8/31/2025 Updates

Struggling these days to buy smaller quantities of transformer parts due to "de minimus" changes.  Unfortunately, while you can still buy some steel and plastic in the USA, minumum buys are often a 3-4 year supply for MPS.  Right now with imports from EU/CA/MX requiring all small entries to see a US Customs broker... nothing is moving.  UPS has had one of my Bobbin and Cover airfeight parcel imports held up in Kentucky for 3+ weeks after it arrived in KY in 4 days.  I can't get a response from the broker....  so this is not just a "Post Office" issue.  Basically 90% of parcels under de minimus bypassed Customs and Border Patrol.  Now they don't.  CBP staff has increased on the Border Partol side- not the Customs side where there is a freeze still in place.  So from that perspective it seems like there is a large lack of planning in goverment currently.   You won't collect billions of dollars in tariffs, not even my $300, if you aren't staffed to plan.  Just Sayin'.

MPS USA will just work with materials we have until this settles out.  May need to get a bit creative!

Previous update 8/17/25

We've had a spurt of activity on Guitar Amp Transformers this Summer.  Generally when a customer asked for something interesting we build 2 or 3 extra and drop them out on the eBay store to see what sticks.  Here's some recent requests-

PT340.2 USA Laydown Champ/Princeton sized PT:
The ask was to beef up the 5V rectifier winding to a solid 3A.  We went larger on the core stack (2IN) vs original size for more heater power.  

OT22PP-DLX-8 USA:
We've had some 7/8 x 1.25IN bobbins, frames and coil covers available.  The idea was to get the same range and performance of the larger OT22PP-HC100 6600 Ohm x 4/8/16 onto the same 2-hole mount (3.125") as most BF Deluxe Chassis's (AB763).

OT12PP-8K4x8 USA:  drop-in for Princeton Reverb type 12W to 15W with 8400 x 8 ohm ratio, built in USA and shielded.

OT19PP-STD-USA had more requests for the 2-hole Mounting Frame version (3.562" Centers).  These drop into the Marshall 18W (1974)  and 20W (2061) amps.  We'll try to keep these in eBay stock going forward

OT5SE-10K-USA-  The "AC4" type low power 4-5W OT

OT10PP-10K-USA-  OT along the lines of the Wright 1580 OT

HiFi-  Having difficulty getting a steady supply of the Hi Perm Z11 laminations in 1INCH size as used in many of my HiFi offerings including the OT19PP-DYN35 v20.  WE worked thru a "Version23" backup plan in 29M6 evaluated by a key customer.  We stayed with the 2400Turn input winding (Dynaco original) and adjusted the lamination stacking for best low end power.  Listening results were good.  Testing of similar coils/cores yielded power at 10W(20Hz), 15W(25Hz), 20W(30Hz) vs the Dynaco OEM 17.5W from 20Hz on the same test stand.  For reference the Z11 v20 tested our at 14W (20Hz) 20.25W(25Hz) and 21W+ from 30Hz to 20KHz.  We will keep going with v23 builds using 29M6 until we can get a new Z11 Hi Perm source on line.

Worked on  300-B Single Ended HiFi PT's and OT's for this past month for Stereo and Monoblock amps:
PT780M-SD-USA for Monoblock (780Vct 100mA 3xFilament)
PT780P-SD-USA for Stereo power (780mA 200mA 4xFilament)
L5M100-SD-USA choke 5H@100mAdc
OT20SE-HF-3K5-USA  (80mAdc 3K5 x 8ohm)

680Vct Laydown Power Transformer for Champ/Princeton style chassis- 
Full 3A Rectifier heater power on oversized lamination stack.

Deluxe Reverb Output Xfmr- oversized bobbin, stock 3.125" mounting centers

HiFi OT's in EI-1 INCH & EI 1-1/8INCH sizesChrome Covers available now

Other recent New Stuff 

Working on several HiFi projects & now have an assortment of better looking covers for HiFi projects including painted and a polished plated version.