Biasing: How hard could it be?

Charlie Bernstein · December 17th, 2007, 06:13 PM

Never get to play my '65 Bassman LOUD, so I just bought a pair of 6V6s so I can crank it without the unwanted dBs.

So now it's going to need biasing. I can either:

1. Get a BiasRite and a voltometer and do it myself.

2. Pay a tech to do it.

I don't know electronics. I can solder in a speaker, but that's about it. I wouldn't mind learning to bias, if it's not too tricky.

Opinions? Thanks!

Freight Twang · December 17th, 2007, 06:18 PM

To run 6V6's you will have to drop the B+ voltage and may have change the resistor on the bias pot to do this, if you rebias and drop in 6V6's they'll be toast. Take it to a tech and have them set it right for you so you can get what you need. Good Luck.

Rob DiStefano · December 17th, 2007, 06:20 PM

A BiasRite is ridiculously easy to use. Less than a no-brainer. However, if the amp(s) in question don't have an easy access bias pot, get one installed.

EMan · December 17th, 2007, 06:52 PM

Typically, 6V6's have a grid bias voltage of ~45V, and 6V6's more like ~35VDC. As mentioned, with a high B+ and a bias voltage of ~45V, it may take some component fanagling to get the thing close.

As well, it's not gonna be that much lower in volume.

Charlie Bernstein · December 17th, 2007, 07:42 PM

As usual at old reliable TDPRI, everyone is in 100% cosmic alignment on a tech question.

Anyone else want to weigh in?

Charlie Bernstein · December 17th, 2007, 07:43 PM

PS -

Even just a little quieter would help.

JohnnyCrash · December 17th, 2007, 07:48 PM

Keep the Bassman as it is and get something smaller for home :)

A tweed Deluxe clone can crunch pretty good at lower volumes (warning, it is still loud)... cathode biased pair of 6V6s with a gnarly tweed preamp...

Or, if you really need low volume crunch, buy a Master Volume amp - OR, a low wat amp.

thepassivevoice · December 17th, 2007, 08:27 PM

Quote:

Originally Posted by Charlie Bernstein

PS -

Even just a little quieter would help.

I had an Allen Old Flame converted from 6L6 to 6V6 for exactly the same reason. Unfortunately, the impact on volume, especially at high levels, wasn't that noticeable.

casadyrocks · December 17th, 2007, 08:27 PM

Eurotubes sells all the stuff you need on their site and can tell you everything you need to know.

keiths · December 17th, 2007, 08:37 PM

Quote:

Originally Posted by JohnnyCrash

Keep the Bassman as it is and get something smaller for home :)

A tweed Deluxe clone can crunch pretty good at lower volumes (warning, it is still loud)... cathode biased pair of 6V6s with a gnarly tweed preamp...

Or, if you really need low volume crunch, buy a Master Volume amp - OR, a low wat amp.

Johnny speaks the supertruth!

Rob DiStefano · December 18th, 2007, 04:48 AM

What other folks have just posted - the 6V6 conversion is still gonna be Loud, so this is a perfect excuse to get a Class A 5F1 and have some real fun.

TelZilla · December 18th, 2007, 07:41 AM

+1 to Rob and JC. Go Champ, baby!

Tim Armstrong · December 18th, 2007, 07:47 AM

Charlie, what kind of speaker setup are you using with that amp? I ask this because I know that when I use bigger/more speakers, my amp gets louder. Maybe doing the opposite will work for you, try something like a single 10" speaker (better make it a high wattage one, though)...

Cheers, Tim

Charlie Bernstein · December 18th, 2007, 10:34 AM

I already have enough amps, thanks. When I sell one, I might buy another. Though I'd rather just make the other three (including the Bassman) more useful. The Pro Junior is out getting better pots and jack. The Ampeg needs some routine maintenance but is otherwise great.

I have two cabs for the Bassman - a 212 and a 210. Tim, I really like the 110 idea. Elegant!

