F Series First Watt Transformers

hifimaker · 20th November 2008, 12:16 AM

I'm perfboarding an F1 and maybe an F2. Is a 250va 18-0-18 toroidal transformer undersized for a mono bloc for these amp types?

What would be the ideal VA rating?

Thank you!

-David

gl · 20th November 2008, 12:36 AM

Hi David,

You're fine for a monoblock. Some might even consider 2 chans from that transformer.

Graeme

Nelson Pass · 20th November 2008, 01:11 AM

VA ratings are a bit dicey. One manufacturer's 250 VA is another's
100 VA.

hifimaker · 20th November 2008, 01:20 AM

Thanks guys for the help.

I'm looking at an Avel-Lindbergh Y23 series. They have a 160VA and 250va in 18-0-18 at Parts Express with a free shipping special offer.

They seem like a good vendor and could probably assume the VA ratings are accurate?

-David

GRollins · 21st November 2008, 02:02 AM

Avel Lindberg is all right in my book.
The thing about VA vs. Watts is that sometimes it's apples to apples and sometimes it's apples to elephant boogers. Setting aside the relative quality that you might expect from one manufacturer or another, the VA only equals W if the load is purely resistive. Once the load becomes reactive (not to be confused with radioactive), then you get into power factor correction. Depending on how far off the current and voltage peaks are from one another, you can get wildly differing numbers.

Grey

preiter · 21st November 2008, 02:33 AM

Have any recommendations for choosing a transformer then?

I was also looking at the Parts Express transformers. Is the 225VA enough for an F4? The next step up is 330VA. They don't have 18-0-18 in that size, but I could get 35-0-35 and wire the primaries in series.

Babowana · 21st November 2008, 02:54 AM

I'm using 18-0-18 300VA covering both channels for F4.
I don't see any problem at all.

>>

<<

SCD · 21st November 2008, 05:13 PM

I built mine with Plitron.
Very nice transformers. It runs cool and is dead quiet.

Tea-Bag · 21st November 2008, 07:38 PM

I use these puppies from ANTEK 18v+18v @ 400VA.

No problems with them. I think Nelson tested a members at one point and found them acceptable. They are fairly inexpesive.

http://cgi.ebay.com/18-18V-400VA-Tor...3286.m20.l1116

hifimaker · 21st November 2008, 07:39 PM

This is the best audio forum. Thank you so much for the guidance. I wish I could buy you all a beer.

-David

20th November 2008, 12:16 AM	#1
hifimaker diyAudio Member Join Date: Oct 2003 Location: San Jose	F Series First Watt Transformers I'm perfboarding an F1 and maybe an F2. Is a 250va 18-0-18 toroidal transformer undersized for a mono bloc for these amp types? What would be the ideal VA rating? Thank you! -David

21st November 2008, 02:54 AM	#7
Babowana Formerly "jh6you". R.I.P. Join Date: Jul 2006	I'm using 18-0-18 300VA covering both channels for F4. I don't see any problem at all. >><<

21st November 2008, 05:13 PM	#8
SCD diyAudio Member Join Date: Nov 2003 Location: 1/2 way up Vancouver Island	transformers I built mine with Plitron. Very nice transformers. It runs cool and is dead quiet. __________________ SCD

21st November 2008, 07:38 PM	#9
Tea-Bag not politcally affiliated diyAudio Member Join Date: Feb 2006 Location: Kennebunk Blog Entries: 11	ANTEK I use these puppies from ANTEK 18v+18v @ 400VA. No problems with them. I think Nelson tested a members at one point and found them acceptable. They are fairly inexpesive. http://cgi.ebay.com/18-18V-400VA-Tor...3286.m20.l1116

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20th November 2008, 12:36 AM	#2
gl diyAudio Member Join Date: Dec 2003 Location: Sierra Foothills - California	Hi David, You're fine for a monoblock. Some might even consider 2 chans from that transformer. Graeme

20th November 2008, 01:11 AM	#3
Nelson Pass The one and only Join Date: Mar 2001	VA ratings are a bit dicey. One manufacturer's 250 VA is another's 100 VA.

20th November 2008, 01:20 AM	#4
hifimaker diyAudio Member Join Date: Oct 2003 Location: San Jose	Thanks guys for the help. I'm looking at an Avel-Lindbergh Y23 series. They have a 160VA and 250va in 18-0-18 at Parts Express with a free shipping special offer. They seem like a good vendor and could probably assume the VA ratings are accurate? -David

21st November 2008, 02:02 AM	#5
GRollins diyAudio Member Join Date: Feb 2001 Location: Columbia, SC	Avel Lindberg is all right in my book. The thing about VA vs. Watts is that sometimes it's apples to apples and sometimes it's apples to elephant boogers. Setting aside the relative quality that you might expect from one manufacturer or another, the VA only equals W if the load is purely resistive. Once the load becomes reactive (not to be confused with radioactive), then you get into power factor correction. Depending on how far off the current and voltage peaks are from one another, you can get wildly differing numbers. Grey

21st November 2008, 02:33 AM	#6
preiter diyAudio Member Join Date: May 2006	Have any recommendations for choosing a transformer then? I was also looking at the Parts Express transformers. Is the 225VA enough for an F4? The next step up is 330VA. They don't have 18-0-18 in that size, but I could get 35-0-35 and wire the primaries in series.

21st November 2008, 07:39 PM	#10
hifimaker diyAudio Member Join Date: Oct 2003 Location: San Jose	This is the best audio forum. Thank you so much for the guidance. I wish I could buy you all a beer. -David

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