Socket Position for 5751 Preamp Tube?

[bluezguy]

First of all, thanks very much for all yer infos on 'biasing'.
What a piece of cake!

Before changing out the original power tubes for my new Tung Sols, I measured both sides. One side was 74.15 .. the other measured 74.74 ... PRETTY WELL MATCHED from the factory I might say. I easily kicked up the values to the max 79s.

The folks at Tube Depot were terrific to talk to, shipping was lightning fast and my 2 boxes were packed with great care.

Now, has anyone replaced one of your pre amp tubes with a 5751 to 'step' down the the volume when you kick in the Drive??
How did you like the new performance??
Which socket did you use? The folks at Tube Depot said it doesn't matter but you may be surprised by experimenting.
I haven't done my changeover yet, will do it on the weekend and let ya know how she goes.

[DoctorStan]

If I understand what you are asking, I think you would want to replace the preamp tube in the V2 position, that's the one that handles HDR. Looking at the back of the amp with the cover off, it's the 2nd tube from the left. It should have a metal tube shield on it. Let us know how it goes.

[bluezguy]

If I understand what you are asking, I think you would want to replace the preamp tube in the V2 position, that's the one that handles HDR. Looking at the back of the amp with the cover off, it's the 2nd tube from the left. It should have a metal tube shield on it. Let us know how it goes.

Thanks Doc .... you understood correctly. I just wanna stuff everything in and go at 'er kinda like when you were first dating your wife - to - be...
What about plate voltages for the new power tubes? Is that as necessary and beneficial as re-biasing?

[DeanM]

You got Tung-sol KT66's?? just a word of warning, if your installing them you will have to remove the bear trap retainers! the metal base is shorted to one of the pins internally, i cant remember which, and the bear trap retainers will then short that pin to chassis ground. so if your usin Tung-sol KT66s you will have to remove those retainers!! or change to a dif stye of retainer.

[bluezguy]

DeanM..... yes, the retainers gotta go.

The KT66 Tung Sols have a huge base compared to the original equipment Shuagangs. Only a drunken blind man stoned on crack would attempt to insert the Tung Sols without removing the retainers.

There is however, a trick to installing these babies. You must put the beartrap screws back into the chassis. Why???
If you don't, you push the bloody VM pcb out of the chassis. . Furthermore, the pins on the Tung Sols are fatter than the stock KT66s. It takes some good pressure to insert and remove them. :cuss . I think it's my passionate hatred of aftermarket stuff biting me in the ass...

So far, I'm not impressed. I'm gonna have a chat with the folks at Tube Depot tomorrow and Tuesday night, I'm gonna 'fire 'er up'. I'll let yaz know...

[yladrd61]

5751 put it in the PI slot

[MartyStrat54]

Adding a 5751 will not be that noticeable. Most 5751's are pretty stout. I've tested many at having 85mU's of gain compared to 92-100+mU gain for a 12AX7.

The 5751 tends to work really well as a V1 tube in the small 5 to 20 watt amps.

One thing about a 5751 compared to a 12AT7. The 5751 is a very musical sounding tube, like the 12AX7. To me, a 12AT7 is not a very good sounding tube.