DAC-Burr Brown PCM1792

Early B.

I'll have to forget about the Burson stuff. In addition to the LM4562, I'll look for other potential replacements for the 2134.

Ben -- we'll have to wait until you heal up before you grab your soldering iron again.

ben62670

Early B. wrote: »

Ben -- we'll have to wait until you heal up before you grab your soldering iron again.

I was soldering last night;) The heat from that was a little uncomfortable, but the kids have to eat, and I have to make good of some stuff I said I would get done prior to the gas thingy. I have a pistol grip Soldering iron so the heat isn't as bad as with a regular iron. A visit from a top notch Polkie is always a blessing.
Ben

Edit:
Some people can't put down the crack pipe. Others can't put down the booze. I can't put down the gun. A couple weeks ago I was thinking of changing my screen name to burnt fingers. Someone has it on another forum, and I thought it was great. Oh the Irony.

Systems

The finished product.

ben62670

Sweet. Did the blue toroid come with it? Also you are only using Coax? The 9-0-9 is for the digital?

Early B.

OK, but will the finished product dethrone your existing DAC?

ben62670

Early B. wrote: »

OK, but will the finished product dethrone your existing DAC?

If this is directed at me I think it will beat my GDA-700 unmodified, and most likely modded. Also when I get a little time I will incorporate my Pre(passive/active/tube), active XO, DAC, and SACD all into one chassis with the Power supplies mounted separately. Hopefully I will get a chance soon to figure out a way to pull the DSD from a cheap transport. If it is too much I may just mod a cheap SACD players analog section.
Ben

Systems

ben62670 wrote: »

. Did the blue toroid come with it?

No but it can be sourced from digi key.(minus the PC board).

Also you are only using Coax?

Yes,it has a Toslink input but IMO coax is the way to go.As well I used a 75ohm BNC chassis connector and 75 ohm coax from the BNC directly to the board.I may add another BNC input later if need arises.

The 9-0-9 is for the digital?

Yes its for the digital section.It feeds two 5 volt regulators on the yellow-ish PC board.The round toroid is for the analog section it has two 18 volt secondaries and was sourced from Digi Key.It is overrated in that it can source many times the current the op amps will need.

ben62670

The 5vdc is just +5vdc I thought?

Systems

Early B. wrote: »

OK, but will the finished product dethrone your existing DAC?

I have yet to do a level matched comparisons but Im thinking my existing DAC has the edge .It does however have 2 distinct advantages.First it has a sample rate convert which gives it very low jitter and it upsamples to 96k.More importantly it uses a discrete BJT class A op amp for the analog section.IMO its the analog section and the power supply that feeds it that makes the biggest difference is SQ between otherwise good DAC's.

Systems

ben62670 wrote: »

The 5vdc is just +5vdc I thought?

Ok I should clarify.One of the regulators feeds 5 vdc to the analog section of the 1792 DAC chip and the other feeds all the digital chips.It is recommended that separate reg's be used.

ben62670

GV#27 wrote: »

Ok I should clarify.One of the regulators feeds 5 vdc to the DAC chip and the other feeds all the digital chips.It is recommended that separate reg's be used.

Now I gotcha;)

Systems

Early B. wrote: »

OK, but will the finished product dethrone your existing DAC?

No not quite.

However IMO it does sound very good with a very smooth analog kinda sound.In direct comparison to my existing unit (dac1)the soundstage is smaller with less apparent depth.Aswell the dac1 beat the BB1792 in the areas of detail retrieval and hi frequecy extension.
When listening to good but simple recordings like the Neck and Neck CD by Chet Atkins and Mark Knopfler, the dac1 made the performers sound more palpable and real.

The dac 1(see pic) is a mostly Diy unit I built about 4 years ago and it has a similar power supply and regulator scheme as the 1792,the DAC chip is also similarly spec'd but made by Crystal ( CS43122).The biggest differences between the two units is that the dac1 upsamples everything to 96k and it has a discrete op amp for the analog stage.I believe the superior SQ is the result of this hi current class A analog stage.

I will continue to experiment with the analog section of the BB1792 by replacing the stock NE 5534's op amp's with OPA627's and I plan to duplicate the discrete op amp used in the dac1.It will be interesting to see if these changes can bring it up to the level of the dac1.

Then when I'm done tweaking I may just Karma the thing.:)

ben62670

In please:D

Systems

ben62670 wrote: »

In please:D

OK you win,since you are the only one to show interest I'll send you this one.;):D

ben62670

GV#27 wrote: »

OK you win,since you are the only one to show interest I'll send you this one.;):D

I feel giddy like a school girl. I got some stuff in today to finish what I am sending you. Friday is tight, but Saturday should be good. So I am looking at Monday to ship:)

Systems

ben62670 wrote: »

I feel giddy like a school girl.

