Fender Hot Rod Deluxe distorting on clean channel

[dan_man]

Recently when I've recorded on my bandmates HRD, the recording usually has this strange distortion. It mainly happens when chords are played louder, when played softer the distortion goes away. The tubes in the amp recently were changed and we tried using new cables but the problem still continues.

[pdf64]

When the replacement power tubes were fitted, was the voltage at TP30 checked, eg 60mV?
http://bmamps.com/Schematics/fender/hotrod_deluxe.pdf

[Jazz P Bass]

The 'Clean' channel can be made to distort.

Where do you have the volume & tone controls set at?

Is the guitar volume all of the way up?

Then again it could be a bad speaker.

[DRH1958]

Also to add to what pdf64 said, did you used a matched set or at least tubes that were somewhat close? Unfortunately this bias check circuit is for both 6L6s, so you have to rely on the tubes being somewhat matched ahead of time. This method won't let you check for balanced output tubes. There is another way but let's put that off for now unless you just threw any old tubes in. Was the amp making these sounds before the tube change and was this an effort to stop the strange sounds? If so, then you could have other problems like bad solder joints. Turning the amp up causes these joints to vibrate more, so quieter playing lessens this. Is the strange distortion a crackly type sound? These Hot Rod amps are known to have this problem. Also you might want to save the old tubes for spares because they could still be good. BTW, welcome to the place!!

[Pedro Vecino]

Relatively common problems in this amplifier causing distortion are:
- Open plate resistor in phase inverter
- Open screen grid resistor in one output tube
Also affect channel 2, but can sometimes go unnoticed.
There are other possibilities, of course.

[dan_man]

So another interesting that I discovered was I dug through my trash folder on my laptop and found some practice takes I did before recording the final take. When I recorded these I had the gain output on my DAW lowered to around -7 to -8. They sounded perfectly normal, however I then turned the gain up to -3 and -4 and forgot to lower it back when recording the final take. The final take was the one that sounded distorted. It wasn't clipping however. Can gain output on a DAW affect my guitar signal this drastically? It's suspicious to me why the guitar sounded normal with very low and healthy output levels. I'll have to try this again when I head to my friends home studio this week. I also wish I knew more about the amp and could test it for longer but it belongs to my friend. Any thoughts though?

[Guitarist]

Just fixed one and it had the "Open plate resistor in phase inverter" problem. I saw the voltage wasn't there, swapped in another 100K and voila! I may've subbed in a 12au7 which draws more current
The dist channel likes caps reduced to .0047. Injection DC into the tube board filament string sure quiets the amp hum/hiss. Pretty sweet amp now, one I can endorse if modded.