Hello,
I'm new to this forum and not to technical either, so please move this post if it doesn't belong here.
We have two power amplifiers that have an input impedance of just 600 ohms. (I don't understand how they work, because also the output of the preamplifier is also 600 ohms and the manual states that one can connect the preamplifier output directly to the power amplifier input 600 ohms -> 600 ohms).
In between the preamplifier and power amplifiers we inserted a processor that has an output impedance of 100 ohms. The output was split to the two amplifiers, thus giving a load of just 300 ohms.
Is there a way we can connect the 100 ohm processor to the 300 ohm power amplifiers?
(between the processor and power amplifiers we also have two passive monitor controllers, if this is a useful information)
Thank you 🙂
I'm new to this forum and not to technical either, so please move this post if it doesn't belong here.
We have two power amplifiers that have an input impedance of just 600 ohms. (I don't understand how they work, because also the output of the preamplifier is also 600 ohms and the manual states that one can connect the preamplifier output directly to the power amplifier input 600 ohms -> 600 ohms).
In between the preamplifier and power amplifiers we inserted a processor that has an output impedance of 100 ohms. The output was split to the two amplifiers, thus giving a load of just 300 ohms.
Is there a way we can connect the 100 ohm processor to the 300 ohm power amplifiers?
(between the processor and power amplifiers we also have two passive monitor controllers, if this is a useful information)
Thank you 🙂
Passive monitor controllers...what is it?...likely something with high input and high output impedance. Not suitable to drive low impedance inputs.
Other thing...what amplifiers have 600 or 300 ohm input impedance? Typically this would be hundreds of kilo ohms, not few hundred ohms. Something very fishy here.
Other thing...what amplifiers have 600 or 300 ohm input impedance? Typically this would be hundreds of kilo ohms, not few hundred ohms. Something very fishy here.
Welcome to diyAudio 🙂
Have you any details on the power amp ? We might be able to turn up some circuit info.
Also, are these 'balanced inputs' meaning they are a three wire connection rather than a two wire ?
Ultimately you may not even have a problem, certainly not in the sense that anything will be damaged.
Have you any details on the power amp ? We might be able to turn up some circuit info.
Also, are these 'balanced inputs' meaning they are a three wire connection rather than a two wire ?
Ultimately you may not even have a problem, certainly not in the sense that anything will be damaged.
Wow, I wasn't expecting such prompt answers,
Sure, I have the names and manuals of all the devices, but I read on the rules that posting names could be considered commercial.
The amplifiers are TOA1724 and TOA1706 [1]
The procesors are Behringer MDX2600 [2] and FBQ1000 [4] and DBX 131s[3].
The controllers are SMPRO Nanopatch+ [5]
The connections are as follows:
TOA1706 LINE OUT -> TOA 1724 AUX
(
TOA 1724 LINE OUT -> DBX 131s-> FBQ1000-> MDX2600 -> Y cable -> 2. and 2. Nanopatch+
(
1. Nanopatch+ -> TOA 1724 PWR AMP IN
2. Nanopatch+ -> TOA 1706 PWR AMP IN
)
)
[1] http://www.toa.co.uk/wp-content/uploads/imported/a1706-as_mt1e.pdf
[2] https://media.americanmusical.com/ItemFiles/Manual/behringer/behmdx2600_manual.pdf
[3] https://3e7777c294b9bcaa5486-bc9563...1/dbx215s_131s_231s_OwnersManual_original.pdf
[4] https://www.soundpro.com/catalog/documents/FBQ1000_um.pdf
[5] https://www.jblpro.com/ProductAttachments/nanopatchplus_JBL_manual_090215.pdf
Sure, I have the names and manuals of all the devices, but I read on the rules that posting names could be considered commercial.
The amplifiers are TOA1724 and TOA1706 [1]
The procesors are Behringer MDX2600 [2] and FBQ1000 [4] and DBX 131s[3].
The controllers are SMPRO Nanopatch+ [5]
The connections are as follows:
TOA1706 LINE OUT -> TOA 1724 AUX
(
TOA 1724 LINE OUT -> DBX 131s-> FBQ1000-> MDX2600 -> Y cable -> 2. and 2. Nanopatch+
(
1. Nanopatch+ -> TOA 1724 PWR AMP IN
2. Nanopatch+ -> TOA 1706 PWR AMP IN
)
)
[1] http://www.toa.co.uk/wp-content/uploads/imported/a1706-as_mt1e.pdf
[2] https://media.americanmusical.com/ItemFiles/Manual/behringer/behmdx2600_manual.pdf
[3] https://3e7777c294b9bcaa5486-bc9563...1/dbx215s_131s_231s_OwnersManual_original.pdf
[4] https://www.soundpro.com/catalog/documents/FBQ1000_um.pdf
[5] https://www.jblpro.com/ProductAttachments/nanopatchplus_JBL_manual_090215.pdf
I can see the line out is nominally marked as 600 ohm/0db which could be taken in two ways, most likely that it is fully specified to drive 600 ohm with no change in output voltage.
