[davidflas]

^^ hooray, Mike Moffat !

I'd like to put in another vote for Mike's work. I got my first DAC in 1990, it was a Theta DSPre Basic, sounded great!

 

[rollinbr]

If I remember correctly, the DAC in the Denon were PCM61 or PCM63, it doesn't get much better than that.

I'm too young to know if you are being sarcastic or not. Do some good, old dacs exist?

Finished both channels of my PCM63 DAC and the digital front end power supply board.



The PCM63 is the Holy Grail of vintage Burr-Brown R2R chips. Each board uses two of them in parallel, the two boards will stack on top of each other, similar to my PCM56 DAC. The output of each board are the current output pins of the parallel chips. I will again be using a Sowter step up transformer for the I/V stage.

I am again planning a tube output stage, but a different flavor this time around. I have a healthy stock of NOS E182CC tubes, a very good sounding audio dual triode. Each section has a relatively high gm of 15mA/V. I'd like to use a pair of E182CC on the output with the sections wired in parallel in a transformer coupled cathode follower output buffer with a 1:1 output transformer, something like this.



Being completely transformer coupled and with a triode well suited for buffer service, I am expecting very good results with this setup. However, since a cathode follower has no voltage gain, the Sowter step up transformers will be responsible for converting the current output of the DAC to a line level output voltage.

Without getting too heavy into the technical details, these current output DACs perform best if presented with a low impedance load. Generally, less than 100ohms is best for PCM63, otherwise it will start generating audible harmonic distortion. To reach 2Vrms output with a 1:10 step up and parallel PCM63, roughly an 8.2K resistor will be needed on the secondary of the step up transformer, presenting the DAC chips with an ~82ohm primary impedance.

This should work well in theory, but I plan to measure the distortion on the secondary of the step up transformers with a dummy load before committing to this I/V stage. If the measurements look good, then I'll order parts for the output buffer and design the chassis. This time around, I plan to include some tube aesthetics with the E182CC buffer tubes sticking partway out of the top plate, should look pretty cool.

I have next week off before starting my new job, going to test this and also devote some time to the Aegis project.

PCM63 DAC is done, still have some tinkering to do but it is up and running! Whatcha think?







It's a little tricky with the transformers mounted on top, have to keep the leads pretty long to be able to remove the top plate.







It can use 5687, EC182CC, and 7044 tubes.



Front LED is amber.



Next thing to do is experiment with secondary loading of the output transformers, but first some lunch and a break.

I made my final edits. I ended up loading the output transformer secondary with a 510K resistor, making it effectively an open secondary. That increased the gain of the output stage and allowed me to reduce my I/V transformer secondary resistor to 1.5K, both improved the sound further.

So it is now done done, I closed up it up for good. Last pic, here with the RCA 7044 which sound really, really good.



I know I've said it before, but here is everything that went into this DAC. I bought the chips March of last year, it has been a lot of work to get this thing done over the past year.

- 1:1 isolation transformer with the secondary wired for balanced AC, as such the DAC circuit is running off balanced mains
- Dual mono boards, one DAC PCB per channel with two PCM63 run in parallel
- Separate cascaded series regulated power supplies for all four DAC power supplies (+analog, -analog, +digital, -digital)
- JLSounds I2SoverUSB digital front end, also powered by cascaded series regulated power supply
- Sowter 1465 I/V step up transformers for converting the current output of the parallel PCM63 into small signal voltage
- HEXFRED solid state rectified B+ supply with transformer snubbing circuit and current-limiting resistance
- Maida style regulated B+ supply with separate regulators for left and right channels
- E182CC / 7044 / 5687 output stage, battery biased and loaded with Sowter 9705 line output transformers
- Ultra low noise regulated DC heater supply for the E182CC / 7044 / 5687 output tubes

Here is a build @L0rdGwyn did recently using 4 PCM63-K DAC chips.

Those chips were used in Mike Moffat's Theta Digital company/business in the Theta Gen V DAC back in the 90's.

So as @sam6550a stated, "If I remember correctly, the DAC in the Denon were PCM61 or PCM63, it doesn't get much better than that."

