Anyone who have used the TL783 ? - diyAudio
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Old 13th September 2005, 07:52 AM   #1
beppe61 is offline beppe61  Italy
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Default Anyone who have used the TL783 ?

Dear Sirs,

I am looking for opinions from people who have used the TL783 regulator.
I would like to build a 60V power supply.
Is the simple schema on the data sheet valuable?
Is there any method to improve noise rejection and to lower the residual ripple?
I intend to use the PS to power an audio preamp.

Thank you very much indeed.

Kind regards,

beppe61
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Old 14th September 2005, 02:02 AM   #2
BWRX is offline BWRX  United States
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the best way to lower the ripple voltage is to use a large amount of capacitance before the regulator. since you're dealing with high input voltages (assuming a max dropout voltage of 20V, so around 80V to get 60V output) the caps would be fairly large. you can improve the noise by bypassing the larger electrolytic caps and rectifier diodes with smaller value film caps. a properly implemented snubber can also remove a bit of noise.
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Old 14th September 2005, 06:57 AM   #3
beppe61 is offline beppe61  Italy
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Quote:
Originally posted by BWRX
the best way to lower the ripple voltage is to use a large amount of capacitance before the regulator. since you're dealing with high input voltages (assuming a max dropout voltage of 20V, so around 80V to get 60V output) the caps would be fairly large. you can improve the noise by bypassing the larger electrolytic caps and rectifier diodes with smaller value film caps. a properly implemented snubber can also remove a bit of noise.
Dear Sir,

thank you very much indeed for your extremely kind and valuable reply.
I would like to take advantage of your competence to ask you the following.
I need the 60V power supply for an audio preamp.
I have the opportunity to buy a Sorensen PS on ebay.it.
Do you think that a DIY project can approach the quality of that lab power supply (it is not that cheap, about 250 USD here in Italy)?
For my application the quality of the power supply is paramount.

Thank you very much indeed again.

Kind regards,

beppe61
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Old 14th September 2005, 05:02 PM   #4
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Default tl783

If you want to really get the noise down you can add an inductor in series with the output of the regulator with a large capacitance down to 0v. I assume you are running at only a few hundred milliamps or less, so would suggest about 47mH to 100mH with say 470ufd as the shunt capacitor (larger the better within reason). This acts as a low pass filter and will not affect the regulation if you keep the resistance of the inductor as low as possible.

regards,

Steve
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Old 14th September 2005, 05:29 PM   #5
BWRX is offline BWRX  United States
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Quote:
Originally posted by beppe61
I have the opportunity to buy a Sorensen PS on ebay.it.
Do you think that a DIY project can approach the quality of that lab power supply (it is not that cheap, about 250 USD here in Italy)?
I assume that you mean this power supply.

Here is the manual for that particular family of supplies.

Seeing that your preamp supply does not need to supply a lot of current, you should be able to make a good supply for less than $250. I made an adjustable voltage dual rail supply capable of about 0 to 20V and up to about 5A per rail with LT1083 regulators for around $200 total (parts, case, connectors, hardware, etc.), but I went a little overkill with the components because I wanted to use it as a supply for a couple of single ended amps.

Your high voltage, low current supply wouldn't need too large of a transformer, which is where most of the cost comes from in good high power linear supplies. You'd probably want to look for a 120VA or 160VA transformer with 55VAC or 60VAC secondaries.

Following the basic circuit on the data sheet with a couple of tweaks will result in a fine supply.

Steve also made a good point about adding the inductor. Again, since this is a fairly low current supply you won't need a huge inductor to keep the losses minimal.

Quote:
Originally posted by beppe61
Thank you very much indeed again.

Kind regards,

beppe61
You're very welcome

Brian
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Old 14th September 2005, 06:39 PM   #6
beppe61 is offline beppe61  Italy
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Quote:
Originally posted by BWRX

I assume that you mean this power supply.
......
Brian

Dear Mr. Bryan,

thank you sincerely for your very kind and valuable support.
I cannot figure out why I told you about an ebay buy.
Silly me.
Anyway, the Sorensen Power Supply I am thinking about buying is the same model as this one: http://www.used-line.com/c4914726s88...SEN_QRD_60.htm

It can provide up to 60 V (my needed voltage) and 1,5 A, where my circuit needs about 0,1 A.
The price is 250 euro but maybe I can get a small discount.
It seems a great PS and I think that the ripple here should be pretty minimal.
I would be very interested in hearing your opinion.
Thank you very much again for your kind help.

Kind regards,

beppe
Italy
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Old 14th September 2005, 06:46 PM   #7
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TL783 is no longer available in TO-220
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Old 14th September 2005, 06:53 PM   #8
beppe61 is offline beppe61  Italy
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Default Re: tl783

Quote:
Originally posted by steve hawkins
If you want to really get the noise down you can add an inductor in series with the output of the regulator with a large capacitance down to 0v.
I assume you are running at only a few hundred milliamps or less, so would suggest about 47mH to 100mH with say 470ufd as the shunt capacitor (larger the better within reason).
This acts as a low pass filter and will not affect the regulation if you keep the resistance of the inductor as low as possible.
regards,
Steve
Dear Mr. Hawkins,

thank you sincerely for your kind and really valuable suggestion.
Actually I need 0- 60V with a consumption of about 0,1 A.
The Power Supply is for an audio preamp.
The quality of the supply is paramount because all the noise will be available at the output and then amplified by the following power amp.
A battery would be my dream (or a virtual battery).
But it is not that convenient to manage.
If I understand correctly, you suggest to put a 47-100 milliH inductor just after the TL783 and then a capacitor of 470 microF.
Am I right?
The circuit is in A class, so it should draw a constant current from the Power Supply.
What about a simpler R-C filter maybe before the regulator?
If you know any great ready off-the-shelf power supply reasonably priced please show me.

Thank you very much again for your kind reply.

Best regards,

beppe
Italy
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Old 14th September 2005, 07:11 PM   #9
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Quote:
Originally posted by beppe61

The price is 250 euro but maybe I can get a small discount.
250? For that?

Are you sure you don't want to try the schematic in the datasheet?
A 44000 uF capacitor bank will not cost you more than 40 euros, the IC costs itself about 5-6 euros and the transformer+rectifiers - 50 euros.
In total from 100 to 120 euros.

Why waste so much on a PSU, that in fact may not perform as equally as the IC? I'd try to understand you if it were a brand new PSU, but it's
second-hand. A preamp doesn't even need a PSU with current/voltage adjustment if you've tested it already and it works.

P.S.: if I were you, I'd buy a transformer, some Schottky rectifiers and the left over money from those 250 euros I'd spend on capacitors.
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Old 14th September 2005, 09:14 PM   #10
BWRX is offline BWRX  United States
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Quote:
Originally posted by jackinnj
TL783 is no longer available in TO-220
Are you sure? It says it's available in TO-220 and PFM (surface mount) on ti's site.

Ah I see. It says it was discontinued on mouser, but they still have stock of the TO-220 TL783 manufactured by NJR.

beppe, it would probably be cheaper and more rewarding to build the supply yourself. I also find that things you build yourself often sound better in the end as well
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