It depends on the output and input impedance of your devices.
if you are using a passive pre on one of the branches of the split. its impedance may change (does it? whats the set up) which might cause odd things to happen on the other input (main amp)
if the output impedance of the source is low enough you should usually be ok. watch out for ground loops. i can become complicated!
if you are using a passive pre on one of the branches of the split. its impedance may change (does it? whats the set up) which might cause odd things to happen on the other input (main amp)
if the output impedance of the source is low enough you should usually be ok. watch out for ground loops. i can become complicated!
Hi,
make sure BOTH power amps have a DC blocking capacitor on the input. Otherwise the input offset current will interact and may cause a problem.
If your two amps are high Zin then the preamp should be able to drive them.
Just try to get a 1:10 ratio between Pre Zout : Power Zin//Zin
eg. pre Zout=1k0 and both power Zin=20k works.
make sure BOTH power amps have a DC blocking capacitor on the input. Otherwise the input offset current will interact and may cause a problem.
If your two amps are high Zin then the preamp should be able to drive them.
Just try to get a 1:10 ratio between Pre Zout : Power Zin//Zin
eg. pre Zout=1k0 and both power Zin=20k works.
Thank you for your replies.
This is obviously a little more complicated than I had thought (why I posted originally, I suppose), so I should have provided more details.
I will be using a cdp as transport, feeding a NOS DAC (powered by 12v DC). The signal will then go to a passive pre-amp, which will be a 50K stepped attenuator such as: http://www.diyfidelity.com.au/product_info.php?cPath=0_33&products_id=32
After the passive pre-amp the signal will be powered by a Charlize T-amp.
I wish to use a sub/satelite combo for the speakers, so the sub (digital amp 12v DC) will need a feed after the stepped attenuator, in order to remain syncronized.
I do not want to feed the satelites through the subs XO, as I wish to preserve signal quality.
AndrewT: Is it simple to add DC blocking capacitors to both amps, without affecting the setup?
This is obviously a little more complicated than I had thought (why I posted originally, I suppose), so I should have provided more details.
I will be using a cdp as transport, feeding a NOS DAC (powered by 12v DC). The signal will then go to a passive pre-amp, which will be a 50K stepped attenuator such as: http://www.diyfidelity.com.au/product_info.php?cPath=0_33&products_id=32
After the passive pre-amp the signal will be powered by a Charlize T-amp.
I wish to use a sub/satelite combo for the speakers, so the sub (digital amp 12v DC) will need a feed after the stepped attenuator, in order to remain syncronized.
I do not want to feed the satelites through the subs XO, as I wish to preserve signal quality.
AndrewT: Is it simple to add DC blocking capacitors to both amps, without affecting the setup?
AndrewT: Thanks again.
Would adding a tube preamp like this http://www.autocostruire.com/catalog/product_info.php?cPath=46&products_id=329
be a solution? The output buffers are capable of sourcing 200 mA.
I am keen to diy, but I do not understand many basic principals. I am trying to learn as I go.
Would adding a tube preamp like this http://www.autocostruire.com/catalog/product_info.php?cPath=46&products_id=329
be a solution? The output buffers are capable of sourcing 200 mA.
I am keen to diy, but I do not understand many basic principals. I am trying to learn as I go.
I dont know about that thing. if it runs from 12 volts it must have an inverter or something for the tube high voltage? in that case ther would be high frequency electronics on the same board as your audio signal.
or may be the tube doesn't do anything
A simple op amp buffer ought to do the trick, you could also balance the main amp so it does not have to try and output the bass frequencies to the satellites. you could make an op amp filter or just block the lower frequencies by choosing the right input capacitor for the charlise.
or may be the tube doesn't do anything
A simple op amp buffer ought to do the trick, you could also balance the main amp so it does not have to try and output the bass frequencies to the satellites. you could make an op amp filter or just block the lower frequencies by choosing the right input capacitor for the charlise.
Hi,
The cables have inherent capacitance and RsC form a low pass filter.
The power amp normally has at least two filters on it's input.
Rs interacts with the low pass filter.
Rs may also affect the bias conditions on the input stage and the manufacturer may recommend an optimum value for minimum noise.
A low value of Rs (=Zout) generally minimises any interactions and if need be a series resistor can be added.
A high Rs has to be treated with kid gloves and seriously limits flexibility.
the source resistance has a profound effect on the filters that follow.
The cables have inherent capacitance and RsC form a low pass filter.
The power amp normally has at least two filters on it's input.
Rs interacts with the low pass filter.
Rs may also affect the bias conditions on the input stage and the manufacturer may recommend an optimum value for minimum noise.
A low value of Rs (=Zout) generally minimises any interactions and if need be a series resistor can be added.
A high Rs has to be treated with kid gloves and seriously limits flexibility.
Right, I have some more info about this setup.
The output impedance from the DAC is 2K Ohms.
The input impedance to the power amp is 20K Ohms.
The nice aussie stepped attenuator that I found (see above) is sold in 10K, 25K, 50k, and 100K guises.
I would still prefer to split off a line level output to the subwoofer amp between the attenuator and the power amplifier, rather than after the power amp, but this is not a deal breaker.
Which attenuator impedance would you recommend?
Can anyone come up with a suitable 12v op-amp that will allow a dual output?
The fog is clearing?
The output impedance from the DAC is 2K Ohms.
The input impedance to the power amp is 20K Ohms.
The nice aussie stepped attenuator that I found (see above) is sold in 10K, 25K, 50k, and 100K guises.
I would still prefer to split off a line level output to the subwoofer amp between the attenuator and the power amplifier, rather than after the power amp, but this is not a deal breaker.
Which attenuator impedance would you recommend?
Can anyone come up with a suitable 12v op-amp that will allow a dual output?
The fog is clearing?
Hi,
Rs=2k and Zin =20k work with only a short cable in between.
If you need an attenuator for volume control then the impedances don't work.
It would be better to put the (now necessary) buffer immediately after the attenuator.
So I am suggesting you will have DAC 2k >> 20k Attenuator >> buffer >> 10k power amps (20k//20k). This way you maintain at least 1:10 ratio of source to load impedances. The output of the attenuator must go straight into the opamp, no long wires inside the box.
Just about any opamp will drive a 10k load. But, you need to select an opamp to also drive the cable capacitance in parallel to that easy resistive load. ne5534 will do it cheaply and most agree it offers a superb sound/price performance.
Rs=2k and Zin =20k work with only a short cable in between.
If you need an attenuator for volume control then the impedances don't work.
It would be better to put the (now necessary) buffer immediately after the attenuator.
So I am suggesting you will have DAC 2k >> 20k Attenuator >> buffer >> 10k power amps (20k//20k). This way you maintain at least 1:10 ratio of source to load impedances. The output of the attenuator must go straight into the opamp, no long wires inside the box.
Just about any opamp will drive a 10k load. But, you need to select an opamp to also drive the cable capacitance in parallel to that easy resistive load. ne5534 will do it cheaply and most agree it offers a superb sound/price performance.
Hi,
For internal connections between PCBs and in/out connections, twisted pairs of insulated 0.6mm single core copper work well. Available in lots of colours.
For external connections, most use coax.
The coax type will depend on the transmit and receive requirements.
internally or externally.
For internal connections between PCBs and in/out connections, twisted pairs of insulated 0.6mm single core copper work well. Available in lots of colours.
For external connections, most use coax.
The coax type will depend on the transmit and receive requirements.
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