Output transformer sizing...again...

[rsumperl]

Greetings one and all,
Just want to make sure I am on correct by saying if I use let's say a 30w transformer in a 100w application, even if the impedance is correct, I will lose low end at high power.

Thanks,
Ray

[Yvesm]

More or less . . .

Just compare a 100W Marshall guitar amp to a 30W McIntosh . . . but not the same design nor the same goal

[pjp]

Wont you ruin your output tubes when the transformer saturates ?

[Yvesm]

Originally Posted by pjp

Wont you ruin your output tubes when the transformer saturates ?

Could be . . . if the PSU does not limit the current before
Just insert some hi pass filter, like lo value link capacitors

[kevinkr]

Originally Posted by rsumperl

Greetings one and all,
Just want to make sure I am on correct by saying if I use let's say a 30w transformer in a 100w application, even if the impedance is correct, I will lose low end at high power.

Thanks,
Ray

You'll probably saturate the transformer long before you get anywhere close to your target power level, particularly at frequencies below 100Hz or so. Not a particularly good design approach if you are looking for anything approaching decent linearity. It all depends on how the core handles the higher flux density, and what sort of other losses are present. (copper, etc) This might be ok in a guitar amplifier though..

[TheGimp]

I would also be concerned about heat and the bias current thorugh the transformer. How much current is the 30W transformer rated for? How much bias current will you be running?

The wire may not like it.

[tubelab.com]

Wont you ruin your output tubes when the transformer saturates ?

This is an often overlooked possibility. I have seen red plateing in my red board when cranking too much power through too small of an OPT. Swapping out the OPT solved the problem. Usualy the sound quality is poor at this point so you won't keep cranking the volume. The results of using a small OPT in a guitar amp can be disastrous.

Way back in the 60's I played in a band. The old wives tale of the day was "don't play bass (guitar) through a Bandmaster, you will blow it up". One of the guitar players had a Bandmaster (and parents with too much money) so he tried it. It did sound rather cool for a while, then the tale proved to be true. I didn't understand the reasons at the time, but now I know that the tiny OPT was severely saturated and the 6L6GC's had to eat all of the power, until one blew up.

If your speakers have a high impedance below 80 Hz or so you can often get away with pushing the ratings a bit. If you use a subwoofer and an active crossover in front of the amp, so that the amp sees no low bass, then the ratings can often be abused....a bunch, like twice the rated power.

[rsumperl]

I'm still playing with the 3.3K, ~30w transformer I got on eBay. Edcor now says my order will ship 10/18. If they truly ship on 10/18, my order will be 10 weeks from time of placing it to shipment.

[BudP]

my order will be 10 weeks from time of placing it to shipment.

Dead normal amount of time. Had you ordered from me it would have been 8 weeks for a custom part. I would be two weeks quicker because I run a smaller operation. Only my distributors have any finished stock and then only for the SLO clone market of 100 watt OPT's.

You must understand that it takes as much time to run one part as it does to run 100 parts, except for the actual labor of making the thing. And even there a competent crew can make 5 to 7 parts of a known product compared to making one of an unknown product.

[rsumperl]

Do you have a website?