Perfecting the USB Isolator

[ggking7]

I've been using the DIY Paradise Ultravox (ADUM4160) to isolate the USB connection between my DAC and computer:

Ultravox - SGD70.00 : Welcome to the diyparadise e-store!

The Ultravox and downstream DAC are powered via an SLA battery connected to the Ultravox. There are a couple problems with this setup and I'd love to get your advice on fixing them.

Downstream USB Connection:
The USB connector on the DAC side of the Ultravox is a female A type and the DAC has a female B type. I've been using a USB cable between the DAC and Ultravox but I'd rather plug them together directly. To do that I need to replace the Ultravox's female A connector with a male B connector but I can't find a USB male B connector anywhere. Do they exist?

Power Supply:
I tried switching from the SLA battery to a series of AA NiMH batteries and the sound was substantially worse. The sound was overall much weaker and thinner and lacked bass. That makes me think I could do better than the SLA battery with a very quiet linear power supply. Does anyone know of an available linear power supply which would be suited to this?

Miscellaneous:
Can anyone with audio DIY experience spot any other possible upgrades or improvements that could be made to the Ultravox. Maybe replace the capacitors with Black Gates? Thicker power leads?

 

[erin]

USB Cable of My Dreams « [email protected]

http://www.circuitsathome.com/mcu/usb/usb-isolator-most-frequently-asked-question

check this out. should answer some questions

Any linear power supply should be OK.

Black gate capacitors are best used in analog circuits not digital.

 

[qusp]

even then i'm of the opinion that BG can be fairly easily bested; this whole thing of just dropping them in anywhere without regard to what the purpose is confuses me. but yes for digital supply decoupling and bypassing, they arent even in the picture IMO. oscons, polypropelene or pps films and npo ceramics are much better choices for digital circuits. even panasonic FM or other really low Z electrolytic

 

[wwenze]

Looks to me that the Ultravox has a linear regulator onboard. Do away with that if you're using your own linear regulator and test the power sources again.

 

[ggking7]

USB Cable of My Dreams « [email protected]

check this out. should answer some questions

I have one of those adapters but I can't get it to pass USB power, only data, so it doesn't work with USB-powered devices. Do you know if a solder-able USB male B connector exists? That way I can plug the Ultravox and DAC straight together.

Black gate capacitors are best used in analog circuits not digital.

Well I was told to use Black Gates for this by the head engineer of a very well-known DAC manufacturer. Plus there are forum posts at DIY Paradise which report an increase in sound quality when the capacitors are switched for Black Gates.

Looks to me that the Ultravox has a linear regulator onboard. Do away with that if you're using your own linear regulator and test the power sources again.

That sounds like a good idea. Can anyone recommend a small but very low-noise linear power supply for this? I don't think I'll be able to build one, but an assembled kit would be great.

I'm also going to try switching the SLA battery for Lithium-Nano-Phosphate batteries:

EP Buddy 3S1P 9.9V 2300mAh LiFe battery pack USA A123 - eBay (item 230442131487 end time Sep-22-10 17:40:21 PDT)

I think they should have better current capabilities than my SLA battery and hopefully lower noise. Plus they should recharge in about 15 minutes as opposed to 15 hours.

 

[erin]

I have one of those adapters but I can't get it to pass USB power, only data, so it doesn't work with USB-powered devices.

Have you measured the volts on the pins? Have you checked the datasheet so you understand how the isolator works?

Are you sure the chip does not need to be reset to "wake it up" as described on the circuits at home website?

I think they should have better current capabilities than my SLA battery and hopefully lower noise. Plus they should recharge in about 15 minutes as opposed to 15 hours.

My SLA battery recharges from flat in about 20 minutes.

 

[ggking7]

Have you measured the volts on the pins? Have you checked the datasheet so you understand how the isolator works?

Are you sure the chip does not need to be reset to "wake it up" as described on the circuits at home website?

I was wrong when I said my USB gender changer did not pass power. It does, although it didn't the last time I checked for some reason. The problem is that it sounds worse than my 1 meter Wireworld Starlight USB cable. I think it's because the gender changer has one or more bright LEDs that light up when it's powered. I think that must be adding noise to the signal and/or power. I've seen just about every other type of solder-able USB connector except for male type B. Does anyone know if they exist?

