[edevinney]

The power supply was a rabbit hole in a rabbit hole... long story short is that it's all switch-mode.

There are actually 4 switch-mode devices in that chassis. The big one on the bottom is a Meanwell switch-mode 24 volt/300 watt PS, and the chip amp (itself a switching device) doesn't care. The DAC chip needs two different feeds: +/- 5V for the digital part and +/- 12V for the analog, then the op-amps need at least +/- 12V as well. So top right is a little board I wired up with two DC-DC converters to make +/- 5V and 12V out of the single 24V supply.

The boffins at diyaudio are pretty clear that the DAC chip itself doesn't really benefit from linear power, but the op-amps might, so the board is designed with some jumpers to allow separate supplies for the two feeds to the DAC and a unique feed for the op-amps. So you can pretty easily feed them from a linear PS, but I didn't. Maybe later if I run out of other projects...

[Dr K]

Ed,
I might be interested in a board and AD1862. How much $$ do you have in this in parts (approx)? I only did 1 semester of EE and that was in 1973, so wiring up a little board with two DC-DC converts might also require a little direction...

Peter

[Dr K]

Kind of off for this thread, but we're going to be redoing the system in our Den soon, and the current system (old but high quality for what it is - Pioneer Elite but NO HDMI) won't do for a new TV. The Pioneer is 17" deep and with all the wires out the back, more like 19. Does anybody know of a relatively high-quality AV Receiver that is COMPACT? It would seem like quality Class 4 amps could be considerably smaller than the older equipment and still quality sound.

[edevinney]

To the DAC question, you don't have to use my weirdo solution for power since you probably aren't trying to stuff everything in one box that already has a 24VDC power supply. The DAC doesn't take a lot of power, a wall wart for +/- 5 and one for +/- 12 should be good.

The board alone was $15 from the US supplier but can be as low as $5 from a Chinese supplier. Miscellaneous electronics parts $40-50, DAC chips (one for each channel) 2 @ $15ea from China or $28ea NOS US, and output op-amps can be anything from 2 5534 @ $1ea to 2 627 @ $28ea.

So a top of the line board runs about $185 in parts. Add $15 or so for a board to convert from optical/coax or USB, $50 for power supplies, and a $50 case and it's not hard to have $300 in the whole thing.

[Dr K]

Sounds good - if you can get others interested, count me in.
Peter

[edevinney]

Looks like there are 5 parties interested in AD1862 chips on diyaudio, so almost there. If anyone here wants a pair let me know in the next week. $60/pr for Dorki.

[JmuRiz]

Anyone have a contact to clean/fix an old tube amp?

My neighbor has a tube amp that needs some repair, but he doesn't have a wiring diagram. Does anyone have a shop that can fix it w/o having a wiring diagram. The last place he took it to sat on it for months and did no research to find a wiring diagram...pocketed a $100 diagnostic fee for nada.

Thanks for any suggestions!

BTW I have an old Marantz that needs cleaned and tuned too, but I might just try to hit it with a duster to blow the crud out and see if that works.

[jbailey930]

Originally Posted by JmuRiz

Anyone have a contact to clean/fix an old tube amp?

My neighbor has a tube amp that needs some repair, but he doesn't have a wiring diagram. Does anyone have a shop that can fix it w/o having a wiring diagram. The last place he took it to sat on it for months and did no research to find a wiring diagram...pocketed a $100 diagnostic fee for nada.

Thanks for any suggestions!

BTW I have an old Marantz that needs cleaned and tuned too, but I might just try to hit it with a duster to blow the crud out and see if that works.

You can try Music Technology in Springfield. Be aware their backlog is 6 months. The owner Bill was the lead tech at Conrad Johnson. They charge $75 hold fee.

Unfortunately Brett Mullins of HIFI Heaven passed away in the spring. Jimmy at http://www.esc-website.net/ in Germantown

Protech is a new one to me - Silver Spring. Just Audio up in Baltimore.

You could join the FB group DC Area Audiophiles and etc. Ed and I are on over there. Might get some better suggestions. Good luck.

Try Deoxit on the Marantz controls - Fader lube for the pots only.

[JmuRiz]

Thanks

[Dr K]

If the tubes have been changed without fixing it, LOOK at the circuit board. There might just be a blown resister or something which will have white ash around it. I have a friend who got a McIntosh tube mono block for $25 (long ago) and just replaced 1 white-ash-covered resister to have a perfect unit.