EDCOR Output transformer for 300B

[jackm]

I am building my first 300B SE (Audio Note type design) and I found EDCOR CXSE OPTs are nice.

I tried to contact EDCOR for advices but got no response.

Can any one please tell me the difference between them and recommend one for 300B SE apm?

CXSE25-8-2.5K

CXSE25-8-3K

CXSE25-8-3.2K

Thanks a lot
Jack

[SemperFi]

The GXSE15 series are better than the CXSE25s.
Go for the 2.5k version.

[tubelab.com]

The GXSE15 series are better than the CXSE25s.

That is not generally the case. The GXSE is a smaller transformer intended for use in guitar amps. The CXSE25 is a large (about 10 pounds) OPT intended for use in HiFi amps. In my opinion the CXSE25 is by far the best SE OPT that you can get for under $100.

Go for the 2.5k version.

A 300B in most circuits wants to see a 3 to 3.5K ohm load. That is the accepted norm. Reducing the load to 2.5K would offer a slight increase in power but a considerable increase in distortion with a loss of damping factor. I tend to favor going the other way. I use a 5K CXSE25 in my 300B amp. This drops the power output slightly but also lowers the distortion and raises the DF.

Examine the characteristics of your speakers. An "8 ohm" speaker is rarely 8 ohms and may be 8 ohms at only one frequency. The impedance VS frequency curve should be available from the manufacturer. If the curve is below 8 ohms a lot, then go for a higher value of OPT. If the curve is above 8 ohms a lot, you consider a lower valued OPT.

[SemperFi]

I must have mixed up which OPT. I didnt check, only used memory. Scary!!! I mean the opt with BW from 40Hz, not the ones from 100Hz (the guitar versions). The 15watt version I meant is the same size as the 25watt version I thought he meant.
Im not going to argue with u about best impedance, u are a lot more experienced than me

[kevinkr]

Originally Posted by jackm

I am building my first 300B SE (Audio Note type design) and I found EDCOR CXSE OPTs are nice.

I tried to contact EDCOR for advices but got no response.

Can any one please tell me the difference between them and recommend one for 300B SE apm?

CXSE25-8-2.5K

CXSE25-8-3K

CXSE25-8-3.2K

Thanks a lot
Jack

Since you live in New Zealand you might also want to check out Silk from Thailand, and James from HK - both of which I'd think would offer affordable alternatives to Edcor, particularly when you factor in the shipping costs from the U.S.

I've no direct experience of transformers made by Silk, however they are very well regarded in Asia, (by friends of mine) and James makes very good transformers indeed based on my very limited direct exposure to them.

If you tried to contact Edcor within the last few days the Labor Day holiday may be why you have not heard back from them.

George is right, 3K - 3.5K is ideal where you are trying to extract maximum power without excessive distortion, and 5K provides exactly the benefits he elucidates.. All of my commercial 300B SE amps used 3 - 3.5K opts, the PP amps 3.8K - 5K..

[807tubenut]

You contacted Edcor, and got no response?


That's quite odd, Iv never had a issue calling, and when i send a email, its (at most) 2 days for a proper response.


Try contacting Phyllis!

Phyllis Weston
EDCOR Electronics Corporation
7130 National Parks Hwy.
Carlsbad NM 88220
Phone (575) 887-6790
Fax (575) 887-6880
pweston@edcorusa.com

[jackm]

Thanks a lot everyone, I think I have learnt something

I will check my speakers' "VS frequency curve" before making decision on the input impedance of the OPT. I am using a pair old Tannoy M15 which I am still loving..

I will talk to Phyllis at EDCOR about the options and cost tomorrow as it is too late in US.

Good to know the alternative OPT (Silk from Thailand, and James from HK, I will check them out as well.

Cheers

Jack

[CLS]

James is in Taiwan:

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[jackm]

I have checked the Silk OPT and James OPT, they both look very nice with outstanding test results vs others, but they cost more than the EDCORD CXSE25-8-3.2K (us$83/each).

Also talked to Phyllis at EDCORD on phone (they just back from holidays), she said that the shipping cost of a pair of CXSE25-8-3.2K to NZ will be US$48.00 only.

Given that 2 x EDCORD CXSE25-8-3.2K plus shipping to NZ= us$214, I believe I will go for the EDCORD in my first SE AMP.

Thanks again everyone

[mashaffer]

BTW, no "D" on the end of Edcor.