Is a Plitron 300VA 22Vx2 toroid enough for an Aleph 3 or 30? - diyAudio
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Old 5th May 2007, 02:50 AM   #1
haziz is offline haziz  United States
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Default Is a Plitron 300VA 22Vx2 toroid enough for an Aleph 3 or 30?

I have a Plitron 300VA 22Vx2 toroidal that I got for my gainclone. I did however since then obtain two of ApexJr's Avel Lindberg 100VA toroids and may be able to spare the Plitron for a Pass DIY Aleph 3 or 30. I will be using BrianGT's PCB boards probably in a stereo implementation with the PSU board populated by either ApexJrs Nichicon 12000 mcF 50V caps or the 22000 caps from Digikey (Which is advisable??).

This is the one I am refering to: http://www.plitron.com/shopping/shopexd.asp?id=164

Does the 300VA toroidal have enough oomph for the two channels?

Does the 22Vx2 toroid deliver the correct rail voltage for this setup?

What transformers do people use in these amps?

How is the Antec 400VA often seen on ebay for approx $40?

I do have ApexJr's Signal transformers (Primary 230V Secondary 48VCT 7A & 28VCT 3A
or Primary 115V Secondary 24VCT & 14VCT). They are awfully bulky though. Are they usable?

Opinions regarding transformers/toroids for this amp? I am a newbie at this so "Toroidals for Dummies" level advice would be appreciated. If possible point or link directly to the unit recommended.

Thanks.

Sinerely,

Hany.
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Old 5th May 2007, 03:07 AM   #2
batee is offline batee  United States
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I built my A30 with a 2x20V Antec 400VA transformer. It runs just fine.

Output Filters are 68mF -> .235 Ohm -> 68mF.

The rail voltages are about 23.4VDC.

After running for about 8 hrs with the case open, the transformer was running at about 58C.

If I had it to do over again, I'd probably get the 800VA Antec with the hope that it'd run a little cooler than my 400VA does. If they had a slightly higher voltage (22-24V maybe), I'd probably do that just to get a little more output power to the speakers.

Good luck,

Bryan A. Thompson
bryan@batee.com
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Old 5th May 2007, 03:41 AM   #3
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It goes something like this:
Transformer secondary voltage x 1.414 = Rail voltage (assuming cap input filter)
...so...
22Vac x 1.414 = 31.1Vdc
...but, the bridge rectifier steals a couple of volts, so your actual rail will be more on the order of 29Vdc.
My experience with Plitrons is that that they tend to be a little generous on their secondary voltages, so don't be surprised if your rail is actually closer to the 30 to 32V level.
As far as VA ratings go, the Alephs tend to dissipate about three times their rated output. In the case of an Aleph 3, that's going to be about 100W per channel. Now, given that you're talking about one transformer serving both channels, that's around 200W. Plitrons are built tough--my feeling is that you'll be okay. If all else fails, use a fan to cool the transformer a bit.
Given that the Aleph 3 had (if I recall correctly) 25V rails, you'll have a little bit of extra voltage. What to do? Well, you can go with it and put up with the fact that you'll get a few extra watts out of the circuit. Breaks your heart, I know. Or you could use a cap multiplier to semi-regulate the rails for somewhat better performance. Or you could fully regulate the rails. Oh, blast and bother, I had something else in mind, but it escaped. Never mind.
Just remember that higher rails will mean higher heat dissipation in the output devices. Heatsink accordingly.

Grey
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Old 5th May 2007, 04:04 AM   #4
batee is offline batee  United States
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I've heard many good things about the Plitrons. Having used Antec, the only good things I see out of them are that they're really cheap and they're available via eBay. They are satisfactory for A30 power requirements, but I'd consider other alternatives.

Other losses to consider are winding resistance of the transformers. Plitrons may have the voltage rated at the rated output current, but not so much for the Antecs. The factory voltage rating for my 20Vx2 400VA transformer is a no-load voltage rating. 20.1VAC at no load, the full load of 18.3VAC at 18.34A (=336W). That's a 0.1 Ohm output coil resistance, so you can calculate your own rail voltages at whatever current you intend to draw. They indicate a 5C temp rise after an hour of operation at full load (which *seriously* is 336W for their 400VA transformer). This temp measurement is an outright lie. I measure at least a 28C rise in temp at 1/2 rated power over the same hour.

If you have a source for Plitrons at a reasonable price, I'd do that instead of the 400VA Antec.

Bryan
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Old 5th May 2007, 10:49 AM   #5
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about piltron transormer....a couple things:

does anybody know where it's possible to get those for a good deal in Europw at least....i mean !! or in the state too but with the primary for 220V...

Second.....has anybody ever compare the sound performances of a piltron an another good one? i mean....the name is famous and everything....been used from many famous brands....but does it actually sound as good as i read.

Just wonder if somebody had experience with this....


Best,
Stefano
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Old 5th May 2007, 03:44 PM   #6
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Assuming that you buy a transformer with a dual primary, you can wire it for either 120V or 240V, your option.
It's not so much a question of how Plitron power transformers 'sound' it's that they deliver voltage and current in the real world.

Grey
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Old 5th May 2007, 03:57 PM   #7
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Quote:
Originally posted by Stefanoo
does anybody know where it's possible to get those for a good deal in Europw at least....i mean !! or in the state too but with the primary for 220V...

Second.....has anybody ever compare the sound performances of a piltron an another good one? i mean....the name is famous and everything....been used from many famous brands....but does it actually sound as good as i read.
Plitron sells directly: http://plitron.com/shopping/shopdisp...evel+%2D+300VA They ususally don't have transformers in stock, the lead time can be 2-4 weeks. All standard transformers are available with dual primaries.

I compared Plitron 300VA against similar size Chinese transformer and the difference was substantial, especially in bass region and PRAT. Although I could get Chinese toroids at 50% of the price of Plitrons I wouldn't consider using them.
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Old 5th May 2007, 04:11 PM   #8
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Quote:
Originally posted by Stefanoo
about piltron transormer....a couple things:

does anybody know where it's possible to get those for a good deal in Europw at least....i mean !! or in the state too but with the primary for 220V...


Best,
Stefano

Derek Walton sells amplimo and plitron, priced in euros. I got this from his website...

http://www.amplimo.com/


it might be what you're looking for.

I've also used the clairtronic toroids that are available from rapid. I've found them good value for money.

Regards

Ed
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Old 5th May 2007, 04:49 PM   #9
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Also, in Europe, a good place for affordable toroids is http://www.toroidy.pl (contact in English is possible as well).

I 've been using their "for Audio" grade toroids with very good results.
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Old 5th May 2007, 05:15 PM   #10
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I have to agree with the above posts about Chinese transformers. I used an Antek 45+45vac @800VA using the 220v primaries connected to 120vac. It works great especially for the price and the Antek folks have awesome customer service. The Antek does buzz or hum at times and a Plitron or Victoria Magnetics would be a better choice.

If you are new to amp building and looking for a lower investment cost for experimentation than Antek is great, otherwise step up to one of the premium transformer companies.

BTW, I was planning on running dual PSU's in my Aleph30 and decided to run just 1 PSU instead. As a result I have 2 Antek 22+22vac @400VA with both 120/220vac primaries. I can make you a deal on them if you like.

At 22vac output adding a small amout of R in your CRC psu setup will make the rails run at 25VDC.

Just my $.02 worth,

-David
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