ECC82 in V3 Position of DSL40C???

Inspector #20

Inspector #20

Ambassador of Tone
Fallen Star
Country flag
Curious...

I was going through my stock of tubes and found a pair of brand new ECC82 JJ's. I think this is a 12AU7??? Which, IIRC is a short plate, low gain version of a 12AX7.

The V3 (IIRC) is the cathode follower in this amp, and short plates seem to work better here. I seem to recall that V3 has some effect on the tone controls as well.

Can this ECC82 be safely substituted for the 7025-WA that is currently in my V3 position???

I would expect a volume reduction here, but perhaps a less "gainy" effect and more headroom too.

Leaving the studio early today for rehearsal (85 mile drive) so a fast answer will afford me time to swap it out before loading up.

Thanks...
 
Robert Herndon said:
@Amp Mad Scientist or @ivan H or anyone with amp builder/serviceability experience...can the ECC82 be safely substituted in V3 of a DSL40C.

Answer needed before 2pm today.

Gracias!@!@!@!
Click to expand...
Yes you can use any of the 12A-__ __ tubes in any preamp position.
There are also a variety of military tubes which you can use.
12AU7, 12AY7, 7025, 12AT7, all have different amounts of sensitivity.
The 12AX7 / ECC83 is the highest sensitivity. The 12AU7 is a much lower sensitivity.

tube gain.png
 
Update:

One of our techs here at the studio said that a ECC82 in V3 will kill a lot of gain and volume. He advised that the ECC82 is a much better choice in V4, and suggestex moving a 5751 into V3 in place of the current 70257025-WA.

His response leads me to assume the tube is compatible....
 
Amp Mad Scientist said:
Yes you can use any of the 12A-__ __ tubes in any preamp position.
There are also a variety of military tubes which you can use.
12AU7, 12AY7, 7025, 12AT7, all have different amounts of sensitivity.
The 12AX7 / ECC83 is the highest sensitivity. The 12AU7 is a much lower sensitivity.

View attachment 47905
Click to expand...

Thank you, AMS!!!@@!!!

I didn't want to create a portable arc welder... :-)
 
Any of the 12_ _7 series can be plugged into the socket, & valves being very forgiving as they are, you won't hurt anything (it'll work in that it will pass a signal & won't let the Genie out of the amp).
The thing is that the supporting circuitry isn't optimised for "all" of the valves in the 12_ _7 series, it will suit some of them better than others.
The substitution chart the AMS provided is very good as it show which types are truly compatible substitutions (supporting circuitry is compatible enough to enable proper operation).
Just for information purposes, the V3 position in you DSL40 is commonly known as the "cathode follower", but that's actually only V3b. The first triode (V3a) is a common gain stage (voltage amplifier). The second triode (V3b) is the (DC coupled) cathode follower & it's job is that of an "impedance buffer" (converts high impedance to low impedance so as to drive the heavy load of the tone stack with less loss).
It is one tube that cannot be overdriven as it will lose its ability to act as an impedance buffer, resulting in nasty tonal artefacts that can't seem to be dialled out.
It does contribute favourably to the overdrive/distortion characteristics though, which is why in very high gain preamps you'll sometimes see two cathode followers (or more).
Ok, rant over,,, hope you find what you're looking for by tube rolling Robert. Cheers
Edit:
Yes, a 5751 is compatible with a 12AX7/7025 as it was originally designed to be a lower gain, ruggedized 12AX7 for avionics applications. Cheers
 
Last edited:
A little after midnight PST and I just got home from rehearsal. What an interesting evening.

The tube combo listed above sounded much cleaner on my clean passages (though its rare that i play clean) but when dialed in on "Lead 2" and pounded with the TS-9, it gave me a great sound with much more flexibility in the tone controls.

Initially, i thought it would quieten the amp, bit i just drove it harder. The gain palette was much more useable and the amp was much tighter and crisper overall.

Gain is now useable all the way to 10, whereas previously, it would just "mud up" at anything past about 1pm on Lead 2.

A very good setup...

20200827_193254.jpg

20200827_193346.jpg
 
Wow, i just noticed this!!!@@@@@!!!

