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-   -   Cheap and nice looking SE OPT (http://www.diyaudio.com/forums/tubes-valves/104478-cheap-nice-looking-se-opt.html)

mus 1st July 2007 10:28 AM

Cheap and nice looking SE OPT
 
Hi,

Has anyone had experience with this SE OPT?

http://cgi.ebay.ca/Output-Transforme...QQcmdZViewItem

I'm wondering is it good for HiFi use? Thanks.

Sal Brisindi 1st July 2007 01:33 PM

I spoke with the seller about a month ago, he said these audio transformers were designed mainly for guitar amplifiers and not audio. He is thinking of designing audio transformersand having them made in Asia in the future.. I am not sure these are them. You can ask.

Regards,
Sal Brisindi

pftrvlr 1st July 2007 04:10 PM

What are the difference between audio opt and guitar opt?

Jeb-D. 1st July 2007 06:09 PM

Quote:

What are the difference between audio opt and guitar opt?
Bandwidth.

Usually guitar OPT's only go down to 100Hz. And some times the upper frequency is limited as well.

tubelab.com 1st July 2007 06:59 PM

The range of fundamental frequencies of a guitar run from 82Hz to around 1000Hz depending on the number of frets. Harmonics range up to 10KHz. Many guitar amp OPT's are designed with this in mind.

A guitar OPT is often wound with cost as the primary factor. There is usually NO interleaving, and there is less iron which is usually power transformer quality. This usually will reduce the bandwidth at both ends of the audio spectrum. Most P-P guitar amp transformers are usually wound with one primary half on first, then the entire secondary, then the other primary half. This causes one primary half to have a higher DC resistance than the other half, although I have seen transformers wound with a larger wire on the outer winding to compensate. Phase balance between the two halves is less than perfect. The efficiency will be poorer than an equal size HiFi OPT due to the poorer iron.

Now that I have trashed the thought of using a guitar amp transformer for HiFi, I must state that there are some guitar transformers out there that do quite well for HiFi in spite of their limitations. My 300Beast (300B P-P) uses guitar amp OPT's. I have tried several other transformers, and I still come back to the $16 Ebay guitar amp transformers. I am running an "80 watt" transformer at 30 watts which makes up for the smaller iron. The HF response rolls off (-3db) at 20 KHz which is still better than my aging ears.

Each transformer will be different, so the only way to tell would be to try one.

pftrvlr 1st July 2007 07:45 PM

I sent a email regarding the frequency range to the seller. Will post the response.

pftrvlr 1st July 2007 11:59 PM

Here is the response from the seller:


It's designed to cover the range of a guitar speaker, 82Hz to 6KHz. It would not generally be usable outside of Guitar or radio applications.

mus 2nd July 2007 04:57 AM

Thanks, everyone!

lt cdr data 2nd July 2007 10:43 AM

and don't forget, guitar tx's are possibly designed to saturate a bit for part of the distorted sound, too.

its not just the preamp sound which causes guitar amp distortion.

preamp distortion is asymetrical clipping, single ended.

you have phase splitter distortion,

power amp distortion, push pull symetrical clipping.

your tx may saturate

your speaker may distort, too

and your power supply may sag.

all are integral for an 'interesting' guitar amplifier,

its the whole darn thing distorting, which is why just rack guitar preamps don't give the full works, as that's just preamp distortion.


what's the difference? smaller cores to start with.

that one is only 2 lbs, so won't do a 300b which needs absolute minimum of 4 lbs, 2 kg or so, typical chinese entry level
7lbs better, 3-4 kg average tx for a 300b
12lbs about the best, 5-6kg, top end

does say its interleaved tho'


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