JCM 2000 Marshall TSL 100 mod to DSL 100 Specs

[Tejaus]

I picked a 2006 TSL 100 amp for cheap that had a loose foot switch jack on the amp and bad plug on the foot switch itself.
After re-soldering the 6 pin DIN jack to the PCB I installed two machine screws to fasten it to the chassis.

Like Marshall did with the DI XLR jack.

I also replaced the DIN plug on the foot switch with a heavy duty metal one. If anyone needs one let me know, I have several left.


I did the Jerry FJA speaker jack ground mod, added a 3H choke, swapped some power supply diodes with some faster UF4007 ones.

I also have a DSL 100 to compare it to. The TSL has more gain on the crunch channel so I have to set the gain lower to match, sounds pretty much the same as the green crunch on the DSL then. To me the clean is better on the TSL not Fender clean but more usable than the DSL

The Red channel is a little too bright if I use 8k PAF style humbuckers and bright speakers like Eminence Wizards or some old Peavey 1230 Sheffields. With hotter pickups it's works out better. Or use dark speakers like some Mesa Black Shadow MC90 knocks a lot of high end out.

Still a bit different compared to the DSL. I really think Marshall designed these and the DSL to be used with high output pickups.

My question is has anyone done these TSL to DSL mods below?

Mainboard:

C18 chang to 470pf - DSL value instead of TSL value, bleeds more high frequencies off after initial distortion stage (V1AA) in crunch and lead channels

TR2 removed - eliminates high-frequency boost @ ~7kHz (cathode bypass, V2AA) in crunch and lead channels
(I read elsewhere on the forum someone did remove the TR2 this and lost the clean channel?)

Remove TR2 10nF C24 bypass cap to 4th cathode and changing 100 pF C18 cap to 470 pF. That should remove fizzyness and stiffness and bring back the tone to classic Marshall crunch territory.

replacing 2nd stage's anode resistor R13 from 100K (TSL) to 220K (DSL) and 1st coupling cap C16 from 2n2 (TSL) to 4n7 (DSL). Increasing anode resistor will give more gain and increasing CC will bring more lows to the sound.

Lead panel PCB:

C9 changed to 100pf - bleeds less high frequencies past gain pot at lower settings (no effect when gain at max).

68pf mica cap added across VR2 (channel volume) - first-order lowpass filter bleeding off treble frequencies above ~4.5kHz

Values of R25 and R26 reversed - increases available reverb mix on clean channel, decreases available reverb mix on both drive channels

Replace C36/C37 with higher voltage parts, i.e. 500V or 630V - for reliability, these caps fail if a power tube shorts plate or screen to control grid, then bias gets mysteriously dragged down and the problem is extremely difficult to locate.


Crunch PCB:

68pf mica cap added across VR2 (channel volume) - first-order lowpass filter bleeding off treble frequencies above ~4.5kHz


Other:

Mercury Magnetics MAR100-OM output transformer - bandwidth, headroom, reliability

Reverb tank replaced with Accutronics Type-9, 9BB3C1D - longer, more complex reverb sound
Notes:

Do NOT increase the size of interstage coupling caps if you downtune, it just makes the distortion farty.

Avoid strapping a cap across R1 on the mainboard for “fizz-reduction,” since it will affect all 3 channels, potentially making the clean channel sound dull.

DSL 100 Circuit Schematic http://www.drtube.com/schematics/mar...01)%20iss7.pdf

DSL 100 Tone Stack Schematic http://www.drtube.com/schematics/mar...01)%20iss5.pdf

TSL 100 Circuit Schematic http://www.drtube.com/schematics/mar...03)%20iss7.pdf

TSL 100 Lead Channel http://www.drtube.com/schematics/mar...98)%20iss4.pdf

TSL 100 Crunch Channel http://www.drtube.com/schematics/mar...98)%20iss2.pdf

TSL 100 Clean Channel http://www.drtube.com/schematics/mar...98)%20iss4.pdf

[Pedro Vecino]

TR2 removed - eliminates high-frequency boost @ ~7kHz (cathode bypass, V2AA) in crunch and lead channels

.
Are you sure? I have not watched the switching circuit but the logic says that it should be assigned to clean channel to create an emphasis on high frequencies leaving the crunch and lead channels untouched.
My advice is to leave the transistor in place and simply lift a side of C24 to check to which channel is assigned.
...
Now, remembering, that capacitor is a small polyester. Probably can not be removed without destroying it but you can put another in place.

