have two going, keeping in mind the wattage of the amp, what do you think about two greenbacks? Two V30's?
 

John Phillips

Member
Messages
13,040
I'd stick with the V30 or other speaker that will take 40+ watts for the combo - that way you can still use it on its own if you need.

Given that, I'd maybe go for a G12H-30 in the cab. These two sound very good together. A Greenback would work too, but it might be a bit overpowered by the V30.
 

rockinlespaul

Member
Messages
3,854
Originally posted by John Phillips
I'd stick with the V30 or other speaker that will take 40+ watts for the combo - that way you can still use it on its own if you need.

Given that, I'd maybe go for a G12H-30 in the cab. These two sound very good together. A Greenback would work too, but it might be a bit overpowered by the V30.
Any other info on these? Thank you sir!:dude
 

cap'n'crunch

Member
Messages
1,398
Theres some DSL401 topics over at:

www.marshallampforum.com/forum/

There's a few simple mods listed too. I did the effects loop mod so far. Since my DSL401 is my backup now I haven't got around to trying other things yet. I did use a Vintage30 closed back cab and it was a substantial improvement in tone. I really could'nt tell much diference between the stock EI EL84 and the JJ EL84's. However there is a difference between the EI preamp tubes and the JJ preamp tubes. Personally, I like the stock EI preamp tubes better then the JJ's. The EI's helped to retain the characteristic Marshall clank. The JJ pre's seemed to muffled for me. Your Mileage May Vary. Another discovery I made was that if you disconnect the reverb tank the reverb pot becomes another tone control. kind of another treble control which some people (not me) find useful.

Hope this helps
 

rockinlespaul

Member
Messages
3,854
Originally posted by cap'n'crunch
Theres some DSL401 topics over at:

www.marshallampforum.com/forum/

There's a few simple mods listed too. I did the effects loop mod so far. Since my DSL401 is my backup now I haven't got around to trying other things yet. I did use a Vintage30 closed back cab and it was a substantial improvement in tone. I really could'nt tell much diference between the stock EI EL84 and the JJ EL84's. However there is a difference between the EI preamp tubes and the JJ preamp tubes. Personally, I like the stock EI preamp tubes better then the JJ's. The EI's helped to retain the characteristic Marshall clank. The JJ pre's seemed to muffled for me. Your Mileage May Vary. Another discovery I made was that if you disconnect the reverb tank the reverb pot becomes another tone control. kind of another treble control which some people (not me) find useful.

Hope this helps
No kidding? Thanks man!:dude
 

Wakarusa

Member
Messages
1,459
I have two customers that are very pleased running Private Jacks in DSL401s.

Another trick is to rework the tone stack on the lead channel(s). The eq curve for these is much brighter than the clean channel tone stack. You can rework it so that the lead channel sounds more like the clean channel (just distorted) instead of the buzzy piercing thing it does naturally (IMHO).
 

Rock Johnson

Member
Messages
4,747
Gotta love resurrecting an old thread.


I called Marshall USA about the overheating problem my DSL 401 was having. Mine was built in March 2002, so it was before the well-documented mod to help cool the dang thing down.

Anyway, the Marshall rep gave me two mods to make, and they've *really* made a big difference in the tone:

Change R31 to 27k ohms
Change R36 to 33k ohms
Set bias to 550 millivolts.

It makes the amp much warmer and more vintage-sounding. Hope this helps.
 

NamaEnsou

Silver Supporting Member
Messages
7,056
Okay this thread has been dormant for a long time but it seems that a couple things I'm interested in possibly doing to my 401 are addressed right here, so...

I have two customers that are very pleased running Private Jacks in DSL401s.

Another trick is to rework the tone stack on the lead channel(s). The eq curve for these is much brighter than the clean channel tone stack. You can rework it so that the lead channel sounds more like the clean channel (just distorted) instead of the buzzy piercing thing it does naturally (IMHO).
By Private Jacks, does that mean the plugging in of bare plugs in the effects loop or is it something else?

Also how would I go about modding the lead channel tone stack to sound more like the clean channel?

...the Marshall rep gave me two mods to make, and they've *really* made a big difference in the tone:

Change R31 to 27k ohms
Change R36 to 33k ohms
Set bias to 550 millivolts.

It makes the amp much warmer and more vintage-sounding. Hope this helps.
Has anyone else tried this mod? "Warmer and more vintage-sounding" is a direction I'd like to go with mine.
 

jhc

Senior Member
Messages
12,528
Okay this thread has been dormant for a long time but it seems that a couple things I'm interested in possibly doing to my 401 are addressed right here, so...

By Private Jacks, does that mean the plugging in of bare plugs in the effects loop or is it something else?
Pretty sure it's a reference to these speakers.

Don't know about the other question.
 

NamaEnsou

Silver Supporting Member
Messages
7,056
Pretty sure it's a reference to these speakers.

Don't know about the other question.
Thanks for responding. I'd almost forgotten about having asked these questions because as I've been getting used to playing through an amp again this little Marshall has been steadily growing on me just as is.

I picked it up here from another member and while my Bad Cat sits in its cover in the corner the 401 has been going to gigs with me. Guess I should update my avatar...
 

jhc

Senior Member
Messages
12,528
Thanks for responding. I'd almost forgotten about having asked these questions because as I've been getting used to playing through an amp again this little Marshall has been steadily growing on me just as is.

I picked it up here from another member and while my Bad Cat sits in its cover in the corner the 401 has been going to gigs with me. Guess I should update my avatar...
There's not a lot of love for Marshall combos, but since I owned 4 or so of them (all ****** solid state or "hybrid") I've always been intrigued by them. I saw a Chicago bluesman kill with a JCM900 combo when I used to live there. If I had found a DSL 401 for $400 I probably would not have purchased my Traynor for $500, although in hindsight my amp is probably better for alt-country which is what I played when I actually gigged.

PS, if you ever want to just give away the Bad Cat... ;)
 

NamaEnsou

Silver Supporting Member
Messages
7,056
I'd love to give the Bad Cat away, but unfortunately I'm not financially secure enough to do things like that! LOL.

I really think that all of the Marshal's I've had, other than the one hybrid, played really well for me doing folk, country, pop, blues and rock.

I'm really loving my 401 at this point and wondering if it wasn't just needing to get acquainted with it that I' needed to do.

I used to really want a JCM900, until I tried the 401. Now my Bad Cat and Marshall 30th Anniversary have taken back seat to the cheapest amp I own!
 




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