So i managed to put 260vdc throough the input of my vox. Neddless to say it cooked the first ic. Looki g at the schematic i tried injecting signal at pin 2 pin 7 and pis 2-7 in parallel. With mixed results it worked but was noisy and on the higher gain models it would oscilate and squeal. Then i tried at r88 and it workec great. Now my dilema is put this 15 cent single transistor boost stage in and be done or put a 6sn7 running at 260vdc in there. The tranny boost has adjustable gain so once its in there i can dial it in just like it was. The 6sn7 sounds great its really clean and its another tube in the signal path.

Hello forum I'm new to the forum. But not to electronics in general. I've built some tube preamps a few transistor boosters, messed with op amps a bit. I have built a few tone stacks as well the james and the muff pi. Now to the matter at hand I have a QSC 1400 with one channel that does not work. I have looked everywhere for a schematic for it. All I can find is one that is unreadable I can make out the signal path on it but cannot see any values for the components. Any help is greatly appreciated thank you in advance.