Okay, so back to the original question - should I have a tech bias the 6V6s or do it myself? My tech skill put the "rude" in "rudimentary"...

Rob DiStefano · December 18th, 2007, 11:00 AM

Quote:

Originally Posted by Charlie Bernstein

... Okay, so back to the original question - should I have a tech bias the 6V6s or do it myself? My tech skill put the "rude" in "rudimentary"...

Get a BiasRite, AND if yer amp(s) don't have a bias pot, get yer tech to put one in. Biasing an amp with one of these gizmos is SO incredibly FREAKIN' EASY.

Excellent BiasRite scoop ...
https://taweber.powweb.com/biasrite/br_page.htm

Check out Bob's (JJ Eurotubes) vids on biasing ...
http://www.eurotubes.com/euro-video.htm

Freight Twang · December 18th, 2007, 12:13 PM

How about switching the amp to Cathode Bias, with 6l6's it will break up a little faster and at a lower volume.

Charlie Bernstein · December 18th, 2007, 04:26 PM

Okay. Some of you are saying the 6V6s will require new components and some are saying it won't.

That's interesting. Can anyone explain the disagreement?

Freight Twang · December 18th, 2007, 04:39 PM

Here's a quote from a customer from www.eurotubes.com:

Hang on... I have been torturing the JJ 6V6's in my 66 Bassman head now for several weeks at 460 plate volts biased at 22mA per tube and they sound GREAT! Jamona told me that they would run at up to 500 plate volts so I decided to give them a thrashing and they are holding up just fine. I also have a pair in a friends Hot Rod Deluxe at 445 plate volts and 24mA per tube and this is a gig amp for him so it will be a good test. So far the JJ 6V6's make a surprising amount of power and tend to breakup a little earlier with a mid and upper end crunch that is VERY cool! I'll keep you all posted on how they do over the long run but so far I'm very impressed! This should be a nice option for players looking for a little earlier breakup and that classic 6V6 crunch in bigger amps.

Dacious · December 18th, 2007, 06:11 PM

Charlie, the Bassman is a fixed bias amp in that the bias point refers to the voltage on the grids are held at, to coax electrons off the cathode. Too little, the tubes shut down or won't even start amplifying. Too many electrons attracted to the grids and they go incandescent, or pulll too much current onto the plate, and the tubes cook. There are two dissipation limits, grid and plate. And both need to be respected for your tubes to live.

But be able to vary this, you either have to solder in a new grid bias resistor after guessing (not good) or calculating plate volts/current draw, or have a variable resistor (potentiometer) installed in the bias circuit, like Blackface amps used to have. The 6V6s will amost certainly pull a different amount of current to 6L6s, as their plate-plate impedance as a pushpull pair is approx 50% higher than the 6L6s.

What this means, is that if you just plug 6V6s in without rebiasing, they may work - or they may light up like roman candles and have a short, spectacular life. The JJs reortedly handle the plate volts, but if you make them dissipate 40 watts instead of 15-20 like they are designed for, they may go pyro on you - and take out your output tranny and maybe some other stuff, too!

The biasrite and other similar instruments can tell you how much current they're pulling - but they can't correct it, it needs an operator (you?) to do that.

TeleBits · December 18th, 2007, 06:16 PM

I can see or watch the greatest players and be filled with admiration .. But I read this stuff and know I'll never be a musician ..

GUITARmole · December 18th, 2007, 06:53 PM

Quote:

Originally Posted by Charlie Bernstein

PS -

Even just a little quieter would help.

IMO you should sell it to someone that would appreciate or can use the additional volume or clean headroom...or...put a master volume in it. -I'm not saying to hack the amp up...you can install the potentiometer in an unused speaker jack so you don't have to drill it.

You could also try less efficient speakers or an attenuator (THD, Weber, etc)

Quote:

Originally Posted by Charlie Bernstein

Okay. Some of you are saying the 6V6s will require new components and some are saying it won't.

That's interesting. Can anyone explain the disagreement?