[Tejaus]

here's that post I referred to about the TR2 http://music-electronics-forum.com/t30041/ Read Post #10
Looks like it affects the clean channel

[Pedro Vecino]

I followed the switching circuit and the TR2 transistor assigns capacitor C24 paralleled with cathode resistor to produce a treble emphasis only on the clean channel. Unrelated to the silence of the clean channel contained in topic (when many things are mixed without control is easy to get confused). Forget it.
On the other possibilities I will give my opinion:

C18 chang to 470pf - DSL value instead of TSL value, bleeds more high frequencies off after initial distortion stage (V1AA) in crunch and lead channels

You will lose some sensitivity in the touch of overdrive. More noticeable with mid/low gain settings. In any case have little effect. If you want to try, better at the end.

Replacing 2nd stage's anode resistor R13 from 100K (TSL) to 220K (DSL)

It is not necessary in this amp.

and 1st coupling cap C16 from 2n2 (TSL) to 4n7 (DSL).

Better keep original value. The lead has enough lows pre-distortion. With 4n7 it sounds more uncontrolled at high gain settings. If you do you can compensate it by reducing the value of cathode capacitor C13 (assigned to the lead). 1uF to 470n (0.47) but there are other more appropriate system if you want more lows in crunch channel, identify C3 in crunch PCB and raise his value (4n7 to 10n, for example, or 15n...) if you want more lows pre-distortion.

68pf mica cap added across VR2 (crunch channel volume) - first-order lowpass filter bleeding off treble frequencies above ~4.5kHz

This really is helpful to give a warmer presentation. You must identify the three active pins of the potentiometer (they have four).

LEAD PCB:

Values of R25 and R26 reversed - increases available reverb mix on clean channel, decreases available reverb mix on both drive channels

I see no problem with reverb levels between channels.

C9 changed to 100pf - bleeds less high frequencies past gain pot at lower settings (no effect when gain at max).

This value is too small. At mid/low gain settings will sound mushy with classic humbuckings. Best not less than 270 pf.

68pf mica cap added across VR2 (channel volume) - first-order lowpass filter bleeding off treble frequencies above ~4.5kHz

OK. You can even raise it to 82 or 100p if you use the lead with high gain settings. 68pf is a good value to start.

Replace C36/C37 with higher voltage parts, i.e. 500V or 630V - for reliability, these caps fail if a power tube shorts plate or screen to control grid, then bias gets mysteriously dragged down and the problem is extremely difficult to locate.`

You can do it but I've never seen a problem with these capacitors.

Mercury Magnetics MAR100-OM output transformer - bandwidth, headroom, reliability

Sincerely: A TSL100 can sound good without it. I do not consider it necessary.
A good selection of tubes has much more impact on the textures and the musicality of the amp.

Reverb tank replaced with Accutronics Type-9, 9BB3C1D - longer, more complex reverb sound

I do not know that tank, or if I know I do not remember. Reverb in Marshall amplifiers should be discreet to not interfere with the crunch and lead sounds. No interest in making it longer or deeper. Original reverb may be more complex/rich for the clean channel but this channel is not the paradigm of harmonic complexity. I think it is appropriate if is well preserved.

[g1]

Replace C36/C37 with higher voltage parts, i.e. 500V or 630V - for reliability, these caps fail if a power tube shorts plate or screen to control grid, then bias gets mysteriously dragged down and the problem is extremely difficult to locate.

This makes no sense at all. Those caps on the lead board are in series with 680K resistors and I don't see how they could connect to the bias circuit or the power tube grids. Where do CON20 and CON19 on TL10-61-02 drawing go?

[Pedro Vecino]

Capacitors are in contact with the grids and the bias voltage but I do not see any problem with them.
SW3 selects 680K resistors in series with the signals (virtual power reduction) or close its ends by a bridge (normal sound).
SW4 makes a mute joining both out of phase signals.
In this composition the complete circuit looks better:

[g1]

Thank you Pedro.
Then I guess this is something we can check if the "bias gets mysteriously dragged down and the problem is extremely difficult to locate".
I think if plate or screen shorts to grid were a common problem we would see much more bias circuit failures in all tube amps.

