Sorry to revisit an old thread which I started in 2006. It may not have been started in this forum, it may have been inappropriately placed here by a robot at some time over the years.
I hesitated during the last 14 years to do this project because on my receiver's schematic (Sony STR-DG500), I could not see the obvious location where I could tap into a low level analog signal path to create the new pre-outs.
So back in 2006, I simply created pseudo pre-outs for my external power amps by putting a voltage divider across the receiver’s speaker outputs with a 100 ohm power resistor substituting for the speakers no longer connected there.
But in recent years, my receiver’s right channel speaker output which was driving the pseudo pre-out was getting flaky, losing about 10 db. compared to the left channel.
So I decided that if I created a real internal pre-out, then I could bypass the bad receiver power amp. Yesterday I discovered on the web how someone else succeeded with a Sony STR-DN1050, so tried the same approach.
After installing the new pre-outs, I learned the hard way that it wasn't the receiver’s right channel power amp that was faulty, but the decoupling capacitor connecting the input selector processing chip to the input of the receiver’s right channel power amp.
Since my new pre-out tap was attached to the downstream side of this faulty cap, my new right channel pre-out was just as flaky as the previous right channel pseudo pre-out.
Fortunately, all I needed to do was place a new decoupling cap in parallel with the old one. I didn’t actually remove the original 4.7 ufd bad cap since it was too much work to remove the main PCB without removing 5 other boards stuck in the way.
My only problem with these new pre-outs which are driven directly off the DSP chip is that the full signal strength is about 100 mv. instead of the preferred line-out voltage of 1 v.
Back in 2002, I had purchased some AD8066 opamps chips in anticipation of upgrading a Sony SACD player, which I never did.
I would now like to use these chips to create an outboard line driver downstream of my new pre-outs wires so that I won’t have to turn up my input pots to 100% on my external power amps to compensate the 100 mv. input signal strength.
Without starting a debate over which opamp chip is best in the year 2020 compared to 2002, does anyone have a simple circuit design for the AD8066 which is stable, has a voltage gain of about 10, and is flat from 20-30khz.?
Thanks
I hesitated during the last 14 years to do this project because on my receiver's schematic (Sony STR-DG500), I could not see the obvious location where I could tap into a low level analog signal path to create the new pre-outs.
So back in 2006, I simply created pseudo pre-outs for my external power amps by putting a voltage divider across the receiver’s speaker outputs with a 100 ohm power resistor substituting for the speakers no longer connected there.
But in recent years, my receiver’s right channel speaker output which was driving the pseudo pre-out was getting flaky, losing about 10 db. compared to the left channel.
So I decided that if I created a real internal pre-out, then I could bypass the bad receiver power amp. Yesterday I discovered on the web how someone else succeeded with a Sony STR-DN1050, so tried the same approach.
After installing the new pre-outs, I learned the hard way that it wasn't the receiver’s right channel power amp that was faulty, but the decoupling capacitor connecting the input selector processing chip to the input of the receiver’s right channel power amp.
Since my new pre-out tap was attached to the downstream side of this faulty cap, my new right channel pre-out was just as flaky as the previous right channel pseudo pre-out.
Fortunately, all I needed to do was place a new decoupling cap in parallel with the old one. I didn’t actually remove the original 4.7 ufd bad cap since it was too much work to remove the main PCB without removing 5 other boards stuck in the way.
My only problem with these new pre-outs which are driven directly off the DSP chip is that the full signal strength is about 100 mv. instead of the preferred line-out voltage of 1 v.
Back in 2002, I had purchased some AD8066 opamps chips in anticipation of upgrading a Sony SACD player, which I never did.
I would now like to use these chips to create an outboard line driver downstream of my new pre-outs wires so that I won’t have to turn up my input pots to 100% on my external power amps to compensate the 100 mv. input signal strength.
Without starting a debate over which opamp chip is best in the year 2020 compared to 2002, does anyone have a simple circuit design for the AD8066 which is stable, has a voltage gain of about 10, and is flat from 20-30khz.?
Thanks
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It is hard for me to imagine that anyone would find this 16 year old thread interesting at this time, but if so, I have some news to add for those readers still following this thread.
In my previous post of 2020-8-26, I noted how my pre-outs were only providing a 100 mv signal to my standalone external amplifiers (a Crown and an Alesis). My HT is composed of 2 types of loudspeakers having different efficiencies, with the weakest loudspeakers (6" dia) powered by the internal surround channel amps of my Sony STR-DG500 HT receiver and the strongest loudspeakers (15" dia) powered by the standalone Crown and Alesis amps.
Using my receiver's setup menu, I tried as best as possible to get all these speakers to balance with each other. Five out of 6 speakers did balance, but the sixth speaker connected to the Alesis power amp was still down a few db in strength relative to the other speakers.
Because I had been warned that using my previously purchased AD8066 opamps as a buffer was dangerous due to the risk of high frequency ringing, I decided not to boost any of my weak pre-outs with an external opamp buffer. Instead I changed a resistor in the Alesis power amp in order to get it to be more sensitive to the weak input signal from the receiver's pre-out that was feeding it. That worked out.
