Crack/Speedball - hearing some distortion in the R channel

[Mr. Electric Wizard]

Good afternoon!
I completed the Speedball upgrade last weekend to my Crack, and the poly on the cabinet is dry now.
This afternoon, I'm listening to it for the first time and I'm hearing some distortion in the Right channel when the volume pot moves past the 12 o'clock position. 
Some albums such as the latest Tame Impala CD are recorded pretty hot, and the distortion appears at roughly the 8 o'clock position.
I'm not going to be listening to anything this loud but if I'm hearing it at this high volume, It's probably there at lower volume as well and I don't want to break the drivers in my headphones.
Is there anything I can do to mitigate?  I'm using some Sennheiser HD6XX drivers.

 

[Paul Birkeland]

I would resolder all of the joints in the amplifier.  When I hear distortion in a Crack that I'm fixing, I can usually trace it down to a bad solder joint that isn't properly conducting.

 

[Mr. Electric Wizard]

Everything was all good before I installed the Speedball.
You think this could be related to my higher (than the manual) voltage readings on OA/OB on the large board?

 

[Paul Birkeland]

I have worked on electronics built 50+ years ago that were "all good" but had joints that weren't soldered or weren't well soldered.  I've attached a photo of a Fisher 500C receiver that I went through and restored, then took back in to do some other mods.  I spent hours working on this thing and missed that bunch of diodes were never soldered back when it was originally made.  It worked fine, but I definitely soldered in those diodes!

When you put the Speedball in, you disturbed and moved connections that wouldn't otherwise be disturbed or moved, and this can introduce new problems.

 

[Mr. Electric Wizard]

Got it. 
Thanks!  I will go in and flow some more solder.
One thing I wasn't exactly sure on.
I was having issues with the bare ends of the tiny wires breaking off (these things are brittle) when I would turn the small board over to screw it down.  So I soldered the OA and 1B wires onto the other side of the board so that there was less stress on them for screwing the board down.
All of the wires enter the board from the bottom except for OA/1B.
Also, on the 1B hole, I accidentally filled the other 1B hole with solder.
Are both of these okay?

 

[Paul Birkeland]

I don't see any issue with that.

A broken wire that's still touching will also pass signal but not sound that great.

 

[Mr. Electric Wizard]

Again, thanks for your support.  8)
I opened her back up and did some minor surgery with re-flowing several joints.
The distortion appears to be gone now.

 

[Mr. Electric Wizard]

Weird.  I don't hear it when the unit is first powered on.
If I let it play for a few minutes at a moderate volume it starts distorting.
I apologize for being the 'problem child'.

 

[Mr. Electric Wizard]

I did try unplugging and plugging the tubes back in to make sure they were seated correctly.
Also, my new cables finally arrived.  Using some good low capacitance cables now.
So far things are sounding great.

 

[Mr. Electric Wizard]

One more thing.
The DAC that is feeding the Crack has an output voltage of 2.1Vrms.
I just wanted to see if this is in the acceptable region for the inputs of the Crack.  Things sound good overall but I am still hearing a little bit of distortion.
Wanted to rule out overloading of the inputs.

 

[Mr. Electric Wizard]

The Crack sounds so good 95% of the time with no distortion, I'm not convinced it's not a mis-setting on my stack somewhere.
Playing with drivers for my DAC.  Will keep reporting back if anything comes up.

 

[Deke609]

What kind of distortion are you hearing? I.e., what does it sound like?

cheers, Derek

 

[Paul Birkeland]

The Crack input shouldn't be fed much more than 100V.  Much above that level, you may damage the pot.  At high signal levels, you'll also have a very sensitive volume control.

 

[Mr. Electric Wizard]

What kind of distortion are you hearing? I.e., what does it sound like?

cheers, Derek

It just sounds like some breakup in the upper frequencies (scratchy?).
This does seem to go away when I lower the volume, but my ears are old so it may be there with the lower volume but I just can't detect it.
It isn't like this all the time either.  Seems to get more pronounced the longer music is playing, not necessarily how long the amp is powered on.
It's been on for several hours this morning, but the source has been paused on and off while I'm in a meeting.
I just pressed play with a decent amount of volume and I don't hear any scratchiness at all now.
It comes and goes which is really annoying and difficult to diagnose.

 

[Mr. Electric Wizard]

The Crack input shouldn't be fed much more than 100V.  Much above that level, you may damage the pot.  At high signal levels, you'll also have a very sensitive volume control.

So my 2.1Vrms going into the Crack is fine.  Comfortable level for me is ~9 o'clock on the pot.

 

[Mr. Electric Wizard]

I tried moving the power cable over being plugged directly into the wall (it was in a power strip before).  Still have some static.
I have REW installed on the PC and it has a section to play sign waves.  I played sign waves from 1,000Hz down to ~45Hz to see if I could hear any static while just playing tones.
I never heard any static, but when I had the tones playing ~300Hz and pulled the volumn pot up from 9o'clock up to 12o'clock I could hear the right channel tonality changing (getting more bright maybe).  There does seem to be some issue internally to the Crack.  Just not sure what it is. 
I've re-flowed all of the joints, and made sure there was solder on all the joints.
I had several days of listening to the Crack without the Speedball installed and I never heard any distortion.

We are talking very faint distortion.  But it's still there, you know.
The distortion is only happening when the volume is louder.
It's not there when the volume is lower.

This is my first tube amp, so is it possible that distortion is just 'a thing' with tube amps at higher listening levels?
My headphones are 300 ohm (Sennheiser HD6XX)

 

[Paul Birkeland]

Have you also re-flowed the joints on the Speedball boards themselves?

The Speedball lowers distortion and increases power available to the headphones, so there shouldn't be an issue like this appearing where there wasn't one before.

 

[Mr. Electric Wizard]

Have you also re-flowed the joints on the Speedball boards themselves?

The Speedball lowers distortion and increases power available to the headphones, so there shouldn't be an issue like this appearing where there wasn't one before.

Yep.  I will monitor for the time being and if it persists, I'll do it again.

 

[Mr. Electric Wizard]

Been playing at normal listening levels and it's sounded awesome all afternoon. 
I have it sandwiched between a computer monitor and a shielded bookshelf speaker.
If it comes back, could it be interference possibly?

 

[Paul Birkeland]

Interference manifests as noise generally, not distortion.