Post by daddyelmis (Greg) on Sept 21, 2018 12:35:36 GMT -7
I currently own 3 amps (all Z's -- Remedy, ZPlus and Z28). The Z28 is the only one that needs biasing when changing the power tubes or rectifier. Since that only happens very infrequently (I love the stock sounds and I'm no longer chasing the NOS fairy), I'm not in need of amp biasing more than once every few years at this point. I considered taking the amp to a local tech (who is good), but like car maintenance I'm fond of doing it myself so I know it's done right and so I know what values I ended up with.
So, with that said, I set out looking for a bias measurement solution that would accomplish the following:
1) Inexpensive - there's no point for me in spending $150+ to solve this problem.
2) Must allow having both power tubes "active" and "readable" in one sitting. I don't want to measure/adjust one tube, shut off the amp and wait for the tubes to cool, and then switch the probe to the other tube and measure/adjust it.
3) I would prefer to measure cathode current rather than voltage across a 1ohm resistor. I understand the "voltage" method is a bit safer, but variance in that 1ohm resistor just seems a variable I'd rather avoid.
4) I'm agnostic as to whether the probe has its own display, or it plugs into a MM. I need a better MM than the one I have now (but don't need a Fluke-level one) so spending a little bit of $ for a more useful MM is fine with me.
So I spent literally hours looking at everything Google, Amazon, and eBay would disclose. The Weber Bias Rite is very nice but very expensive, as is the Eurotubes Pro One (and it only has one probe). The SRS model measures the volts across the 1ohm resistor, as do many of the Chinese versions of that. In fact, most of the units sold by U.S. companies are quite expensive, and I cannot imagine that they are not sourcing their hardware overseas.
So at the end of this investigation, I bought this:
EL34-KT88-6L6-6V6-6550-Quad-Vacuum-Tube-Amplifier-Bias-Match-Tester
It allows measurement of up to 4 tubes, and plugs into a MM so you get better accuracy, and it was under $40. I'll update once it arrives and I give it a go.
So, with that said, I set out looking for a bias measurement solution that would accomplish the following:
1) Inexpensive - there's no point for me in spending $150+ to solve this problem.
2) Must allow having both power tubes "active" and "readable" in one sitting. I don't want to measure/adjust one tube, shut off the amp and wait for the tubes to cool, and then switch the probe to the other tube and measure/adjust it.
3) I would prefer to measure cathode current rather than voltage across a 1ohm resistor. I understand the "voltage" method is a bit safer, but variance in that 1ohm resistor just seems a variable I'd rather avoid.
4) I'm agnostic as to whether the probe has its own display, or it plugs into a MM. I need a better MM than the one I have now (but don't need a Fluke-level one) so spending a little bit of $ for a more useful MM is fine with me.
So I spent literally hours looking at everything Google, Amazon, and eBay would disclose. The Weber Bias Rite is very nice but very expensive, as is the Eurotubes Pro One (and it only has one probe). The SRS model measures the volts across the 1ohm resistor, as do many of the Chinese versions of that. In fact, most of the units sold by U.S. companies are quite expensive, and I cannot imagine that they are not sourcing their hardware overseas.
So at the end of this investigation, I bought this:
EL34-KT88-6L6-6V6-6550-Quad-Vacuum-Tube-Amplifier-Bias-Match-Tester
It allows measurement of up to 4 tubes, and plugs into a MM so you get better accuracy, and it was under $40. I'll update once it arrives and I give it a go.