Well, name one person on the forum that has actually ran 6V6s in a 6L6 amp. Everyone's 2 cents is speculation based on their experience and knowledge. From what I've read, everyone (besides Eurotubes) has suggested alternatives and thought that 6V6s aren't a good idea and won't get you THAT much of a volume reduction. As for the component requirement it's difficult to say for sure without seeing your amp and measuring voltages (reason enough for disagreement).

It also depends on WHAT 6V6 tubes you've purchased...as already mentioned Eurotubes claim the JJs can handle it. I guarantee if you put in Sovtek or some NOS tubes you're asking for fireworks...

You could always go ahead and run them in your amp then report back if it sounds good and doesn't explode! Then we'll have the definitive answer!

I'm in the opposite boat...I have a Deluxe Reverb w/ 6V6 and I want MORE volume and clean headroom.

xjazzy · December 19th, 2007, 03:13 AM

Quote:

Originally Posted by GUITARmole

I'm in the opposite boat...I have a Deluxe Reverb w/ 6V6 and I want MORE volume and clean headroom.

You probably have a BIG BIG house or play at BIG clubs cause I have a DRRI and wish I can turn the volume up to 3 minimum!!!

I'm thinking on getting a Weber attenuator. I think the autor of this thread should do the same.

quackerz · December 19th, 2007, 12:02 PM

Quote:

Originally Posted by xjazzy

You probably have a BIG BIG house or play at BIG clubs cause I have a DRRI and wish I can turn the volume up to 3 minimum!!!

I'm thinking on getting a Weber attenuator. I think the autor of this thread should do the same.

I have a SFDR and a Weber MiniMASS. It sounds like utter garbage at low levels. Save your money and put it towards a tube pre-amp / distortion. At bedroom levels, the DR on 2 with a Duncan Twin-Tube or a DamageControl Womanizer sounds a billion times better than the DR on 8 though the MiniMASS.

Naturally this is my opinion and according to my wife, I know nothing.

chet · December 19th, 2007, 12:07 PM

I looked at the Fender Amp Field Guide and it says that the '65 Fender Bassman has an adjustment pot or bias pot. So I'd just get a Weber Bias Rite and do it myself.

xjazzy · December 19th, 2007, 01:33 PM

Quote:

Originally Posted by quackerz

I have a SFDR and a Weber MiniMASS. It sounds like utter garbage at low levels. Save your money and put it towards a tube pre-amp / distortion. At bedroom levels, the DR on 2 with a Duncan Twin-Tube or a DamageControl Womanizer sounds a billion times better than the DR on 8 though the MiniMASS.

Naturally this is my opinion and according to my wife, I know nothing.

I have a Twin tube, but I can't get to the 2 on my DRRI cause it's a little louder!!!
The attenuator is one option. Champion 600 is another... I have to decide.

So you don't have a good opinion on the MiniMass... hummm, I have to re-check my options.

Thanks.

December 17th, 2007, 06:13 PM	#1 (permalink)
Charlie Bernstein Friend of Leo's Join Date: Apr 2003 Location: Augusta, Maine Posts: 2,295	Biasing: How hard could it be? Never get to play my '65 Bassman LOUD, so I just bought a pair of 6V6s so I can crank it without the unwanted dBs. So now it's going to need biasing. I can either: 1. Get a BiasRite and a voltometer and do it myself. 2. Pay a tech to do it. I don't know electronics. I can solder in a speaker, but that's about it. I wouldn't mind learning to bias, if it's not too tricky. Opinions? Thanks!

December 17th, 2007, 07:48 PM	#7 (permalink)
JohnnyCrash Poster Extraordinaire Join Date: Mar 2005 Location: Lost Angeles and Orange County Posts: 6,976 39 Photos	Keep the Bassman as it is and get something smaller for home :) A tweed Deluxe clone can crunch pretty good at lower volumes (warning, it is still loud)... cathode biased pair of 6V6s with a gnarly tweed preamp... Or, if you really need low volume crunch, buy a Master Volume amp - OR, a low wat amp. __________________ . Learn about safety before building/repairing/modding an amp. When in doubt, take it to a shop. Never drink yellow snow. Have fun.

