So I put 5881's and G12-65 in my DSL20CR and this is how it sounds...

[scozz]

Hi,
Does this mean that any of the tubes listed above will be a direct replacement for the EL34's it came with? as easy as, get these out and out the other in?

Sorry, noob here about these.

Loved the clean tones you getting………

Also 6ca7 power tubes, I have a set of them in my SC20, also a cathode biased amp.

I found them to be fuller sounding and have a bit more low end than the el34’s I’ve used in the past, JJ el34 and EHX el34’s. Kt88’s are next on my list.

I really like the DSL20s clean channel, but I just could not get on with the red channel. I’ve tried most all of the lower gain preamp tubes in my Dsl, they helped some, but the tone I’m looking for just is not there to my ears. A 5751 seemed to be the best.

 

[PentodeLicious]

I'd love to see the newer, revised schematic with board # DSL20M2-60-00-V9. I had no idea that the DSL20 has had any revisions, since its release. Any idea of production dates that correlate with said revisions? And what, if any revisions there were to the circuit?
Just Wonderin'
Gene

After looking again today on the new version guts, I can say that most of the schematic posted earlier in this thread is correct.
there are a few changes in a few cathode resistors values and number and a few capacitors.
Most of it is the same...

After figuring that out, I managed to find how to bypass the whole DFX board.
I soldered a shielded wire from the treble output (where R43 & R49 are connected together to form a voltage divider) straight to the phase inverter input.
I had to lift R43 & R49 and snip the signal wire from the connector(CN20).
From there I connected the stripped wire from CN20 to the junction of R43 & R49.
This way the signal goes straight to the phase inverter and without compromising any ground connections that are connected to the CN20(DFX out) and CN21(PI Grid).
Maybe nothing is using that ground of the connectors.
But because it is double sided board I didn't want to take the chance of creating ground loops.

The amp sounds like a blanket was removed from the speakers.
Suddenly it feels raw and less compressed. less fizzy. also gain is up a bit.
Big con: no FX loop, Reverb, emulated out, and aux in.
But who cares I never use those anyway

Here is a short clip with the Marshal 425A cabinet:

 

[PelliX]

Big con: no FX loop, Reverb, emulated out, and aux in.

The loop is a bit of a shame, but I can't remember using it the last time, either.

After looking again today on the new version guts, I can say that most of the schematic posted earlier in this thread is correct.

If you care to post the details it might be helpful for some. If not, it's good to know that nothing substantial has changed in any case.

Nice to hear you're happy with it, mate!

 

[PentodeLicious]

The loop is a bit of a shame, but I can't remember using it the last time, either.



If you care to post the details it might be helpful for some. If not, it's good to know that nothing substantial has changed in any case.

Nice to hear you're happy with it, mate!

After a deeper look I can say that it is almost the same schematic.
So sorry if I got some people confused
On first sight I thought they changed the components number but it is not the case.
I haven't gone thru all the schematic but I can say that the cathode resistor on V2:1 has changed to 10K (R28)
And C74(now the infamous bright cap) is not installed.
There might be more changes but not that I noticed.
I will take a deeper look tonight see if there are more changes and report .

 

[PentodeLicious]

OK! I think I reached perfection.
swapped preamp tubes and wow now we are talking.
The amp now spits fire with rich harmonics.
With 4x12 loaded with vintage 30's, it stands great against my other high gainers.
Hopefully I'll upload a short audio clip soon.

I'll summarize the mod for those who wish to take this quest and for future reference:

Disclaimer:
- You will lose your warranty
- Please don't touch the guts of a high voltage tube amplifier if you do not know what you are doing!
You can die!

Tubes:
Replace stock tubes with:
Power: Sovtek 5881WXT
V1: 5751 NOS Philips (If you don't have NOS put JJ 5751 in it)
V2: 12AX7 Shaguang
V3: ECC83S JJ

Preamp Voltages:
Add 100K in parallel to the original plate resistors R4 & R10, used to be 210VDC now its 245VDC

DFX Board Bypass(You will lose FX loop, Reverb & DI out.... Who needs those anyway):
1. lift R43 & R49

2. Cut the signal wire from the DFX out connector, the white wire(CN20). leave the black wire connected!

3. Solder shielded wire to R43 & R49 lifted legs
4. Solder the other side of the shielded wire to the the signal wire you just cut in step 2 (white one).

Best way is to use SPDT and the add another shielded wire.
Connect the signal wire(white) from CN21 to the middle of the switch and connect 1 pole to R43 & R49 lifted legs and the other to the CN20 signal wire.
This way you can switch between DFX bypass on/off

Speaker:
Replace stock speaker with:
Celestion G12-65
It sounds really good with this mod.
It also has the same resonance frequency as the stock speaker which makes it fit perfectly in the combo cabinet.

Celestion Vintage 30 will work great to. but... it's going to be harder to get good sound in low volume.
Also will make the amp heavier.

Edit:
Soundclip added with combo speaker.

 

[BC108]

Great mod! i've never imagined about the impact that would cause DFX board. I've seen on the schematic that there's some kind of complex buffering filtering after the DFX board, maybe "jumpling" over there could give a more "straight" signal back to PI, but losing a lot of frqs in the DFX board anyway. Good decision you've made.

I'm looking ideas to tweak 4 preamp triodes to look for some more Friedman gain, maybe look for Pink Taco values