Hot Rodding a DSL40C???

Robert Herndon said:
@chilipeppermaniac - the amp guru is talking about a "three resistor modification that will allow use of 6550 power tubes."

???????????
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rabbit+hole.jpg
 
I know Robert is not calling me the amp guru. BUT he is referring to a fella at Marshall amp Forum who supposedly has a similar DSL 40C as Robert's and claims if Robert tells him how he wants his amp to sound, plus takes the chassis out and mails it to him, he will swap 3 resistors and change things to go from EL 34 to 6550.

Now my only knowledge of this is due to having purchased the 1978 MkII JMP Super Lead/Bass I did and being told by SYSCO, Bastard, IvanH, 67 etc that my amp and the transformers spec for USA models the amp specs call for 6550's in the 100 watt Supers. For me to explain the differences between an EL34 and 6550 amp within a particular model such as his DSL 40 and all that a conversion will require means far more homework on my part to summarize the differences for Robert.
 
chilipeppermaniac said:
I know Robert is not calling me the amp guru. BUT he is referring to a fella at Marshall amp Forum who supposedly has a similar DSL 40C as Robert's and claims if Robert tells him how he wants his amp to sound, plus takes the chassis out and mails it to him, he will swap 3 resistors and change things to go from EL 34 to 6550.

Now my only knowledge of this is due to having purchased the 1978 MkII JMP Super Lead/Bass I did and being told by SYSCO, Bastard, IvanH, 67 etc that my amp and the transformers spec for USA models the amp specs call for 6550's in the 100 watt Supers. For me to explain the differences between an EL34 and 6550 amp within a particular model such as his DSL 40 and all that a conversion will require means far more homework on my part to summarize the differences for Robert.
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Here are some of the other modifications..

"That would be the first gain stage cathode bypass cap that is 4.7uF. That would be the first place to start to get rid of the problem you are on. Try 1uF. From the DSL 40 schematic I have seen, it shows as C12, same as the JCM 2000..."

"You could also try lowering R27 a bit. Maybe down to 470K for a start. That will reduce the gain/signal going into the Red channel only. That allows you to run the Gain higher. But it is a trade off and balancing act basically. It reduces sensitivity somewhat and will make the channel sound a bit smoother. Less harsh and not as much attack and maybe remove some fizz and hash...."
 
Here's a soundclip of my Gibson Les Paul (498T/496R) running through the VS265 miked from 4 feet away with a vocal microphone.

Tone Sample using Boss GE-7, Boss CS-3, Boss DD-3 and Boss NS-2 AMP SETTINGS: Gain 1/2, Bass 10am, Mids Full, Treble 1pm

You can literally feel the air coming off the VS265's twin speakers on this clip....THE SPEAKER MOVEMENT IS CRAZY.

I know the Scarlett Studio CM25 MKII microphone is limiting in this application, but I just wanted to get a soundsample out there.

I'm really happy with this tone.

Marshall VS265 Demo Gibson Les Paul
 
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Robert Herndon said:
EXACTLY!!!!

Power Tubes????

It was my understanding the DSL uses pre-amp tubes for overdrive?????
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That gets tricky.

I know others can explain better than me but I'll speak from my limited experience owning a bunch of amps over the years. Basically, all the tubes introduce some amount of harmonic content to the sound you hear coming out, depending on the levels (how hard they are driven). In a high gain, master-volume amp like yours most of the distortion is generate by the preamp, likely some combination of the tubes and clipping diodes. At lower volumes pretty much all the distortion is generated by the preamp. But at higher volumes the power tubes come into play, and they also distort but in a different way, and the louder you go the more they will clip.

These days, distortion is cheap. We have cascading gain preamps that can produce more dirt than you could need, but back in the day with non-master-volume amps they didn't have that luxury. A lot of the distortion came from sheer volume - the amps were dimed and the power sections broke up. People also put fuzz/overdrive/distortion in front of the amp to generate dirt and also "push" the preamp into additional distortion. But the biggest difference I hear between 1960's/1970's and 1980's-to-now rock guitar tone is the availability of high gain master-volume amps. They just react and sound different.

Sometimes If I am going for a particular "throwback" kind of tone, I will switch to the green channel, turn the gain almost all the way down and the master pretty much all the way up. Then I get that solid CRUNCH from the power tubes and can control it all with the guitar volume and a pedal or two.
 
Ok....

So tonight I messed with the DSL40C a little bit more. I started by dialing in identical settings to the VS265.

Lead 2 (Marshall manual says "mid-boosted tone with higher gain.")

Gain: 1pm
Bass: 11am
Mids: Full
Treb: 1pm
Reso: 1pm
Pres: 3pm

The amp sounded a lot better here, but the low end needs to be tightened as it is still a bit undefined on palm muted sections....but this is the best tone yet from it.
 
gball said:
That gets tricky.

I know others can explain better than me but I'll speak from my limited experience owning a bunch of amps over the years. Basically, all the tubes introduce some amount of harmonic content to the sound you hear coming out, depending on the levels (how hard they are driven). In a high gain, master-volume amp like yours most of the distortion is generate by the preamp, likely some combination of the tubes and clipping diodes. At lower volumes pretty much all the distortion is generated by the preamp. But at higher volumes the power tubes come into play, and they also distort but in a different way, and the louder you go the more they will clip.

These days, distortion is cheap. We have cascading gain preamps that can produce more dirt than you could need, but back in the day with non-master-volume amps they didn't have that luxury. A lot of the distortion came from sheer volume - the amps were dimed and the power sections broke up. People also put fuzz/overdrive/distortion in front of the amp to generate dirt and also "push" the preamp into additional distortion. But the biggest difference I hear between 1960's/1970's and 1980's-to-now rock guitar tone is the availability of high gain master-volume amps. They just react and sound different.

Sometimes If I am going for a particular "throwback" kind of tone, I will switch to the green channel, turn the gain almost all the way down and the master pretty much all the way up. Then I get that solid CRUNCH from the power tubes and can control it all with the guitar volume and a pedal or two.
Click to expand...

@gball - Did you by chance get to hear this VS265 clip yet???

Marshall VS265 Demo Gibson Les Paul
 
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