Do you mean when used in asynch mode? I'm also interested in the difference between the Sabre operating in synch mode & asynch mode - any opinion?
Why limit yourself to op-amps - go with transformer output!Neoy2k said:
I love transformer output. It sounds very good. And you can play with the way it behaves with loading/zobel etc, so you can choose "smoother" "faster" and avoid ringing (or not, you can do what you want).
However even the best ones have a distortion level 50dB higher than the DAC's distortion (-70/80dB vs -120dB...). And their sound will vary with what they are plugged to.
This is not a path I'm following, but it doesn't means it doesn't sounds good. In fact, I love to sometimes add transformers in the signal path
and I love the crappy ones that will color the sound a lot. BUT I use this as a conscious effect.I intend my DAC (at least, this one) to be a monitoring DAC, thus just sending me the signal the most accurate way. So if I hear that I lack transformer color, then I have to work it in the recording. If it sounds harsh, then it is that my recording sounds harsh - and I have to work it out.
Cheers
Yes they do sound wonderful on Vout DACs anyway, which is what I have heard them on. So even with the higher distortion ther is obviously something else that the transformer is doing better than op-amps to allow it to sound better - could it be slew rate limiting on the DAC or the settling time as you mentioned above? Something seems to work better on transformers than op-amps in this situation & don't say that I just like the sound of distortion, please.
This is not a path I'm following, but it doesn't means it doesn't sounds good. In fact, I love to sometimes add transformers in the signal path
I intend my DAC (at least, this one) to be a monitoring DAC, thus just sending me the signal the most accurate way. So if I hear that I lack transformer color, then I have to work it in the recording. If it sounds harsh, then it is that my recording sounds harsh - and I have to work it out.
Cheers
Hmm, but you are just chasing specs not sound! I know a lot of audio is a numbers game & maybe you have to play this to stay commercial but let your ears into the equation at some point. I'm not talking about using transformers that obviously colour the sound but ones that give a more natural analogue-like or live-like sound.
BTW, how are all the boards going that you sent out?
Yes, it could be true but it sounds so damn good & that is the important final arbiter - I don't care for infinitesimally small distortion if it doesn't sound good! Let's not lose sight of what this whole hobby is about - being transported by music!
Yesterday, we listened playback of four 2L DXD files on SDHC memory card tranport with external Rubidium oscillator based master clocking.
I2S signals based on the clocking mechanism were input into ES9018 2ch evaluation board and all of us, 6 people recognized a wonderful result.
http://www.diyaudio.com/forums/digi...ry-card-transport-project-10.html#post2068079
I was much impressed by a hyper performance of ES9018 chip again.
Bunpei
Hi, all,
I finally got round to building a DC protect circuit, so I can now try my Sure 4*100 Watt amp on my main speakers (no way I was going to do this without basic DC protection)...
Initial results are VERY promising, and this was only running directly from a cheap USB sound card (C-Media). I couldn't test the Sabre DAC yet due to the noise issue (my slightly weird setup is explained a few pages back).
Ok, I'll try to get to the point - I've tried all possible grounding methods to try to get rid of the huge amount of noise when connecting the Sabre DAC directly to the Sure amp, but without success (I don't have any I/V stage at all)...
I don't yet have any proper audio transformers to try, so I've connected the Sabre +/- DAC outputs to the primary side of a small power trafo (measures 1.9K ohms). The secondary side measures around 8 ohms, and is connected to the terminal block input of the sure amp (bypassing the cheapo input cap)...
This has solved the noise problem completely, so it seems that isolation is the key for my amp project. Of course, the output isn't amazingly loud, but it already sounds great (even with the rubbish trafo and only one speaker!)
So, I'm interested in using audio transformers to connect between the Sabre outputs and Sure amp inputs. The problem is, I'm on a tight budget and I eventually intend to buy another Sure 4*100 Watt amp to do 7.1 (or even 8.1 if I want). This would require 8 or 9 audio trafos (maybe one for the subwoofer output), so the cost would probably be prohibitive.
