The Amp Garage

Rewiring the PAB switch to 10thtx's example brought the tone circuit to life, now all controls function with good range. I've done a little work on the cab for this new amp, photos to follow.
Thanks again for your help and advice

I like Switchcraft jacks and plugs. I like JJ tubes, I find them to be more consistent than other current manufacture tubes (admittedly, that's not saying that much, but they work well for me).

Where's my checkbook

Wow, that's a lot different than Mat's 86 special or the other variations of the 101HRM preamp layouts I've seen, you completely eleminate the two 20M resistors? Sorry for being a noob about it, this is my first experience with a PAB switch. Thanks for your help and patience.

New Question: Mat mentioned in the original 86 Special thread that the tone circuit did not work correctly. I built mine to his layout and it does not work either. The Bright. Mid and PAB switchs seem to work correctly. So.... can you take a look at the layout and schematic and recommend a fix? I se...

SUCCESS! Robert was right, I tracked back through the OD drive wiring and discovered two wires were reversed. Once corrected, the OD channel has nice, sweet sustain. It sounds great with a little delay. Thanks everyone for your input, especially Robert. Now I'll try a version with 2 EL-84s, double s...

That's interesting. I think you are right about the schematic, but... I have it wired like the layout which has the grid (pin 9) going to a 150k resistor and then to the middle (wiper) lug of the Drive pot.

Check out the sound files for the post SE EL84 Mini ODS PTP, this is the sort of overdrive I was expecting from this similar circuit.

Yes, these are the voltages I used to compare with my amp in the previous post. They seem to be close enough to me, I don't see that the original amp (meaning Mat's) has "substantially higher voltages". 10thth, didn't you build one of these circuits?

Compared to the posted voltages, my amp is with in a few volts (on the low side). The first value is the posted voltage, the 2nd value is my amp Point A: 263v/257v Point B: 257v/ 247v Point C: 261v/ 250v Point D: 259v/ 240v EF86 voltages: bias: .8v/.86v Grid: 51v/50v Plate: 105v/ 118v This circuit d...

Agreed, I checked the 820r, 82k & 820k first thing, all correct.

Dang, it's not the tube. I checked the component values for the EF-86 stage. the bias and plate voltages match those listed on the schematic.
Now I think it's gonna be one of those embarrassing ah-ha things.....
I'm still looking.....

Yes, indeed the OD channel stops working with the EF-86 is removed BUT after confirming that the channel switching is wired correctly and that the OD channel controls (level, drive and tone) all work correctly, I discovered that even though the filament circuit is supplying power to the EF-86, the t...

Thanks, Here's the schematic and layout I built too (with the effects loop omitted). I agree that it sounds like the 12AX7 stage and the EF-86 stage are working independent of each other. I'm going to the check the channel switch wiring to see if there is an error there. The sound files that Mat pos...

I've just constructed an EF86 Special using Mat's layout, schematic and BOM, The B+ voltages measure about 8 to 10 volts low but the amp sounds very nice. The issue is, the OD side is just about a clean as the clean side, there is no significant over-driven tone to speak of. Both channels are plenty...