[Tejaus]

68pf mica cap added across VR2 (channel volume) - first-order lowpass filter bleeding off treble frequencies above ~4.5kHz
OK. You can even raise it to 82 or 100p if you use the lead with high gain settings. 68pf is a good value to start.

That's a good idea Pedro. I have another amp I know you're very familiar with, a Fender Super Sonic 60 as you know uses a bleeder cap on the both the volume and gain.
http://support.fender.com/schematics...atic_Rev-A.pdf

I modded my SS with some lower than stock values. I also tried it with both caps removed and just like my TSL is was too shrill, harsh. I'll try the same dual approach on the TSL and see what happens. At least the Marshalls are easier to get the boards out.

I also have a pretty good stash of NOS and like new 12ax7 tubes, some original EI's, Amperex Heerleen Holland, Sylvania etc. Both the DSL and TSL still have the stock EL34 power tubes so I might try a new set of those too.

[Pedro Vecino]

I usually use 82pf on the crunch channel master and 100pf on the lead. At first glance it would seem necessary to increase the filter on the crunch but in this channel, with gain at 10 and the treble knob down to minimum something occurs: there is still a lively harmonic content at very high frequency. Elevating the filter value excessively has a negative effect on the texture.
In the lead however the effect by lowering the treble is different (more natural) and accept higher filter values.
To equip the TSL100/122, along with other operations typically I use these tubes:
V1. ECC83 Tungsram
V2. ECC83 RFT
V3. 12Ax7 Shuguang
V4. 12Ax7 LPS with E34L JJ tubes / ECC83JJ with EL34 Svetlana (Winged C) tubes

[Tejaus]

Have you ever tried a 12AY7 in V2? Aspen Pittman wrote in The Tube Amp Book Page 119 The Tube Amp Book - Aspen Pittman - Google Books that tube will make the DSL and TSL more touch sensitive like a Plexi.

I don't have any 12AY7 tubes to try that, just a bunch of NOS JAN 12AT7 tubes.

I did try out an experiment with my DSL and TSL amps to hear the differences between the two. I have some 2x12 stereo ported cabs that I used to build and sale. What I did is hook each amp up to one side of the cabinet. The two speakers in this cab are some 16 ohm prototypes Eminence built for the Blackheart amps, essentially Private Jacks.

Then, using an AB box I plugged a Gibson DC Les Paul with a 498T in the bridge position feeding both amps. Now I could easily switch amp in and out.

Setting the TMB knobs on 5 on both amps, no Mid Shift, no Deep the main difference between the amps are:
The DSL has quite a bit more bass on all channels. More than needed actually. On the TSL you have to kick in the Deep switch and add some bass to match the DSL set flat.

The TSL has more gain than the DSL on the Crunch and Lead Channels. On the Crunch channel setting the gain on the DSL to 5 equals 2 on the TSL. That being said with the TSL higher gain settings sounded better than the DSL.

On the Lead channels the TSL has a thicker midrange which is better for leads. The DSL sounds a bit thinner. Rolling the mid back to 4 and turning the bass up on the TSL matches the DSL very closely.
The TSL has I think more usable high gain vs the DSL Ultra Lead. The DSL gets flabby.

The Clean channels are similar except you can't EQ them separately on the DSL.

[Tejaus]

Well I put some better tubes in it and it was sounding good but now there's crosstalk on the clean and crunch channels. On the clean with the volume and gain at 0 there's I can still hear the guitar coming through. On the crunch if the volume is at 0 I can turn the gain up and get quite a bit of volume. The lead channel works fine. Last night when I played though the amp it the volume was kind of cutting in and out on the crunch channel. I read others have had a similar experience with the TSL. Anything I should check first?

Update: I measured Optocoupler NSL-32. OPTO1 and OPTO2 on the Clean board. I think OPTO1 is a little under spec.

NSL-32 Datasheet http://www.alliedelec.com/images/pro...C/70136794.pdf

With the Clean button engaged I measured
327 ohms on OPTO1, 337 ohms OPTO2
Crunch/Lead:
OPTO1 437K ohms OPTO2 1.158M ohms

Datsheet says Minimum 500K Off Resistance.

I also found this post about the same issue:
Post #20
http://music-electronics-forum.com/t15742/