I was wondering if using some THAT1200 chips would work well as a cheaper alternative to audio trafos? This would apparently provide a high level of isolation as well as converting the Sabre's balanced output to single-ended for the Sure amp(s). Also, does anyone think the THAT1200 chip work well without an I/V stage preceeding it (perhaps with a passive I/V resistor on the inputs?)
I realize it might be more ideal to use proper opamp I/V stages on the Sabre, but I'll probably need the isolation in either case - Can anyone suggest an opamp (or discrete) I/V stage which would provide isolation between the Sabre and the amp inputs?? (or, an I/V which only uses the balanced +/- DAC outputs)?
Many thanks,
OzOnE.
I finally got round to building a DC protect circuit, so I can now try my Sure 4*100 Watt amp on my main speakers (no way I was going to do this without basic DC protection)...
Initial results are VERY promising, and this was only running directly from a cheap USB sound card (C-Media). I couldn't test the Sabre DAC yet due to the noise issue (my slightly weird setup is explained a few pages back).
Ok, I'll try to get to the point
- I've tried all possible grounding methods to try to get rid of the huge amount of noise when connecting the Sabre DAC directly to the Sure amp, but without success (I don't have any I/V stage at all)...I don't yet have any proper audio transformers to try, so I've connected the Sabre +/- DAC outputs to the primary side of a small power trafo (measures 1.9K ohms). The secondary side measures around 8 ohms, and is connected to the terminal block input of the sure amp (bypassing the cheapo input cap)...
This has solved the noise problem completely, so it seems that isolation is the key for my amp project. Of course, the output isn't amazingly loud, but it already sounds great (even with the rubbish trafo and only one speaker!)
So, I'm interested in using audio transformers to connect between the Sabre outputs and Sure amp inputs. The problem is, I'm on a tight budget and I eventually intend to buy another Sure 4*100 Watt amp to do 7.1 (or even 8.1 if I want). This would require 8 or 9 audio trafos (maybe one for the subwoofer output), so the cost would probably be prohibitive.
I was wondering if using some THAT1200 chips would work well as a cheaper alternative to audio trafos? This would apparently provide a high level of isolation as well as converting the Sabre's balanced output to single-ended for the Sure amp(s). Also, does anyone think the THAT1200 chip work well without an I/V stage preceeding it (perhaps with a passive I/V resistor on the inputs?)
I realize it might be more ideal to use proper opamp I/V stages on the Sabre, but I'll probably need the isolation in either case - Can anyone suggest an opamp (or discrete) I/V stage which would provide isolation between the Sabre and the amp inputs?? (or, an I/V which only uses the balanced +/- DAC outputs)?
Many thanks,
OzOnE.
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Hi, all,
I finally got round to building a DC protect circuit, so I can now try my Sure 4*100 Watt amp on my main speakers (no way I was going to do this without basic DC protection)...
Initial results are VERY promising, and this was only running directly from a cheap USB sound card (C-Media). I couldn't test the Sabre DAC yet due to the noise issue (my slightly weird setup is explained a few pages back).
Ok, I'll try to get to the point
I don't yet have any proper audio transformers to try, so I've connected the Sabre +/- DAC outputs to the primary side of a small power trafo (measures 1.9K ohms). The secondary side measures around 8 ohms, and is connected to the terminal block input of the sure amp (bypassing the cheapo input cap)...
This has solved the noise problem completely, so it seems that isolation is the key for my amp project. Of course, the output isn't amazingly loud, but it already sounds great (even with the rubbish trafo and only one speaker!)
So, I'm interested in using audio transformers to connect between the Sabre outputs and Sure amp inputs. The problem is, I'm on a tight budget and I eventually intend to buy another Sure 4*100 Watt amp to do 7.1 (or even 8.1 if I want). This would require 8 or 9 audio trafos (maybe one for the subwoofer output), so the cost would probably be prohibitive.
