12AU7 As Phase Inverter or Cathode Follower in DSL40C???

Installed and tested a new combination this morning and it impressed with its low noise floor and high volume level:

V1: TAD7025WA
V2: JJ5751
V3: TAD7025WA
V4: JJ5751

With this tube rollout, I'm running 'Lead 1' gain at dial position '4' and the TS-9 gain all the way off and level at 10am.

This gives a very nice "chug" on muted F#'s with complete clarity and it's very loud yet still controllable at stage volumes.

Amp settings taken just now:

20190815_082858-1032x581.jpg






 
The 12AU7 in V1 reduced the gain too much for my liking, but tonally it was a very great, classic rock sound.

In V2, with a standard ECC83 in V1, it has a really nice classic rock tone, but it loses its punch - you must run an overdrive pedal to get it cooking....

I have not tried 12AU7 in V3.

In V4, it reduced the amp's volume level about 2 dial position markers. Good clarity, but too much volume loss.

The 12AU7 has great potential as a classic rock tone tool, but if you like higher gain levels, it's not the right tube, IMHO.

The BEST combo I have used yet is:

V1: ECC823
V2: ECC83s
V3: ECC83MG
V4: JJ5751
 
You my brother have done quite a bit of experimenting in tube rolling
with the Dsl40c’s, I have only changed the first 3 positions on only one of our amps!
Sovteck 12ax7 in V1, ruby12ax7’s in the next 2 slots, Ruby EL34’s
And that’s where I stopped!
Cheers Mitch
 
Mitch Pearrow SJMP said:
You my brother have done quite a bit of experimenting in tube rolling
with the Dsl40c’s, I have only changed the first 3 positions on only one of our amps!
Sovteck 12ax7 in V1, ruby12ax7’s in the next 2 slots, Ruby EL34’s
And that’s where I stopped!
Cheers Mitch
Click to expand...

Each change has brought unexpected results!!!

I can completely alter the amp's character with just a single tube change.
 
Ok,

If you are shooting for a very classic rock kind of tone, like early AC/DC for example, it's hard to beat a 12AU7 in the V2 position with a standard ECC83 (12AX7) in the V1 spot.

If you want a little less gain and more volume, put a JJ5751 in V1 with a standard 12AX7 in V2.

V3 is the cathode follower position, and the tube used here needs to be tough. Spiral filament 12AX7 tubes have problems in cathode follower circuits due to the fact that most cathode follower circuits in guitar amplifiers exceed the maximum cathode to heater rating of 100 volts. It's also said that you should avoid long-plate tubes in this position in the DSL's because it can cause unwanted feedback.

I tend to stick with a JJECC83s or JJECC83MG here exclusively with good results. However, the TAD7025WA has also worked very well in this position.

Of all the tube combinations I have experimented with, the best tube in V4 continues to be the 5751 or the ECC81 (12AT7)

Now, I am in the habit of using what I have on hand before buying more tunes. That being said, here are some noted substitutions:

The TAD7025WA can be used in any position as you would use a standard 12AX7/ECC83. It is a quiet tube and is rugged.

I often use the JJ ECC803 Long-Plate (because I got quite a few of them) in place of a standard ECC83/12AX7, except in the V3 cathose follower position.

The JJ 12AT7 (ECC81) is a lower gain variant of the 12AX7 and it can be used in place of a 12AX7 - NOTE that I mentioned "JJ 12AT7" specifically - because it is a short-plate tune. The TAD, Electro-Harmonix, Genelex and Mullard 12AT7's are long-plate versions and they don't seem to work that well in the V3 of the DSL's,

Thus far, I am very pleased with the JJ ECC823 in V1, a JJ ECC803 in V2, a JJ ECC83MG in V3 and a JJ 5751 in V4.

Overall, that combination has the most natural, organic gain structure, with rich sustain, absent of fizziness and the cleanest overdriven chug of any combination I have tested....
 
67plexi said:
If your using EL34'S @ 25 watts each, on the PI you need a gain factor of 75 minimum

For my 6L6GC or EL34 or KT77 or 6550A or KT88 amps this is my PI tube of choice hands down

www.tubemuseum.org

ECC83 12AX7 ''LONG PLATES'' 1950's ''D-FOIL-GETTER'' NOS

ECC83 12AX7 'LONG PLATES' 1950's 'D-FOIL-GETTER' NOS
www.tubemuseum.org

Out of all the tubes the PI takes the most abuse
Click to expand...

Can you help me better understand that??? I do not recall seeing a 'gain factor' listed for any of these tubes!!!!!
 
gball said:
My own personal experience, and I think that video above illustrates it well, is that the effect changing tubes has is far far less then simply turning a couple of knobs. So I don't bother.
Click to expand...

If you make big changes - like going from 12AX7 to 5751, the difference is like night and day!!!
 
Robert Herndon said:
If you make big changes - like going from 12AX7 to 5751, the difference is like night and day!!!
Click to expand...

I've rolled many a tube in my day. Just have not heard anything that changes the fundamental character of an amp, just things that reduce distortion (gain knob), change clarity (presence knob), emphasize different freqs (EQ knobs) or change perceived output (volume knob).

Not saying people shouldn't experiment, and if we're being honest I really do believe that a 5751 in V1 of a Fender-style amp is a must-do to make the amp less scooped sounding. Just saying that in the high-gain amps that I actually use the changes are minimal enough as to not be worth the time or expense in changing the tubes out and I feel that the guy that designed the amp probably optimized it for the tubes it shipped with.
 
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