OT transformer mismatching

[catalin gramada]

Hello All
Have to replace a smoked OT transformer into a power amp. The tranny is a Hammond 3400k primary impedance. I allready have in stock his brother of 6600k and thinking to use this one, using 16 ohm output tap for 8 ohm speaker load. The power ,primary current capability is allright in respect with original but my concern regards the transfer function, freq reponse. Do You think will be any diferences in sound , please ? Thank You.
Best regards
Catalin

[Silvertone Jockey]

In my limited experience it should sound great. I have replaced 3 different OT on 3 different amps using what I had available and it always sounded good to me. Will it sound the same? probably not. Would a casual listener or you 6 months from now be able to tell the difference? Unlikely. My vote is go for it. Other more experienced techs may disagree and you should listen to their advice before mine YMMV

[The Dude]

If you have doubts, hook it up and try it. You don't have to drill holes or mount it up to give it a whirl. Let your own ears be the judge.

[catalin gramada]

Hi.
I know what you mean, but is not my amp and is not a project aso. I thinking to do a "economy" using what I have in my house.
I did a test using 16 ohm output with a 8 ohm resistor load, that means my 6600k present a 3300k impedance to power valves, pretty close to original 3400K. The current draw in overdriven condition reach 160 mA and is in range of mine 200mA capabilities. The irons of both trannies looks the same size. Both transformers are from the same series. Only diference is the original was designed for 3400k and have biger current rating.I just wonder if will sound the same, please ?. ( I had not the oportunity to hear it before)
Cheers
Catalin

[The Dude]

If it's not your amp or a customer unit, I would discuss it with the customer. I wouldn't think it would make the amp sound horribly different. In a side by side comparison you might notice the difference, but that won't likely be the case. Explain no shipping costs, repair will be done quicker, etc. and see what he says.

[catalin gramada]

Thanks for support but hope someone can offer a tech explanation if works,please. If both are electrical equivalent and have the same irons does it exist any reponse diferences, please? 3400k OT 8ohm tap/ 8ohm load vs 6600k OT 16ohm tap/ 8ohm load replacement. Thanks
Cheers
Catalin

[pdf64]

See http://music-electronics-forum.com/t32435/#post295064
For a guitar rig, I can't see that the difference would have much if any impact.

[Enzo]

And don't get caught up in thinking impedance is the only thing that might be different. Transformers are complex things having inductance and other qualities.

[catalin gramada]

So,as conclusion: have to understand that will be a poor implementation and not a perfect matching, and not a "engineering way" for sure. Maybe it works, but in different way than circuit was designed for. Thank You.
Best Regards
Catalin

[Dave H]

So,as conclusion: have to understand that will be a poor implementation and not a perfect matching, and not a "engineering way" for sure. Maybe it works, but in different way than circuit was designed for.

I'd ignore all that. Why not try it? You are not going to let the smoke out so all that really matters in a guitar amp is how it sounds. It could even sound better than the original.

[catalin gramada]

Hi,
hundred procent agree but was not the point. My concern was if I can do a perfect matching equivalence using a double rated tranny impedance with half of load. My knowlegements are pretty limited regards transformer phisics. As Enzo says over impedance matching there are many other parameters which can afect the transfer function. If those parameters are not the same as original or in range at least I have not a perfect matching in my understanding.
Btw. I tried it and works spectacular. Thank you.
Cheers
Catalin

[Dave H]

I'm glad it's working great

It doesn't have to be perfect matching. It's not driving an 8 ohm resistor. Have a look at the impedance/frequency curve of a speaker. The impedance is all over the place.