Tube Positions, Gain Stages, And Amp Channels.

[mbornhorst23]

Hey Marshall fans. I have a question regarding the relationship between tubes, gain stages, and amp channels. I have a DSL40C which has 2 channels (clean and ultra drive), 4 modes (clean, crunch, lead 1, and lead 2) and 3 preamp gain stages (V1-3). There are some frequencies that I'd like to tame and others I'd like to accentuate when selecting tubes for these positions. However, I'm not entirely certain what the relationship is between the tube positions and the channels/modes. Do both channels and all four modes run through all three gain stages? Does the clean channel run only through V1 while the ultra drive channel runs through V2? If both channels do run through all gain stages, the does V2 influence the ultra drive channel's tone more than the clean channel's? Thanks.

 

[Matt_Krush]

No, both channels do not use all the tubes all the time.
I don't have a schematic in front of me....but like so many other tube amps, 1/2 a 12AX7 may be for clean, the other half for one of the overdrives.
What may happen, is the taming of both channels.
The modes (if like the JVM) switches in & out different resistor values to increase the 'gain' available from each pre-amp tube section.

You want the most noiseless 12AX7 first (since each stage after will just compound to the noise) and preferable it has the fullest dynamics.
Unlike many, I find that long plates sound best in V1 (Sovtek LPS, Mullard reissues or NOS). They're also great for phase-inverters.
In amps such as DSL or other 'hi-gain' heads...China branded tubes last the longest (in my experience) in the cathode follower spot (without the schematic I am not sure which one that is in a DSL).
For general gain stages, I like Tung-Sol slightly over Electro Harmonix. Either of these also makes for a good V1 position or phase inverter.

In my experience & amplifiers, J&J pre-amp tubes are dull and lifeless....they'll tame shrill highs if you are fighting with that. They do make a reliable power tube however.

 

[Jethro Rocker]

I believe V2 is strictly for lead channel, if that tube dies, you still have Clean Crunch channel. I have found the Tung Sol weak in a PI V4 slot, I've had 3 go real early on me in different amps. For some reason, I cannot seem to find the tube layout in the huge 40C thread and, of course, I forget. It is fairly subtle, I don't think you'll find a huge difference in accentuating certain frequencies with the pre tubes. Some will be brighter, some more neutral, some gainier but certain frequencies can't really be picked with pre tubes. I've tried a large number of CP and NOS tubes.
V1 may be first gain stage for both channels, V2 is gain stage for ch2, and V3 might be second gain stage for ch2 plus tone stack but can't recall.....

 

[Micky]

My answer is always to refer to this post:
http://www.marshallforum.com/index....nformation-thread.53780/page-285#post-1484473

The answers to your whole OP can be found in that thread, unfortunately it is large and unweildy. The search function works a lot better now, and the ability to search within the thread is a LOT easier.

 

[mbornhorst23]

Thanks for the info. I'm having a little trouble taming the highs. I sometimes get shrill ice pick tones on the upper frets of the high e string. I have replaced the stock speaker with a 10 year old, well broken in, WGS Veteran 30 and I've done the C19 mod but I'm still struggling with the highs. I have some JJ ECC803s gold pin tubes that might take off some of the highs but I really don't want to lose clarity or make my amp sound "dull and lifeless". I put a Tung Sol in V1 and I really like the clarity and articulation compared to the JJs but even with the Tung Sol I can't run the treble above 2 and presence above 0 or else it starts to get very bright and shrill. In fact, I also have to set the bass around 3 and mids around 4. It seems odd to me to have to cut all the frequencies to get a good sound out of it. I have a Ruby ECC803 in V3 and I'm running one of the JJs in the PI. I'm happy with these. It's V1 and V2 that I'm having issues with. Any suggestions? Thanks.

 

[Micky]

V1 needs to be a lo-noise (not microphonic) full-range tube like a TAD 7025, NOS Mullard or similar quality tube. JJ's and Tung-Sols just don't cut it here. Think about it for a moment, because V1a is the input buffer for everything, you want the best tube you can find there, as it is amplified over and over again. If you limit the frequency response (fidelity) there with a lesser (expensive) tube the whole tone chain suffers. The custom Shug-Yangs that come standard are a mediocre tube and are generally best kept as working spares.

There is a fine line between 'dull and lifeless' and 'shrill and ice-picky'. The 40c is a bright amp, and ANY speaker you put in the cab is gonna lack some bass and be a little trebly in comparison to a closed-back external cab. The C19 mod only affects the Ultra Channel, that mod right away will strip a bunch of highs off the signal. It might help a little, but my suggestion is to work with the EQ to add bass and mids to offset the brightness. Sure the treble is kept low, but you also have controls on the guitar (most times) so use them as well.

V2 is strictly a gain stage (cascaded) tube, between the input buffer and the tone stack. Again you want a tube that doesn't constrain the low freqs, but can handle the voltage hit the amp puts on it. A new Ruby is a good tube for this spot, but anything that is not too bright should work well. Read thru the DSL40c Information thread to see what others are using. It should be required reading for anyone with a new DSL40c, and I don't say that because I started the thread, but because there are a hundred or so GREAT contributors there.

Many complain that it is too bright, but I have found it is exactly what you need to cut thru the mix, and the louder you can get the volume, the less bright it becomes. I am certain with the right combination of tubes, speaker and pickups you will find what you are looking for.

 

[ken361]

check your bias? adjust your pickups? I dont get it when people struggle with the brightness i still havent done the c19. I run the treb and pres around 3 and works fine I do have 3 old stock tubes in for smoothness. Cut the mids a tad to 4!

 

[mbornhorst23]

No problems with low end whatsoever. It has so much bass that it shakes the whole room when I set it anywhere above 3. The pickups are set as they should be. I don't have any issues with excessive brightness on any other amps. The amp is very quiet regardless of what tube I put into V1 (at least of the few so far I have tried). Sounds like its just a very bright amp and there's little I can do about it. Thanks for all the help.

 

[Jethro Rocker]

I'm thinking bias as well maybe. I have a Celestion V30 and I run treble about 5 and presence around 4, use NOS tubes and I sit right in front of it. C19 mod as well. Treble on 2, Presence zero should be duller than an evening at the opera...

 

[mbornhorst23]

Update. I put in some new power tubes (JJ E34L) and checked/set the bias. One side measured around 38 milliamps but the other was up around 45. I set both sides to 38 and now it sounds great. I can get the treble up as high as 4 and presence around 3 which is a big improvement. However, an even big change is how much tighter the bass is now. Previously it was really loose and boomy even around 3. Now I can run it as high as 6 without issue. Thanks for all the advice.