I was wondering if using some THAT1200 chips would work well as a cheaper alternative to audio trafos? This would apparently provide a high level of isolation as well as converting the Sabre's balanced output to single-ended for the Sure amp(s). Also, does anyone think the THAT1200 chip work well without an I/V stage preceeding it (perhaps with a passive I/V resistor on the inputs?)
I realize it might be more ideal to use proper opamp I/V stages on the Sabre, but I'll probably need the isolation in either case - Can anyone suggest an opamp (or discrete) I/V stage which would provide isolation of the grounds between the Sabre and the amp inputs?? (or, an I/V which only uses the balanced +/- DAC outputs)?
Many thanks,
OzOnE.
Hi,
Your noise problem are #noise due to the pseudo differential mode with 7bit quantizer..
Re-program the ES9018 to use 6bit quantizer and you will run in full differential mode without the #noise.
A transformer or balanced amplifier will cancel most of the #noise...
You do NOT need isolation as the noise will be gone with 6bit quantizer and full differential mode..
If you use two amplifier channels and connects one channel to the positive phase of the ES9018 and the second channel to the negative phase - and connect your speaker between the + outputs of these two amplifier channels - the #noise will then cancel out over the speakers (if the amplifier channels are identical) and you will have a 400 watt amplifier...
I do not recommend this setup as the #noise will still be creating unwanted distortion in the amplifiers,
but you can start listening to the ES9018 DAC in minutes...
And you can fix the programming later...
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Hi,
The noise is not subtle in any way - when the Sabre is connected directly to the amp, there is a huge buzzing sound even when not playing music (sounds like SMPS noise).
When connected this way, I also get strange digital crackling sounds when the DAC comes out of auto-mute. This is likely to be due to lack of any I/V stages though.
When using the trafo between the Sabre and amp, the buzzing is completely absent and the sound quality is great.
Unfortunately, I haven't sorted the I2C programming for the Sabre yet - I don't have a Buffalo any more, I'm using Nicolas' (Neoy2k) 8-channel Sabre DAC which doesn't have an on-board PIC for the I2C stuff.
The DAC is running on defaults, although I can hook up the buspirate to control the Sabre from the PC if need be.
Does the pseudo differential / 7-bit mode create VERY noticable digital noise and DSP type noises in similar setups to mine, or is it a much more subtle thing?
OzOnE.
btw, I'm using an ES9008 - not sure if this makes much difference to the 7-bit / I2C stuff?
The noise is not subtle in any way - when the Sabre is connected directly to the amp, there is a huge buzzing sound even when not playing music (sounds like SMPS noise).
When connected this way, I also get strange digital crackling sounds when the DAC comes out of auto-mute. This is likely to be due to lack of any I/V stages though.
When using the trafo between the Sabre and amp, the buzzing is completely absent and the sound quality is great.
Unfortunately, I haven't sorted the I2C programming for the Sabre yet - I don't have a Buffalo any more, I'm using Nicolas' (Neoy2k) 8-channel Sabre DAC which doesn't have an on-board PIC for the I2C stuff.
The DAC is running on defaults, although I can hook up the buspirate to control the Sabre from the PC if need be.
Does the pseudo differential / 7-bit mode create VERY noticable digital noise and DSP type noises in similar setups to mine, or is it a much more subtle thing?
OzOnE.
btw, I'm using an ES9008 - not sure if this makes much difference to the 7-bit / I2C stuff?
Without programming you will only use the first two channels (unless you have connected the three remaining I2S data inputs to the first), but in full differential mode with 6bit quantizer and you should not have any #noise.
Then the noise might be caused by the DSP, but due to the transformer cancels the noise you have a common mode type of noise,
and if you connect two amplifier channels as I described you will know for sure if the problem are common mode noise or anything else.
#noise sounds like the DAC or amplifier are destroyed...
More noise and distortion than music..
Then the noise might be caused by the DSP, but due to the transformer cancels the noise you have a common mode type of noise,
and if you connect two amplifier channels as I described you will know for sure if the problem are common mode noise or anything else.
#noise sounds like the DAC or amplifier are destroyed...
More noise and distortion than music..
