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Post by c0rtland on Jun 8, 2016 8:49:22 GMT -6
Hello all. I have some tube mics that prefer 117v. Some are quite finicky and I'd like to give them what they want.
I have really only found one good option so far for a voltage regulator. The furman p1800ar. It's like $750. Ouch. Also, this unit does not let me specify the output voltage.
So far searching the web I can only find work bench units and I'd like something that is a little simpler and made for running equipment, not testing it.
Any suggestions would be appreciated. Thank you!!!
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Post by EmRR on Jun 8, 2016 8:54:45 GMT -6
What problems do you experience?
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Post by svart on Jun 8, 2016 9:17:13 GMT -6
Hello all. I have some tube mics that prefer 117v. Some are quite finicky and I'd like to give them what they want. I have really only found one good option so far for a voltage regulator. The furman p1800ar. It's like $750. Ouch. Also, this unit does not let me specify the output voltage. So far searching the web I can only find work bench units and I'd like something that is a little simpler and made for running equipment, not testing it. Any suggestions would be appreciated. Thank you!!! I assume this means 117VAC? I'm not sure why you'd need exactly 117VAC.. 120VAC is normal here in the USA, and can change from region to region, up to 10%. It can change from minute to minute as well, and most analog electronics don't care. A 10% difference in AC voltage can mean more like 1% difference at the mic, and less than a dB or two difference in the levels from the mic. Older tube mics usually have transformer/rectifier/RC voltage reduction/conditioning, not regulation, so the voltages that hit the mic can vary with temperature and loading,etc. Newer mics might have silicon based regulators usually, and the input AC voltage has very little impact on what voltages hit the mic. Now, to answer specifically, AC is hard to "regulate". The furman calls itself a "conditioner" which typically means that it filters the AC heavily, but does not electrically change the primary AC signal. Another aspect is that it claims to also "regulate", but that definition means that it electrically adjusts the AC, which is NOT the same as "conditioning". I did find an internal picture of the 2400 sister product to the 1800: Which clearly shows an isolation or autoformer as the main portion of the unit. Isolation is not the same as regulation, nor is it the same as conditioning, but the large core of the transformer can offer a filtering effect as the flux field is relatively slow at transferring line transients. The other possibility is that it's an autoformer, or "ferro" transformer which uses feedback between the windings to self-regulate the output voltage. Most "ferros" don't offer isolation and can be dangerous in this aspect, so I doubt it's a ferro. All in all, I think this is simply a large isolation transformer with filtering and a protection circuit.
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Post by c0rtland on Jun 8, 2016 9:48:28 GMT -6
My main issue is with my m269c with power supply nn48h. I'm having trouble calibrating the heater voltage. Even when it is warmed up the voltage at the tube varies from 3.77-4.08vdc at the tube pin 3. I'm shooting for 3.95vdc, never over 4.08vdc. Pin 2 reacts immediately to the trim pot inside the psu and reads 1.41vdc
I checked the outlet I was using and it read 122vac. The other day it read 119vac. It wouldn't be a major issue but I don't want to have to replace that ac701k anytime soon. Or ever if I can do anything about it.
Perhaps there is another issue I am unaware of that is causing this other than the outlet's voltage sway.
And to be clear I am more concerned with voltage regutalors than conditioning/isolation at this point. Haven't had any issues really.
Thanks for the extremely quick replies. This forum kills.
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Post by EmRR on Jun 8, 2016 9:55:14 GMT -6
If 119VAC gave 3.95VDC, then 122VAC would give 4.047VDC. 3.77-4.08 is a larger spread than line AC would account for.
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ericn
Temp
Balance Engineer
Posts: 14,978
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Post by ericn on Jun 8, 2016 11:19:59 GMT -6
My main issue is with my m269c with power supply nn48h. I'm having trouble calibrating the heater voltage. Even when it is warmed up the voltage at the tube varies from 3.77-4.08vdc at the tube pin 3. I'm shooting for 3.95vdc, never over 4.08vdc. Pin 2 reacts immediately to the trim pot inside the psu and reads 1.41vdc I checked the outlet I was using and it read 122vac. The other day it read 119vac. It wouldn't be a major issue but I don't want to have to replace that ac701k anytime soon. Or ever if I can do anything about it. Perhaps there is another issue I am unaware of that is causing this other than the outlet's voltage sway. And to be clear I am more concerned with voltage regutalors than conditioning/isolation at this point. Haven't had any issues really. Thanks for the extremely quick replies. This forum kills. I think you might be better off sending the mic and PSU to Shannon !
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Post by c0rtland on Jun 8, 2016 11:24:12 GMT -6
A. is that a joke like he wants an m269c or B. he does good work on mics? If it's the latter I'll definitely take his info. Thanks man. You can pm me or whatever you feel comfortable with. I have a call with a tech today. We will see how that goes...
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ericn
Temp
Balance Engineer
Posts: 14,978
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Post by ericn on Jun 8, 2016 11:40:46 GMT -6
A. is that a joke like he wants an m269c or B. he does good work on mics? If it's the latter I'll definitely take his info. Thanks man. You can pm me or whatever you feel comfortable with. I have a call with a tech today. We will see how that goes... Shannon is the guy behind Mic rehab, probably the top mic tech in Nashville, and one of maybe 3 guys I would trust with a Classic Mic. The other 2 would be Andreas Grosser, and Klaus Heynes.
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Post by mulmany on Jun 8, 2016 11:44:57 GMT -6
Shannon is the man behind Mic Rehab, the guys that take care of Blackbirds collection.
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Post by svart on Jun 8, 2016 12:19:29 GMT -6
My main issue is with my m269c with power supply nn48h. I'm having trouble calibrating the heater voltage. Even when it is warmed up the voltage at the tube varies from 3.77-4.08vdc at the tube pin 3. I'm shooting for 3.95vdc, never over 4.08vdc. Pin 2 reacts immediately to the trim pot inside the psu and reads 1.41vdc I checked the outlet I was using and it read 122vac. The other day it read 119vac. It wouldn't be a major issue but I don't want to have to replace that ac701k anytime soon. Or ever if I can do anything about it. Perhaps there is another issue I am unaware of that is causing this other than the outlet's voltage sway. And to be clear I am more concerned with voltage regutalors than conditioning/isolation at this point. Haven't had any issues really. Thanks for the extremely quick replies. This forum kills. It's common to slightly underheat the filament by a small amount. You'll get much longer valve life with very little difference in performance. Just undervoltage it by 1/4-1/2 volt or so, or figure what your highest AC readings are over a period and then set the heaters to something rather low, like 3.8V at an average line voltage (120VAC) and you should be OK.
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Post by Ward on Jun 8, 2016 22:00:46 GMT -6
Run source voltage into a variac before a Furman conditioner and watch the readout. Adjust accordingly to 110VAC for older tube microphones.
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