Bias measuring unit -which one?

mrocker · 9th February 2010

Hi there, ust wondering if any of you have had experience with e Weber Bias Rite

https://taweber.powweb.com/biasrite/br_page.htm

or the Tad Bias Master

Mojotone Replacing and Biasing Tubes

Any other good ones?

Acuracey?
Quality?
Cheers.

diezel_addict · 9th February 2010

Hi there

I find the best way to bias an amp is to install 1 ohm resistors from the cathodes to ground. that way you can measure the voltage across the resistor. this reading will be in mV but translates to mA because of ohms law.

mrocker · 9th February 2010

Yeah,but I gotta screw around and spend time doing that ...then hope I haven't messed it up and blow the amp

Victory Pete · 9th February 2010

Those Webers look nice, but I would be afraid the adapters are too tall and you wont be able to fit a tube in it while in a head like a marshall, there might not be enough clearance. I use this Welcome to the Home of The Bias King™ It has worked great and setting bias now is easy.
VP

mrocker · 9th February 2010

I understnad they do fit into Marshalls.
YouTube - Strange meter reading while biasing a Marshall 50 watt Super Lead

I like the fact you can have current & dc reading.

The bias king looks good too.

Victory Pete · 9th February 2010

Quote:

Originally Posted by mrocker

I understnad they do fit into Marshalls.
YouTube - Strange meter reading while biasing a Marshall 50 watt Super Lead

I like the fact you can have current & dc reading.

The bias king looks good too.

I like the plate voltage measurement feature. It is important to know the plate voltage to calculate the idle cathode current. How do you know it will fit in a head without taking the chassis out of the cabinet?
VP

Joe Porto · 9th February 2010

Quote:

Originally Posted by Victory Pete

I like the plate voltage measurement feature. It is important to know the plate voltage to calculate the idle cathode current.

True, but you can just as easily read the plate voltage off of pin 3 with a multimeter.

Victory Pete · 9th February 2010

Quote:

Originally Posted by Joe Porto

True, but you can just as easily read the plate voltage off of pin 3 with a multimeter.

Yes, I have a seperate adapter just for measuring plate voltage.
VP
PS I now need a rabies shot after visiting your website!

KingDiamond · 9th February 2010

Quote:

Originally Posted by Victory Pete

Those Webers look nice, but I would be afraid the adapters are too tall and you wont be able to fit a tube in it while in a head like a marshall, there might not be enough clearance. I use this Welcome to the Home of The Bias King™ It has worked great and setting bias now is easy.
VP

Don't you need to remove the amp chassis out of the head enclosure anyway to adjust the bias pot?

Victory Pete · 9th February 2010

Quote:

Originally Posted by KingDiamond

Don't you need to remove the amp chassis out of the head enclosure anyway to adjust the bias pot?

Some modern amps have the adjustment pot accessible. Laneys, Marshalls.

drtechno · 10th February 2010

one mod you can do is a couple of 1 ohm 5 watt resistors and put them between ground and cathode or cathode resistors (depending on output amp tube) and permanently mount some panel meters on your chassis. then another between cathodes.

alot of people forget to look at differential current. this is caused by either the phase splitter tube getting weak, or associated circuit, or the bias feed grid resistors drifting out of tolerance from each other ( bias voltage screening resistors after voltage adjust trim pot like in JCM800's)

mrocker · 12th February 2010

Can someone show me on the schematic where pin 3 plate voltage is measured?

Joe Porto · 9th March 2010

Quote:

Originally Posted by mrocker

Can someone show me on the schematic where pin 3 plate voltage is measured?

Well, that would be on pin-3 of the octal base.

Mylithra · 11th March 2010

I have a weber BiasRite and it works great. Makes doing bias adjustments very easy. The other recommended methods (1ohhm resistor off the cathode then measure the voltage drop across the resistor to get the Cathode Current) work great as well but for a quick, pull tubes, get the readings, adjust the knob and lock it.. cant beat it.

Joe Porto · 11th March 2010

I just picked up a Compu-Bias, which is a dual octal bias tool. It displays plate voltage, plate current, and wattage. Similar to the Bias-Right, but calculates dissipation as wattage, so no need for a separate plate reading and calculator.

9th February 2010	#1
mrocker Gear interested Joined: Dec 2009 Posts: 26 Thread Starter	Bias measuring unit -which one? Hi there, ust wondering if any of you have had experience with e Weber Bias Rite https://taweber.powweb.com/biasrite/br_page.htm or the Tad Bias Master Mojotone Replacing and Biasing Tubes Any other good ones? Acuracey? Quality? Cheers.

10th February 2010	#11
drtechno Lives for gear Joined: Aug 2006 Location: Rapid City, SD Posts: 602	one mod you can do is a couple of 1 ohm 5 watt resistors and put them between ground and cathode or cathode resistors (depending on output amp tube) and permanently mount some panel meters on your chassis. then another between cathodes. alot of people forget to look at differential current. this is caused by either the phase splitter tube getting weak, or associated circuit, or the bias feed grid resistors drifting out of tolerance from each other ( bias voltage screening resistors after voltage adjust trim pot like in JCM800's) __________________ In live sound, we make the band one with the environment, In recording, we define the environment in which the vision of the song is recorded.

12th February 2010	#12
mrocker Gear interested Joined: Dec 2009 Posts: 26 Thread Starter	Can someone show me on the schematic where pin 3 plate voltage is measured? Attached Thumbnails

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9th February 2010	#2
diezel_addict Gear nut Joined: May 2009 Posts: 91	Hi there I find the best way to bias an amp is to install 1 ohm resistors from the cathodes to ground. that way you can measure the voltage across the resistor. this reading will be in mV but translates to mA because of ohms law.

9th February 2010	#4
Victory Pete Gear addict Joined: Jan 2010 Location: Rhode Island Posts: 439	Those Webers look nice, but I would be afraid the adapters are too tall and you wont be able to fit a tube in it while in a head like a marshall, there might not be enough clearance. I use this Welcome to the Home of The Bias King™ It has worked great and setting bias now is easy. VP

11th March 2010	#14
Mylithra Gear addict Joined: Mar 2008 Posts: 359	I have a weber BiasRite and it works great. Makes doing bias adjustments very easy. The other recommended methods (1ohhm resistor off the cathode then measure the voltage drop across the resistor to get the Cathode Current) work great as well but for a quick, pull tubes, get the readings, adjust the knob and lock it.. cant beat it.

11th March 2010	#15
Joe Porto Lives for gear Joined: Apr 2007 Posts: 1,673	I just picked up a Compu-Bias, which is a dual octal bias tool. It displays plate voltage, plate current, and wattage. Similar to the Bias-Right, but calculates dissipation as wattage, so no need for a separate plate reading and calculator.