I have the other three I2S lines connected to the DSP board (for 7.1).
The sound quality is fine when connecting via the trafo to the amp, so it's not directly due to the DSP or DAC. The noise disappears completely whether I connect the Sabre +/- via the trafo, or even just Sabre +/GND via the trafo, so I don't think it's common mode noise.
I'll try hooking up across two amp channels as you said though. I still haven't tried a traditional +5V supply to the DSP board, so I'll build a quickie now.
I know the noise is not due to a ground loop to the PC (used as a source), as it still happens when using optical only, or even when it's disconnected from the PC completely? (The coax input on the DSP board is isolated anyway.)
The problem only occurs when connecting the Sabre directly to the Sure amp (no I/V at all). I know that not having a proper I/V or incorrect loading on the DAC outputs can cause "scratchy" horrible audio, but the buzzing sound is quite loud, and always present with a direct connection.
It worked fine when connecting the Sabre to the Sympatico modules - I know they have a differential input opamp, but both differential and single-ended connection to the Sympatico's also worked fine?
("minus" input on Sympatico's were connected to GND when trying single-ended. ie. Sabre "plus" to Symp "plus" / Sabre GND to Symp GND.)
I would be more than happy to use audio trafo's which would solve the problem, but it would be very expensive to buy 8 or 9 decent quality trafos.
Is this type of problem common when using SMPS / Tripath amps, or does it sound like a general ground-loop / no I/V type issue?
OzOnE.
The sound quality is fine when connecting via the trafo to the amp, so it's not directly due to the DSP or DAC. The noise disappears completely whether I connect the Sabre +/- via the trafo, or even just Sabre +/GND via the trafo, so I don't think it's common mode noise.
I'll try hooking up across two amp channels as you said though. I still haven't tried a traditional +5V supply to the DSP board, so I'll build a quickie now.
I know the noise is not due to a ground loop to the PC (used as a source), as it still happens when using optical only, or even when it's disconnected from the PC completely? (The coax input on the DSP board is isolated anyway.)
The problem only occurs when connecting the Sabre directly to the Sure amp (no I/V at all). I know that not having a proper I/V or incorrect loading on the DAC outputs can cause "scratchy" horrible audio, but the buzzing sound is quite loud, and always present with a direct connection.
It worked fine when connecting the Sabre to the Sympatico modules - I know they have a differential input opamp, but both differential and single-ended connection to the Sympatico's also worked fine?
("minus" input on Sympatico's were connected to GND when trying single-ended. ie. Sabre "plus" to Symp "plus" / Sabre GND to Symp GND.)
I would be more than happy to use audio trafo's which would solve the problem, but it would be very expensive to buy 8 or 9 decent quality trafos.
Is this type of problem common when using SMPS / Tripath amps, or does it sound like a general ground-loop / no I/V type issue?
OzOnE.
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Sounds like a ground loop problem/no IV problem (not enough current? Hmm... 4mA in stereo mode aren't small!).
If you were to go for transformers and would need some good cheap ones, go buy EDCOR trafos. They have a new one, supposedly a Lundahl copy. May not be as good as the originals, but they know their job so they won't be bad anyway. You could try a That 1200, they are cheap, and easy to mount on protobard. If they were to provide enough performance, go for it!
Please note though that both trafo and That1200 will heavily limit the specs of the Sabre DAC. Despite that, this DAC has some sonic qualities not found in others, what this is down I don't know and it can shine through limited output circuit quality.
Please also note that no IV and driving directly the amplifier through cables a few meters long may result in strange behavior: you will get some filtering effects (loose mediums, while bass and treble don't move). At least, from what I tested.
If you were to go for transformers and would need some good cheap ones, go buy EDCOR trafos. They have a new one, supposedly a Lundahl copy. May not be as good as the originals, but they know their job so they won't be bad anyway. You could try a That 1200, they are cheap, and easy to mount on protobard. If they were to provide enough performance, go for it!
