My ONLY Gripe: Scratchy/Gravely Tone to QR/PS

[jyd]

<sub>I've got at 2015 Pro Stock B+, and as long as I've had it, it can have a 'scratchy, squelchy, gravely' sound to it.  I know others have described it this way.  I'm not saying it's bad as I do love the amp, but compared to some of my other amps (Friedman's, BFG modded Marshalls), they don't have quite that quality.  

I'm wondering if anyone else has noticed this on this board (heard on it others), and what you do about it.  I even thought if having it slightly modded would help, and of course, certain speakers not broken in don't help. 

Perhaps the mid cut and new/old help with this sound? 

Cheers.</sub>  

[splawndude]

I'll be the first to say I do not know of what you speak.

Those are adjectives I have not heard used before in describing a Splawn.

New speakers are not necessarily a fun sound I will admit.

Are you sure all your contact points (jacks and tube pins) are clean and/or microphonic tube/pickups? Based on your posts about your other amps I'm assuming you've already checked this stuff out.

Just trying to think out loud and help.

[gtrjunior]

I know exactly what you’re talking about....
Here’s what I discovered...long story.
From day one I heard what you’re talking about.
A while back I was playing in a small band where my QR was too much amp. So I was using my Blackstar HT-Studio.
So I’m at a gig and thinking WOW this amp sounds KILLER....why doesn’t my QR sound this good?
So I went back to basics. I unplugged everything and plugged guitar straight into the amp...and BOOM! There it was. Killer Splawn tone.
Then I started adding one pedal at a time back to the signal....when I got to my non true bypass wah...there was the culprit. I was using one of the switchless crybaby wah pedals. I swapped it out with a crybaby classic which is “hardwired bypass”. Issue #1 solved.
A few months later I blew out a power tube. So I replaced the set and before I biased them, I shot an email to Scott asking what he set the bias to.
I fully expected to get a response in a couple of days but much to my surprise he emailed me back about 5 minutes later. Here is his response cut and pasted from the email:

“I normally set it around 30ma per tube on the full power side which will be around 40ma per tube on the Drop B+ side.”

I set the bias as instructed and the amp sounds PHENOMENAL.

I’d recommend starting from scratch as I did and see where that takes you.
I can honestly say that I have never had an amp that is this good. And I struggled to find my tone for a while with this amp. I’m sure if you searched this forum for posts started by me you’ll see my struggles.

All of my struggles were user error.

[jyd]

Jul 23, 2018 12:07:19 GMT -5 gtrjunior said:

I know exactly what you’re talking about....
Here’s what I discovered...long story.
From day one I heard what you’re talking about.
A while back I was playing in a small band where my QR was too much amp. So I was using my Blackstar HT-Studio.
So I’m at a gig and thinking WOW this amp sounds KILLER....why doesn’t my QR sound this good?
So I went back to basics. I unplugged everything and plugged guitar straight into the amp...and BOOM! There it was. Killer Splawn tone.
Then I started adding one pedal at a time back to the signal....when I got to my non true bypass wah...there was the culprit. I was using one of the switchless crybaby wah pedals. I swapped it out with a crybaby classic which is “hardwired bypass”. Issue #1 solved.
A few months later I blew out a power tube. So I replaced the set and before I biased them, I shot an email to Scott asking what he set the bias to.
I fully expected to get a response in a couple of days but much to my surprise he emailed me back about 5 minutes later. Here is his response cut and pasted from the email:

“I normally set it around 30ma per tube on the full power side which will be around 40ma per tube on the Drop B+ side.”

I set the bias as instructed and the amp sounds PHENOMENAL.

I’d recommend starting from scratch as I did and see where that takes you.
I can honestly say that I have never had an amp that is this good. And I struggled to find my tone for a while with this amp. I’m sure if you searched this forum for posts started by me you’ll see my struggles.

All of my struggles were user error.

Yup, I'm playing straight in, no FX.  I can say I did notice it more after the last retube back in November last year, AND it's a B+, so perhaps I can rebias it.  

So based on Scott's response in your cut and paste: I have a 100w B+, so I should bias it around 40ma per tube?

Also, as an example, I have a Friedman BE50.  It came biased colder than Dave recommends.  My tech and I think a lot of amps come biased colder than where builders recommend so that the tubes last longer.  The BE50 was awesome, but had somewhat a 'raspiness' to it I wasn't liking.  ...We checked the bias and it was cold, 13.5w per tube; Dave recommends 15w per tube, and we put it up to 16w per tube and that raspiness that was hard to dial out went away.  

One think I will say comparing the BE50 and the Splawn is the EQ/tone controls on the Friedman have way more range across the dial.  ...I  would love to add options like NFB control, Mid/Cut, New/Old, and make the OD1/OD2 'tight'-er, more TS like, like the 'tight' switch on the new Mesa TC's.  

[gtrjunior]

What you want to do is flip the B+ switch to the off position and then bias at 30mA. Then when you flip back to B+ the plate voltage drops which results in a higher mA reading.

I have a JCM800 which is stock (with the exception of a tube driven Fx loop a previous owner installed). A non high gain amp like that often benefits from a hot bias.
I made the mistake of thinking the Splawn, which is very Marshall-like would benefit from a high bias as well.
I can now say that from experience that is not the case with the Splawn.

So B+ in the off position and bias up at 30mA

[jyd]

Jul 23, 2018 17:25:21 GMT -5 gtrjunior said:

What you want to do is flip the B+ switch to the off position and then bias at 30mA. Then when you flip back to B+ the plate voltage drops which results in a higher mA reading.

I have a JCM800 which is stock (with the exception of a tube driven Fx loop a previous owner installed). A non high gain amp like that often benefits from a hot bias.
I made the mistake of thinking the Splawn, which is very Marshall-like would benefit from a high bias as well.
I can now say that from experience that is not the case with the Splawn.

So B+ in the off position and bias up at 30mA

I don’t have a B+ switch: it’s fixed B+. This is a 2015, right before they added the B+ as a switch.

So what do you recommend since it’s a fixed B+?

Thanks!

[gtrjunior]

I see...
I think I’d shoot Scott an email and see what he recommends.
I’m going to guess that he will tell you somewhere around 30-32mA.
But it really should be calculated according the plate voltage in your particular amp and what percentage of dissipation is right for your amp.
If you do email him, let us know what he recommends. I’m curious.

[jyd]

Jul 23, 2018 20:12:03 GMT -5 gtrjunior said:

I see...
I think I’d shoot Scott an email and see what he recommends.
I’m going to guess that he will tell you somewhere around 30-32mA.
But it really should be calculated according the plate voltage in your particular amp and what percentage of dissipation is right for your amp.
If you do email him, let us know what he recommends. I’m curious.

Scott emailed me back.  He said: "It should be set around 40ma per tube." 

I also asked what the tone is like, brighter/harsher, at 30-32ma, and he said: "Maybe a little, it's more of a different breakup."

In my experience, biasing it colder/lower, amps get more harsh, raspy. 

 
So what do you think about biasing the B+ at 40ma? 

[gtrjunior]

If Scott says 40mA, then 40mA it is.