December 18th, 2007, 07:41 AM	#12 (permalink)
TelZilla Tele-Afflicted Join Date: Jan 2007 Location: Cleveburg, USA Age: 38 Posts: 1,489 6 Photos	+1 to Rob and JC. Go Champ, baby! __________________ Thanks,Nick You are what you is You is what you am A cow don't make ham -Zappa

December 18th, 2007, 07:47 AM	#13 (permalink)
Tim Armstrong Moderator Poster Extraordinaire Join Date: Mar 2003 Location: Berlin, Maryland, USA Age: 49 Posts: 7,510	Charlie, what kind of speaker setup are you using with that amp? I ask this because I know that when I use bigger/more speakers, my amp gets louder. Maybe doing the opposite will work for you, try something like a single 10" speaker (better make it a high wattage one, though)... Cheers, Tim __________________ http://www.moodswingers.org

December 18th, 2007, 06:11 PM	#19 (permalink)
Dacious Friend of Leo's Join Date: Mar 2003 Location: Godzone Posts: 2,602 35 Photos	Charlie, the Bassman is a fixed bias amp in that the bias point refers to the voltage on the grids are held at, to coax electrons off the cathode. Too little, the tubes shut down or won't even start amplifying. Too many electrons attracted to the grids and they go incandescent, or pulll too much current onto the plate, and the tubes cook. There are two dissipation limits, grid and plate. And both need to be respected for your tubes to live. But be able to vary this, you either have to solder in a new grid bias resistor after guessing (not good) or calculating plate volts/current draw, or have a variable resistor (potentiometer) installed in the bias circuit, like Blackface amps used to have. The 6V6s will amost certainly pull a different amount of current to 6L6s, as their plate-plate impedance as a pushpull pair is approx 50% higher than the 6L6s. What this means, is that if you just plug 6V6s in without rebiasing, they may work - or they may light up like roman candles and have a short, spectacular life. The JJs reortedly handle the plate volts, but if you make them dissipate 40 watts instead of 15-20 like they are designed for, they may go pyro on you - and take out your output tranny and maybe some other stuff, too! The biasrite and other similar instruments can tell you how much current they're pulling - but they can't correct it, it needs an operator (you?) to do that. __________________ My other Telecaster is a Thinline The Tele Bible, Ch 1, v 10 Love thy Telecaster, covet not thy neighbour's Strat! Last edited by Dacious : December 18th, 2007 at 08:01 PM.

December 17th, 2007, 06:18 PM	#2 (permalink)
Freight Twang TDPRI Member Join Date: Dec 2007 Location: Montgomery,Al Age: 40 Posts: 93 2 Photos	To run 6V6's you will have to drop the B+ voltage and may have change the resistor on the bias pot to do this, if you rebias and drop in 6V6's they'll be toast. Take it to a tech and have them set it right for you so you can get what you need. Good Luck.

December 17th, 2007, 06:20 PM	#3 (permalink)
Rob DiStefano Friend of Leo's Join Date: Mar 2003 Location: Park Ridge, NJ Age: 62 Posts: 4,458	A BiasRite is ridiculously easy to use. Less than a no-brainer. However, if the amp(s) in question don't have an easy access bias pot, get one installed.

December 17th, 2007, 06:52 PM	#4 (permalink)
EMan Tele-Holic Join Date: Apr 2003 Location: Dallas, Texas Posts: 939	Typically, 6V6's have a grid bias voltage of ~45V, and 6V6's more like ~35VDC. As mentioned, with a high B+ and a bias voltage of ~45V, it may take some component fanagling to get the thing close. As well, it's not gonna be that much lower in volume.