That implies that it is a low impedance output which (without me being particularly knowledgeable in PA stuff) seems likely. That also means that in practice it should drive pretty much whatever you dangle off it.
Without seeing a circuit diagram it would only be possible to confirm all this by doing actual measurements and seeing if the output voltage falls under loading or not.
A rough and ready check is simply noting if the level from the amplifier falls as you parallel the second one to the input.
That implies that it is a low impedance output which (without me being particularly knowledgeable in PA stuff) seems likely. That also means that in practice it should drive pretty much whatever you dangle off it.
Without seeing a circuit diagram it would only be possible to confirm all this by doing actual measurements and seeing if the output voltage falls under loading or not.
A rough and ready check is simply noting if the level from the amplifier falls as you parallel the second one to the input.
I think there is some misunderstanding:
The impedance stated in the TOA manual refers to the microphone inputs: 600Ohms/-60dB.
You will not use these for a line level signal anyway. The line inputs have an impedance of 10kOhms.
Regarding the use of a split cable, this will no problem, all devices (except the Nano Patch of course, which is a passive volume control) have lo-impedance outputs that will easily drive two or even more line inputs.
The impedance stated in the TOA manual refers to the microphone inputs: 600Ohms/-60dB.
You will not use these for a line level signal anyway. The line inputs have an impedance of 10kOhms.
Regarding the use of a split cable, this will no problem, all devices (except the Nano Patch of course, which is a passive volume control) have lo-impedance outputs that will easily drive two or even more line inputs.
Two things.
1. Are you using the Nano patch devices as a remote volume control for each amp? If so then why aren't you just using a TOA remote volume pot hard wired directly to the amps.
2. Your amps are single channel mono but all your processing is dual channel so why don't you connect this way.
TOA1706 LINE OUT -> Ch1 DBX 131 -> CH1 FBQ1000-> CH1 MDX2600 ->TOA1706 PWR AMP IN.
TOA1724 LINE OUT -> Ch2 DBX 131s -> CH2 FBQ1000-> CH2 MDX2600 ->TOA 1724 PWR AMP IN
1. Are you using the Nano patch devices as a remote volume control for each amp? If so then why aren't you just using a TOA remote volume pot hard wired directly to the amps.
2. Your amps are single channel mono but all your processing is dual channel so why don't you connect this way.
TOA1706 LINE OUT -> Ch1 DBX 131 -> CH1 FBQ1000-> CH1 MDX2600 ->TOA1706 PWR AMP IN.
TOA1724 LINE OUT -> Ch2 DBX 131s -> CH2 FBQ1000-> CH2 MDX2600 ->TOA 1724 PWR AMP IN
Ah, really...
Even the power amp input reads 600 Ohms. No idea what sense this should make nowadays.
If this is correct there could be problems wtih the JBL Nano Patches, as their internal potentiometers are 5k, you may get a unconvenient coltrol characteristic. A splitter cable before(!) them should work anyway, The outputs of the other devices will probably have no trouble driving even 300 Ohms. I suppose their internal output capacitors are 47µF or greater, so also no noticeable bass rollof will occur.
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I don't think those published specs are accurate, I'll bet only the mic inputs are 600ohm. What are referred to as AUX 1&2 are also mic inputs
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Nobody knows. Level switching is obviously done by a DIP switch, whether this just reduces gain (and leaves the input at 600 Ohms) or engages an input attenuatur is unclear.
Thank you very much for these very prompt answers.
The big problem is the 600 ohms input impedance of the PWR AMP IN of the power amplifiers, not the microphone or auxiliary inputs. I see that GeorgK mentioned this, but I don't understand the problem with the Nanopatch controllers or why there should be no problem driving 300 ohms (I'm not that technical 🙁 but I would be very glad if you could explain because I'm willing to understand)
conanski: (why use the Nanopatch controllers and not the remote volumes of the TOA amplifiers) This is because we want to input a constant volume in the processors, especially in the compressor, thus we need a way to modify the volume after the processing step.
