Members maggotspawn Posted October 10, 2010 Members Share Posted October 10, 2010 Wanting to learn how to bias my tube amp. Reading up on it and I came across these: http://www.amp-head.com/product_info.php?cPath=21&products_id=30&osCsid=a6462c483ba81bf889911270a9dd0653http://www.amp-head.com/product_info.php?cPath=21&products_id=31&osCsid=a6462c483ba81bf889911270a9dd0653 Which would be better for my use? My amp has 2 EL34 power tubes. Link to comment Share on other sites More sharing options...
Members Casey4s Posted October 10, 2010 Members Share Posted October 10, 2010 This one is the best IMHO.>>>---> https://taweber.powweb.com/biasrite/br_page.htm Make sure you get one that lets you read plate voltage (PV). Link to comment Share on other sites More sharing options...
Members maggotspawn Posted October 10, 2010 Author Members Share Posted October 10, 2010 This one is the best IMHO.>>>---> https://taweber.powweb.com/biasrite/br_page.htmMake sure you get one that lets you read plate voltage (PV). Thanks for the reply. I'll look into those. Link to comment Share on other sites More sharing options...
Members Zozobra Posted October 10, 2010 Members Share Posted October 10, 2010 +1 on the biasrite. its super quick and easy. Link to comment Share on other sites More sharing options...
Members PopsBdog Posted October 12, 2010 Members Share Posted October 12, 2010 Wanting to learn how to bias my tube amp. Reading up on it and I came across these: http://www.amp-head.com/product_info.php?cPath=21&products_id=30&osCsid=a6462c483ba81bf889911270a9dd0653http://www.amp-head.com/product_info.php?cPath=21&products_id=31&osCsid=a6462c483ba81bf889911270a9dd0653 Which would be better for my use? My amp has 2 EL34 power tubes. I use the Dual one to check and adjust bias, I like it because lets you do both tubes with a flip of a switch. It has some decent instructions and specs for some common amps. You will need a multimeter. You should have one anyway if you are poking around in there. I use it on my Marshall Superbass (4 x EL34), and my Sunn 100S (2 x 6550) and both my Reverend Hellhounds (2 x 6L6). Link to comment Share on other sites More sharing options...
Members RalphL Posted March 2, 2015 Members Share Posted March 2, 2015 The Amp-Head dual bias tester does not test EL34s correctly. As well, they are slow to ship, have made numerous errors when I ordered tubes. Each encounter while trying to solve the tube issue was insulting. Bad customer service. Link to comment Share on other sites More sharing options...
Members WRGKMC Posted March 2, 2015 Members Share Posted March 2, 2015 You responded to a thread 5 posted in 2010. The Info may be good for someone looking at that item but most electronic techs simply need a good VOM to set bias. Link to comment Share on other sites More sharing options...
Members motterpaul Posted April 15, 2015 Members Share Posted April 15, 2015 Weber actually quit selling the Bias-rite for many years (round 2010 to 2014) because of people with complaints like this. Now they are selling them again, and also sell kits where you can build your own. I have an older one and while it has a flaw (one side always tests about 3v higher than the other, even if I switch them around to the opposite tubes) it is still certainly close enough to bias an amp within spec and I use it all the time. Better to be close than way off. I don't think 3v is a big deal when it comes to biasing (if you have ever listened to amps where you vary the bias by any degree you know its close enough). Link to comment Share on other sites More sharing options...
Members WRGKMC Posted April 16, 2015 Members Share Posted April 16, 2015 Weber actually quit selling the Bias-rite for many years (round 2010 to 2014) because of people with complaints like this. Now they are selling them again' date=' and also sell kits where you can build your own. I have an older one and while it has a flaw (one side always tests about 3v higher than the other, even if I switch them around to the opposite tubes) it is still certainly close enough to bias an amp within spec and I use it all the time. Better to be close than way off. I don't think 3v is a big deal when it comes to biasing (if you have ever listened to amps where you vary the bias by any degree you know its close enough).[/quote'] You actually want to find one that measures milliamps instead of volts. http://www.musiciansfriend.com/accessories/vht-tube-tester?cntry=us&source=3WWRWXGP&gclid=CK-e4rz8-sQCFQwbaQodNxwAuQ&kwid=productads-plaid^82228610307-sku^J05021000000000@ADL4MF-adType^PLA-device^c-adid^51870555867 If the volts are off on yours its likely because it has fixed resistors the voltage is measured across and the values of one of those resistors have changed its tolerance. You actually do read voltage over a resistor that's inside a Volt Ohm meter when measuring current. Its just a matter of calculating those values using ohms law to convert it to amps. A a volt meter measures across a load, and a current meter is placed in series with a load. The current meter uses a fixed resistor depending on the dial setting to measure the current. With tubes, you do want to measure current because you're dealing with very low current differences. The voltage being off a little on each tube doesn't matter so long as the currents on both tubes are the same. When they match you'll get both the north going and south going waves to match equally. Using a scope is another excellent test tool for setting up amps because you can visually see the wave forms and remove all guesswork using a primitive meter as your eyes to see into the circuit. Link to comment Share on other sites More sharing options...
