Self biasing?

Weldaar

V.I.P. Member
Joined
Mar 25, 2007
Messages
2,460
Reaction score
431
I picked up this small Stage Right 15 watt tube amp for practice.
Sounds pretty good actually. I am just curious about the tubes.It has EL84 for power and 12 AX7 for pre stage.
Is this amp self biasing, how do I know for sure?SR sm.jpg
SR sm.jpg
 
Last edited:

Weldaar

V.I.P. Member
Joined
Mar 25, 2007
Messages
2,460
Reaction score
431
Thanx, I read that. I never heard of small Class A amps being biased, this is why I am questioning. I have a Friedman Runt that is also class A and is twice the amp of a Stage Right and that is self biasing. If I do not bias the SR amp, will the tubes adapt to whatever it's biased at?
 

Weldaar

V.I.P. Member
Joined
Mar 25, 2007
Messages
2,460
Reaction score
431
That's what I was thinking because my Friedman which is EL84 powered does not need to be biased. This little Stage Right should not need it either. Thanx for your help and insight.
 

ehb

Chief Discombobulator
Premium Member
Joined
Feb 20, 2013
Messages
33,943
Reaction score
148,564
I have the old version of that with the top knobs instead of front... Still a Laney 12R I believe....

I bought one just out of idle curiosity after reading about others here liking them....

Liked it when I first played through it. I thought the speaker (Celestion 70/80 12" I think) could be better.... I haven't changed anything though.... Nothing...

Odd thing is after a while the amp started sounding damn good all of a sudden. Chalk it up to speaker cone break in, tubes breaking in, rotation of the Earth or whatever, it got really sweet all of a sudden. It has sat in the same spot on a small Harbor Freight dolly since I got it a couple years ago.

I am FAR from amp poor. I play through the Monoprice every single day....I'll forget to turn it off and it can run for a couple of days, no issues at all.... Damn good amp....


I will say this, part of my new speaker or new amp (which is new speaker) break-in process involves one of my fiver basses at low volume... No thump slap, just smooth stuff like walks, etc.. Flexing dat paper at a LOT of different freqs...

Only thing I regret is not buying at least TWO of em....... Mine was 192.00 to my door...
 

Weldaar

V.I.P. Member
Joined
Mar 25, 2007
Messages
2,460
Reaction score
431
I am inquiring for a friend that has the same amp. I have changed the tubes in mine due to a bad crackling. I also swapped the crappy 70/80 for one of my Eminence Red Coat Wizard. Thicker bottom
 

ehb

Chief Discombobulator
Premium Member
Joined
Feb 20, 2013
Messages
33,943
Reaction score
148,564
Mine actually opened up... I thought it would never break in but did..... I am a fan of Emi Red Coat Private Jacks... I had thought about slapping one in my Mono but after the stiff ass 70/80 FINALLY broke in, nah... Leaving it like it is till it blows up... Damn should have bought two amps and left one in the box... At one time, considered putting a vintage JBL 12" in it after hearing a bud's black face Princeton Reverb with a 12" JBL that made me moist.... but not now..... I like mine better than his PR now....
 

Skit

Witch Doctor
Joined
Jun 10, 2009
Messages
5,470
Reaction score
5,206
I have a '90s Peavey Classic 20 that has EL84's and is self biasing but I didn't know if all EL84 amps are the same. I'm just wondering if the Stage Right is self biasing why does it have a bias pot and not a cathode resistor? Unless they changed how they build them at some point.
 

Weldaar

V.I.P. Member
Joined
Mar 25, 2007
Messages
2,460
Reaction score
431
According to the manufacturer, they are not self biasing. They need to be biased when installing new tubes. Just found this out.The newer ones are self biasing, not the 15 nor 5 watt amps..
 

Weldaar

V.I.P. Member
Joined
Mar 25, 2007
Messages
2,460
Reaction score
431
Yeah, I was checking for a friend who wants new tubes. I changed my three months ago without biasing. Sounds good to me.
 

CB91710

Premium Member
Joined
Jul 19, 2019
Messages
4,241
Reaction score
8,589
According to the manufacturer, they are not self biasing. They need to be biased when installing new tubes. Just found this out.The newer ones are self biasing, not the 15 nor 5 watt amps..
Ya... This is generally the case.

The Blues Junior is also EL84, but Fender went the other way... not only did they not put a bias pot on the board, the thing is biased hot from the factory.
So hot that red plating is not uncommon when the tubes are changed.
There was (was) a good conversation about this on the Fender forum. Apparently JJ offers matched sets in several different levels, and one of the three (4?) is generally going to work well with the BJ.

Some manufacturers get away with claiming self-bias by setting on the cold side to reduce the plate dissipation to well-under design limits.
Some, like Peavey and Mesa, claim self-biasing, but only if you use their tubes (which are screened for compatibility.)

But any fixed-bias amp is going to need to be checked.
 

Weldaar

V.I.P. Member
Joined
Mar 25, 2007
Messages
2,460
Reaction score
431
Can someone post the manual for the Stage Right link
 

CB91710

Premium Member
Joined
Jul 19, 2019
Messages
4,241
Reaction score
8,589
I keep thinking about doing a kit build... but like newer features such as the loop, and full EQ.
At the price for these things, seems worth it to buy one just for the chassis and iron, gut it, and build a nice handwired amp into it.
 

Weldaar

V.I.P. Member
Joined
Mar 25, 2007
Messages
2,460
Reaction score
431
I mainly use mine for rehearsal, but I could gig with this if need be. Got mine for under $200. They are nearly $300 now.
 

Skit

Witch Doctor
Joined
Jun 10, 2009
Messages
5,470
Reaction score
5,206
I mainly use mine for rehearsal, but I could gig with this if need be. Got mine for under $200. They are nearly $300 now.
Yeah I see a lot of people saying they are a hell of a bang for the buck.
 


Latest Threads



Top