Output transformer for Akai M8

Hello,

I recently acquired an Akai M8 for conversion to a pair of monoblock SE tube amps.  Unfortunately, one side does not output and I have tested the output transformer and it failed.

I compared it to the other that works and the primary taps differ greatly.  I get 3.4 ohm across the bad one and 454 ohms across the one that works.  Both secondaries were 2.4 ohms.

Any line on getting an exact replacement from anyone?  I want them to match.

Thanks,

James

Hi James,

I have two or three outputs from either M7 or M8.  Send me a PM and I'll dig them up and check the DCR.  Do yours have a part number?

Yours,
Mike

I measured one of these when I did the frequency response test you can look at on my Google Drive share linked in the Chamber post titled "A Bunch Of Transformer Frequency Response Curves".  I came up with 8k:8 ohms measured impedance ratio.  Found that reflected impedance on the secondary was little effected between 6k - 8k on the primary. So I measured response with 6k and 8k on primary to 8 ohms and found little difference in response. Very nice little OPTs with pretty flat response between 20 - 20k, if I recall correctly.

So I think you'd want to look at replacements specified around 7k:8.  Optimum load resistance for the 6BQ5 (used in the M8) in SE config is between 4500 - 7k, so my experience with it aligns pretty well to that.

Hope this helps.

BT

Hi,

Thanks BT. That helps a lot.

James

Hi,

I got a new OT in a trade with a GroupDIY member and replaced most of the electrolytic caps in the amp. It is working beautifully now.

Thanks all.  Learned a lot.

James

Glad to hear it, James. Enjoy!

BT