• 12AX7
o Has a published spec gain of 100
o Has a publishes spec current output of 1.2 milliamps

• 12AT7
o Has a published spec gain of 60-70
o Has a published spec current output of 10.0 milliamps (ten times that of the 12AX7 as a side note)

In the V4/PI of a DSL40C, would this then drive the power tubes even harder, despite having a lower Mu factor???
 
Reading through I can't tell if you are trying to achieve a specific sonic goal by rolling tubes or if it's just an exercise to hear what happens when you switch out different things.

I had a big box of NOS Mil-Spec tubes that came my way many years ago when the Naval Research Lab (where my father worked) phased-out all of their vacuum tube-based testing and R&D equipment. Instead of throwing them all away he brought home a huge stack, all different types. I had at least 100 different preamp tube types (all of the different 12A types plus an unopened package of RCA 5751's and a quartet of 6L6's) and that became my tube stock for all my amps for a long time, so I got to try out a lot of different types and combinations in both vintage-style and modern amps. They are all gone now, some given away and a lot I just didn't take out of amps I sold. Why did I just let all those "valuable" NOS tubes go? Cos in the end they really didn't make much difference. Some, yes, and much more noticeable in vintage amps that I owned than in any of the modern high-gain circuits, but not enough to justify messing around with to me. No magic combination of tubes ever made as much difference as turning knobs on a pedal or adjusting the EQ and gain on the amp. Just one old dude's experience.
 
Robert Herndon said:
it gave me a great sound with much more flexibility in the tone controls.
Click to expand...
This might be caused by a different property of the 12AU7 - its small output resistance - less than 10k compared with the 80k of the 12AX7. Divide both by 2 when there is a cathode cap present. Which means less loaded by a tone stack.

And one further effect: Miller effect. Causes los of treble, depends on the gain of a stage. large gain, large treble loss, usually unnoticeable except in large gain stages (12AX7, 12AT7 with cathode caps). Often desirable in high gain guitar amps.
 
Robert Herndon said:
Gonna swap a 5751 into V3 and a ECC82 into V4 before rehearsal tonight...

Predictions, @Amp Mad Scientist ????
Click to expand...
It won't make a lot of difference because there is only a little change between 100 and 70.
If you want to make it cleaner you will probably go lower than 70.
I might try 12AU7 or 12AY7 and drop it down to 40...

But really I might change the circuit instead.
Change the control microprocessor chip first, this is known to have a firmware issue. Unless it's already been changed.
The chip can be purchased (per-programmed) from a service center or dealer.
I would probably start there.
 
gball said:
Reading through I can't tell if you are trying to achieve a specific sonic goal by rolling tubes or if it's just an exercise to hear what happens when you switch out different things.

I had a big box of NOS Mil-Spec tubes that came my way many years ago when the Naval Research Lab (where my father worked) phased-out all of their vacuum tube-based testing and R&D equipment. Instead of throwing them all away he brought home a huge stack, all different types. I had at least 100 different preamp tube types (all of the different 12A types plus an unopened package of RCA 5751's and a quartet of 6L6's) and that became my tube stock for all my amps for a long time, so I got to try out a lot of different types and combinations in both vintage-style and modern amps. They are all gone now, some given away and a lot I just didn't take out of amps I sold. Why did I just let all those "valuable" NOS tubes go? Cos in the end they really didn't make much difference. Some, yes, and much more noticeable in vintage amps that I owned than in any of the modern high-gain circuits, but not enough to justify messing around with to me. No magic combination of tubes ever made as much difference as turning knobs on a pedal or adjusting the EQ and gain on the amp. Just one old dude's experience.
Click to expand...

This band is a paying job. As such, i am finding myself way outside my Comfort Zone in terms of tone, and i am learning lots of songs - some 40 years old and older - that i have never heard all the way through. As such, i have had to overhaul my tone and generate cleaner tones...
 
So you did change out V4? I went extreme once amd put an AU7 in there and the volume dropped way off so I coild turn it up higher or just to adjust for the eealky touchy JCM800 volume control.

I found little difference as well with a 5751 simoly because gain factor is not too different. I did try an AU7 or AY, I can't recall, in the 6505 but it killed too much gain.
 
You must log in or register to reply here.
Back
Top