I've just finished the tube power supply for Steve Bench's tube active crossover. The schematic for the supply can be found at
http://members.aol.com/sbench101/#Power
Anyway, this is my first project in over 25 years (first one was a Heathkit radio Dad helped me build when I was just 6), and I am pretty pleased I got this far-- tubes glow, values are *almost* right. So, I want to know two things at this point:
1. On the filament wires coming off the supply I've got 7.3v rather than 6.3. Does this matter? If so so, what should I check and possibly fix? (The schematic gives you a 6v DC and 6.3v AC option; I'm using the latter.)
2. One of the OA2's appears a little "off"-- it glows a pinkish and when I test the B+ wires, I get 146 rather than 150 (with the other I get a perfect 150). I can tell the 146 reading is due to the tube, because I swapped the tubes into the opposite supplies & my readings switched accordingly. Should I just buy another OA2? Do these tend to be finicky? (So, should I buy a few and hope one works?)
Thanks for any help you can give!
http://members.aol.com/sbench101/#Power
Anyway, this is my first project in over 25 years (first one was a Heathkit radio Dad helped me build when I was just 6), and I am pretty pleased I got this far-- tubes glow, values are *almost* right. So, I want to know two things at this point:
1. On the filament wires coming off the supply I've got 7.3v rather than 6.3. Does this matter? If so so, what should I check and possibly fix? (The schematic gives you a 6v DC and 6.3v AC option; I'm using the latter.)
2. One of the OA2's appears a little "off"-- it glows a pinkish and when I test the B+ wires, I get 146 rather than 150 (with the other I get a perfect 150). I can tell the 146 reading is due to the tube, because I swapped the tubes into the opposite supplies & my readings switched accordingly. Should I just buy another OA2? Do these tend to be finicky? (So, should I buy a few and hope one works?)
Thanks for any help you can give!
Hi,
I am no expert, but love tube audio. I believe that you use a resistor to drop the voltage to 6.3v a/c. E=I*R will give you the value you need(R=E/I) I believe in parallel and use a 5 watter or better.
Buy another tube. glow I believe equals leakege, outside air coming in.
Wait till one of the experts gives solid advice before doing anything to your filament wires.
I am no expert, but love tube audio. I believe that you use a resistor to drop the voltage to 6.3v a/c. E=I*R will give you the value you need(R=E/I) I believe in parallel and use a 5 watter or better.
Buy another tube. glow I believe equals leakege, outside air coming in.
Wait till one of the experts gives solid advice before doing anything to your filament wires.
Thanks
Thanks-- I am wondering, since there's no apparent voltage-dropping resistor in the schematic, if the problem could be the transformers themselves-- I forgot to record their outputs, and maybe they are just supplying the 7.3 (this would be consistent with the problem being identical on both of the supplies filament outputs). I'll check this. Thanks again.
Thanks-- I am wondering, since there's no apparent voltage-dropping resistor in the schematic, if the problem could be the transformers themselves-- I forgot to record their outputs, and maybe they are just supplying the 7.3 (this would be consistent with the problem being identical on both of the supplies filament outputs). I'll check this. Thanks again.
Hi,
The OA2 is a glow discharge gas tube. It's supposed to glow.
And the 7.3V across the filament winding is due to taking the measurement in an unloaded state. After the tubes are drawing current off of it, it will go down - but may still be slightly high due to the 117V primary. Unfortunately, almost everywhere in the US has 120V, or more, coming out of the wall sockets. I have 124V here in Brooklyn. A reading of 6.7V would not be unusual, and is within a modern tube's tolerance.
The OA2 is a glow discharge gas tube. It's supposed to glow.
And the 7.3V across the filament winding is due to taking the measurement in an unloaded state. After the tubes are drawing current off of it, it will go down - but may still be slightly high due to the 117V primary. Unfortunately, almost everywhere in the US has 120V, or more, coming out of the wall sockets. I have 124V here in Brooklyn. A reading of 6.7V would not be unusual, and is within a modern tube's tolerance.
Ah-- ok.
Thanks, Joel-- I'm just learning, and I appreciate your help. One thing-- the problem isn't that the OA2 glows, but that one glows substantially pinker than the other, and whichever of the two supplies it's plugged into also shows the off reading for the B+, or at least it's more like 146 rather than 150.
BTW, in my apt, the wall sockets give consistently 126, or higher-- I even asked about this, and I was told, "That is within Ohio's 10% tolerance regulation." I have a TrippLite voltage regulator and its lights are always bouncing around "high."
Thanks, Joel-- I'm just learning, and I appreciate your help. One thing-- the problem isn't that the OA2 glows, but that one glows substantially pinker than the other, and whichever of the two supplies it's plugged into also shows the off reading for the B+, or at least it's more like 146 rather than 150.
BTW, in my apt, the wall sockets give consistently 126, or higher-- I even asked about this, and I was told, "That is within Ohio's 10% tolerance regulation." I have a TrippLite voltage regulator and its lights are always bouncing around "high."
Woe is me! HUM!
