A short while back I was talking with a friend who brought up the Marshall DSL1.
This got me looking into the amp and realising that they have a lot of modding potential.
The first place I will be focusing on is the tone stack as it is very ineffective stock and the mids are centred very strangely.
Here is a simulation of the current tonestacks and my intended changes.
- Red = Stock
- Blue = Stock with the tone shift engaged
- Black = My intended changes
As you can see in both stock forms there is a large low frequency peak at 60-70hz which is not really ideal for guitar. Another further issue is that the mid band is centred too high at 900hz-1khz (Red) and >1khz (blue)
This is not ideal for guitar as it is where the note intelligibility is which results in the amp being somewhat flat and uninspiring to play.
The changes I am doing will return it to a regular Marshall-ish voicing with the low peak being ~100hz and the mids ~600-700hz. Further to this I am going to rewire the shift toggle to get an approximation of a Soldano tone stack range as seen in the chart below.
- Red = Marshall tone stack
- Blue = Soldano tone stack
I will update the blog with changes as I move along with this.
Part II
So first of all here is a clip of it stock on the red channel with the gain & tonestack all set to 5. I measured the resistance of each so I could ensure it was the same for each clip.
Then after doing the above clip I changed the 47nf caps in the tonestack to the more traditional Marshall 22nf and changed the 18k slope resistor to 47k. The difference is subtle on the recording but it feels a lot better to play, punchier and better attack in the low end. The tone controls now all have a good range. One of the biggest issues I had with the amp was the Treble control barely did anything these changes fixed that.
At this point I was much happier with the amp but felt it could use a bit more saturation and bite. So i changed the 1st stage plate resistor to 220k ala Soldano and added a 470nf bypass cap on the second stage of the lead channel.
Across all of the clips I measured the pots to ensure nothing had been changed accidentally while working on the amp. Also the same DI tracks were reamped straight into the amp.
And finally here is a clip of it dialled in a bit with a different track.
Whats next?
I still think there is a lot more that can be got from this little amp. I am tempted to fully convert the lead channel into the SLO lead or maybe Krankenstein. I will see how I feel and order the correct sized parts soon.
Final Update 14/04/2023
I changed a few more bits. I didn’t end up going fully SLO as it didn’t really suit the power amp so I tweaked things as I went along with feedback from the buyer before sending it off to him. I have documented all of the changes in the following PDF. Changes in red anything with an X just means simply remove. The change of R17 after the tonestack is simply to balance the 2 channels volumes better. You can go right up to about 470k comfortably here and still have balanced channels.
And finally here is a clip of the finished amp.