Tube rolling in my amp with surprising results.

  • Thread starter Thread starter Music&Chaos
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Old Guitar Player said:
My wonderful little Marshall DSL20CR has a little more edge/bite on the RED channel than I, and most prefer. So, I was told that simply swapping the V2 over to a 5751 should work nicely, is a straight swap, and has no side effects! I know that a 5751 has 70% of the gain of a 12AX7, so it made sense to me (and it worked exactly like I was told it would!) However, I'm being told in "some" of the online forums that the difference in Plate voltage between these two tubes is a BIG issue, and could damage my amplifier (which concerns me!). Does the plate voltage in both the V1 & V2 slots need to be the same (match)?. While I am a 40+ year guitar tech/repairman, I have limited knowledge about rolling different 9 pin tubes in a Marshall pre-amp slot. Could someone with actual experience and knowledge please give me (a humble old guy) some reliable input on this? I'll owe you big time! Thanks in advance... :cool:
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I am looking forward to someone with more information and technical experience answering this question. I do not believe mixing and matching pre-amp tubes would be a big deal, even if they are all different gain levels, as this has been done for years in vintage amps. 12ax7 mixed with 12au/12at is pretty common but again, I am ignorant when it comes to that specific knowledge. Hope someone comes along to enlighten us!
 
GuitarGuy08 said:
I am looking forward to someone with more information and technical experience answering this question. I do not believe mixing and matching pre-amp tubes would be a big deal, even if they are all different gain levels, as this has been done for years in vintage amps. 12ax7 mixed with 12au/12at is pretty common but again, I am ignorant when it comes to that specific knowledge. Hope someone comes along to enlighten us!
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Someone just sent me this:
"Plate voltage is provided by the amp circuit, and each tube type has a plate voltage rating. In this case, both 12AX7 and 5751 have a maximum plate voltage rating of 330v. I’m certain your DSL20 will have no problem with a 5751 in V1 or V2."
 
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Old Guitar Player said:
Someone just sent me this:
Plate voltage is provided by the amp circuit, and each tube type has a plate voltage rating. In this case, both 12AX7 and 5751 have a maximum plate voltage rating of 330v. I’m certain your DSL20 will have no problem with a 5751 in V1 or V2.
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I never thought it would be an issue with pre amp tubes but now I know. I'm glad to have the confirmation!
 
GuitarGuy08 said:
I never thought it would be an issue with pre amp tubes but now I know. I'm glad to have the confirmation!
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I also received this response:
"The whole discussion starts with a false premise: there is little plate voltage change when switching from 12AX7 to 5751,
and that change will leave less voltage on the 5751 plate. (about 175v for a 5751 where a 12AX7 might have 195v)."
So evidently, it's splitting hairs, on hairs... loll Both tubes have almost twice that capacity, so it shouldn't be an issue.
 
Hey guys, i grabbed a quick clip here.

Strat bridge pickup on the Lead channel w some reverb on it.

I was unable to dial anything in or make adjustments-No monitors currently. This is untouched output from the 'C' selection on the Rivera and direct into a recording interface. So.... this could sound like total trash. I will be sure to get some actual recordings when I have my studio monitors and stuff set back up. Anyway, here is a clip of me doing some random lick on my strat:


Zed_Lead_C



2 of the same clean tracks with Reverb (Heavy) going through the output selector B and C straight to the interface.

Zed_Clean_C_Heavy_Verb


Zed_Clean_B_Heavy_Verb
 
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Did some tube rolling again!

After rolling many, many tubes in V2 and V3, the black plates retain detail like no other.

Moving forward with the test, I left RCA black plates in V2 and V3 and just swapped between V1.

CBS Hytron, Mullard Long Plate, Herleen, etc.... This amp just loves the Black plates. The harmonic richness, detail, and articulation shine through. Slam it with effects and it enhances them, hit it with tons of gain and low end and it never flubs out. Using a strat, LP, and a custom with Bare knuckle Silos. Will test my 7 string later but I'm expecting great results and definition and tightness in the low end ;) oh yeah, just like we like it!
 
Roll report: Tried Ken Rad outputs with the black glass inputs.

Enough bottom end coming through a 2x12 that you don't need a bass. HUGE.

Top end extension to match.

The mids are extremely Open and the tubes do not add any midrange at all like the RCAs.

This pairing is the 'King of Fender Clean ' sound, no doubt about that.

I did not prefer this for my setup and playing tastes though and after doing a ton of rolling have wound up with the old RCA blackplates in all 3 input stages and RCA smoked glass for outputs.


There is just something so articulate and detailed while having immense depth and punch. Definitely going to be leaving RCAs in this amp!

Onward to my next tube adventure :)
 
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