Ordering guitar amp OT

[hayun]

How that?

Oh I was half joking.. maybe the tone was wrong, limited English thing..
just on the fact that old Schumaker OT of Fender was obviously not interleaved.

I wouldn't say that. Both started out using audio transformers that could be sourced locally.

Again, half joking

And, Marshall literally copied the Fender Bassman (as best they could using available components) so they could market an amp at a lower cost than the imported Fenders.

Yes, I agree with those, Both did what they could and made legends. Fender has credit to originality, Marshall had an advantage in cost

[martin manning]

...old Schumaker OT of Fender was obviously not interleaved.

I believe the larger OT's were interleaved.

[hayun]

I believe the larger OT's were interleaved.

Based on the post on DiyAudio I linked;

https://www.diyaudio.com/community/thre ... st-5260982

the Schumaker OT was from 80’s, rated 80w. So it could be tweed twin, maybe late CBS era.. hard times.
And usually Fender OT is smaller than Marshall’s with same rating. Size is the important facter on the structure of OT

..I think they‘d have improved after all.

Ironically, Fender has a more hi-fi feel than Marshall. (again, half joke.. when it comes to OD sound, that’s different story, and the bandwidth of guitar sound is very narrow anyway..)
man I shouldn’t joke with poor English.

[Helmholtz]

I've measured quite a few Fender OTs and can state that the ~45W types (Triad, Schumacher, reissues) all measure excellent (better than the Drake 784-139) having high primary inductance and very low leakage, making me assume they have at least 5-fold interleaving.
Higher grade laminations allow for smaller size.

[martin manning]

Someone must know for sure, but I thought the 50 and 100W output transformers from the late 50’s and 60’s made by Schumacher (note spelling) were interleaved.

[Helmholtz]

Someone must know for sure, but I thought the 50 and 100W output transformers from the late 50’s and 60’s made by Schumacher (note spelling) were interleaved.

Thanks, editing my post above.
No doubt about the interleaving.
What counts is measured data, not construction details.

To my knowledge the Fender '59 BM OT was a Triad 45249. I measured an original.

[GrayDigger]

Would it be inappropriate here to ask your process(es) for quantitatively measuring a transformer and inferring (I.e non-invasively) construction/quality of components?

[hayun]

I apologize for making sloppy statements based on only fragmentary information.

Thank you guys for sharing valuable information from your long experience. I learned a lot.

[Helmholtz]

Would it be inappropriate here to ask your process(es) for quantitatively measuring a transformer and inferring (I.e non-invasively) construction/quality of components?

E.g. leakage inductance is measured at the primary with shorted secondary.
I use my PeakTech 2170 LCR meter at 1kHz.

[GrayDigger]

Copy. Thank you!

[nuke]

Just remember that the internet is full of doo-doo-heads everywhere.

While there were guitar amps "..made cheaply and hap hazzard" the good ones were not.

Heck, the Silvertone 1484 I just restored, was clearly designed by qualified electrical engineers (at Dan Electro), and it was competently manufactured. It also sounds remarkably good. I did a quick check with an LCR bridge and I'd wager there was a decent interleave in the OPT.

They tend to get maligned, since they're built to a cost point, but they're surprisingly good. The point-to-point wiring is harder to work on, and people who haven't worked on PtP wiring won't like it, but as PTP goes, it is pretty good.

Many guitar and bass amps were built with Dynaco hi-fi transformers, such as Sunn. Those are really very good hifi transformers. It was the secret to the Dynaco/Dynakit amps. Heck, they were the basis of some incredibly good early Audio Research monoblock tube amps.

For my money, I'd spec a hi-fi transformer with a big core. Lots of iron is good in my book, and bandwidth high and low, is also worth it.

[hayun]

Thank you for the reply! I’ll keep that in mind.

Actually, I'm a bit skeptical now about OT replacement for ‘lo-fi thing’.
As far as I gather information, including your advice, it would be not that worth it I suppose..

And the more crucial part is;
I think the problem was on PT, not OT.

I suddenly realized, It seemed like the PT was ringing..
When I flip the bright switch(4.7n) or just crank it up, I can hear some constant buzz on top end. (it’s not the thing I concerned about OT though)

At first I thought it is from outside of amp, or some ground noise.. but I couldn’t find a way to get rid of it.

Today I tried to install CRC snubber on HV secondary, the buzz is completely gone!
Moreover entire sound of the amp became somewhat more stable.

[solderhead]

My recollection of the complexity of interleaving, as far as Fender OTs go, is pretty simple -- the cheap OT that mount using 2 bolts, (ie: the low power OTs) were minimally interleaved if at all. The larger 4-bolt OT's in the 40-50W+ amps is where Fender started spending money on interleaving, with formulas that had ratios somewhere around 5-7. I can't quote any forensic disassembly data, but that's my recollection from decades of talking to the people who've done bulk winding for me.

I think Pete Farrington / @pdf64 might have some knowledge in this area.

[Helmholtz]

Some Fender OT primary to secondary leakage inductance data:

- '59BM, BF SR originals and reissues: 5mH to 8mH,
- BF Twin: ~6mH,
- Vibroverb, Vibrolux Rev.: ~90mH,
- Deluxe Rev. : 15mH to 18mH,
- Super Champ, Princeton Rev. : 9mH.

Marshall OTs with 16 Ohm secondary shorted:

- '66 JTM 50 (Drake 784-128): 17mH
- JMP 50/2204 (Drake 784-139): 11mH
- '67/68 100W Plexi (Dagnall): 14mH.

[martin manning]

Interesting, thanks for sharing your data.