5150 III preamp tube issue?

[ledvedder]

Another question I have. Lots of posts were saying they're biased cold from the factory and suggested biasing around 30. I checked mine at the test points and it read 57. I'm assuming that's the sum of each 6L6?

 

[LP Freak]

Well to further confuse things, I just popped in a set of Winged C 6L6GC’s and No more of those annoying hi’s and they brought the mids forward a bit.

I have some Tungsol 6L6-STR's, and some Ruby STR's I thought of trying, but figured they'd be brighter than the JJ's. Might be a good thing for channel 2.

Right now, I'm running:
V1 Mullard CV4004
V2, V3, V4 JJ
V5 Tungsol
V6 Ruby
V7 JJ (balanced)

My only complaint is the amount of gain on channel 3. Didn't really care for a 5751 in V2, V3, or V4. But, I live on channel 2. Channel 3 as a lead channel only, but channel 2 works just as well.

I was thinking they’d be brighter too but figured what do I have to loose.

 

[LP Freak]

Another question I have. Lots of posts were saying they're biased cold from the factory and suggested biasing around 30. I checked mine at the test points and it read 57. I'm assuming that's the sum of each 6L6?

My plate voltage is 500 so I biased mine at 38mA which is 60%. It was set at 50% from the factory.

 

[ledvedder]

Another question I have. Lots of posts were saying they're biased cold from the factory and suggested biasing around 30. I checked mine at the test points and it read 57. I'm assuming that's the sum of each 6L6?

My plate voltage is 500 so I biased mine at 38mA which is 60%. It was set at 50% from the factory.

So, you set it so it read 76 at the test point, or 38? Mine read 57.

 

[LP Freak]

Another question I have. Lots of posts were saying they're biased cold from the factory and suggested biasing around 30. I checked mine at the test points and it read 57. I'm assuming that's the sum of each 6L6?

My plate voltage is 500 so I biased mine at 38mA which is 60%. It was set at 50% from the factory.

So, you set it so it read 76 at the test point, or 38? Mine read 57.

I’m not sure what test point you’re referring to. I use a Weber Bias Rite.

 

[bhuard75]

I’m not sure what test point you’re referring to. I use a Weber Bias Rite.

Weber bias rite BR4, one of the best $150 purchase ive ever made.

 

[ledvedder]

Another question I have. Lots of posts were saying they're biased cold from the factory and suggested biasing around 30. I checked mine at the test points and it read 57. I'm assuming that's the sum of each 6L6?

My plate voltage is 500 so I biased mine at 38mA which is 60%. It was set at 50% from the factory.

So, you set it so it read 76 at the test point, or 38? Mine read 57.

I’m not sure what test point you’re referring to. I use a Weber Bias Rite.

This one.

 

[ledvedder]

I did some more tube rolling tonight. This is what I ended up with.
V1 - Mullard cv4004
V2 - Ruby 12ax7ac7
V3 - JJ 5751
V4 - JJ 5751
V5 - stock
V6 - stock
V9 - Sovtek LPS

Now I'm loving all 3 channels. And it quieted the amp down considerably.

 

[napalmdeath]

I did some more tube rolling tonight. This is what I ended up with.
V1 - Mullard cv4004
V2 - Ruby 12ax7ac7
V3 - JJ 5751
V4 - JJ 5751
V5 - stock
V6 - stock
V9 - Sovtek LPS

Now I'm loving all 3 channels. And it quieted the amp down considerably.

Yeah, the 5751's cut the gain 30%.

 

[311boogieman]

Looks like you got it sorted.
Big fan of 5751s.
You took your video down?
Was the 'popping' coming through the speakers?
That is one way to test for microphonics.
New production tubes seem to be more prone these days.
Otherwise, don't tap on tubes unless you need to.

 

[Racerxrated]

Well to further confuse things, I just popped in a set of Winged C 6L6GC’s and No more of those annoying hi’s and they brought the mids forward a bit.

See, now I've read all over the internet that different power tubes didn't make much difference.

Only one way to find out. Everyone hears things different too. And some can’t hear at all.

No tube is going to transform it into a new amp but it’s all part of the recipe. Just like the cabinet you’re using. Swapping speakers will make a more noticeable change than any tube will.

I think the first thing to figure out, is what speakers to use. That's where these forums are so helpful. Once you match a good cab with your amp, then fine tuning with tubes can be the next step if you want to continue down that path.
I've spent the past week rolling pre tubes with my 2210. I have a good stash of vintage 12ax7s, but its been a while since I messed around and rolled different combos. It's fun and surprising what a difference it makes when you just move the same set around in different positions. Winged C EL34s in the power section.
V1-Vintage Mullard. V2-Ei pre war. V3-RCA Black long plate. V4-GE Grey long plate. V5-Tungsram. Good times.