pete_mac Posted November 8, 2013 Posted November 8, 2013 I snaffled one of these Teradak U9VA linear power supplies recently from A&B Systems in Hong Kong, as I was after a cheap clean USB power supply for my DAC. http://www.ab-system.hk/index.php?route=product/product&path=73&product_id=64 Dirt cheap at around $65 landed. The power supply came with a 5.5mm equipped cable for the 9V output (which, incidentially, is adjustable via the trimpot on the PCB from 0.25V to 9V). To my very great surprise, the power supply also comes with a power-only USB cable which works perfectly for my needs. Importantly, it is the kind of USB cable which passes through the data, but severs the power supply from the original source and injects the clean 5V from the Teradak PSU instead. I am most impressed with this inclusion, as I was considering making up my own power-only USB cable anyway. I note that the transformer inside these units is now a 120/240V configurable unit, rather than 115/230V as was previously the case. It appears to be fairly well designed and constructed, and weighs just under 1kg. I note that the advertising mentions the use of Panasonic FC caps. Nope, that's definitely not the case - these caps are some other kind of 105 degree low ESR cap. Now for some listening comparisons to see if there is any perceivable difference using this power supply vs the 5V USB output from the SBT. Some people reckon that the SBT sounds better with the least possible load on the power supply, but whether I can actually hear a difference remains to be seen. If there's no difference, then at an absolute minimum I've bought a nice and heavy $65 power switch for my DAC Considering the actual price of the unit is USD$44 + around $USD15 for registered shipping (so about $65 AUD as mentioned earlier) I reckon it's pretty darn good value for money. 12
Sir Rab of Everest Posted November 8, 2013 Posted November 8, 2013 Hmmm, nice find! I await your results with interest. Given the price, i might buy one anyway! Thanks for the tip.
SteveC Posted November 8, 2013 Posted November 8, 2013 (edited) You could run the SBT off this as well couldn't you? I do this with the iUSB . Edited November 8, 2013 by SteveC
gavtron Posted November 8, 2013 Posted November 8, 2013 You could run the SBT off this as well couldn't you? I do this with the iUSB . I want to hear the 9v of this psu running the iusb... I think it would be a good combo and it would also be interesting to compare the 5v teradak out to the 5v iusb out, to see which one is cleaner
pete_mac Posted November 8, 2013 Author Posted November 8, 2013 You could run the SBT off this as well couldn't you? I do this with the iUSB . Possibly so! Whist the standard PSU for the SBT is a 3A, I believe the current draw is less than 1A if you're not drawing any current via the USB output on the SBT. I will try it some day. I couldn't use this power supply unit to power both the SBT and DAC, though.
A J Posted November 8, 2013 Posted November 8, 2013 The SBT draws about 650ma on boot up then settles to 500ma at rest. Depending on what screen stuff you have going while music is playing it rarely gets above .6A AJ
pete_mac Posted November 8, 2013 Author Posted November 8, 2013 The SBT draws about 650ma on boot up then settles to 500ma at rest. Depending on what screen stuff you have going while music is playing it rarely gets above .6A AJ Thanks AJ! Hrmm... I might be able to run both the SBT and DAC from this power supply after all!
zog Posted November 8, 2013 Posted November 8, 2013 These look like they would be great for miniDSP units! - I've already built a linear PSU for mine though.
A J Posted November 9, 2013 Posted November 9, 2013 The only thing to point out is that they use a 9VA transformer - that means at 1 amp these things are being pushed hard. Other than that - looks like a ref hit bargain. It would interesting to scope the output because at the end of the day - what you generally want is a stable, low impedance and low noise floor supply. 1
skippy124 Posted November 9, 2013 Posted November 9, 2013 I will get Pete to bring it over and I can put a scope on the output. Cheers John 1
pete_mac Posted November 9, 2013 Author Posted November 9, 2013 I will get Pete to bring it over and I can put a scope on the output. Cheers John That's a sterling idea! Probe-fest tomorrow afternoon. 1
evil c Posted November 9, 2013 Posted November 9, 2013 That's a sterling idea! Probe-fest tomorrow afternoon. I also am very interested in any improvements this might offer to my SBT if compatible
A J Posted November 9, 2013 Posted November 9, 2013 I will get Pete to bring it over and I can put a scope on the output. Cheers John That's a sterling idea! Probe-fest tomorrow afternoon. Hmmmm ðŸ˜
pete_mac Posted November 10, 2013 Author Posted November 10, 2013 (edited) OK, we threw the Teradak PSU on the scope today at skippy124's place. This wasn't intended to be exhaustive testing, but a quick comparison with the tools we had at our disposal. Whilst I didn't drag my SBTalong for testing the output of its USB port when fed via the SBT switching PSU, we did have an apple 5V USB power supply and a generic 5V USB power supply. The generic power supply revealed around 250-300mV of noise under no load, and an increase over this figure when under load. The Apple power supply revealed around 80mV of noise under no load, and an increase over this figure when under load. The Teradak linear PSU showed 2mV of noise... but unfortunately this was the limit of our testing, as there was 2mV of noise with nothing connected to the scope. So, all that I can say is there is definitely less than 2mV of noise. There was no change in the measured noise under load, but again with the caveat of not being able to measure below 2mV in this instance. There's a chance that the linear PSU did get noiser under load, but if both measurements are beneath the noise floor of the measuring equipment, then we'll never know. In short, there is definitely much lower noise offered by this PSU compared to other generic switchmode USB 5V PSUs. One day I might get Dad to take the power supplies to work so that he can arrange for them to be tested on more sophisticated, higher resolution equipment. In future we'll also measure the SBT USB output and the output of a laptop USB port. Edited November 10, 2013 by pete_mac 2
adamg Posted November 10, 2013 Posted November 10, 2013 (edited) Thanks for the info Pete Are you familiar with this DAC PSU by HiFimeDIY Cheap but couldn't comment on quality Edited November 10, 2013 by adamg
pete_mac Posted November 10, 2013 Author Posted November 10, 2013 I'm not, but I am now! It looks like a fairly simple design which is non-adjustable, so only suited to fairly specific applications. I can't see any filter caps nor regulators anywhere.
