New/upgraded TC-7520 power supply?

[Dougr33]

Stan, aren't you basically saying (said I think) that there's little or no audible gain to be had with a different power supply on the 7520 due to your current design?

[StanleyB]

You got it.

[Spod]

Just goes to show, everyone hears differently.
Hate being contradictory, but I definitely hear an improvement using the 7250+4032 when powering it with the Maplin (at 12v) over the supplied 2nd-gen PSU (music seems to have more solidity to it). But I'm quite willing to believe I just hear "a difference" and on my system I just happen to prefer it with that difference.

[Dougr33]

Well, my statement he agreed to was "little or no" audible gain... People pay $$$ for that last little bit!! So if you can hear it, it's a good thing!

[Covenant]

I think its a good thing to put the improvement in context though. Paying a lot for an upmarket supply doesnt make sense if you can get better performance through changing an op-amp for a tenner (or the other improvements that Stan has yet to tell us about )

[lovejoy]

I'm afraid I have to be contradictory here too. I guess it's all completely system dependent and a sprinkle of voodoo going on, but I found my discrete power supply over the standard wall wart to be as big an improvement as replacing the op-amps. I'm extending an open invitation to anyone passing through Swindon to drop in and hear it (although avoid Swindon this weekend as it's Radio 1's big weekend).

I did purchase a battery on my way home from work last night. The jury is currently out. I'd concur with things sounding softer. At the moment I think I will probably go back to my discreet supply, but I'll give it a week and see how it goes.

[Covenant]

If Swindon was a bit nearer Ormskirk I would take up that kind invite Lovejoy.
As you said yourself though, you already had most of the parts for your PSU so it cost you very little. I am all for getting the best from my Standac but realise that costs in the region of £150 do not make sense (to me). YMMV.
Stans battery comments were interesting-if I read it right you may get an improvement at first which rapidly tails off.

[lovejoy]

Yes, depends how big your battery is and how long your average listening session is. I bought a 2.2Ah battery from Maplin and as the DAC apparently will only draw in the region of 100mA, that's plenty for a good day of music without allowing the charge in the battery to get too low. Then once I've finished listening, I switch the battery over to a trickle charger which keeps it topped up while not in use.

The trick with batteries is not to get into the habit of allowing it to fully discharge and then completely recharge it. They don't like it very much. When I had my DDDAC, this happened a couple of times as the thing was drawing so much current and I noticed that after a couple of full charges the sound quality was noticeably worse, even when the battery was fully charged so it had to be replaced. As Stan's DAC only draws a small amount of current, I thought it was worth a try as I can have an evening of entertainment and then trickle charge during the day, comfortably replacing the energy I've used.

[lovejoy]

Well, I've had a good weekend of experimentation with various power sources and I seem to have settled on a setup I'm very happy with now.

The battery approach isn't the best. Too soft, dynamics get squashed, there's just no excitement and it doesn't take long to get bored.

I took the battery out and put Stan's new supply back in and it was immediately much better. The dynamics are back, focus is much better and everything gets cleaned up.

I've come to the conclusion that the law of diminishing returns kicks in with anything above Stan's new power supply and I think the difference between the original wall wart and the new one is bigger than that between the new supply and my own discreet supply.

One thing I did pick up on this weekend is how much I prefer the sound of a USB connection from my PC to using either optical or coax. Strangely, I can tell no difference whatsoever if I'm using a Mac between optical and USB but on the PC, USB brings more realism to instruments like piano and guitar. It's one of the only digital setups I've ever heard where you can actually feel the amount of weight going into a played piano note. There's much more of a sense of being able to look into a recording too. It's thoroughly engaging.

So to sum up my findings so far (of course I'm not going to stop playing), first and foremost, digital source is paramount and for me it's got to be a PC running Foobar through ASIO with a USB connection. I'd love to use a Mac as the interface and music management is so much better, not to mention quieter and faster to load, but (and I know people will argue that iTunes gives bit perfect output - but there's so much more to it than that) I find the sound from a Mac flat, lifeless and lacking in any ability to stir the emotions. So I'll stick with the PC until I find something that is as good if not better in a smaller box - maybe something along the lines of an SB3 possibly.

Then Stan's new supply is a no brainer if you haven't already got one. For the outlay, it's a big improvement. Yes, you can get better, but unless you've got lots of bits lying around that you can construct your own supply with, it's going to cost a fair bit for a modest improvement.

A nice new op-amp or two in the output stage is also a no brainer. I can't think of anything else you can spend a tenner on and get such a huge improvement, except for maybe a nice bottle of wine, but the op-amps are a more permanent upgrade.

Then, if you're on a PC, have a play with a USB connection and if you're using Foobar use the Kernal Streaming plugin. I guarantee you'll be listening for hours.

This poses a question.. I see that the USB input has a crystal for clocking the data coming in. Would there be anything to be gained by swapping this standard crystal out for a low jitter alternative like a Tent Labs clock?

[StanleyB]

The battery approach isn't the best. Too soft, dynamics get squashed, there's just no excitement and it doesn't take long to get bored.

I seem to recall pointing that out as well. I even abandoned my own battery psu design when I noticed that problem.

I took the battery out and put Stan's new supply back in and it was immediately much better. The dynamics are back, focus is much better and everything gets cleaned up.

The TC-7520 psu was designed for me by someone who makes a living out of designing these things.

One thing I did pick up on this weekend is how much I prefer the sound of a USB connection from my PC to using either optical or coax. Strangely, I can tell no difference whatsoever if I'm using a Mac between optical and USB but on the PC, USB brings more realism to instruments like piano and guitar. It's one of the only digital setups I've ever heard where you can actually feel the amount of weight going into a played piano note. There's much more of a sense of being able to look into a recording too. It's thoroughly engaging.

Many have tried and failed in their attempt to design a DAC with a USB input that could give SPDIF and optical a stiff challenge. I myself consider the DAC1 from Benchmark to be the only serious competitor with a USB input that can rival the TC-7520. Everyone else is way behind us on USB performance. My feeling is that maybe other designers see USB input on a DAC as a gimmick that does not require professional design commitments, or they haven't got a clue how to design a professional USB circuit.

This poses a question.. I see that the USB input has a crystal for clocking the data coming in. Would there be anything to be gained by swapping this standard crystal out for a low jitter alternative like a Tent Labs clock?

The crystal I use is good enough for the purpose. I tried more expensive ones, but the jitter in PPM is even lower than the jitter from the receiver IC I use. So I couldn't get an improvement.

Stan