Please note though that both trafo and That1200 will heavily limit the specs of the Sabre DAC. Despite that, this DAC has some sonic qualities not found in others, what this is down I don't know and it can shine through limited output circuit quality.
Please also note that no IV and driving directly the amplifier through cables a few meters long may result in strange behavior: you will get some filtering effects (loose mediums, while bass and treble don't move). At least, from what I tested.
Hi, Nicolas,
I'll definitely get some THAT 1200 chips. I still have two of the PCB's which you supplied to try them out in 2-channel stereo. I just wish that more of these electronic companies had a lower minimum order amount.
I've just found the cause of the noise problem though. For reasons I still can't explain, all I needed to do was to connect the V- output of the TracoPower 24V PSU to the PE (Power Earth) point... This also connects the PSU's V-output to the amp's chassis earth / mains earth point!
This has cured the major buzzing problem when using a direct connection (single-ended) between the Sabre and amp. The reason I'm so confused is that I tried the exact same thing two days ago with no effect.
I think I also just found the route cause of most of the ground loop noise - the "standby" PCB I'm using was from a Marantz receiver. It's only a simple small trafo for the +5V supply to the CPU, and a relay for switching the mains to the TracoPower PSU / LCDPS...
The problem was, I mounted this board to the back panel of the amp and the screw holes are connected to the GND connection which goes to the CPU / DSP / DAC! The back panel also has the 9-0-9 toroid for the LCDPS bolted to it. The metal back panel was also not making proper contact with the rest of the chassis, so it was almost floating! This explains a lot.
The 9-0-9 toriod is probably inducing a small amount of hum into the back panel too. I need to seriously rethink the layout and ensure all amp panels are properly earthed (I thought I'd already sorted this problem ages ago, but obviously the earthing points aren't good enough).
What I'm getting now with a direct single-ended connection is the usual sort of "crackling" audio effect I would have expected when not using I/V stages. This can be sorted out now, so I'll probably go with standard opamp I/V stages.
Those EDCOR trafos look super cheap, but I can see they've had some very good reviews. I will definitely buy a couple of those in the future. For now though, I'll see what the opamp I/V is like.
Can anyone suggest an opamp I/V stage for the Sabre which has had good results in the past? Please keep in mind that I'm using each DAC channel separately (not quad-stereo), so the output currents will be different.
Thanks everyone for your help, and sorry for being such a pain with the noise issue. I've obviously made a fair few basic mistakes as this is the most complex amp build I've done.
OzOnE. (finally, some success)
Oh, quick question - what's the lowest value resistor which can be safely used on each Sabre output for passive I/V ? I'm assuming that shorting the DAC outputs to ground is a VERY bad idea?
I'll definitely get some THAT 1200 chips. I still have two of the PCB's which you supplied to try them out in 2-channel stereo. I just wish that more of these electronic companies had a lower minimum order amount.
I've just found the cause of the noise problem though. For reasons I still can't explain, all I needed to do was to connect the V- output of the TracoPower 24V PSU to the PE (Power Earth) point... This also connects the PSU's V-output to the amp's chassis earth / mains earth point!
This has cured the major buzzing problem when using a direct connection (single-ended) between the Sabre and amp. The reason I'm so confused is that I tried the exact same thing two days ago with no effect.
I think I also just found the route cause of most of the ground loop noise - the "standby" PCB I'm using was from a Marantz receiver. It's only a simple small trafo for the +5V supply to the CPU, and a relay for switching the mains to the TracoPower PSU / LCDPS...
The problem was, I mounted this board to the back panel of the amp and the screw holes are connected to the GND connection which goes to the CPU / DSP / DAC! The back panel also has the 9-0-9 toroid for the LCDPS bolted to it. The metal back panel was also not making proper contact with the rest of the chassis, so it was almost floating! This explains a lot.
The 9-0-9 toriod is probably inducing a small amount of hum into the back panel too. I need to seriously rethink the layout and ensure all amp panels are properly earthed (I thought I'd already sorted this problem ages ago, but obviously the earthing points aren't good enough).