Before I ship it to you Im going to let my 8yr old daughter use it for solder practice.She really needs to brush up on soldering and de soldering the surface mount stuff.:D

SteveSun

Hi GV#27: PCM-1792 is probably the best DAC that BB makes. For your information, the new Sony SCD-XA5400ES SACD/CD player uses the following for D/A converting:

1. DAC Chip: PCM-1796 (which is pin-to-pin and function compatible with 1792)
2. I/V OP amps: BB OPA-2132UA (NOT 2134, 2132 sounds much better)
3. Low pass filter/output buffer: BB OPA-2132UA for RCA outputs, and JRC-2114 for XLR outputss

I will change the I/V OP and DAC in XA-5400ES to THS-4032 and PCM-1792A after burning-in this baby...

Systems

Hi Steve, the 1792 is likely the most widely used DAC these days.Good luck on modding the Sony,I'd be interested in hearing your impressions of the THS4032 as I/V converters.

Systems

SteveSun wrote: »

I will change the I/V OP and DAC in XA-5400ES to THS-4032 ...

According to the data sheet the THS4032 is a screamer with a 100volts per ms.The high slew rate makes it very suitable for I/V conversion but I would worry about its potential instability or tendancy toward oscillation.Proper bypassing of the supply rails will be very important with this fast chip.

ben62670

Well I checked my stock and I have exactly 6 2134's:) I am going the 2v output instead of the 4.5. I have been studying the light-speed (LED photocell(google it;))) attenuator I may need to change the output R's to 25-50r instead of 100r;)
The first string of 4 OpAmps are for filtering of the digital noise, summing of the DAC's differential output, gain, and stability? The second set appears to be a straight up gain stage. I may change out the signal path resistors to Vishey's just because they sound so sweet compared to generic metal films(thanks for the recommendation:)). Also I have been dabbling with the idea of jumping into the analog section (second stage)where the jumpers are JP2, and 4. Leave 1 and 3 open. then toss the gain stage in my Pre.

Systems

ben62670 wrote: »

Well I checked my stock and I have exactly 6 2134's:)

The board only accepts single op amps so your 2134's are not compatable.

I am going the 2v output instead of the 4.5.
The first string of 4 OpAmps are for filtering of the digital noise, summing of the DAC's differential output, gain, and stability?

No, the first row of 4 (U1-U4)following the DAC convert the current output of the DAC to voltage.(I/V converter)

The second set appears to be a straight up gain stage.

U5-U8 are the low pass filter/output buffers and sums the differential sigs.The low pass filter around U5 and U8 are optimized for redbook CD and with the standard 2 volt output. U6 and U7 are for the 200khz low pass filter optimized for SACD with 4.5 volts.

ben62670

Damn. I forgot about those being singles. I ran into another problem today that has me a little frazzled.

Systems

ben62670 wrote: »

Also I have been dabbling with the idea of jumping into the analog section (second stage)where the jumpers are JP2, and 4. Leave 1 and 3 open. then toss the gain stage in my Pre.

You'll want add any gain after the filter/output buffer.You don't want to amplify all that nasty high freqency noise.

ben62670

I won't have time to mess with it for a little while. I just want to get it going as is so I can sell my DAC to pay some bills, food, gas... I am glad I have all the power stuff here, and seeing my tube pre is back burner again I have a 6-0-6 troid to power the DAC.

ben62670

HeHe HeHeHe:)

ben62670

Well I have been having fun with it. The sound stage, dynamics, and details are awesome, but the sound is a little thinner than I like. I have tried both the 2v, and 4.5v outs, and the 4.5 definitely beats the 2 in sound stage and SQ. This is at the same volume level??? The sound is kinda harsh. I am not sure if it is the stock Ops, or the fact I am using only a single 5v for digital and analog. I think I am going to go with the OPA134's for now. There aren't as many choices in single channel chips as in dual:(

ben62670

Well I have been having fun with it. The sound stage, dynamics, and details are awesome, but the sound is a little thinner than I like. I have tried both the 2v, and 4.5v outs, and the 4.5 definitely beats the 2 in sound stage and SQ. This is at the same volume level??? The sound is kinda harsh. I am not sure if it is the stock Ops, or the fact I am using only a single 5v for digital and analog. I think I am going to go with the OPA134's for now. There aren't as many choices in single channel chips as in dual:(

Systems

ben62670 wrote: »

There aren't as many choices in single channel chips as in dual:(

Unless you want to use adaptors,there are many excellent singles that are only available in surface mount packages.:(

ben62670

I have seen that, but I am shy about surface mount. Time for me to design some custom boards? Then we would only need 4 chips instead of 8? I know that we really only need 6, but I would like to have the option of dual outputs still, or maybe another gain stage for other inputs? You help withe the design, and I ship you a board?

Systems

ben62670 wrote: »

You help withe the design, and I ship you a board?

I'm game.:)