Anyone know of GC that works from +/-50v - diyAudio
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Old 28th November 2006, 06:13 PM   #1
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Default Anyone know of GC that works from +/-50v

Hi All,

A friend just donated a partly broken Sony reciever. It is rated at 5x110w RMS into 8ohms and uses +/- 50v rails. I've fixed this thing once, one channel had dead output transistors, plus minor damage to ancillary resistors etc. It is now clear that it's a little too fragile for my tastes, so I'm thinking of replacing the 5 amplifiers with GC's...

So, do any of the current crop of chipamps work well from 50v rails...I checked the NatSemi site and their product seems limited to high 30's and low 40's. I'd like to be able to safely use 4ohm speakers, so using any of the 3886 based amps seems out of the question with rails this high...

The next critical quality is size, the heatsink has enough room and is drilled for 5 pairs of T0247 transistors (mounting surface is ~10" x ~2"), so size is an issue, a major plus for a chipamp based solution...a PCB can extend about 2" in front of the heatsink, along it's entire length...or 5 2"x2" pcbs could stand in front of the thing...

At a lower priority, the amp modules should allow muting, and of course since I ultimately need 5 of them, they need to be reasonable in price...

I know you guys will have ideas...

Stuart
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Old 28th November 2006, 06:32 PM   #2
traw is offline traw  United States
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could use emitter-follower regulator to shave off volts, but would be wasting power.

i'd just throw 5 ucd180's for that voltage or greg ball gbd150 modules, but might be tight fit.
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Old 28th November 2006, 07:07 PM   #3
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Default excellent ideas...

I thought of regulating and since I'm still 'thinking' it may end up being part of the answer, just wanted to hear from the community here to make sure I was considering all the options...

The UCD modules would be great if they were cheaper, the 180 module might fit with no problem, need to take some accurate measurements ...no worries from heat and more efficiency, probably represent a quality and quantity upgrade for this receiver...However, the cost of ~300euro for 5 channels is, IIRC, more than the unit cost new...

WRT the GB150, IIRC the price was approx $40. I'm pretty sure I'll have all the parts so the real question is does he sell pcb's? Not sure why, but Gregs website seems to be down, so unless someone else can chime in with sizes & prices, not sure whether this is a solution or not...

Thanks

Stuart
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Old 28th November 2006, 11:11 PM   #4
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Default ...tda7294...

After a little more searching the TDA7294 comes to light... Has anyone used it? Searching shows a number of people were thinking of using it, but not much seems to have happened since...

It is spec'ed to survive at +/-50v as long as it is only operated at +/- 40v...not sure if I can guarantee that part yet, I need to measure the power supply and see how fast it's voltage drops as the current draw is increased...couple of resistors might be all this needs to work...

Kits are available from a number of places that seem to be in the $20-$30 / channel range, so it might be a real contender...

Wondering at this point if it has any serious drawbacks not obvious from the specs...

Stuart
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Old 28th November 2006, 11:20 PM   #5
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Hi Stuart

The TDAs are just about the only chips I haven't used, simply 'cos I couldn't get hold of any. I suspect that is the only one that will go that high, the National ones go to about 42 V and TI's usually around 30V, and the OPA541 only gets to 40V.

Have you looked at the Class D kits from 41Hz? I keep looking at their site and thinking I really must give them a go one day.
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Old 28th November 2006, 11:23 PM   #6
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What about the sanyo STK series?
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Old 28th November 2006, 11:23 PM   #7
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I thought they were all obsolete?
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Old 28th November 2006, 11:42 PM   #8
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Check the TDA7293, the older sibling of the 7294. It's datasheet states it can work from +-50V (+-60V no signal).

I'm just about finnish instaling two of these in an older broken amp but I'm only running them on +-35V. Bought 10 of them fairly cheap of ebay about a year ago. Can't find them there now but there was a guy there selling them for a long time.

At +-50V into 4 ohm you probably should put 3 in parallell. (These chips are very easily parallelled.)

space
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Old 28th November 2006, 11:53 PM   #9
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Greg sells the GB150 PCBs separate, at $40 a piece. I'm pretty sure if you buy 5 of them he would be prepared to bargain a little
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Old 29th November 2006, 12:26 AM   #10
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Stuart,

LM4702s with a pair of 150W Sanken darlingtons is a no-no ?
The driver has a built-in mute, does 100 watts on 50vdc rails.

(assuming the Sony doesn't already have darling Sankens that enjoy blowing up, and you want to get rid of them)
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