My SLA battery recharges from flat in about 20 minutes.

I've never heard of an SLA battery charging so fast. What is its capacity and what are you using to charge it? Mine is 8Ah and I'm using a cheap 2 stage charger.

 

[ggking7]

I did find these:

20Pcs USB Type-B Male Plug Connector Socket For DIY - eBay (item 170520488212 end time Sep-27-10 07:40:15 PDT)

10Pcs USB Male Type-B Plug Connector Socket For DIY - eBay (item 180539614008 end time Sep-27-10 08:56:54 PDT)

Should I be able to replace the USB connector on the Ultravox below with one of the above?

Ultravox - SGD70.00 : Welcome to the diyparadise e-store!

 

[qusp]

Well I was told to use Black Gates for this by the head engineer of a very well-known DAC manufacturer. Plus there are forum posts at DIY Paradise which report an increase in sound quality when the capacitors are switched for Black Gates.

sorry but just because he is an engineer in an audio firm does not make him right in this instance. some people report increased sound quality when using massive NOS oil caps with huge long inductive leads for decoupling digital clock supplies too.

some people say BG are great for just about anything, the simple fact is they have high impedance at the high frequencies needed for decoupling digital circuits.

get the real deal lifepo4, not cheap ebay ones. get A123 they are fantastic and beat out any low noise regulator I have tried and I have tried many. if batteries are convenient, then I whole heartedly recommend them. the real A123 have larger capacity, last for much longer and have much higher current capability.

 

[erin]

I've never heard of an SLA battery charging so fast. What is its capacity and what are you using to charge it? Mine is 8Ah and I'm using a cheap 2 stage charger.

I'm using a 1.2Ah SLA from here:
RPG - SXKK0525 - SEALED LEAD ACID
I think it charges fast because its only 1.2Ah

The charger I use is also from Radio parts here:
http://www.radioparts.com.au/ProdVi...ProdDesc=PS665+2V/+6V/+12V+DC+TRICKLE+CHARGER

 

[ggking7]

the real A123 have larger capacity, last for much longer and have much higher current capability.

I'm going to do exactly that. I've been reading a lot about the A123 batteries lately and they're supposed to be superior to anything else out there. I'm actually thinking of buying some AONE stock. The price is very low because they haven't turned a profit yet, but I figure their technology is excellent and they're in a high-growth industry.

I'd like to get a 9.9v 4600mAh battery pack, but the A123 Racing (Enerland) pack with those specs stretches the pack out to 3 battery lengths which won't work in the space I have. One of their retailers suggested I use a parallel connector to combine two 2300mAh packs. Should that be just as effective as a single 4600mAh pack?

How would the current from such a battery pack compare to that from a linear power supply fed by mains AC? Surely the noise would be lower from the batteries but I wonder about the difference in current. I tried NiMH batteries and they paled in comparison to SLA, maybe because of the different current capabilities.

 

[qusp]

hahaha, you will melt the wires before you run out of current capability on these things; quite literally. a single A123 M1 cell at peak charge will put out 3v6 at 70 amps continuously and burst of 120 amps

dont buy the packs, as you found they are all a bit chunky and have unnecessary padding for our purposes. I bought single cells, the ones with solder tabs, but I removed the tabs and soldered packs of 4 and 6 in series directly to the end caps with 14AWG silver for lowest resistance (be quick when doing this, prolonged heat will lower the capacity, so use an iron tip with lots of mass)

I then wired this up to a hybrid Dsub connector so I could use a balance charger (charges each cell in a pack separately) and then tapped it for -6v6, '0v' 3v3 and 6v6. each cycle will vary between 3.65v and you should cut off at 3v. it drops from 3.65 fairly quickly to 3v4 and then between 3.4 and 3.2 over pretty much all of the useable charge cycle, then drops off a cliff.

my 4 cell pack is 14.6v at peak charge (+7.3v -'0v'- -7.3v) and I have another for 21.6v (+10.8 -'0v'- -10.8v)

using 2 in parallel will make a higher capacity, yes its the same as 4600mah

quite handy voltage for digital, I use them directly with some devices, but others I still use a low noise linear regulator in front of them. so yeah if you are using them in a situation that can have a fault condition tghat means massive current is drawn, best to put some sort of protection there, because they will put out more current than heavy duty wires, heavy duty connectors and most heavy duty components will handle.

low voltage; current for miles. SLA isnt even in the same ballpark

good idea on the stock, i'm doing the same, they producing results in a field that will inevitably replace fossil fuels and we all know how much money is there. I dont think anyone is really close to them at the moment.

