help, biasing my Splawn with new tubes

[Lord Toneking]

I just tried to put a quad of Tung Sol EL34B's in my amp tonight. When I hooked up the weber it read 19ma, so I turned the bias pot until it maxed out and it only went up to 24ma

I put in an old old set of Mullards and it went to 26ma...maxed once again

Then my buddy had some winged c's that were at 32ma and sounded really good...but the bias trim was maxed

The TS tubes were rated at 27ma, bought from Doug's Tubes. Do you think that the tubes were just too cold for my amp?...as were the Mullards? The winged C's fell into range but I cant figure why my bias screw is maxing out. It sort of clicks when it's maxed, is that the way it's supposed to be??

I'm wondering if I buy tubes at 40ma-45ma if my bias trim will have room on both sides (hot and cold)...or is something wrong with my bias trim pot?

 

[Dale B]

I just tried to put a quad of Tung Sol EL34B's in my amp tonight. When I hooked up the weber it read 19ma, so I turned the bias pot until it maxed out and it only went up to 24ma

I put in an old old set of Mullards and it went to 26ma...maxed once again

Then my buddy had some winged c's that were at 32ma and sounded really good...but the bias trim was maxed

The TS tubes were rated at 27ma, bought from Doug's Tubes. Do you think that the tubes were just too cold for my amp?...as were the Mullards? The winged C's fell into range but I cant figure why my bias screw is maxing out. It sort of clicks when it's maxed, is that the way it's supposed to be??

I'm wondering if I buy tubes at 40ma-45ma if my bias trim will have room on both sides (hot and cold)...or is something wrong with my bias trim pot?

Yes, 27 mA tubes at 400 vdc at the negative grid voltage Doug grades at on the Maxi Matcher is too cool for the Splawn. I had the same thing happen to me when I had the Quick Rod. Those amps like tubes in the 35 to 40 mA range.

The only other way around this is swapping out your bias resistor.

 

[Lord Toneking]

I just tried to put a quad of Tung Sol EL34B's in my amp tonight. When I hooked up the weber it read 19ma, so I turned the bias pot until it maxed out and it only went up to 24ma

I put in an old old set of Mullards and it went to 26ma...maxed once again

Then my buddy had some winged c's that were at 32ma and sounded really good...but the bias trim was maxed

The TS tubes were rated at 27ma, bought from Doug's Tubes. Do you think that the tubes were just too cold for my amp?...as were the Mullards? The winged C's fell into range but I cant figure why my bias screw is maxing out. It sort of clicks when it's maxed, is that the way it's supposed to be??

I'm wondering if I buy tubes at 40ma-45ma if my bias trim will have room on both sides (hot and cold)...or is something wrong with my bias trim pot?

Yes, 27 mA tubes at 400 vdc at the negative grid voltage Doug grades at on the Maxi Matcher is too cool for the Splawn. I had the same thing happen to me when I had the Quick Rod. Those amps like tubes in the 35 to 40 mA range.

The only other way around this is swapping out your bias resistor.

These were tubes that Doug sold my buddy for his JVM, he gave them to me because I was in a bind and have a gig Sat. Now my buddy is wondering if they'll work in his JVM


any thoughts??

 

[Dale B]

I just tried to put a quad of Tung Sol EL34B's in my amp tonight. When I hooked up the weber it read 19ma, so I turned the bias pot until it maxed out and it only went up to 24ma

I put in an old old set of Mullards and it went to 26ma...maxed once again

Then my buddy had some winged c's that were at 32ma and sounded really good...but the bias trim was maxed

The TS tubes were rated at 27ma, bought from Doug's Tubes. Do you think that the tubes were just too cold for my amp?...as were the Mullards? The winged C's fell into range but I cant figure why my bias screw is maxing out. It sort of clicks when it's maxed, is that the way it's supposed to be??

I'm wondering if I buy tubes at 40ma-45ma if my bias trim will have room on both sides (hot and cold)...or is something wrong with my bias trim pot?

Yes, 27 mA tubes at 400 vdc at the negative grid voltage Doug grades at on the Maxi Matcher is too cool for the Splawn. I had the same thing happen to me when I had the Quick Rod. Those amps like tubes in the 35 to 40 mA range.

The only other way around this is swapping out your bias resistor.

These were tubes that Doug sold my buddy for his JVM, he gave them to me because I was in a bind and have a gig Sat. Now my buddy is wondering if they'll work in his JVM


any thoughts??

It all depends on the sweep of the bias pot in the JVM, how the bias circuit is set up and the plate voltage it's running at, which is probably between 460 and 480 depending on what is coming in from the wall. They will probably be fine.

I run 25's to 30's in my XTC 101B and they bias up fine, but that amp has a higher plate voltage and a narrower sweep.

 

[killertone]

These were tubes that Doug sold my buddy for his JVM, he gave them to me because I was in a bind and have a gig Sat. Now my buddy is wondering if they'll work in his JVM


any thoughts??

They should work on the JVM no problem. The plate voltage on my JVM is around 475DCV and the sweep on the bias pots is fairly wide. Shouldn't be a prob.

 

[Bantam Menace]

Did the pot actually stop turning? I think the pot they use just keeps turning and turning and turning...and it take a lot of turns to get anything done.

 

[Dale B]

Did the pot actually stop turning? I think the pot they use just keeps turning and turning and turning...and it take a lot of turns to get anything done.

It will eventually stop turning.

 

[John4021]

No,the trim pot on the Splawn has a infinite amont of turns.
Keeps turning but will 'click" within 10 turns either way and thats the range of the sweep,but it will keep turning forever(just runs out of adjustment)