I recently acquired this passive converter:
Single Stereo to Dual Mono Audio Converter Mono Out retains L/R Input Isolation
Attaching one device to one output channel works well. But when I plug both devices into the converter simultaneously the signal is barely audible.
Is that to be expected?
If so, I am struggling to imagine what the use case for sending two mono channels to a single device is. Something out of my range of experience, perhaps.
Single Stereo to Dual Mono Audio Converter Mono Out retains L/R Input Isolation
- Input connectors: Stereo L/R RCA
- Output connectors: 2 x Mono RCA
- Utilizes independent 1:1 ratio dual audio transformers
- Dimensions (L x W x H): 2 5/8" x 1 5/8" x 1 1/4", Gold plated connectors
- Passive circuitry, no external power required
Attaching one device to one output channel works well. But when I plug both devices into the converter simultaneously the signal is barely audible.
Is that to be expected?
If so, I am struggling to imagine what the use case for sending two mono channels to a single device is. Something out of my range of experience, perhaps.
Does it make a difference which channel you connect first to a power amp?
If you only plug in the offending power amp, and not the other one, is the issue still there?
Just to isolate the problem to the converter and not one of the power amps.
Jan
If you only plug in the offending power amp, and not the other one, is the issue still there?
Just to isolate the problem to the converter and not one of the power amps.
Jan
But why do you want to convert stereo to mono?
I would put the gadget aside, and use one amp per channel.
I would put the gadget aside, and use one amp per channel.
Thank you for the quick response.
Your advice was helpful. Long story short, one of the devices used a homemade cable that has always worked fine, but for whatever reason was creating havoc when paired with the converter and the other device.
I'll have to run a new cable and then the problem will be solved.
Cheers!
I see no energy source input to this converter. In that case it is a passive transformer, unless there is a battery powered amplifier inside. This is diyaudio. You have bought a consumer electronics device designed to sell to you, not to solve your problems.
The problem is probably not the 2nd amplifier, the problem is the second cable. RCA cables contain about 100 pf per foot of capacitance. Two 6' cables in parallel is ~1200 pf. Possibly your 2nd amplifier also has an input capacitor, maybe .01 uf or so. This goes to the plate input, so not in parallel with the mixer output as cable capacitance is. The transformer demonstrably does not have the current drive to produce a full 1.6 vac signal into the 2nd cable & amplifier. If you constructed a 1" long RCA cable to connect the box to one amplifier, it might work at reasonable volume. Of course you can't buy such a cable, people want a full 6' of cable for their $2.
stereo to mono converters can also be constructed with two resistors from the hots of the two RCA inputs, to the input of one amplifier, typically an op amp. The amplifier consumes power to produce the low impedance output voltage. If the op amp has 2000 ohm drive it can drive about 10' of RCA cable. If it has 600 ohm drive, much longer. Look at the voltage swing at what load specification on the op amp datasheet.
At 12' I start picking up AM sports talk radio with my RCA cable. That has to be filtered out by a bigger capacitor at the input to my solid state amp. My tube amp (dynakit ST70) lacks a capacitor from the RCA input to the grid of the first tube, which is a demonstrable safety hazard. If the plate to grid shorts in the tube, the rca cable center becomes charged to plate voltage. Possibly shocking you or blowing the output of a solid state driving amplifier.
The problem is probably not the 2nd amplifier, the problem is the second cable. RCA cables contain about 100 pf per foot of capacitance. Two 6' cables in parallel is ~1200 pf. Possibly your 2nd amplifier also has an input capacitor, maybe .01 uf or so. This goes to the plate input, so not in parallel with the mixer output as cable capacitance is. The transformer demonstrably does not have the current drive to produce a full 1.6 vac signal into the 2nd cable & amplifier. If you constructed a 1" long RCA cable to connect the box to one amplifier, it might work at reasonable volume. Of course you can't buy such a cable, people want a full 6' of cable for their $2.
stereo to mono converters can also be constructed with two resistors from the hots of the two RCA inputs, to the input of one amplifier, typically an op amp. The amplifier consumes power to produce the low impedance output voltage. If the op amp has 2000 ohm drive it can drive about 10' of RCA cable. If it has 600 ohm drive, much longer. Look at the voltage swing at what load specification on the op amp datasheet.
At 12' I start picking up AM sports talk radio with my RCA cable. That has to be filtered out by a bigger capacitor at the input to my solid state amp. My tube amp (dynakit ST70) lacks a capacitor from the RCA input to the grid of the first tube, which is a demonstrable safety hazard. If the plate to grid shorts in the tube, the rca cable center becomes charged to plate voltage. Possibly shocking you or blowing the output of a solid state driving amplifier.
