[Bill Lamb]

I own an Altmann DAC, BYOB amp and audio PC setup.  I've been reading about various mods people have created for the DAC and would like to hear opinions about which power supplies and mods yield the best sound. 

Paul's regulators for the voltage stepdowns and an SR3 regulated AC supply?  A regulated battery supply instead of the AC?  Or forget the voltage stepdowns and rewire the DAC to take discrete SR3s for each voltage stage?

I currently have the whole system running directly on Red Top batteries, but have become dissatisfied with this setup as it seems to push the pitch of the system upwards.  It's not that the bass is flabby or nonexistent, but the emphasis always seems to be on the midrange on up.  Other than that, the system is extremely clear with excellent soundstaging.

Any help is appreciated.

Thanks,

Bill

[richidoo]

Hi Bill, it is important to add proper cooling to the amplifier chip. Without cooling, it will enter protection mode during normal playback which sounds like clipping. After a minute or two the chip is hot enough to protect on slightest call for power. The cooling fins that came with mine were intended for T-03 metal can, not a flat plastic chip, so there is minimal surface contact, basically it is useless.  I fitted a real heat sink with silicon grease and eliminated the problem. It made a lot more power without protection and looked better. I have an extra heatsink if you want it, just PM me. I think I have posted the Mouser part number elsewhere on AC.

A battery is a convenient source of current, you can listen during lightning storm! Battery is  relatively quiet compared to unfiltered AC PS, but a regulator will improve the current delivery dramatically for improved bass and more intense mids/highs for the amp, and lower the noise floor also. 

The SMD coupling caps are a good target for upgrade on amp and DAC. Regulator upgrades on the DAC analog sections and clock will make a big difference. You might also consider upgrading the 2134 output opamps to something more linear. There is a little bit of upper midrange zing in the stock opamps which you may be hearing. But the regulators will fill in the bass nicely.
Rich

[chips666]

Hello Bill
I am also using Altmann BYOB AMP and DAC with the Optima redtop battery
Many others and myself are very pleased with the result The batt works fine and is dead-silent I never had the change to hear the BYOB system with a Paul Hynes power supply but i feel no need for it Sorry Paul
For more body/bass respons I think this is what you mean
Depending on your speakers choice you could add an amp to help the woofer
I use a Reckhorn amp A-403 to help the Emminence alpha 15A woofer with fullrange Visatons B200 in a NOBOX open baffle set-up
Infact I copied the system from Audiotone wich is also a member of audiocircle and diyaudio Tony became a good audiofriend
Goodluck
Enjoy
Chips666

[Paul Hynes]

Hi Bill,

Rich is right about using good regulation on the supplies even with batteries. I use individual ALTREG1A shunt regs on the digital interface chip (3v3), clocks (5v) and the TDA1543 DAC chip (5v) and a PR3DC-12 as the master supply regulator powering the analogue output stages and the shunt regs. I have spiral wound gel batteries stacked to give 24 volts to allow for the PR3 regulator headroom requirement so it does not drop out of regulation as the battery voltage drops. I have tried PR3 series regs in place of the shunt regs and in all cases the shunt regs are the preferred types in this position and the PR3 series reg is the preferred reg type for the 12 volt supply. Upgrading the Altmann Dac with these regulators is a major sonic upgrade.

The SR3-12 makes a good mains powered alternative to the PR3DC-12 with the battery source, for those who do not want the hassle of battery management, as the performance of either method is very close through bass and midrange. This is because the same regulator is used in either option. I have a slight preference for the battery source in the higher frequencies although I can listen with either battery or mains as the power source and still enjoy the music.

I have tried a number of different battery types directly connected to the 12 volt rail without using the PR3DC-12 regulator and I do not like the bass end performance like this. In all cases the PR3 with battery source was preferred as the bass end is much more integrated with the music as a whole.

Ideally each shunt regulated section and the analogue section on the dac board would have its own completely separate supply to eradicate any supply/ground return interaction and I have been intending to do this for a while now, to my own DAC, but I have just been too busy to get on with it. I have done this for others with mains powered supplies with excellent results. This is another nice upgrade and the DAC becomes a stellar performer with individual high performance supplies on everything. This also happens with other equipment with multiple signal processing stages whether digital or analogue.

I have posted a layout drawing on Photobucket at the following address so you can assess the upgrade work required.

http://i700.photobucket.com/albums/ww7/paulhynes/AltmannShuntRegulatorUpgrades.jpg

The clock power feed needs cutting to separate it from the TDA1543 supply feed.

If you have any questions about how to go about an upgrade like this I would be pleased to help. For those who are not confident with upgrades like this I can do them for you.

