Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Amplifier Discussion => Topic started by: syndromet on March 12, 2007, 03:36:14 PM

Title: I'm about to order my transformer
Post by: syndromet on March 12, 2007, 03:36:14 PM
Just to be absoloutly sure, I wanna check with you guys (once again...) that I'm ordering the right transformator for my stereo LM1875 kit. Don't want to buy a trafo for $100, and find it's not suiteable for the job.

This is what I'm looking at: http://www.elfa.se/pdf/56/05612569.pdf (http://www.elfa.se/pdf/56/05612569.pdf)
Would this be good for my purpose?

Looking at the prices, I see that transformersare way cheaper over at parts express than here in Norway. Unfortunatly they wanted to charge me $79 for shipping it via USP Express. That got me thinking about ordering it to one of you guys, and having you to ship it with USPS to me for way cheaper. If anyone feel like helping me out with this, please let me know.
Title: Re: I'm about to order my transformer
Post by: joecool85 on March 12, 2007, 07:26:38 PM
Well, its about twice the VA rating you need for a dual LM1875 setup, but it should work great.  The voltage output is near perfect, so I'd go with it.  But if you can find one the same but with maybe...100-150VA that would be fine as well.  Of course, as I always say, it's better to have more than needed.  That's how I build my amps.

For $53 I could have this: http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=122-610 (18+18v toroidal) at my door. 


Shipping included I could get it to you (after it gets to me) in 4-6 weeks for $75 USD total, or in 4-6 days for $85 total.  Not a huge savings and it could potentially take a really long time to get it since it would have to get to me first and then get shipped again.
Title: Re: I'm about to order my transformer
Post by: ApexJr. on March 12, 2007, 08:45:08 PM
Joe Cool is quoteing Air Mail which I find to come out to 7 - 10 days
and surface mail which takes 6-8 weeks

Now another way is to fit it in the Global Priority Envelope and I charge
$12.50 to ship and thats 3-5 days unless it gets caught in customs.

I have a couple of toroids you might consider

1 ----   0 - 120-   0 - 120 Voly Primary
           21  -  0  -  21 volts      42 Vct       80Va  @  $12.50 ea

2 -----  2 X 120 Volt primary
            2 X 25V Secondary             $17.95ea
These are pictured on my website at www.apexjr.com under misc

And I can fit 1 of these in the envelope ...

Steve @ Apex Jr.

Steve
Title: Re: I'm about to order my transformer
Post by: syndromet on March 13, 2007, 04:23:55 AM
that are some great prices, ApexJr, but doesen't those transformers put out a little to high voltage?
Title: Re: I'm about to order my transformer
Post by: joecool85 on March 13, 2007, 06:13:37 AM
A little high voltage, not not high enough VA ratings.  21+21v is really the max you could run, so it *should* work. 

Ideally for a dual LM1875 setup you should have 18-20v secondaries and between 100-150VA rating.
Title: Re: I'm about to order my transformer
Post by: ApexJr. on March 13, 2007, 11:27:28 AM
I have been selling all 3 of those toroids listed on my website for the chipamp
boards made by BrianGT, and Digi01 and people making there own,
There is also a LM 338 Regulator board around to limit the voltage to the chips
There are 3 or 4 chip boards out there using the LM 1875, LM 4760, LM 3886 and
can't remember thr other one so you do have choices...

Also since the price is right customers have been buying 2 each of the 21-0- 21 Volt
one for each channel.

Steve @ Apex Jr.
Title: Re: I'm about to order my transformer
Post by: joecool85 on March 13, 2007, 01:02:54 PM
21-0-21 is going to be a little closer than I would want to be on the max voltage of 60v.  21 + 21 = 42 x 1.4 = 58.8v DC.  If your line voltage was just a little high, it could easily put you over 60v DC.  While it probably does work fine in *most* circumstances, I would hate to say to anyone that it is totally ok to use it.
Title: Re: I'm about to order my transformer
Post by: syndromet on March 14, 2007, 09:56:59 AM
ApexJr, I'll try with one of the 21-0-21 trafos. Line voltage where I live is just 225V, and since I'm only planning to use the amp at home it should be OK.
Title: Re: I'm about to order my transformer
Post by: ApexJr. on March 14, 2007, 12:30:07 PM
Syndromet..
OK, THe toroid is $12.50 and so is the shipping Total 25.00

PM Me at   steve.apexjr@prodigy.net  and we can work on payment

Steve @ Apex Jr.