 

[Chicagorob]

I need to put together a work system for my wife as well, except she cant wear HPs. I need to put together a good sub 500 near field system.

Thinking Modi 3+ for the dac, but I don't know what to do about speakers and amp, or if I should do a sys and some active monitors.

Any suggestions would be appreciated.

The following for near-field or mid-field:

Kali Audio LP-6 V2(ridiculous performance for the price)
Kali Audio IN-5(step-up-your-game truth tellers)

Throw in a nice Schiit pre with the Modi 3+ and you’re done.

 

[LobalWarming]

I have no idea what that means, but I'm pretty sure I like the last word.

Me too. That's why I used the Tardis to insert that made-up Latin word into the Roman vocab. Tubeous the Mighty, they called him.

 

[NigelJ]

I'll have to try to find some old ad copy. The marketing department made it out to be the second coming of all things digital. In a nutshell, the digital section was optically coupled to the analog section, and this optical coupling eliminated all interference, noise, etc that occurred with typical electrical connections. Sounded logical to me, so I bought one....and then returned it because it sounded so bad I thought it was defective. To be fair, this was in the very early days of perfect sound forever when most all digital was a putrid pile of festering monkey puss. I didn't dip my toes back in that water for several more years until I purchased a Theta DS Pro which made digital not only listenable, but actually enjoyable (with a decent recording).

Initially sounds logical to me, and I might also have fallen for it, especially as I am a mechanical engineer . However, it ignores a number of potential issues including:

• electromagnetic coupling between the digital and analogue circuits within the same box (assuming that neither were in separate enclosures able to provide reliable screening);
• coupling of noise via the power supply or supplies;
• coupling of noise via the circuits grounds;
• noise already in the signal being passed to the optocoupler will not be removed (unless attenuated by the optocoupler‘s frequency response);
• degradation of the signal through the optocoupler due to nonlinearities and frequency response.

Obviously, all except the last are also issues with direct electrical connection. Consequently, while an optocoupler might be able to reduce interference and noise it cannot eliminate interference and can add its own degradations to the signal.

 

[OldRoadToad]

I need to put together a work system for my wife as well, except she cant wear HPs. I need to put together a good sub 500 near field system.

Thinking Modi 3+ for the dac, but I don't know what to do about speakers and amp, or if I should do a sys and some active monitors.

Any suggestions would be appreciated.

The Bose Soundwear Companion is no longer available but the Monster Boomerang is and works just fine. I personally own two of the Bose and one of the Monster and have given several of the former as presents. I recently gave two of the Boomerang models to relatives and they like them very much for listening to music and talking on the phone.

No, they are not suitable for "critical" listening but then most of us are not "critics", LOL! Just prior to his retirement Tyll Hertsens did a review on the Bose and declared it to be more than good enough and so I bought seven of them for my self and family members! The near field set up you speak of sounds great and she will doubtless enjoy it!

For walking around whilst connected to my home stuff I use a BlooToof extender for the Soundwear or Boomerang and this allows me to be up to approximately 100+ feet from the source when it is not my Cell phone, LOL! The Boomerang is approximately $80 and some times goes on "sale" for about $50 and as I said, it is just fine.

All the best!

ORT

 

[corndog71]

My girlfriend works from home and while she was using my 18 year old old Cambridge Soundworks 2.1 PC speakers, she had to move them off of her crowded desk. So I hung the satellites on the wall and added a Schiit Fulla4 to a WiiM streamer so she could play wirelessly from her phone. She loves it! It’s not the prettiest arrangement but it’s fine for now.

 

[Roy G. Biv]

The Bose Soundwear Companion is no longer available but the Monster Boomerang is and works just fine. I personally own two of the Bose and one of the Monster and have given several of the former as presents. I recently gave two of the Boomerang models to relatives and they like them very much for listening to music and talking on the phone.

No, they are not suitable for "critical" listening but then most of us are not "critics", LOL! Just prior to his retirement Tyll Hertsens did a review on the Bose and declared it to be more than good enough and so I bought seven of them for my self and family members! The near field set up you speak of sounds great and she will doubtless enjoy it!

