You should not drive the speaker with an amp without bias voltage on it. It will destroy your step up transformer. Make sure the bias wire (the red one) is securely in the socket. The bias appears to not be getting to the panel. The panel is pretty robust, so it must be a disconnect inside the Interface.
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Sorry, I don't know the output current rating for the standard bias transformer - I don't think I ever saw that specification. However, it WILL be very low: remember this is a constant-charge system, feeding the panels through a 500-Mohm resistor, so the resulting current flow from the multiplier is miniscule. I suspect most of the transformer's output power is actually consumed as waste heat in the multiplier.
In actual use, it's probably a lot less than the 40 mA you calculated, since the primary current will only reach 250 mA due to a major failure.
Just a point of clarification: driving the speaker with no bias voltage will NOT automatically destroy the audio step-up transformer. However, there is the danger of driving the speaker too hard (which CAN damage the transformer), since there is no sound output to gauge how much the speaker is being driven.
So, your warning is valid, just not quite as dire as you suggest. For the reason mentioned above, it's a good idea to avoid driving a speaker when no bias voltage is present (or even when it's much lower than it should be).
Yeah, I found my chart (to determine current capacity of unknown voltage transformers), and it is more near 30ma - 40ma at best... attached...secondary DC resistance/secondary voltage gives a ratio you can look up to see approximate current...the secondary dc resistance on the bias tranny was 1200 ohms, giving 1.6 ratio. Chart says around 30ma. This is cool!!
Regarding driving the speaker without bias - just had a friend destroy his quads this way...His wife wanted to hear some music when he was not around, and didn't know to turn them on...he was not happy...but then again, those were ultra sensitive quads....
Regarding driving the speaker without bias - just had a friend destroy his quads this way...His wife wanted to hear some music when he was not around, and didn't know to turn them on...he was not happy...but then again, those were ultra sensitive quads....
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Hmmm...you've got me scratching my head. I wonder if you have an earlier version of the ultrasonic bias power supply that could sometimes give troubles. Here's an easy way to check which version you have: inside the interface, on the printed circuit board, there is a small air-core transformer: roughly a 2" cube. Note the red wire exiting from the top of that transformer. Is there another wire wrapped around the red wire? (note that this wire is not electrically connected to the red wire - it acts as an 'antenna' for the circuit's feedback loop). If that extra wire is there, then you have the improved version. If not, upgrading the circuit is easy and I can supply you with instructions.
Another question: do you have access to a high voltage probe, or at least a digital voltmeter? The next step is to measure the high voltage bias output and see where you are. Note that if your speaker needs the circuit upgrade, you will also need to measure and adjust the bias voltage after the modification. I can supply instructions for checking and adjusting the bias voltage, too.
Here's another thought: make sure the plug on the wall transformer's cord is making good contact with the jack on the speaker. It should be a reasonably snug fit. You could also remove the input cup on the back to make sure the jack's contacts are making good contact with the plug.
Don't give up hope yet - we'll get them going again!
Oh, a truly sad story. Just goes to show that one should ALWAYS leave the bias supply on. The current consumption is minimal and therefore only a few cents a day, but the peace-of-mind is priceless.
Sad Day in clarks vill or is it Quad vill...........
From the work i done with ML ......these NO ESL panels sound there best till thay been bias up........... for 4-6 days.......oh thay work like the logans as soon as the bias is turned on.............but as with the Acoustats you can only hear what thay can relly do.....till there full up to the top with Bias V.....
all these panels are as you know are big pol-caps....the a lot of ML panels out there that would still be working an sounding better than any knows.........if the bias had been on all the time....dust are no dust.....just what i an others that have heard in my setup where all the ESL panel stay on all the time......
An as for runing the interface with out bias.....just put you hand on the tranfourmers in the inrface....................it well get Hot righ off...............It well KILLL.......... Any tranfourmer.............
..good luck with that!
Long live Acoustats & ML
From the work i done with ML ......these NO ESL panels sound there best till thay been bias up........... for 4-6 days.......oh thay work like the logans as soon as the bias is turned on.............but as with the Acoustats you can only hear what thay can relly do.....till there full up to the top with Bias V.....
all these panels are as you know are big pol-caps....the a lot of ML panels out there that would still be working an sounding better than any knows.........if the bias had been on all the time....dust are no dust.....just what i an others that have heard in my setup where all the ESL panel stay on all the time......
An as for runing the interface with out bias.....just put you hand on the tranfourmers in the inrface....................it well get Hot righ off...............It well KILLL.......... Any tranfourmer.............
..good luck with that!
Long live Acoustats & ML
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Yes Andy you're right, when the panels are fully charged the current consumption from what i was told is only 5 watts.
In about two weeks I will be visiting Analogue Associates in Oklahoma City to hear their heavily modified Acoustat ServoCharge amps. I've been contemplating upgrading mine (actually looking at doing so to two pairs), but it's a big financial step to do so without first-hand experience with them, so I'm excited to check them out. I have obtained Mike Savuto's permission to report my findings here, so I will have an update around the end of the month.
Thank you for your reply Andy. There is no wire wrapped around the red wire coming from the small air-core transformer. I will acquire a high voltage probe or digital voltmeter to install the wire and do whatever is necessary. Where should the antenna wire go and how should i go about installing it? I believe the wall transformer is plugged in properly and giving electricity to the interface.
AHA! There is a good chance your problem has now been identified. Even if there is another culprit causing your problem, the modification to the ultrasonic power supply should be done anyway, for long term reliability. When I get home I will post the instructions for the modification and for measuring and adjusting the bias.
To Mindsquirrel:
Attached are some documents that should help you:
UltraWhy - a little background on the Ultrasonic bias power supply
UltraFix - instructions on upgrading the circuit
Bias Fix Diagram - a drawing to accompany the instructions
BiasAdj - instructions on measuring and adjusting the bias voltage
Attached are some documents that should help you:
UltraWhy - a little background on the Ultrasonic bias power supply
UltraFix - instructions on upgrading the circuit
Bias Fix Diagram - a drawing to accompany the instructions
BiasAdj - instructions on measuring and adjusting the bias voltage
Hi guys, does anyone know what happened to Roy Esposito? I contacted him back in January about refurbing my interfaces, but now his email bounces back as undeliverable. The phone number I found is several years old and no longer his. Has anybody talked to him recently and can direct me how to get in touch with him?
I copied a post from the Audiocircuit website, written by Roy on September 06, 2013:
Hello Friends --
This is just to let you know that my email contact
has recently changed. It seems AT&T/Yahoo could no
longer support my very old prodigy.net email address.
For those of you requiring fantastic restorations
and upgrading of Acoustat MK and Spectra Interfaces
and Acoustat Power Amplifiers and Preamplifiers
my new email address is
acoustat.service.usa@gmail.com
(please notice the dots/periods between the words)
Email is the preferred method for initial contact with me
for Acoustat Service and questions.
Thank you for your continued friendship, kind comments and reviews,
and support of my work.
All the Best,
Roy A. Esposito
Hi everyone. Say, can anyone recommend service like Roy's but here on the west coast? I've considered several times sending my Spectra interfaces to Roy for service/upgrading, but shipping these heavy beasts all the way to Florida would be expensive and take awhile. If I was on the east coast, it'd be a 'no-brainer'.
Thanks, and Long live your Acoustats!
Thanks, and Long live your Acoustats!