Members motterpaul Posted April 17, 2015 Members Share Posted April 17, 2015 WRG - I have read some of your posts and I KNOW you are way ahead of me in electronics knowledge. Ohm's law is more like a suggestion to me, but I am not afraid to go inside an amp or build a pedal circuit on Vero. Thanks for clarifying my post. This is the one I have Link to comment Share on other sites More sharing options...
Members WRGKMC Posted April 17, 2015 Members Share Posted April 17, 2015 WRG - I have read some of your posts and I KNOW you are way ahead of me in electronics knowledge. Ohm's law is more like a suggestion to me, but I am not afraid to go inside an amp or build a pedal circuit on Vero. Thanks for clarifying my post. This is the one I have Ah, then that one will measure both voltage and current. The only thing you'll need to be sure is the tubes read the same current when set in the IK mode. Not sure if the voltage differences is also affecting you're current readings. You can swap probes (keeping the tubes in the same socket positions) to see if the current moves from one socket to the other. You only need one good probe to match the two tubes. You simply write down the settings and match them up. The site for that meter does give allot of warnings against damaging the meter. Apparently they added that disclaimer when they started getting allot of complaints instead of improving their design. So long as it works you're still allot better off then most. I still do it the old fashioned way removing a tube socket wire and placing a meter in between. Its a pain in the butt, but I haven't done tube amp servicing in a long time and only need to maintain the two I own, and one is a Fender Bassman with a hum balance pot so it doesn't even need the bias set, just balanced. Link to comment Share on other sites More sharing options...
Members SoulSonicFX Posted April 29, 2015 Members Share Posted April 29, 2015 I used to actually build Bias Rites for Weber, and I thought at the time that it was a horrible, and even potentially unsafe, design. For one, you have this freakin copper tube with a bunch of wires crammed in it with high voltage everywhere...imagine what's going to happen to your amp if something inside it shorts against the copper and in turn then shorts against the chassis (or your hand...). And the resistors making up the voltage divider inside were tiny little SMD things that weren't even rated for the voltages that were passing through them. Just a horrible horrible product. Same goes for the "Copper Cap" rectifiers... damn copper shell with a bunch of high voltage stuff crammed inside it with no insulation to keep it from shorting against the case if the person assembling it wasn't careful. No way in hell would I ever put one of those inside my amp. And the design isn't anything special...some silicon diodes with a power resistor in series with the output - he would choose a value that was nominally the equivalent resistance to whatever rectifier it was "simulating", but there's alot more going on inside a valve rectifier than just being a virtual resistor....yeesh.. Link to comment Share on other sites More sharing options...
Members motterpaul Posted June 17, 2015 Members Share Posted June 17, 2015 I used to actually build Bias Rites for Weber, and I thought at the time that it was a horrible, and even potentially unsafe, design. For one, you have this freakin copper tube with a bunch of wires crammed in it with high voltage everywhere...imagine what's going to happen to your amp if something inside it shorts against the copper and in turn then shorts against the chassis (or your hand...). And the resistors making up the voltage divider inside were tiny little SMD things that weren't even rated for the voltages that were passing through them. Just a horrible horrible product. Same goes for the "Copper Cap" rectifiers... damn copper shell with a bunch of high voltage stuff crammed inside it with no insulation to keep it from shorting against the case if the person assembling it wasn't careful. No way in hell would I ever put one of those inside my amp. And the design isn't anything special...some silicon diodes with a power resistor in series with the output - he would choose a value that was nominally the equivalent resistance to whatever rectifier it was "simulating", but there's alot more going on inside a valve rectifier than just being a virtual resistor....yeesh.. This is really interesting. Thanks! The current does stay constant on both of my testers, it is just the bias that comes up different. Do you have any recommendations to make the bias-rite safer? Link to comment Share on other sites More sharing options...
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