A J Posted November 10, 2013 Posted November 10, 2013 I'm not, but I am now! It looks like a fairly simple design which is non-adjustable, so only suited to fairly specific applications. I can't see any filter caps nor regulators anywhere. Yeah no regulation - also IMHO and I do have experience - those voltage LEDs introduce sound into the output.
brenden Posted November 10, 2013 Posted November 10, 2013 I recently installed a Teradac crystal clock from Valab in my CD94 mk2 . Sounds great ,and better than another well known brand I had in there, and way cheaper ..Fantastic value. The clock also houses a decent low noise power supply that is the key to clocking CD .But I am going to hook the clock up to a battery soon LOL.
zog Posted November 10, 2013 Posted November 10, 2013 Thanks for the info Pete Are you familiar with this DAC PSU by HiFimeDIY Cheap but couldn't comment on quality It looks like an AC (out) power supply to me so not directly comparable?
Guest fordgtlover Posted November 10, 2013 Posted November 10, 2013 The simple TREAD LM317 based power supply that used to be available from Tangentsoft.net had a published noise figure of 0.060 mV. I use one of these with my SB gear. I don't hear any difference in sound, but I had a spare one so I used it.
Essence Posted December 20, 2013 Posted December 20, 2013 I am using a similar PSU for my Duet, Valab TeraDak Duet PSU. Did not compare directly to having the wallwart but against other sources the difference is clearly discernible.
jackaudio Posted December 20, 2013 Posted December 20, 2013 I have a squeezebox duet as transport feeding my Tda1541 dac, changed the std wall wart for a 12v battery with 9v regulator there is no comparison sound is so much better now those wall warts are absolute garbage and don't deserve any place in a hifi system.
gypr1961 Posted December 20, 2013 Posted December 20, 2013 I got one of these to try with my ifi headphone amp but there is a very low quiet bass rumble that isn't there with the supplied wallwart.
georgehifi Posted December 21, 2013 Posted December 21, 2013 (edited) I snaffled one of these Teradak U9VA linear power supplies recently from A&B Systems in Hong Kong, as I was after a cheap clean USB power supply for my DAC. http://www.ab-system.hk/index.php?route=product/product&path=73&product_id=64 Dirt cheap at around $65 landed. The power supply came with a 5.5mm equipped cable for the 9V output (which, incidentially, is adjustable via the trimpot on the PCB from 0.25V to 9V). To my very great surprise, the power supply also comes with a power-only USB cable which works perfectly for my needs. Importantly, it is the kind of USB cable which passes through the data, but severs the power supply from the original source and injects the clean 5V from the Teradak PSU instead. I am most impressed with this inclusion, as I was considering making up my own power-only USB cable anyway. I note that the transformer inside these units is now a 120/240V configurable unit, rather than 115/230V as was previously the case. It appears to be fairly well designed and constructed, and weighs just under 1kg. I note that the advertising mentions the use of Panasonic FC caps. Nope, that's definitely not the case - these caps are some other kind of 105 degree low ESR cap. Now for some listening comparisons to see if there is any perceivable difference using this power supply vs the 5V USB output from the SBT. Some people reckon that the SBT sounds better with the least possible load on the power supply, but whether I can actually hear a difference remains to be seen. If there's no difference, then at an absolute minimum I've bought a nice and heavy $65 power switch for my DAC Considering the actual price of the unit is USD$44 + around $USD15 for registered shipping (so about $65 AUD as mentioned earlier) I reckon it's pretty darn good value for money. Hi Pete, these look like a good option to power my Lightspeed Attenuator for customers, who want something a bit more robust than just a dc wall wart that I supply, even though that's all that's needed, but you know Audiophiles! Can you tell me 2 things, if your able. The 9vdc output, you say it's a 5.5mm plug that's the length, but is it 2.1mm or 2.5mm plug inside diameter? (the hole) it is hard to tell by eye, maybe a drill or calipers will measure. The other question is, is the 9vdc positive centre or negative centre? Cheers George Edited December 21, 2013 by georgehifi
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