Elberoth, have you added the BNC and did you hear any appreciable difference?
Metrum Octave Mod and cable suggestion
Further down the Head Case Forum was this little ditty.
Craig Sawyers
High Roller
High Rollers
1,072 posts
Posted 04 February 2012 - 11:49 AM
I bought one of these around 10 days ago, based on Martin Colloms' recommendation in HiFi Critic, in which he billed it as a real giant-killer. Initial thoughts were exceptionally good, and as it warmed up progressively better. But I can't resist getting things right that are wrong. The first problem is common to most DAC's and CD transports - RCA connectors. I did a whole host of measurements using Time Domain Reflectometry, and basically putting a fast pulse into a 75 ohm coax terminated with an RCA, into an RCA socket, with a surface mount 75 ohm resistor tacked onto it - and it is a disaster. Massive reflections - and reflections add jitter.
The only way to do things *properly* is to maintain a clinical 75 ohm environment for the whole digital signal chain, and that means 75 ohm BNC connectors throughout. And most digital cables, if not terminated in RCA's are terminated in 50-ohm BNC's! In fact the only audio high-end 75 ohm BNC's are Oyaid. I just use regular clamp-on greenpar and RG302 teflon cored coax.
After doing that (and measuring the TDR response into the Octave) the DAC really started to sing.
Then I spotted the hokey little pulse transformer (visible in the picture above). This is a $2 part, a standard Murata ferrite cored pulse transformer. I replaced it with a far better (electrically) Lundahl LL1572, which uses an amorphous ribbon core. In the UK this is £35 - so not cheap.
After swapping transformers (invalidating the warranty of course) I can honestly say I have never heard a DAC sound that good regardless of cost. I've just ordered an Audio Note toroidal pulse transformer wound on a mumetal ribbon core, so it will be interesting if that improves it further, or otherwise.
I can't stop listening to it!
Craig
PS The DAC's are intersting. They are 16-pin devices (with the type number taken off, of course), so they are definitely not Burr Brown or any of the other audio DAC's, which have far more pins. So I think they must be DAC's intended for instrumentation or data acqisition applications. And they are supposedly R2R ladder DAC's too. I've done an initial trawl of manufacturer's data, but have not been able to find anything that looks like those.
When all is said and done, lots more gets said than done.
If a job is not worth doing, it is not worth doing well.
It's a Norwegian Blue.
Craig Sawyers
High Roller
High Rollers
1,072 posts
Posted 04 February 2012 - 11:49 AM
I bought one of these around 10 days ago, based on Martin Colloms' recommendation in HiFi Critic, in which he billed it as a real giant-killer. Initial thoughts were exceptionally good, and as it warmed up progressively better. But I can't resist getting things right that are wrong. The first problem is common to most DAC's and CD transports - RCA connectors. I did a whole host of measurements using Time Domain Reflectometry, and basically putting a fast pulse into a 75 ohm coax terminated with an RCA, into an RCA socket, with a surface mount 75 ohm resistor tacked onto it - and it is a disaster. Massive reflections - and reflections add jitter.
The only way to do things *properly* is to maintain a clinical 75 ohm environment for the whole digital signal chain, and that means 75 ohm BNC connectors throughout. And most digital cables, if not terminated in RCA's are terminated in 50-ohm BNC's! In fact the only audio high-end 75 ohm BNC's are Oyaid. I just use regular clamp-on greenpar and RG302 teflon cored coax.
After doing that (and measuring the TDR response into the Octave) the DAC really started to sing.
Then I spotted the hokey little pulse transformer (visible in the picture above). This is a $2 part, a standard Murata ferrite cored pulse transformer. I replaced it with a far better (electrically) Lundahl LL1572, which uses an amorphous ribbon core. In the UK this is £35 - so not cheap.
After swapping transformers (invalidating the warranty of course) I can honestly say I have never heard a DAC sound that good regardless of cost. I've just ordered an Audio Note toroidal pulse transformer wound on a mumetal ribbon core, so it will be interesting if that improves it further, or otherwise.
I can't stop listening to it!
Craig
PS The DAC's are intersting. They are 16-pin devices (with the type number taken off, of course), so they are definitely not Burr Brown or any of the other audio DAC's, which have far more pins. So I think they must be DAC's intended for instrumentation or data acqisition applications. And they are supposedly R2R ladder DAC's too. I've done an initial trawl of manufacturer's data, but have not been able to find anything that looks like those.
When all is said and done, lots more gets said than done.
If a job is not worth doing, it is not worth doing well.
It's a Norwegian Blue.
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- 30 posts total
PS The DAC's are intersting. They are 16-pin devices (with the type number taken off, of course), so they are definitely not Burr Brown or any of the other audio DAC's, which have far more pins. So I think they must be DAC's intended for instrumentation or data acqisition applications. And they are supposedly R2R ladder DAC's too. I've done an initial trawl of manufacturer's data, but have not been able to find anything that looks like those. Burr Brown DAC8580. Datasheet here. Best wishes, Alex Peychev |
I have had my Metrum Octave for some weeks now and am truly shocked how good it is! I have compared it to a number of much more expensive upsampling DAC's costing 3 to 4 times the price and also an Audio Note NOS costing 3.5 times as much. The Octave was faster, much more saturated and preferred due to its excellent balance of detail and timber of the instruments. Equally at home with Biffy Clyro or Bruckner. I have found though its is very sensitive to the SPDIF cable used which needs to be as near to true 75 ohms as possible. I have tried VDH First Ultimate, Black Cat Veloce and Mark Levinson Fat Boy, all of which sound slightly different. |
- 30 posts total