Members Crunchtime Posted January 18, 2012 Members Share Posted January 18, 2012 I'm wanting to buy a bias probe so I can bias my amp myself. I wish all amps had rear bias points and adjust. Anyway, I saw this one ebay. Its a bit expensive but seems quality. What do you think? http://www.ebay.com/itm/Dual-Analog-Meter-tube-amp-bias-probe-tool-No-Batteries-6L6-6V6-EL34-KT66-KT88-/120840909490?pt=LH_DefaultDomain_0&hash=item1c22adf2b2 Link to comment Share on other sites More sharing options...
Members metalguy Posted January 18, 2012 Members Share Posted January 18, 2012 I bought the one off of eurotubes and it worked great. Used it on my amp and I didn't die not my amp explode. Then again I already had the multimeter to use it with. Link to comment Share on other sites More sharing options...
Members NaturalBornBoy Posted January 18, 2012 Members Share Posted January 18, 2012 My DSL has external bias points. Should I get one of those or just buy a digital multimeter? How do I get plate voltage measurements with either? Link to comment Share on other sites More sharing options...
Members Crunchtime Posted January 18, 2012 Author Members Share Posted January 18, 2012 My DSL has external bias points. Should I get one of those or just buy a digital multimeter?How do I get plate voltage measurements with either? When I had my DSL I just used my multimeter. Link to comment Share on other sites More sharing options...
Members NaturalBornBoy Posted January 18, 2012 Members Share Posted January 18, 2012 When I had my DSL I just used my multimeter. How did you measure plate voltage with a multimeter? Link to comment Share on other sites More sharing options...
Members Crunchtime Posted January 18, 2012 Author Members Share Posted January 18, 2012 I didn't. I just gave them what I thought was a safe bias, like around 35ma per tube according to my multimeter. Btw, it was a DSL 50. Link to comment Share on other sites More sharing options...
Members NaturalBornBoy Posted January 18, 2012 Members Share Posted January 18, 2012 I didn't. I just gave them what I thought was a safe bias, like around 35ma per tube according to my multimeter. Btw, it was a DSL 50. So that would mean 70ma per side on my 100 right? Marshall recommends 90ma per side on the 100 but isn't that a tad high? Link to comment Share on other sites More sharing options...
Members Crunchtime Posted January 18, 2012 Author Members Share Posted January 18, 2012 So that would mean 70ma per side on my 100 right? Marshall recommends 90ma per side on the 100 but isn't that a tad high? I may have been higher. I can't say for sure, that was at least a couple years ago. 90 a side does seem a bit high to me. I know when I had my Peters 50 watt, James Peters recommended 30-40 per tube when using EL34's so 35 seemed a safe median to me. Also, I believe at the time I got the DSL, I found a lot of good info on the Marshall forum. Link to comment Share on other sites More sharing options...
Members Crunchtime Posted January 18, 2012 Author Members Share Posted January 18, 2012 So that would mean 70ma per side on my 100 right? Marshall recommends 90ma per side on the 100 but isn't that a tad high? Oh yeah, that would be 70ma per side on the 100. Link to comment Share on other sites More sharing options...
Members NaturalBornBoy Posted January 18, 2012 Members Share Posted January 18, 2012 Oh yeah, that would be 70ma per side on the 100. Cool. Imma go get myself a multimeter and check the bias soon. Link to comment Share on other sites More sharing options...
Members bilbo71070 Posted January 18, 2012 Members Share Posted January 18, 2012 I just built two of these. http://www.hoffmanamps.com/MyStore/perlshop.cgi?action=template&thispage=Tools&ORDER_ID=646583490 Link to comment Share on other sites More sharing options...
Members Crunchtime Posted January 18, 2012 Author Members Share Posted January 18, 2012 I just built two of these. http://www.hoffmanamps.com/MyStore/perlshop.cgi?action=template&thispage=Tools&ORDER_ID=646583490 Link not working for me. Link to comment Share on other sites More sharing options...
Members LA-Ü-RA Posted January 18, 2012 Members Share Posted January 18, 2012 Bias king or compu-bias. I can get you the bias king for quite bit less than the compu-bias. I have the Weber Bias Rite but they don't make that unit anymore. Link to comment Share on other sites More sharing options...
Members maggotspawn Posted January 18, 2012 Members Share Posted January 18, 2012 Amphead Bias Probe. Measures plate voltage as well. http://www.amp-head.com/product_info.php?cPath=21&products_id=70 Link to comment Share on other sites More sharing options...
Members NaturalBornBoy Posted January 18, 2012 Members Share Posted January 18, 2012 Amphead Bias Probe. Measures plate voltage as well. http://www.amp-head.com/product_info.php?cPath=21&products_id=70 How do you get your bias readings using that? I don't see any displays Link to comment Share on other sites More sharing options...