Hi @NareshBrd
There's nothing wrong with what you suggested so long as one only listen to mono music.
But, as I'm sure you realize, stereo tracks contain different audio information in each channel.
So if you only plugged one channel (let's say the left channel) straight into a mono device, you'd be missing elements of a stereo recording.
That's why it's better to mix a stereo signal down to mono if you're going to listen to it on a mono device.
There's nothing wrong with what you suggested so long as one only listen to mono music.
But, as I'm sure you realize, stereo tracks contain different audio information in each channel.
So if you only plugged one channel (let's say the left channel) straight into a mono device, you'd be missing elements of a stereo recording.
That's why it's better to mix a stereo signal down to mono if you're going to listen to it on a mono device.
Guys, it has inside only 4 or 5 resistors making a passive resistance mixer/combiner. No need for power supply.
Suplied in a pretty box but no more than that.
Suplied in a pretty box but no more than that.
Hi @indianajo
Thank you for the absolutely incredible response.
I'd already resolved the issue before I had a chance to read your comment. But you were absolutely correct, the issue was with the second cable.
Long story short the second vacuum tube amplifier lives in another part of the house. I had been using speaker cable with RCA jacks on either end to send a signal from my audio source to that amp. It always worked fine until now.
I didn't use a speaker cable by choice, of course. It was nearly impossible to get an actual cable manufactured with RCA connectors through the route it had to take.
But for testing purposes I ran a 25 ft cable up the stairs and connected the converter directly to the amp. Now both of my vacuum tube amps are working beautifully with no detectable ground loop issues whatsoever.
As it happens I already have a fish rod kit on order. And when I receive it I will take another run at running a proper cable to the remote amp.
Thank you for the absolutely incredible response.
I'd already resolved the issue before I had a chance to read your comment. But you were absolutely correct, the issue was with the second cable.
Long story short the second vacuum tube amplifier lives in another part of the house. I had been using speaker cable with RCA jacks on either end to send a signal from my audio source to that amp. It always worked fine until now.
I didn't use a speaker cable by choice, of course. It was nearly impossible to get an actual cable manufactured with RCA connectors through the route it had to take.
But for testing purposes I ran a 25 ft cable up the stairs and connected the converter directly to the amp. Now both of my vacuum tube amps are working beautifully with no detectable ground loop issues whatsoever.
As it happens I already have a fish rod kit on order. And when I receive it I will take another run at running a proper cable to the remote amp.
I think there's still a confusion. A stereo amp is just two mono amps. If you take the stereo amp and replace it by two moinoblocks like you did, you still have a stereo system if you plug the L sourse in the left monobloc and the R source in the right monobloc.
There would be no need fot the gadget and you got great stereo.
Jan
The two mono amps are in different parts of the house, that is why he wanted to use one amp at a time.
At least I think that is his meaning.
Building a stereo 1875 kit will cost him 50 or so Canadian...may be a better option, and more effective than whatever this gadget contains, quite possibly a few resistors as Osvaldo said above in post #7.
At least I think that is his meaning.
Building a stereo 1875 kit will cost him 50 or so Canadian...may be a better option, and more effective than whatever this gadget contains, quite possibly a few resistors as Osvaldo said above in post #7.
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Yes, his second, mono, amplifier is in another part of the house.
The gadget also contains dual isolating transformers to avoid ground loops.
The gadget also contains dual isolating transformers to avoid ground loops.
You could put both amplifiers in the downstairs room, with short RCA cable. Then you could run speaker output from the 2nd amplifier upstairs to the speaker. Speaker level outputs have no trouble driving capacitance, they have an 8 ohm or 4 ohm current source. You might find bass damping suffers from a 16 ga zip cord, because of the resistance deteriorates damping factor. In that case you use 14 ga or 12 ga cable.
If you want to turn on/off the downstairs amp from upstairs, use a remote car starter. I did that for a pipe organ blower in the basement, with the remote on the console in the upstairs sanctuary. The blower will start or stop from the remote anywhere in the 200 seat sanctuary. I put a 12 v coil relay after the car starter to engage 120 vac in the basement. Put 120 v wiring & controls in a grounded steel box to prevent fire.
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That would be true, except this scenario is two totally unique mono devices that reside in different zones of my house. And although they are both fed and audio signal from my main rig, they each have different applications and it's unlikely they would be used at the same time.