Paul

[Bill Lamb]

Richidoo:

I've checked the heatsink and the chip on my BYOB amp many times and have never found it to get particularly hot.  Like yours, my heat sink doesn't mate very well to the chip, but it doesn't seem to bother the amp.  I definitely don't hear clipping.  Thanks for the suggestions, I'll keep them in mind.

Paul:

The setup you described sounds great, but I'm a little concerned about needing to use two batteries in parallel.  How do you charge them?  Are you powering both the DAC and amp with the same source, or is this just for the DAC?  It seems like two batteries in parallel really raises the bar for battery maintenance.  Do you have to disconnect everything when you charge, or is there an easier way?

As a practical matter, I will probably get a power supply or supplies for my equipment and leave upgrades to the shunt regulators for a future date.  Most likely I would purchase another Altmann DAC and then have you perform the upgrades to it before sending it on to me. 

What would you recommend as a power source for an audio PC?  I'm running a mini-ITX motherboard with an Atom processor.  The M/B is one of those which takes a 12V (or a little higher) power supply and does the voltage downconversions on the board instead of using an external power supply.

Thanks for your help,

Bill

[Paul Hynes]

Bill,

The batteries are series connected to give 24 volts DC. My set up is on the DAC only as I use a completely different power amplifier in my system. I have tried the Altmann power amp in my system and it worked fine and sounded very good. This was with an SR3-12 powering it.

Battery management is a pain in the butt. At present I use a 12 volt charger to charge the batteries separately. This is based on an old National Semiconductor application note. I must re-design this to charge the two batteries in series, which will save time.

I would recommend an SR7-12 for the Atom motherboard. This power supply uses the same regulator topology as the SR3 but engineered for high current output with a very beefy output stage and a custom-built mains transformer to give quiet operation both electrically and mechanically. This works very well and is big improvement over the usual switching supplies. The SR7-12 can provide more than enough power for mini-ITX boards (up to 8 amps continuous at 12 volts). I am currently selling the SR7-12 for £525.  This is a big, heavy duty power supply weighing in at just under 5 Kg packed so shipping to the USA would be in the region of £110 express.

Paul

[Bill Lamb]

Hi Paul,

I have to say the SR7-12 sounds like overkill for this computer.  The audio PC is really nothing more than the motherboard with a Juli@ card and a solid state drive.  I don't think it draws more than about 20 watts at full use.  Wouldn't an SR3-12 be able to handle it?

[Paul Hynes]

Hi Bill,

As long as you run your server lean the SR3-12 should provide enough power although it will run hot used continuously near it’s limits so do not site it in a cupboard or draw where airflow is restricted. If you add any external hard drives make sure they have their own power source. I have compared the SR7 with the SR3, powering a variety of different items of equipment, and without fail the SR7 gives an improvement in sound quality that is well worth the additional expenditure.

I have used this analogy before but it is a good one. The SR3 can be considered the equivalent of the Ford Mustang. It’s Zippy and fun to drive. The SR7 has much more under the hood and takes you into Bugatti Veyron territory. The response is much better and very well controlled. Both cars will get you from 0 to 60 mph and back to 0 again but they do it very differently. The Veyron may well seem like overkill for a pleasant day out driving but I know which one I would chose if I could afford it.

Regards
Paul

[anubisgrau]

If you have any questions about how to go about an upgrade like this I would be pleased to help. For those who are not confident with upgrades like this I can do them for you.

Paul, can you be a bit more detailed on what kind of effect on Altmann sound all these upgrades have?

Also how much this would cost to bring Altmann to the top level spec - I understand a unit should be sent to you.

Re battery, do you still feel it sounds superior to a good regulated linear PS?

My only worry is that the DAC is "tuned" how to sound with a battery.

[Paul Hynes]

Anubisgrau,

Sorry about the tardy reply. We had severe storms for a week from 7th December with winds at hurricane force at times. There was a lot of damage to the power grid and we only got power back last Thursday. I have been a little busy since then trying to catch up.

There are very noticeable large improvements in the following areas :-

Dynamic range at both ends of the scale
Quieter background
Image dimension
Image stability especially when the music gets busy and dynamic
Musical timing and coherence – it is much easier to understand how the musicians are playing together.
Timbre – there is better definition in the harmonic structure of instruments and voice making the music sound more natural.

Perhaps some of my customers who have had the modifications can give their views on the improvements they have heard to give you a fuller picture.

Re Battery, I preferred the spiral wound gel batteries with the PR3 regulator for the 12 volt supply over the SR3 power supply marginally. I prefer the SR7 over the battery/PR3 regulator. The SR7 is a much higher level of performance across the board over the SR3 and the battery/PR3.

After hearing your music with the regulator/power supply upgrades there is no way you would want to go back to using just a battery for the power supply. The upgrade in performance is that radical. Every time I get an Altmann dac in for upgrade I listen to it in stock form, but not for long, as the modified dac is so much better at presenting music.

Regards
Paul