Tube Amp Archive

I did rotate the OT 90 degrees so it wouldn't be the same orientation as the PT. Would this make any difference? Definitely could be an issue. The axes of the coils should be oriented at 90 degrees to one another to minimize hum pickup in the OT from the PT. Hum produced in this way will be present...

I hooked it up like this, which I hope is what you meant by shorting wire across R136 and R137. It did not change the level of hum. I did rotate the OT 90 degrees so it wouldn't be the same orientation as the PT. Would this make any difference? The output tubes are right next to the OT. Though I've ...

A few extra pieces of info: As I mentioned in a previous reply, upon closer listening my hum sounds like 120hz. This hum is still present with all preamp tubes, the reverb tubes, AND the phase inverter tube pulled. This would possibly imply that the hum is happening after the PI? What confuses me is...

If you unplug the Reverb pan fully and put a short across the output jack rca does the him go away? Other then the pan and or something on the recovery side of the reverb circuit picking up the 60 hz hum from the power transformer I can’t see how you would be getting 60 hz hum 120 hz I can see and ...

Did you just jump out the effects loop with a short shielded cable, which is all that should have been needed? Yes, I used a shielded cable, as short as possible. The PCB is designed in a way that things kind of go all over, so I did what I could to keep it short. The hum is present with nothing pl...

I have a Fender Supersonic 112 (the original with the block letter name on the plate). This amp is known to be inherently noisy, especially with hiss. In attempt to lower the noise floor, one of the suggestions on the web is remove the send and return+effects loop. I did this by taking the signal ri...

Do that resistor load test, but I think your wasting your time . There's flat out no reason why a good 1085 can't power up the filaments on only three AX7s, unless the brand / make of your chosen 1085 is substandard. Like in the schematic I posted yesterday. A LM1084 not even a 1085 as in your case...

Hello -- What is the DC voltage on the input side of your regulator? Ideally this should at most be 4V or so higher than your desired filament voltage. If it's significantly higher, that regulator will be dissipating all the excess as heat. Best .. The thought had crossed my mind as well. It is an ...

I'm wondering if the low resistance of the cold heaters is pulling so much current that the regulator just can't recover. You might try putting a resistor across the output that is equal to the normal heater current and see if it can handle that. Each 12AX7 with heaters wired for 6.3V will have 6.3...

Based on the schematic, it would appear I am hooking everything up correctly, but seems that even bolting to the chassis is not enough heat dissipation to prevent thermal shutdown. I've tried with several 1084s and 1085s with the same behaviour. I'm using silicon insulator sheet designed for to-220;...

I'm powering 3 12ax7s. I've got it bolted to the amp's chassis. The chassis gets mad hot as you've described as well. The diagram includes the recommended heatsink for your regulator . I assumed bolting to the chassis would be a far better heatsink as it's much larger than that heatsink. My assumpt...

Do you have C3 4 and 7s polarity correct? Are they good? If you lift them one at a time does the voltage output level return? The polarity is correct. The circuit works as it should when not hooked up the tubes; ie outputs the appropriate voltage Hey Sluckey, Yes, I've got it insulated! (learned th...

Hey Sluckey,

Yes, I've got it insulated! (learned this the hard way in the past)

I'm powering 3 12ax7s.

I've got it bolted to the amp's chassis. The chassis gets mad hot as you've described as well.

I'm considering switching the transformer and running the heaters in series at 12.6v, but I did want to make sure I'm not just hooking this up wrong.

Hi folks, I know that the topic of should you or should you not use DC heaters has been discussed many times before, this is not that. I am going to be using DC filament on my preamp section for two amplifiers. I am using a pre-made regulated+filtered pcb from Pete Millett. The schematic is attached...