December 17th, 2007, 07:42 PM	#5 (permalink)
Charlie Bernstein Friend of Leo's Join Date: Apr 2003 Location: Augusta, Maine Posts: 2,295	As usual at old reliable TDPRI, everyone is in 100% cosmic alignment on a tech question. Anyone else want to weigh in?

December 17th, 2007, 07:43 PM	#6 (permalink)
Charlie Bernstein Friend of Leo's Join Date: Apr 2003 Location: Augusta, Maine Posts: 2,295	PS - Even just a little quieter would help.

December 17th, 2007, 08:27 PM	#9 (permalink)
casadyrocks Tele-Meister Join Date: Jan 2007 Location: colorado Posts: 110	Eurotubes sells all the stuff you need on their site and can tell you everything you need to know.

December 18th, 2007, 04:48 AM	#11 (permalink)
Rob DiStefano Friend of Leo's Join Date: Mar 2003 Location: Park Ridge, NJ Age: 62 Posts: 4,458	What other folks have just posted - the 6V6 conversion is still gonna be Loud, so this is a perfect excuse to get a Class A 5F1 and have some real fun.

December 18th, 2007, 10:34 AM	#14 (permalink)
Charlie Bernstein Friend of Leo's Join Date: Apr 2003 Location: Augusta, Maine Posts: 2,295	I already have enough amps, thanks. When I sell one, I might buy another. Though I'd rather just make the other three (including the Bassman) more useful. The Pro Junior is out getting better pots and jack. The Ampeg needs some routine maintenance but is otherwise great. I have two cabs for the Bassman - a 212 and a 210. Tim, I really like the 110 idea. Elegant! Okay, so back to the original question - should I have a tech bias the 6V6s or do it myself? My tech skill put the "rude" in "rudimentary"...

December 18th, 2007, 12:13 PM	#16 (permalink)
Freight Twang TDPRI Member Join Date: Dec 2007 Location: Montgomery,Al Age: 40 Posts: 93 2 Photos	How about switching the amp to Cathode Bias, with 6l6's it will break up a little faster and at a lower volume.

December 18th, 2007, 04:26 PM	#17 (permalink)
Charlie Bernstein Friend of Leo's Join Date: Apr 2003 Location: Augusta, Maine Posts: 2,295	Okay. Some of you are saying the 6V6s will require new components and some are saying it won't. That's interesting. Can anyone explain the disagreement?

December 18th, 2007, 04:39 PM	#18 (permalink)
Freight Twang TDPRI Member Join Date: Dec 2007 Location: Montgomery,Al Age: 40 Posts: 93 2 Photos	Here's a quote from a customer from www.eurotubes.com: Hang on... I have been torturing the JJ 6V6's in my 66 Bassman head now for several weeks at 460 plate volts biased at 22mA per tube and they sound GREAT! Jamona told me that they would run at up to 500 plate volts so I decided to give them a thrashing and they are holding up just fine. I also have a pair in a friends Hot Rod Deluxe at 445 plate volts and 24mA per tube and this is a gig amp for him so it will be a good test. So far the JJ 6V6's make a surprising amount of power and tend to breakup a little earlier with a mid and upper end crunch that is VERY cool! I'll keep you all posted on how they do over the long run but so far I'm very impressed! This should be a nice option for players looking for a little earlier breakup and that classic 6V6 crunch in bigger amps.

December 18th, 2007, 06:16 PM	#20 (permalink)
TeleBits Tele-Meister Join Date: Sep 2007 Location: san Antonio texas Age: 65 Posts: 103	I can see or watch the greatest players and be filled with admiration .. But I read this stuff and know I'll never be a musician ..

December 19th, 2007, 12:07 PM	#24 (permalink)
chet Poster Extraordinaire Join Date: Aug 2004 Location: The Jersey Shore Posts: 5,536	I looked at the Fender Amp Field Guide and it says that the '65 Fender Bassman has an adjustment pot or bias pot. So I'd just get a Weber Bias Rite and do it myself. __________________ Nets-Jets-Giants