I finally hooked the whole assembly up between my pre-amp and amp (using one channel each for the high and low, since for the moment I have no second-amp for biamping). So, I run the pre-amp output to one of the inputs on the X-o, and I run the X-o's high to one channel of the amp and the low to the other. When I powered up, I got a nasty hum than kept building until I got spooked and shut the whole main power down. I tried a few obvious checks (use other channel of x-o, in case one is bad, e.g.), but no luck. I have been very careful, the readings off the power supply were good, the x-o itself was built on a pre-fab pcb, so miswiring isn't likely there.
The only thing I can think of is a grounding problem-- I'd run the supply and the x-o's ground connections all to a common ground. Any ideas?
I really do appreciate the help here-- any tips are most welcome.
I finally hooked the whole assembly up between my pre-amp and amp (using one channel each for the high and low, since for the moment I have no second-amp for biamping). So, I run the pre-amp output to one of the inputs on the X-o, and I run the X-o's high to one channel of the amp and the low to the other. When I powered up, I got a nasty hum than kept building until I got spooked and shut the whole main power down. I tried a few obvious checks (use other channel of x-o, in case one is bad, e.g.), but no luck. I have been very careful, the readings off the power supply were good, the x-o itself was built on a pre-fab pcb, so miswiring isn't likely there.
The only thing I can think of is a grounding problem-- I'd run the supply and the x-o's ground connections all to a common ground. Any ideas?
I really do appreciate the help here-- any tips are most welcome.
reply to Joel
Hi Joel,
The amp and pre-amp are both commerical-- Acurus A150 for the Amp and Melos MA111 for the pre. Everything works swell until I hook in the x-o as described in my last message. I understand the idea of feedback-- could this be a ground loop? I ask that because a "loop" in my mind is "feedback." I know phono players have grounding problems, but that's just a steady hum, not something that builds.
What could be causing the feedback?
Hi Joel,
The amp and pre-amp are both commerical-- Acurus A150 for the Amp and Melos MA111 for the pre. Everything works swell until I hook in the x-o as described in my last message. I understand the idea of feedback-- could this be a ground loop? I ask that because a "loop" in my mind is "feedback." I know phono players have grounding problems, but that's just a steady hum, not something that builds.
What could be causing the feedback?
More situation description
I should add that the feedback noise starts building in one speaker and shifts to the other before it gets really scary.
Could this somehow be related to the makeshift way I've set up the "biamp", that is, by running the highs out of the x-o to one amp input and the lows to another? I'm just guess, based on the idea that I'm doing the makeshift "pseudo-bi-amp mono" thing with an amp that normally is stereo.
I should add that the feedback noise starts building in one speaker and shifts to the other before it gets really scary.
Could this somehow be related to the makeshift way I've set up the "biamp", that is, by running the highs out of the x-o to one amp input and the lows to another? I'm just guess, based on the idea that I'm doing the makeshift "pseudo-bi-amp mono" thing with an amp that normally is stereo.
A stereo is two mono amps, usually sharing a common powersupply. This is not your problem. Prove it to yourself by hooking your cd player up to one input, and another source (tape deck, etc) to the other. You get two mono programs.
And a "ground loop" is hum. This is not your problem either.
My guess is you've wired something wrong in the crossover circuit.
And a "ground loop" is hum. This is not your problem either.
My guess is you've wired something wrong in the crossover circuit.
Thanks
Thanks for the clarifications, Joel. At this point, though, I don't know what to do. I was just guessing on possible causes, and I understand your points. I don't see how I could have miswired the crossover, since it was on a printed circuit board produed by the designer-- unless there's a design problem.
I'll keep checking things, though.
Thanks for the clarifications, Joel. At this point, though, I don't know what to do. I was just guessing on possible causes, and I understand your points. I don't see how I could have miswired the crossover, since it was on a printed circuit board produed by the designer-- unless there's a design problem.
I'll keep checking things, though.
o-scope, or back-burner...
yeah, I know I'm flying a little blind here. I'd hoped if I were careful enough about writing all the components & used the pre-printed pcb, then I could cross my fingers and the thing would just work.
In lieu of the o-scope, are there any possible obvious causes for this kind of feedback? I know in my previous posts I might have come across a little dim on electronics, but I understood everything Joel was saying-- the dimness is about possible causes, because that sort of thing requires a more expert level of knowledge &/or as you say the o-scope to check it out. All I can do now is test all the components individually with a multimeter and eyeball the layout for possible goofs.
If that doesn't work, it's onto my speaker project, which is more woodworking than electronics...
Thanks.
Jay
yeah, I know I'm flying a little blind here. I'd hoped if I were careful enough about writing all the components & used the pre-printed pcb, then I could cross my fingers and the thing would just work.
In lieu of the o-scope, are there any possible obvious causes for this kind of feedback? I know in my previous posts I might have come across a little dim on electronics, but I understood everything Joel was saying-- the dimness is about possible causes, because that sort of thing requires a more expert level of knowledge &/or as you say the o-scope to check it out. All I can do now is test all the components individually with a multimeter and eyeball the layout for possible goofs.
If that doesn't work, it's onto my speaker project, which is more woodworking than electronics...
Thanks.
Jay
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