What I'm getting now with a direct single-ended connection is the usual sort of "crackling" audio effect I would have expected when not using I/V stages. This can be sorted out now, so I'll probably go with standard opamp I/V stages.
Those EDCOR trafos look super cheap, but I can see they've had some very good reviews. I will definitely buy a couple of those in the future. For now though, I'll see what the opamp I/V is like.
Can anyone suggest an opamp I/V stage for the Sabre which has had good results in the past? Please keep in mind that I'm using each DAC channel separately (not quad-stereo), so the output currents will be different.
Thanks everyone for your help, and sorry for being such a pain with the noise issue. I've obviously made a fair few basic mistakes as this is the most complex amp build I've done.
OzOnE. (finally, some success)
Oh, quick question - what's the lowest value resistor which can be safely used on each Sabre output for passive I/V ? I'm assuming that shorting the DAC outputs to ground is a VERY bad idea?
Aha ground current return paths are a big problem to everyone I think...
But yep, in theory, only things tied to a chassis should be the interconnect shields (if any). This is not where I would plug a trafo... I'd probably connect a +5V trafo's "ground" (with no CT) directly to the CT of the dual trafo following...But I may be wrong as well...
For best I/V, the one in the ESS datasheet... To my opinion. I wasn't pleased with the THS4131, though it still measured correct (but not up to the DAC's specs... For that you'll need a single board, and AD797s everywhere... well, you have the Datasheet too I suppose).
Shorting to ground isn't a problem, but what resistor value is another question. You have current (specified in the datasheet), you want a voltage (but which?), you need to find the resistor. Just don't forget the internal resistor in the DAC.
But why do you want to connect one of the dac outputs to the ground? Sound will be greatly degraded! Seperate dacs are used for positive and negative, so the things they have in common (distortion, glitches etc) will be attenuated by the next stage's CMRR. If you want SE output, you will need a bal to se converter circuit, like the That, or an opamp circuit. Or a trafo.
Cheers,
Nicolas
But yep, in theory, only things tied to a chassis should be the interconnect shields (if any). This is not where I would plug a trafo... I'd probably connect a +5V trafo's "ground" (with no CT) directly to the CT of the dual trafo following...But I may be wrong as well...
For best I/V, the one in the ESS datasheet... To my opinion. I wasn't pleased with the THS4131, though it still measured correct (but not up to the DAC's specs... For that you'll need a single board, and AD797s everywhere... well, you have the Datasheet too I suppose).
Shorting to ground isn't a problem, but what resistor value is another question. You have current (specified in the datasheet), you want a voltage (but which?), you need to find the resistor. Just don't forget the internal resistor in the DAC.
But why do you want to connect one of the dac outputs to the ground? Sound will be greatly degraded! Seperate dacs are used for positive and negative, so the things they have in common (distortion, glitches etc) will be attenuated by the next stage's CMRR. If you want SE output, you will need a bal to se converter circuit, like the That, or an opamp circuit. Or a trafo.
Cheers,
Nicolas
I would like to do buffalo24 volume control with a PIC and the code posted by Russ on posts #531 and #534.
I don't have the datasheet for the es9008 and i don't know the meaning of all the parameters so i can't know if the parameter settings on that code are optimal (it was written near two years ago an maybe need some modifications).
I would be grate if someone with more knowledge (and the datasheet) could read that code and see if the parameters are correctly set.
Thanks
Ciao
Andrea
I don't have the datasheet for the es9008 and i don't know the meaning of all the parameters so i can't know if the parameter settings on that code are optimal (it was written near two years ago an maybe need some modifications).
I would be grate if someone with more knowledge (and the datasheet) could read that code and see if the parameters are correctly set.
Thanks
Ciao
Andrea
Hi, Nicolas,
I didn't intend to short any of the DAC outputs to ground as such, but I was just wondering if it would cause damage if I did? Purely because I'm still not sure how to calculate the resistor I would need, and I wondered if a very low value resisotr would cause any damage to the DAC?
I'm assuming there's a big difference between the datasheet linked below and the full NDA one, but the basic datasheet is the only one I have.