Another issue with this configuration that was becoming more annoying back in 2021 was the tendency for the Sony STR-DG500 receiver to shut down due to what it detected as a DC voltage at the speaker output connectors even though no speakers were actually connected there. I concluded that DC voltage from the input stage of the Crown amp was finding a path back to a place in the receiver where I had inserted a tap for my pre-outs, thus upsetting the DC part of the receiver’s internal audio signal. I solved this problem by inserting a new 4.7 uf capacitor in series with the receiver's pre-out cable and the external Crown power amp's input connector, effectively blocking DC from flowing between the two units. This was an easy fix and also worked.
It is now summer 2022 and my latest challenge for my perfectly working HT system is one posed by my cable television service provider. After 2 decades, my service provider wants to migrate away from set-top box PVRs (Cisco or Samsung), which feature internal disk storage for pre-recorded content and super fast channel switching for surfing, to streaming devices that fetch all live and pre-recorded content from their "cloud".
Their new streaming box has no SPDIF/Toslink coax or optical digital out, so the multi-channel audio content is only available via the streaming box's HDMI output. I know that a lot of users of these new streaming devices find that they are very slow for channel surfing.
For the time being, I can continue to be a subscriber with my old PVR, but at some point, I will be obliged to move to this streaming device. Since my Sony STR-DG500 receiver has no HDMI inputs, I must find a way to intercept the Dolby Digital audio from the HDMI cable that will run between the streaming box and my television set. That will call for the use of an after-market HDMI audio stripper. I hope there is one that will be compatible with current and future audio formats.
It is ironic that I started this thread in 2006 because at that time I owned a Sony SACD player that fed directly 3 stereo power amps and 6 loudspeakers, and because I had just bought a HD PVR, but I did not already own a HT receiver, I needed a new device that would decode the PVR's digital audio to eventually feed my 6 speakers. That new device turned out to be the Sony STR-DG500 receiver.
Sixteen years later I now risk losing access to the same digital audio signal because the now popular television streaming devices don't provide easy access to this same digital audio signal.
In my previous post of 2020-8-26, I noted how my pre-outs were only providing a 100 mv signal to my standalone external amplifiers (a Crown and an Alesis). My HT is composed of 2 types of loudspeakers having different efficiencies, with the weakest loudspeakers (6" dia) powered by the internal surround channel amps of my Sony STR-DG500 HT receiver and the strongest loudspeakers (15" dia) powered by the standalone Crown and Alesis amps.
Using my receiver's setup menu, I tried as best as possible to get all these speakers to balance with each other. Five out of 6 speakers did balance, but the sixth speaker connected to the Alesis power amp was still down a few db in strength relative to the other speakers.
Because I had been warned that using my previously purchased AD8066 opamps as a buffer was dangerous due to the risk of high frequency ringing, I decided not to boost any of my weak pre-outs with an external opamp buffer. Instead I changed a resistor in the Alesis power amp in order to get it to be more sensitive to the weak input signal from the receiver's pre-out that was feeding it. That worked out.
Another issue with this configuration that was becoming more annoying back in 2021 was the tendency for the Sony STR-DG500 receiver to shut down due to what it detected as a DC voltage at the speaker output connectors even though no speakers were actually connected there. I concluded that DC voltage from the input stage of the Crown amp was finding a path back to a place in the receiver where I had inserted a tap for my pre-outs, thus upsetting the DC part of the receiver’s internal audio signal. I solved this problem by inserting a new 4.7 uf capacitor in series with the receiver's pre-out cable and the external Crown power amp's input connector, effectively blocking DC from flowing between the two units. This was an easy fix and also worked.
It is now summer 2022 and my latest challenge for my perfectly working HT system is one posed by my cable television service provider. After 2 decades, my service provider wants to migrate away from set-top box PVRs (Cisco or Samsung), which feature internal disk storage for pre-recorded content and super fast channel switching for surfing, to streaming devices that fetch all live and pre-recorded content from their "cloud".
Their new streaming box has no SPDIF/Toslink coax or optical digital out, so the multi-channel audio content is only available via the streaming box's HDMI output. I know that a lot of users of these new streaming devices find that they are very slow for channel surfing.
For the time being, I can continue to be a subscriber with my old PVR, but at some point, I will be obliged to move to this streaming device. Since my Sony STR-DG500 receiver has no HDMI inputs, I must find a way to intercept the Dolby Digital audio from the HDMI cable that will run between the streaming box and my television set. That will call for the use of an after-market HDMI audio stripper. I hope there is one that will be compatible with current and future audio formats.
It is ironic that I started this thread in 2006 because at that time I owned a Sony SACD player that fed directly 3 stereo power amps and 6 loudspeakers, and because I had just bought a HD PVR, but I did not already own a HT receiver, I needed a new device that would decode the PVR's digital audio to eventually feed my 6 speakers. That new device turned out to be the Sony STR-DG500 receiver.
Sixteen years later I now risk losing access to the same digital audio signal because the now popular television streaming devices don't provide easy access to this same digital audio signal.
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