Hi. I need to convert Unbalanced outputs to Balanced outputs on my vintage mixer. Specs say:
Output level: 2v
Output min load: 10kOhm
I will be driving 35 ft. balanced cables followed by an active crossover.
Would it be better to use a balancing transformer, like Jensen JT-11-Emcf or a balancing electronic circuit?
Can you share your thoughts/offer advice?
So far I like the idea of transformers -- simple and reliable.... but I may be missing something.
thanks, Herman
Output level: 2v
Output min load: 10kOhm
I will be driving 35 ft. balanced cables followed by an active crossover.
Would it be better to use a balancing transformer, like Jensen JT-11-Emcf or a balancing electronic circuit?
Can you share your thoughts/offer advice?
So far I like the idea of transformers -- simple and reliable.... but I may be missing something.
thanks, Herman
Transformers do pick up hum but no need for powering them, and have nonlinearities.
Active devices need powering, are more linear (If proper designed/used) and has almost no hum pick up, but some extra noise.
Active devices need powering, are more linear (If proper designed/used) and has almost no hum pick up, but some extra noise.
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Hum pick up -- not a problem and can be reduced with proper shielding.
Driving power?
Sound character?
Driving power?
Sound character?
What kind of mixer? There arnt many old mixers worth using that dont have ballanced outputs. are you sure the outs arnt ballanced (TRS 1/4 inch) And are you sure spending the $200 on Jensen output xformers is worth it?
It depends in the characteristics of the transformer (Inductances, capacitances, leakage) driver performance (Output resistance) and load (Load impedance, cable capacitance), etc.
cbdb,
Ol' but rare Vestax dj mixer that I am restoring. It's rca out only. I will need to make it balanced out. The question is transformer or electronic and either way will cost money.
Plus/minus $200 is not as important as best performance out of this mixer. Hence the original post.
Ol' but rare Vestax dj mixer that I am restoring. It's rca out only. I will need to make it balanced out. The question is transformer or electronic and either way will cost money.
Plus/minus $200 is not as important as best performance out of this mixer. Hence the original post.
Reducing LF transformer distortion is complex, generating a balanced signal with an opamp is simple. No contest unless you need the isolation.
If it is not an adverse room (nasty power lines), I sure would just run RCA through 35 feet of coax to a balanced input. Any good "balanced" input accepts unbalanced sources fine. The RANE site used to have text and pictures for almost any connection.
10k minimum load is discouraging for transformers. Unbal/bal active converter boxes are a standard thing.
10k minimum load is discouraging for transformers. Unbal/bal active converter boxes are a standard thing.
Can you tell us which one??
Vestax was in business near 4 decades, many-many products over sevral generations of electronics.
I found a source of service manuals. However I am not going to read all 45 of these looking for your "rare" machine.
Vestax - KevinChant.com
Vestax MW-3000. It's a rare beast and I'd like to have it up to modern PA standards, with balanced outputs. Like all decent PA gear.
Go to the Jensen transformer website and retrieve application note AN003 there. In it, you will find an extremely simple means of converting an unbalanced single-ended output in to a fully balanced (though, still single-ended) one. It utilizes just one or two passive components, a resistor and possibly a capcitor. The result will have the full common-mode noise rejection of any other balanced interface. Neither transformers or active inverter amplifiers are required at the output to make it balanced.
While the Jensen AN003 plan works, it does not increase signal swing, and that DJ mixer appears to run on rather low supply voltage.
Vestax *already* designed a fix. The PCM-05 Pro IV has the unbalanced output main board, and another board to balance the output (and double the max output on the same supply), AND protects it against 48V Phantom (a real risk when sending XLR cable to strange soundmen). There's other ways to do all this, sure. But I like a known-good factory-thought-out plan.
Vestax *already* designed a fix. The PCM-05 Pro IV has the unbalanced output main board, and another board to balance the output (and double the max output on the same supply), AND protects it against 48V Phantom (a real risk when sending XLR cable to strange soundmen). There's other ways to do all this, sure. But I like a known-good factory-thought-out plan.
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That alone tells me it won´t be happy driving a transformer.
Build an Op Amp balanced output stage, very simple and guaranteed low impedance.
Unity gain, of course, plus cheaper, cleaner and flatter than any physical transformer.
> That alone tells me
Read the blurry schematic. It appears to be a NJM4580 (hi-current) opamp, 10uFd, 220r resistor. "10k" is gross under-rating... 10k was the number on the minimum product spec, so they did not bother to put the true ability on record. The 10uFd suggests we'd like >1k loading, the 220r would like >2.2k for -1dB drop, but it would not suck in 600r, except only +7dBm. (It really is intended to go just to a power amp or a line-level input on a mixer.)
I've just noticed the PCM-05 uses different supply rails. It might be best/simplest to build the boost/balance as a separate box with a cut-down PCM-05 supply, RCA in, XLR out.
Read the blurry schematic. It appears to be a NJM4580 (hi-current) opamp, 10uFd, 220r resistor. "10k" is gross under-rating... 10k was the number on the minimum product spec, so they did not bother to put the true ability on record. The 10uFd suggests we'd like >1k loading, the 220r would like >2.2k for -1dB drop, but it would not suck in 600r, except only +7dBm. (It really is intended to go just to a power amp or a line-level input on a mixer.)
I've just noticed the PCM-05 uses different supply rails. It might be best/simplest to build the boost/balance as a separate box with a cut-down PCM-05 supply, RCA in, XLR out.
There's the curious and charming Vestax.
...if you're wondering what the fuss is about. It has a nice nostalgic feel but only lacks the balanced outputs. They don't make em like that anymore!
JMFahey and PRR: so it sounds like the Jensen 600ohm transformer is not the best idea for this mixer, after looking at the schematic, as the minimal loading is around 2kOhms, correct?
Ken Newton suggested the passive balancing circuit.
Cost not an issue (I really like this mixer), what would be your choice or word of advice to get balanced out with minimal loss in sound quality? Hopefully without using an external box.
There's plenty of space inside and it's got 15v dc on the input of the mixer.
Can I stuff something good inside that will do the job? Good universal balancing board?
note: Neurochrome will be releasing a new one now that "THAT driver board" is not available due to "LME49710NA is no longer available"
...if you're wondering what the fuss is about. It has a nice nostalgic feel but only lacks the balanced outputs. They don't make em like that anymore!
JMFahey and PRR: so it sounds like the Jensen 600ohm transformer is not the best idea for this mixer, after looking at the schematic, as the minimal loading is around 2kOhms, correct?
Ken Newton suggested the passive balancing circuit.
Cost not an issue (I really like this mixer), what would be your choice or word of advice to get balanced out with minimal loss in sound quality? Hopefully without using an external box.
There's plenty of space inside and it's got 15v dc on the input of the mixer.
Can I stuff something good inside that will do the job? Good universal balancing board?
note: Neurochrome will be releasing a new one now that "THAT driver board" is not available due to "LME49710NA is no longer available"
Is that +/- 15V or just +15V? Single supply operation requires some tweaks.
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