So, in the datasheet (below), it says that the full-scale differential output current (per DAC channel?) is 4.224mA (p-p)...
For the simplest passive I/V to the Sure amp, I would only use the positive output of each DAC channel - The Sure amp says to only input a maximum of 2V p-p, so I would use a resistor of around 470 ohms to get just under 2 volts with full-scale DAC output??
ie. (ohm's law) 0.004224 Amps X 470 ohms = 1.98528 Volts?
But, datasheet also says that the DAC current is offset at half the peak range (2.122mA), so I really don't know how to calc this. I don't think the basic datasheet mentions internal resistance?
I don't know what the "virtual ground" refers to, but I'm guessing that the current offset would mean that 0.99264 Volts is produced when the DAC is idle (with a 470 ohm resistor)?
The resulting voltage offset wouldn't be a problem if I used a caps on the Sure amp inputs. I guess that an opamp I/V or trafo would be the only simple way to zero the offset though?
I've probably made all the wrong assumptions here, but how to calc?
All I can say about the AD797's is.. DAMN, those things are expensive! Not too bad for stereo, but I'm going to need at least 8 of them (for voltage out mode). This would probably cost more in total than the rest of the amp.
I'm not overly fussy about absolute quality at this stage because I'm certain that my amp will sound way better than anything else I've owned in the past (even when using cheaper opamps on the Sabre outputs).
I could put together a quick opamp board pretty easily if it would sound any good at all with cheaper opamps like OPA2134's? (Basically, I'm just itching to hear it in multichannel surround, so I'd rather get it running for now then upgrade it later on.)
@anbello, below is the datasheet that I have. This one was disclosed publicly many months ago (as Russ once said). It might not be the "full" datasheet, but it shows most of the common internal registers etc...
ES9008_DataSheet.pdf
OzOnE.
I didn't intend to short any of the DAC outputs to ground as such, but I was just wondering if it would cause damage if I did? Purely because I'm still not sure how to calculate the resistor I would need, and I wondered if a very low value resisotr would cause any damage to the DAC?
I'm assuming there's a big difference between the datasheet linked below and the full NDA one, but the basic datasheet is the only one I have.
So, in the datasheet (below), it says that the full-scale differential output current (per DAC channel?) is 4.224mA (p-p)...
For the simplest passive I/V to the Sure amp, I would only use the positive output of each DAC channel - The Sure amp says to only input a maximum of 2V p-p, so I would use a resistor of around 470 ohms to get just under 2 volts with full-scale DAC output??
ie. (ohm's law) 0.004224 Amps X 470 ohms = 1.98528 Volts?
But, datasheet also says that the DAC current is offset at half the peak range (2.122mA), so I really don't know how to calc this. I don't think the basic datasheet mentions internal resistance?
I don't know what the "virtual ground" refers to, but I'm guessing that the current offset would mean that 0.99264 Volts is produced when the DAC is idle (with a 470 ohm resistor)?
The resulting voltage offset wouldn't be a problem if I used a caps on the Sure amp inputs. I guess that an opamp I/V or trafo would be the only simple way to zero the offset though?
I've probably made all the wrong assumptions here, but how to calc?
All I can say about the AD797's is.. DAMN, those things are expensive!
Not too bad for stereo, but I'm going to need at least 8 of them (for voltage out mode). This would probably cost more in total than the rest of the amp.I'm not overly fussy about absolute quality at this stage because I'm certain that my amp will sound way better than anything else I've owned in the past (even when using cheaper opamps on the Sabre outputs).
I could put together a quick opamp board pretty easily if it would sound any good at all with cheaper opamps like OPA2134's? (Basically, I'm just itching to hear it in multichannel surround, so I'd rather get it running for now then upgrade it later on.)
@anbello, below is the datasheet that I have. This one was disclosed publicly many months ago (as Russ once said). It might not be the "full" datasheet, but it shows most of the common internal registers etc...
ES9008_DataSheet.pdf
OzOnE.