 

[ggking7]

low voltage; current for miles. SLA isnt even in the same ballpark

I don't really need the extra capacity of 4600mAh vs. 3200mAh, but I want to be sure I have more than enough current. Would a single 2300mAh pack have greater current capability than an 8Ah SLA? I'm using such an SLA now and I'd like for this to be a performance upgrade. I think my DAC (which I'm also using as a preamp) must be current-sensitive because of the poor performance exhibited on NiMH.

good idea on the stock, i'm doing the same, they producing results in a field that will inevitably replace fossil fuels and we all know how much money is there. I dont think anyone is really close to them at the moment.

Seems like a no-brainer. I'm in.

 

[qusp]

I don't really need the extra capacity of 4600mAh vs. 3200mAh, but I want to be sure I have more than enough current. Would a single 2300mAh pack have greater current capability than an 8Ah SLA? I'm using such an SLA now and I'd like for this to be a performance upgrade. I think my DAC (which I'm also using as a preamp) must be current-sensitive because of the poor performance exhibited on NiMH.


Seems like a no-brainer. I'm in.

errmm, just checking, you did see that I said it could output 70amps continuously and 120 amps in bursts? thats insane. it will do this at whatever voltage you end up with my putting them in series. if you put them in parallel, output impedance gets even lower and current output increases yet again. a single cell will put out 120amps at 3v3 (will probably sag to about a consistent 3v1 under that load briefly, but will recover to 3v2), meaning that given you can provide a wire that will not melt (i'm serious), it can empty its entire charge into a load in a touch over a minute. like I said, SLA is not even in the same ballpark, not by a LOOONG shot.

have you seen the speeds these things can propel RC cars, planes and helis? 1/4 scale A123 powered helis can pull outside inverted loops and then stop dead in a hover upside down

indeed its a nobrainer.

 

[erin]

One of these Dewalt batteries certainly unarguably is capable of a high rate of discharge, but whether this is necessary for a circuit of low current draw is debatable. An SLA is more than capable of providing the necessary current peaks.

 

[ggking7]

I'm going to get one of the 9.9v 4600mAh packs and see how it goes. It's called AR26650-3S2PS here:

RC Lipos - Free World Wide Shipping on A123 Racing Systems Nanophosphate Lithium Ion Packs.

$135 is expensive but the cells look to cost $16.50 each:

RC Lipos - Free World Wide Shipping on A123 Racing Systems Nanophosphate Lithium Ion Cells.

so an extra $35 isn't bad to have them put together by the manufacturer.

 

[qusp]

but those packs are not designed for audio, there is quite a bit of extra metal messing with the output impedance, crappy steel leads and connectors designed for RC and not audio. even the RC guys that are serious about their sport make their own to get better performance. its really not difficult to make your own

 

[qusp]

One of these Dewalt batteries certainly unarguably is capable of a high rate of discharge, but whether this is necessary for a circuit of low current draw is debatable. An SLA is more than capable of providing the necessary current peaks.

its not just the current capability. output Z is better and noise lower. then of course you have the massive stonking size of the SLA and the fact they dont last for 2000 cycles and still be at over 80% capacity like the nano phosphate, in fact they dot even know when they will start losing capacity really, they should last for 10 years charging it every day before you even notice

 

[erin]

but those packs are not designed for audio

I didnt think any battery was "designed" with audio in mind.

 

[erin]

its not just the current capability. output Z is better and noise lower. then of course you have the massive stonking size of the SLA and the fact they dont last for 2000 cycles and still be at over 80% capacity like the nano phosphate, in fact they dot even know when they will start losing capacity really, they should last for 10 years charging it every day before you even notice

My SLA battery is about 12cm x 4cm x 5cm. I wouldnt call that a stonking size.
Indeed the Dewalt battery may be good, but dont discount the SLA as a viable alternative to linear power supplies in a low current audio circuit. Many people happily use them with pleasing results, I still prefer my SLA to any plugpack I have tried.

QUSP, when you have compared both, please report your results, as Im sure there would be many people interested in your findings.