(solution for connecting the devices), I'm very glad that you could offer a new way of connecting the devices, but unfortunately we need to connect them this way because we have 11 microphones and we use 6 microphones on the first station and 5 on the second, and connect the line out of the first to the aux of the second.This means that we only have the entire combined signal at the output of the second station. We need the full signal, because it then goes to a set of exterior monitors (through the PWR AMP IN of the 240W amplifier) and to a set of interior monitors (through the PWR AMP IN of the 60W amplifier). A mixer would have been perfect for this split, but I'm afraid we are out of budget...
Mooly: I'm sorry, this is all I could find about the schematics. But I can say that between the processors we only have balanced lines and between pre-amplifiers and processors / processors and amplifiers only unbalanced lines (the outputs / inputs in the TOAs are all unbalanced, except for the microphones).
The big problem is the 600 ohms input impedance of the PWR AMP IN of the power amplifiers, not the microphone or auxiliary inputs. I see that GeorgK mentioned this, but I don't understand the problem with the Nanopatch controllers or why there should be no problem driving 300 ohms (I'm not that technical 🙁 but I would be very glad if you could explain because I'm willing to understand)
conanski: (why use the Nanopatch controllers and not the remote volumes of the TOA amplifiers) This is because we want to input a constant volume in the processors, especially in the compressor, thus we need a way to modify the volume after the processing step.
(solution for connecting the devices), I'm very glad that you could offer a new way of connecting the devices, but unfortunately we need to connect them this way because we have 11 microphones and we use 6 microphones on the first station and 5 on the second, and connect the line out of the first to the aux of the second.This means that we only have the entire combined signal at the output of the second station. We need the full signal, because it then goes to a set of exterior monitors (through the PWR AMP IN of the 240W amplifier) and to a set of interior monitors (through the PWR AMP IN of the 60W amplifier). A mixer would have been perfect for this split, but I'm afraid we are out of budget...
Mooly: I'm sorry, this is all I could find about the schematics. But I can say that between the processors we only have balanced lines and between pre-amplifiers and processors / processors and amplifiers only unbalanced lines (the outputs / inputs in the TOAs are all unbalanced, except for the microphones).
I also contacted technical support at TOA and they were nice to offer a schematic of how to connect the processor to the PWR AMP IN. They recommended using a resistor, at list 600 ohms, on wire 3, at the inputs of each power amplifier.
I sent a reply asking if the Nanopatch passive volume controllers, never set at max volume, would give the same result as a resistor, because then the problem would be solved: just use half the range of the volume controllers 🙂 I'm waiting for the reply now, because I didn't think of mentioning the controllers in the first mail sent to them.
I sent a reply asking if the Nanopatch passive volume controllers, never set at max volume, would give the same result as a resistor, because then the problem would be solved: just use half the range of the volume controllers 🙂 I'm waiting for the reply now, because I didn't think of mentioning the controllers in the first mail sent to them.
If the 600 Ohms are correct, the problem with the Nanos will that they are passive potentiometers whose output impedance increases when they are turned down below 100%. In contrast, to drive an input as low as 600 Ohms you need a rather low output impedance. This will result in a rather unconvenient characteristic of the volume control, with quite quickly decreasing volume as you go below 100%. If you can live with this in your setup, you will be fine.
Have you tried it already?
Another way to go could be a modification of the pwr amp in, but this would involve a soldering iron and, if applicable, loss of warranty. I am quite sure that the 600 Ohm are essentially determined by a single resistor that can be changed to make impedance higher. But from here this is impossible to tell exactly without a service manual (or just the schematics of the input)
i don't get it, what is wire 3? The input is RCA I suppose?
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Thank you GeorgK, I don't mind the nonlinear volume response, because the volume will mostly be fixed at two stages (room empty and room full). But nonlinear frequency responses could be a problem. Trying to understand your post, I came across this forum [1] where someone states: "Passive controllers only work well if connected to a source with a very low output impedance, and a destination with a very high input impedance -- and with short, low-capacitance cables. Anything else risks the kinds of spectrum imbalances described... "
Does this mean that it would be a good idea to insert the resistors mentioned at the input of the power amplifiers? I was thinking of inserting them on the cables, not inside the amplifier to invalidate the warranty.
[1] SOS Forum • SM Pro Audio Nano Patch + vs. Palmer Monicon
Does this mean that it would be a good idea to insert the resistors mentioned at the input of the power amplifiers? I was thinking of inserting them on the cables, not inside the amplifier to invalidate the warranty.
[1] SOS Forum • SM Pro Audio Nano Patch + vs. Palmer Monicon
I'm sorry, wire 2 (hot), I was under the impression it was a XLR cable and no ground was drawn 🙂
I'm sorry scottjoplin, but we are out of budget and active controllers are to expensive. We already have these passive controllers.
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