DSL 401 mods

[Chimp93]

Hi all,

New to the forum and amp building/modifying, firstly any good books/resources/starting points that you guys would recommend? As a second year Electrical and electronic engineering student I was hoping for something aimed at both a full rundown of guitar amps/mods from both an engineering view and a tone hunter/guitarist view.

Secondly and mainly I have a marshall DSL401 that was my first tube amp that I can't let go of. I don't mind the base tone(but liking it less and less) but thought I'd as if anyone new any good mods. I have done the 12dw7 in V2 mod which I thought was a huge improvement over the stock sound. Also I hear changing the speaker will do wonders(Is this worth it). Basically I'm going to be using it as my first amp modifying/building project. I have never been happy with the buzzy fizzy tope end/hi mid, and the lack of fullness over all channels. Also the clean channel lacks depth and sparkle and sounds "dry" compared to other amps, and the reverb is quite weak. Anyone know a good starting point for modifying this amp, circuit and all, I'm really keen on modifying things like tonestacks, reverb circuits, caps, resistors cutting highs boosting lows, that kind of things.

Thanks for all your help, Ryan.

[laterider]

This is one of my favorite amps. Mine is a 2003 and just sings - my only issue is the volume of the clean channel vs OD1/OD2 when cranked. Its hard to get the volume up on the clean channel without some break up. But I don't find mine thin on clean or buzzy on OD1/OD2 - of course this is with my ears.

Did you buy it used? Did a previous owner tube swap?

Marshall changed the bias spec on these around 2003 or so, I run mine at the original bias spec which runs it hot and can contribute to extra heat inside the chassis which some say may relate the bridge rectifier problems these amps also had. The bridge rectifier that overheats is actually in the DC filament circuit from what I remember so again running the bias up hotter just causes more heat which may or may not add to the heat issue with the br. I tried mine on the lower bias setting and went right back.


First - check your bias voltage - do a search on the web to get specific instructions for the DSL401 - even tho you are studying - remember lethal voltages lurk in tube amps.
Try the original bias spec (1.3v on test point) and the newer one (don't know what that is, I like mine hot!) If you do like it better at the hotter setting
and leave it there don't blame me if it becomes toast! I love the tone of mine so I'm willing to live with the consequences.
Also - maybe it needs new power tubes - tell me what brand is in there. Mine came with the great Ei EL-84s that can no longer be sourced and it was a sad day when
mine went. Took forever to find a brand that I thought sounded good in this amp. TAD EL84STRs are the only tubes I found to do this amp justice.

My 2 cents, to me these are great sounding amps that just need normal maintenance, so I'm just suggesting to look at tube issues before modifying it.
It should have Marshall labeled preamp tubes in it (which are higher end Chinese variants and work well in these amps as they were designed for them). If you do
have something like JJs or sovtek preamp tubes stuffed in there this could be part of the problem too.

[Chimp93]

I've biased it recently with new jj's in pre and power section, biased to 65% plate voltage which is where i like it. I bought it brand new. Yea I think all it really needs is a new speaker it is a nice sounding amp I am just being picky, however I'm excited to get into working with it for experience and was just wondering if anyone new any proven mods. Also I will not do any mods that are not reversible.