For walking around whilst connected to my home stuff I use a BlooToof extender for the Soundwear or Boomerang and this allows me to be up to approximately 100+ feet from the source when it is not my Cell phone, LOL! The Boomerang is approximately $80 and some times goes on "sale" for about $50 and as I said, it is just fine.

All the best!

ORT

I also have a Bose Soundwear and find it to be fine for casual listening. I like that I can hear my music but still be able to hear what's going on around me. IIRC Tyll Hertsens gave them a positive review on InnerFidelity.com.

 

[Luckyleo]

I also have a Bose Soundwear and find it to be fine for casual listening. I like that I can hear my music but still be able to hear what's going on around me. IIRC Tyll Hertsens gave them a positive review on InnerFidelity.com.

I have them as well, and they are great for certain use cases. I also purchased because of Tyll's review. Happy I did!

Leo

 

[Paladin79]

TIDY! - back home after a few days dealing with some family issues (no big deal). Minimus 7's arrived and are now gracing workspace.....

We use the same soldering iron, I have at least three of them in my shop and a couple unopened. I ran my own business so I have multiples of many such things. I would love to see a view of the amp from directly above it.

I need to upgrade speakers in my shop but I need to do justice to a Carver amp and preamp so I am searching for the perfect pair of bookshelf speakers. I am looking at Elac, Warfdale, Klipsch, Definitive Technology, and Kef. I do not mind them being used and I hope to keep the price around $350 or less. Any suggestions are appreciated. I will be trading gear in and out as I do some testing and repair so I do not want expensive speakers in that situation yet I do not like weak links in an audio chain.

 

[sam6550a]

And the diff between that and adding $$$ in Mundorf, Slegehammer, Clarity Caps and other parts is…. ???

So is a mod an upgrade, whilst an uprade isn’t a mod, or arsy versy? Meh… As I open a bottle of Uncle Nearest, best bourbon I’ve had in a goodly while.

The difference is that you do zero work. Someone else takes care of the parts search, procurement, parts removal, parts install and magic smoke avoidance.

 

[golfbravobravo]

More info: migraines started in my late teens. Mine could last hours. Eventually I found strong coffee and aspirin, or Advil when it OTC (over the counter; non-prescription in the USA). Then avoiding food triggers, chocolate, strong red wines, hard cheeses. You know, the stuff you want to eat! By my mid 30's they faded to very infrequent. Then in the mid-90s' I entered a time/sharing space business agreement with a college. After we got going I tried to renegotiate so I could have some more time. He quipped, "Steve. The whole point of us doing this is to have very overhead and enjoy a Bohemian lifestyle."
That was the message migraines were trying to tell me. I mostly pay attention...

I reassure my son that as he gets to 50 the headaches will improve. Though he has the combo of both my and his mother's migraines. So, maybe later for him......

 

[45longcolt]

Found this elsewhere (not my cat,) but couldn't resist sharing.

 

[golfbravobravo]

My speakers are 97dB, an easy 8 ohm load, and Tyr makes them sing. Power isn’t just about volume. It’s also about control. Tyr brings out the best of the speakers I’ve tried them on. (Granted, I’ve only tried 2)
Best amps I’ve ever owned.

I'll echo that the Tyrs drive sensitive Double Impacts very well!

 

[cricket]

We use the same soldering iron, I have at least three of them in my shop and a couple unopened. I ran my own business so I have multiples of many such things. I would love to see a view of the amp from directly above it.

I need to upgrade speakers in my shop but I need to do justice to a Carver amp and preamp so I am searching for the perfect pair of bookshelf speakers. I am looking at Elac, Warfdale, Klipsch, Definitive Technology, and Kef. I do not mind them being used and I hope to keep the price around $350 or less. Any suggestions are appreciated. I will be trading gear in and out as I do some testing and repair so I do not want expensive speakers in that situation yet I do not like weak links in an audio chain.

Consider Paradigm speakers, too. I moved a pair of Monitor SE Atoms from my main system to the basement shop a few years ago. They've seen more use in the past two weeks than since the "banishment". An Onkyo A25 integrated amp from the early 80's drives them. I'll only replace it if Schiit releases a desktop speaker amp. In the meantime, it needs a serious Deoxit treatment.