My first time biasing new tubes...

[jumpnblues]

......I'm installing new Sovtek 5881 power tubes in my Victoria 35115T Tweed Pro and I'm using Ted Weber's Bias Rite. Two questions: 1. Is that little plastic screw on the amp chassis the bias adjustment? 2. What should the Bias Rite read (What reading should I bias the tubes to?)? Thanks. http://www.tdpri.com/forum/images/smilies/icon_cool.gif http://www.tdpri.com/forum/images/smilies/icon_cool.gif

Tom

[Blue Strat]

I can't answer your first question, but my guess would be "yes".

Before installing your new tubes (BTW, there were much better choices for those) practice biasing your existing tubes. Adjust up and down and follow the action on the meter. When you're done, set the bias pot to the lowest possible setting BEFORE installing the new tubes. Adjust the new tubes to about 35mA each. There are some calculations that are often done but these require knowing what your amp's plate voltage is. 35mA is always safe though.

Have fun and good luck!

[jumpnblues]

Hi Mike,

Thanks for the info. Yeah, I know there are better choices. Those are the only ones I have available right now. What would you recommend for power and preamp tubes with this amp?

Tom

[Blue Strat]

Hi Mike,

Thanks for the info. Yeah, I know there are better choices. Those are the only ones I have available right now. What would you recommend for power and preamp tubes with this amp?

Tom

For new production tubes, either SED 6L6GCs or Tung Sol Reissue 5881s (less headroom) and Tung Sol Reissue 12AX7s.

For REALLY good tubes, NOS RCA 12AX7As and NOS GE 6L6GCs or NOS Tung Sol 5881s. Another, less expensive, 5881 are the JAN Philips 6L6WGBs.

[jumpnblues]

Mike,

I just found some JAN Phillips 6L6WGBs and tried to bias them but they must not be matched very well...they're about 20 milliamps apart regardless of how I adjust the bias??? Will I be able to use them?

Tom

[epluribus]

Before installing your new tubes (BTW, there were much better choices for those) practice biasing your existing tubes. Adjust up and down and follow the action on the meter...



I learned this right here on TGP too, just like you are. Run while you still have the strength... :crazy

I like Mike's approach, adjusting things with a DMM safely attached--you'll pick up a practical grasp of the results quick. But I'm a big fan of keeping the guitar by the workbench and spending some time auditioning each change throughout the rig's range too, just to develop an intuitive grip on what your tweaks really do. Ear training, sort of.

Have fun and good luck!

+1!

--Ray

__________

Shut up 'n' solder yer amp. :)

[Blue Strat]

Mike,

I just found some JAN Phillips 6L6WGBs and tried to bias them but they must not be matched very well...they're about 20 milliamps apart regardless of how I adjust the bias??? Will I be able to use them?

Tom

Sorry dude, you should've gotten them from a reliable dealer.

[Blue Strat]

I learned this right here on TGP too, just like you are. Run while you still have the strength... :crazy

I like Mike's approach, adjusting things with a DMM safely attached--you'll pick up a practical grasp of the results quick. But I'm a big fan of keeping the guitar by the workbench and spending some time auditioning each change throughout the rig's range too, just to develop an intuitive grip on what your tweaks really do. Ear training, sort of.



+1!

--Ray

__________

Shut up 'n' solder yer amp. :)

Excellent suggestion! Try different settings and then listen to the impact.

[epluribus]

Excellent suggestion! Try different settings and then listen to the impact.

Thanky Mike. Amazing what leaks into my little Jethro brain sometimes. :)

[Blue Strat]

Thanky Mike. Amazing what leaks into my little Jethro brain sometimes. :)

Just don't let any of that leak out! :rotflmao:BEER

[epluribus]

:roll:roll:roll

[jumpnblues]

"Sorry dude, you should've gotten them from a reliable dealer."


Yeah, I don't know where or when I bought them. Didn't even know I had 'em. I must've had them for awhile. I went ahead and installed the Sovteks and biased one at 35 and the other about 37 until I order better tubes. That's as close as I could get them to match. How far from the 35 reading can you safely take them? What difference in tone does it make? Thanks again.

Tom

[Blue Strat]

"Sorry dude, you should've gotten them from a reliable dealer."


Yeah, I don't know where or when I bought them. Didn't even know I had 'em. I must've had them for awhile. I went ahead and installed the Sovteks and biased one at 35 and the other about 37 until I order better tubes. That's as close as I could get them to match. How far from the 35 reading can you safely take them? What difference in tone does it make? Thanks again.

Tom

Depends on the amp and plate voltage. 30 to 40mA is typically safe. Try that range and listen to see what happens. If you go to 20 or lower you're more likely to hear a difference.

[harryjmic]

Most Victoria amps should have a blue resistor attached to pin 8 (I believe). This resistor is used as a measuring point to set the bias of the amp. All you have to do is measure across the resistor (one lead on each side of the resistor). You will set your DVM to dcmv and measure the voltage in millivolts. This number is technically the same value as the bias current.

I have owned 3 Victorias and now own a Fender Bassman. For me the best sound has been achieved when the bias was set between 31 and 33 ma. Personally I have the bias set on my Fender at 31.5ma. I prefer to set the bias so the tubes still remain clear sounding. It's easy to hear the difference, as you turn up the bias (more ma's) the amp will reach a point where it thickens up and gets more midrangy. I like to set the amp so it's just below this point as it yields a beautiful clean tone without all the harshness that can occur at higher setting.

BTW, the variable bias pot (resistor) should be blue with a white set screw. The pot is square and normally located on the left side of the tag board in about the middle.

[jumpnblues]

Harry and Mike,

Thank you so sincerely for your help. Mike you'll be getting a call for tubes.

Tom