Members maggotspawn Posted January 18, 2012 Members Share Posted January 18, 2012 How do you get your bias readings using that? I don't see any displays You hook it up to a digital multimeter. Link to comment Share on other sites More sharing options...
Members Wyatt Posted January 18, 2012 Members Share Posted January 18, 2012 How did you measure plate voltage with a multimeter? You go inside the amp and measure the DC voltage between pins 3 and 8 of one of the power tubes. You really only have to do it once. It won't change with the tubes, and ballpark is fine because it changes relative to the wall current anyway. But there are probes/bias meters that let you measure plate voltage and bias current. Link to comment Share on other sites More sharing options...
Members jenksdrummer Posted January 18, 2012 Members Share Posted January 18, 2012 I bought a Weber Bias Rite probe (not the one with the attached display), bought another for 9-pin when I bought my JCA22H recently. Link to comment Share on other sites More sharing options...
Members BigTimeFun Posted January 18, 2012 Members Share Posted January 18, 2012 Relevant to my interests, yadda yadda yadda... Link to comment Share on other sites More sharing options...
Members NaturalBornBoy Posted January 18, 2012 Members Share Posted January 18, 2012 How do I use something like this http://www.ebay.com/itm/Quad-Tube-Amp-Bias-match-Meter-6L6-El34-KT88-6BQ5-Probe-/300601127735?pt=Vintage_Electronics_R2&hash=item45fd393337#ht_1635wt_1398 to bias a quad of power tubes? Link to comment Share on other sites More sharing options...
Members Wyatt Posted January 18, 2012 Members Share Posted January 18, 2012 How do I use something like thishttp://www.ebay.com/itm/Quad-Tube-Amp-Bias-match-Meter-6L6-El34-KT88-6BQ5-Probe-/300601127735?pt=Vintage_Electronics_R2&hash=item45fd393337#ht_1635wt_1398to bias a quad of power tubes? Honestly, you don't need more than one probe, though it takes a little longer, assuming... 1. Ideally, your tubes will be matched within 5mA for EL34's. 2.Very, very few product amps use individual bias, you have one bias pot to bias all 4 tubes. So, you use the probe with one tube, dial in the necessary voltage on the bias pot. And then you swap the probe from tube to tube to check the bias off all four tubes. Assuming the tubes are matched close enough, you may be done, but if one is a little hotter than the rest, you may want to set the bias to make sure it's not dissipation too much and then double check the rest of the tubes. While having more probes may speed things up some, you still have to install and remove a probe to all four tubes, and you can bias an amp within 10 minutes with one probe. As for the meter you linked, it still does not do plate voltage. You can buy a single probe for ~$30 to use with any DMM. Link to comment Share on other sites More sharing options...
Members NaturalBornBoy Posted January 18, 2012 Members Share Posted January 18, 2012 Honestly, you don't need more than one probe, though it takes a little longer, assuming...1. Ideally, your tubes will be matched within 5mA for EL34's. 2.Very, very few product amps use individual bias, you have one bias pot to bias all 4 tubes.So, you use the probe with one tube, dial in the necessary voltage on the bias pot. And then you swap the probe from tube to tube to check the bias off all four tubes. Assuming the tubes are matched close enough, you may be done, but if one is a little hotter than the rest, you may want to set the bias to make sure it's not dissipation too much and then double check the rest of the tubes. While having more probes may speed things up some, you still have to install and remove a probe to all four tubes, and you can bias an amp within 10 minutes with one probe. My DSL 100 has 2 bias adjustment pots. Each for a pair of 34s Link to comment Share on other sites More sharing options...
Members Wyatt Posted January 18, 2012 Members Share Posted January 18, 2012 My DSL 100 has 2 bias adjustment pots. Each for a pair of 34s Well, you still don't have to adjust them at the same time. But it means you only have to match each pair of tubes instead of the whole quad. Link to comment Share on other sites More sharing options...
Members LA-Ü-RA Posted January 18, 2012 Members Share Posted January 18, 2012 OP, here is a bias rite for sale on ebay. http://www.ebay.com/itm/Bias-Rite-BR-4-Digital-Tube-Amp-Cathode-Current-Meter-/400270913949?pt=LH_DefaultDomain_0&hash=item5d3201719d#ht_619wt_1398 Link to comment Share on other sites More sharing options...
Members Megadeth Man Posted January 19, 2012 Members Share Posted January 19, 2012 I'm wanting to buy a bias probe so I can bias my amp myself. I wish all amps had rear bias points and adjust. Anyway, I saw this one ebay. Its a bit expensive but seems quality. What do you think?http://www.ebay.com/itm/Dual-Analog-Meter-tube-amp-bias-probe-tool-No-Batteries-6L6-6V6-EL34-KT66-KT88-/120840909490?pt=LH_DefaultDomain_0&hash=item1c22adf2b2 I can't make out what model the milliammeters are but if they're OK quality i.e. Link to comment Share on other sites More sharing options...
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