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Old 22nd March 2006, 12:33 AM   #1
PAICE69 is offline PAICE69  Canada
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Default audio alchemy powersupply

I have come into an audio alchemy VAC in the box

however it has no power supply

I would like to either build or buy a power supply at low cost

does any one know the dc voltage and amp requirements of the
VAC in the box?

does any one have a power supply for sale for this preamp

thanks David P
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Old 23rd March 2006, 08:47 AM   #2
AndrewT is offline AndrewT  Scotland
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Hi,
open up the box and see if Jack jumps out.

It should be possible to recognise the input side and identify the presence of a bridge rectifier or not. This will inform you of the need for a DC or AC wallwart supply.

Try to find if there are voltage regulators inside DAC in a box.

LM317, LM337, LM78xx, LM79xx.

If these exist then find the highest of each polarity.

You will need a supply that puts out at least 3Volts higher than these regs. But I suspect you might be better with about 6V or 7V higher to avoid ripple and voltage droop causing hum on the output i.e. for LM7815 use 21Vdc input and use a 15Vac transformer. This matching of AC to final regulated DC holds over a range of voltages (12Vac to 24Vac).

If you need a DC supply you may have trouble locating exactly what you need and it would then become feasible to construct your own. It may give better performance that way. Have a look at Trichord (Michell) to see how much money they threw at the PSU in the upgraded models.

Come back with more info if you cannot source the original.
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Old 23rd March 2006, 03:15 PM   #3
Bobken is offline Bobken  United Kingdom
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Hi,

If its any help, the Audio Alchemy 'Power Station One' which was supplied with the "Dac-in-a-Box" has a 14Vac supply at 400mA.

There was a factory 'improved' alternative PS for this, but I don't know any details of this, unfortunately.

The power input plug to suit the Dac in a Box, is a stereo 3.5mm jack, with the tip and middle sections (i.e. those used normally for left and right audio signals) being the 'hot' poles for the AC voltage.

The diodes which rectify this AC to DC voltage are inside the Box, near to the input socket.

Many years ago when I used one of these DACs, I found considerable sonic improvements were to be had with using a DIY PS, so as Andrew said, it is worth considering something better than maybe Audio Alchemy used originally.

I don't know if the VAC in a box you mention is the same, but I hope this helps.

Regards,

P.S. Although I still have the original PS for this, I don't think the voltage would be suitable for your country, as I am in the UK.
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Old 24th March 2006, 08:33 PM   #4
PAICE69 is offline PAICE69  Canada
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Default audio alchemy power supply

thanks for the response

the 14.1 v coincides with other info i have

paice69
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Old 25th March 2006, 09:41 AM   #5
Bobken is offline Bobken  United Kingdom
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Hi David,

I didn't mention it before, but I did a search on Audio Alchemy under "DAC", "VAC", and whatever else I could come up with.

The interesting thing I found was that all of the PSs I saw mentioned anywhere (and there was another maker's 'upgraded' supply, too) were 14V ac, although some PSs were more robust and better made than others, of course.

This was what lead me to believe that at least some (possibly most) of their PSs are common across several of their products.

If your input uses the same 3.5mm jack as on A.A.'s "Power Station One", I would say that you should be quite safe with using a similar AC voltage, and I guess using a higher current supply would doubtless give better sonic results, too, as I found with my DAC.

Also, if you think about it, 14V ac (when lightly loaded) will give approx. 20-ish volts DC when rectified, and this would be a suitable voltage to feed many regulator chips (like LM7815), just like Andrew has just advised.

Regards,
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Old 15th April 2006, 06:46 PM   #6
PAICE69 is offline PAICE69  Canada
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further to my earlier posts re the Audio alchemy I have another question

the gain adjustment jumpers are self explanitory

however the the jumper pins adjacent to each input jack to adjust the loading are not

Does anyone out there know the loading values for each of the 5 available positions

thanks david p
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Old 15th April 2006, 08:42 PM   #7
anatech is offline anatech  Canada
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Hi David,
I did warranty for Audio Alchemy until they folded. I have some diagrams for these, but they are buried at the moment. Later on I can try to dig they up. I can't remember what power supplies went with what products anymore. That's got to be about 10 years ago now.

These are generally on large format paper, I can not easily scan the darn things. No one has ever asked about the jumpers on the VAC-in-the-box. Most Audio Alchemy products went down due to overheated regulators.

-Chris
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Old 26th November 2006, 12:00 AM   #8
Fin is offline Fin
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Quote:
Originally posted by Bobken
Hi,

If its any help, the Audio Alchemy 'Power Station One' which was supplied with the "Dac-in-a-Box" has a 14Vac supply at 400mA.

There was a factory 'improved' alternative PS for this, but I don't know any details of this, unfortunately.

The power input plug to suit the Dac in a Box, is a stereo 3.5mm jack, with the tip and middle sections (i.e. those used normally for left and right audio signals) being the 'hot' poles for the AC voltage.

The diodes which rectify this AC to DC voltage are inside the Box, near to the input socket.
I just got hold of a Dac In The Box.....and all info I can find on it refers to it requiring a DC voltage input (not AC).

I cannot see any rectifier diodes in the attached schematics or pictures.

Also - if you still have that original PS.....I am interested......

Pic of DIBT PCB
Attached Images
File Type: jpg dibt pcb.jpg (94.3 KB, 703 views)
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Old 26th November 2006, 12:29 AM   #9
Fin is offline Fin
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Can't see any rectifier here....and I'd like to be sure before plugging in an AC supply.

DIBT PS
Attached Files
File Type: pdf bibt ps.pdf (36.0 KB, 214 views)
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Old 26th November 2006, 08:49 AM   #10
AndrewT is offline AndrewT  Scotland
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Hi Fin,
I can't see any tiny cap on the second pair of reg inputs.
You have small caps on the outputs of both but they should be pin to pin.
You have small caps on the input of the left reg but again they should be pin to pin.
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