Cannot Find Source of Amp Crackle

[caveing]

plate resistors on the extra gain stage in the reverb channel!!!

Problem solved!!!
v4 voltages back to normal
The amp is really gainy, surprisingly enough... When i first got it about 6 years ago... it had stock preamp tube set with sovtek 5881's and a 5ar4 rectifier tube. I took out a 115k and a 130k plate resistor out of the reverb channels first gain stage. and there were some lower valued cathode bypass caps in some spots- like a 4.7uf and a 2.2uf. everything else stock values AFAIK.

it used to be SUPER clean and SUPER LOUD- I mean headroom for days with a les paul. I never got gain without a pedal.... with 5881's. The amp also didnt sound as good as it does now... not even close. it was sterile and flat. now it's warm and punchy and chimey- great shit here.

I'm wondering how it could have behaved like that... and how 5881's could have even survived with the high plate voltages a 5ar4 makes in this amp. Could that have just been super cold bias?

Thanks to you all the amp sounds great now!!! I mean really, really good. Thanks so much!

[Cygnus X1]

Congrats!

Now take the rest of the day off.

[sliberty]

Great news about the amp. Enjoy!

[caveing]

anyone got any idea why it has so much less clean headroom than it used to?? could that be bias alone? i mean it had 5881's! they were sovtek's though, so i guess they could be more like 6l6's. but i mean it had the 115k and 130k plate resistors! it used to be like i couldnt get any dirt at all with my humbucker epi les paul that was decently high output. but i could with my danelectro because the pickups were so much weaker i was able to turn the amp up to 8 and get a very moderate tube breakup... weird

[surfsup]

Just a guess, but if all tou changed was the plate resistors, if the old ones drifted and produces less gain at each stage perhapsmthat is an explanation? I don't have much experience with resistors drifting in value so notmsureifnthat is even viable...

[caveing]

Just a guess, but if all tou changed was the plate resistors, if the old ones drifted and produces less gain at each stage perhapsmthat is an explanation? I don't have much experience with resistors drifting in value so notmsureifnthat is even viable...

what does that even mean? english is preferred.

I have replaced every component in this amp in the past 3 months. the only mods to the measured original components were the plate resistors were like 120k but measured at 115k and 130k... i didnt measure anything else that had drifted too far outside its tolerance if at all. granted I didnt measure every single part I removed. But whatever, is there anything that would even give you that much more headroom?

[Jana]

Caveing,

If you want to get picky about grammar and punctuation, I counted 10 errors in your last post.

[statorvane]

Another possibility is a bad solder joint.

Yep. It took me a couple of weeks to find this was causing similar problems on a clone JCM800 build for my son. The way I eventually found it was chopsticking around. Initially it sounded like I had microphonic wire, but it was a loose solder joint on V1. Listen for some noise when you choptick the wires, and fi one stands out, trace it to its solder joints.

Could also be a tube socket - loose pin somewhere in the vibrato channel.

Good luck, and hope this helps.

[Structo]

In my limited experience those old carbon comp resistors usually drift upwards in value.

[caveing]

Caveing,

If you want to get picky about grammar and punctuation, I counted 10 errors in your last post.

Sorry, i'm from kentucky and am definitely not exposed to correct grammar very often--i also dont associate with people that give a shit about grammar-- i honestly just didnt take the time to translate his post- i really had no idea what he was saying. but now i get it.

yeh plate resistors have always drifted up on me. why i'm wondering how the amp had so much more clean headroom a few years ago... that thing was LOUD

[Jana]

Being from Kentucky is nothing to be sorry about.

[thejaf]

If it was cold biased before, then probably lowered B+ voltage to the preamp some when you biased correctly (power tubes now draw more current). Lower voltage in the preamp usually = easier overdrive.

[caveing]

If it was cold biased before, then probably lowered B+ voltage to the preamp some when you biased correctly (power tubes now draw more current). Lower voltage in the preamp usually = easier overdrive.

Plus the 5ar4 rectifier... that increases preamp voltages an increases headroom right? I'm wondering if I could pull some extra clean headroom.

Are sovtek 5881 wxt's true 5881 tubes? I'm thinking I could have some 5881s and the 5u4 with my single 12" speaker for low headroom.. and I could thow in sme 6l6gcs and a gz34 with cold bias and a 2x12 cab with my cannabis rex speakers for increasing the headroom... seems like that might change my clean headroom quite a bit