Any issues? - Antek 400VA - 20v dual Sec for LM3875 Gainclone kit

GAH · 7th May 2009, 11:59 PM

I'm considering building Peter Daniel's LM3875 Gainclone Kit to use with 8 ohm speakers. I live in Fiji that uses 240 volt mains. Are there any issues with using a Antek 400 VA with 20v dual secondaries toroidal transformer with this kit.

For example:
1) is 20 volt on the secondaries enough to gain optimum performance from this amp?
2) Would the 400 VA trannie require some sort of soft start circuitry etc?

Or would I be better off buying a better quality transformer with 22 to 25 secondaries?

Regards
Glen

pacificblue · 8th May 2009, 07:29 AM

What is optimum performance for this amp? Depending on the capacitance in your power supply you can expect 30 W ±10 % into 8 Ohm. If that is fine for you depends on the speaker's effciency and your average listening volume.

The 400 VA transformer would probably be okay without, but it is nevertheless good to have a soft-start, because you may have other appliances connected to the same circuit and the inrush current combined with the other consumptions could lead to convenience tripping of the fuse/circuit-breaker for that circuit.

A transformer of half the power rating would be enough even for two amplifier channels at 2x20 V.

BTW, why is it called "convenience blowing", when it is really inconvenient, if it happens?

AndrewT · 8th May 2009, 02:16 PM

what is the primary (mains) voltage of the Antek transformer?

quadtech · 8th May 2009, 05:43 PM

Anteks typically come with dual 115V primary windings.

GAH · 9th May 2009, 03:59 PM

Thanks your comments and advise.

This Antek has dual 115v primaries.

I intend to use Harbeth SHL5 speakers with the amp. I would rather use a trannie that will provide a bit more power output which may better suit these speakers.

AndrewT · 9th May 2009, 05:07 PM

Hi,
a pair of 3875 will operate well with a transformer bewteen 120VA and 240VA.
The only reason to select higher VA rating is to gain the advantage of the lower regulation available with bigger transformers.

Anything bigger than 400VA is wasting money and space.
What's the difference in regulation of 400VA and 500VA? Have you even asked?

7th May 2009, 11:59 PM	#1
GAH diyAudio Member Join Date: Apr 2009	Any issues? - Antek 400VA - 20v dual Sec for LM3875 Gainclone kit I'm considering building Peter Daniel's LM3875 Gainclone Kit to use with 8 ohm speakers. I live in Fiji that uses 240 volt mains. Are there any issues with using a Antek 400 VA with 20v dual secondaries toroidal transformer with this kit. For example: 1) is 20 volt on the secondaries enough to gain optimum performance from this amp? 2) Would the 400 VA trannie require some sort of soft start circuitry etc? Or would I be better off buying a better quality transformer with 22 to 25 secondaries? Regards Glen

8th May 2009, 07:29 AM	#2
pacificblue diyAudio Member Join Date: May 2008	What is optimum performance for this amp? Depending on the capacitance in your power supply you can expect 30 W ±10 % into 8 Ohm. If that is fine for you depends on the speaker's effciency and your average listening volume. The 400 VA transformer would probably be okay without, but it is nevertheless good to have a soft-start, because you may have other appliances connected to the same circuit and the inrush current combined with the other consumptions could lead to convenience tripping of the fuse/circuit-breaker for that circuit. A transformer of half the power rating would be enough even for two amplifier channels at 2x20 V. BTW, why is it called "convenience blowing", when it is really inconvenient, if it happens? __________________ If you've always done it like that, then it's probably wrong. (Henry Ford)

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8th May 2009, 02:16 PM	#3
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	what is the primary (mains) voltage of the Antek transformer?

8th May 2009, 05:43 PM	#4
quadtech diyAudio Member Join Date: Oct 2007	Anteks typically come with dual 115V primary windings.

9th May 2009, 03:59 PM	#5
GAH diyAudio Member Join Date: Apr 2009	Thanks your comments and advise. This Antek has dual 115v primaries. I intend to use Harbeth SHL5 speakers with the amp. I would rather use a trannie that will provide a bit more power output which may better suit these speakers.

9th May 2009, 05:07 PM	#6
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, a pair of 3875 will operate well with a transformer bewteen 120VA and 240VA. The only reason to select higher VA rating is to gain the advantage of the lower regulation available with bigger transformers. Anything bigger than 400VA is wasting money and space. What's the difference in regulation of 400VA and 500VA? Have you even asked?