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Musical Power Supplies, Inc.

Lake St Louis, MO 63367




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MPS New Projects

New PT285Mi-  Created a version of the PT285M using the Dual Voltage Mains approach from the PT275Mi.  Theres a PDF attached to the Product Page now.   So this will have (2) parallel 120Vac mains- used in parallel concetion for 120VAC/60Hz and in series for 240Vac/50Hz.  120/240Vac:  285-0-55-285Vac (150Ma): 3.15-0-3.15Vac (4A): 5/6.3Vac (2A).  Basically a good option for Marshall 18W and Vox AC15 projects if you want to use a surface mounting PT and need dual mains.

I've picked up some EI7/8 x 1-1/4in Bobbins.  The 1st thing we wound on that was a version of the OT17PP called an OT17PP+VOX (8K: 4/8/16 ohm 20VA 25Hz-20KHz) using a 5-section interleave.  With the extra iron I should be able to create HiFi versions of the OT10SE and OT17PP or 20PP .

It has been VOX month.  Besides the OT17PP+VOX, I was also asked to build a Laydown version of the PT285M power transformer.  Also worked out a small PT205.1 power transformer for a Lil Night Train (See gallery pix).  Might need to drop the B+ just a bit more on that one, but it seems to be somewhere in the 260Vdc to 290Vdc range.  If you know the exact B+ target, drop me a message.  This will pair up nicely with the OT2PP or OT5PP+ output transformer for repairs and upgrades

Current new projects include:

PT110.1 (USA)- EI87 Power Transformer-  There has been some activity for small 50L6 and similar tube guitar amps lately. This is a small power 20VA transformer the size of an OT20PP USA in VC87 covers.  Specs 115/120Vac Mains & 110-0-110Vac (Approx 150Vdc B+) at around 40mA.  We did one with a 50Vac heater.  It should fit in a pedal......  This is a variation on the PT190.1 and PT240.1 design for 2W - 3W amps.

Other USA

PT260.2 Version has been running lately.  It's similar to a Hammond 270D but with a 55V bias tap & center-tapped Heater.

PT275Mi has been running fairly often on custom orders.  It's basically a little larger 275-0-55-275 Vac (120mA) + 3.3-0-3.3Vac(3A) and 5/6.3Vac(2A) heaters.  I've been setting this up with a pair of 120Vac mains windings that are used in Parallel for US (120Vac) and in Series for Int'l (240Vac) operation.  I have a PT330Mi and PT285Mi design ready and proven as well.  

2016 Amp Build Project

It seems like I find time around the holidays each year to build myself an Amp.  This year I built a Classix Audio NSV6B kit with custom OT20PP (5K1:8ohm) and PT290.2  updated Traynor Bassmate 20 6v6 circuit .  My first PCB based kit.  Nice circuit with Basic Traynor Bass input plus a high gain for guitar.  It works OK as a bass practice amp & rocks nicely as a guitar amp.  Got the nice lows with the custom OT I whipped up for this build.  It's good to be the Xfmr guy ;-)


OT16PP (USA)- simple 6K6:8 ohm USA built OT for the economically minded Deluxe or 6V6 P-P combo builder

OT17PP (USA)- simple 8K:8 ohm USA built OT for the economically minded Tweed/Princeton/18W builder

OT12PP (USA)- Some builders are really liking this Tweed sized EI75 P-P OT.  It's got a 1" stack instead of 3/4" stock size trannies.  The inductance on this is up over 40H so the low end is there.  8K: 4/8/16ohms at 20W maximum

PT240.1 (USA)- I've had a nice little 2-section PT Bobbin hanging around for a while & have built a couple of filament transformers with it.  This month I finally got around to building a small HiV PT with it for 12AU7-ish circuits running at 1W to 5W.  It is the same size as the OT20PP USA in VC87 bells & on the bench I dropped it into my 20VA resistive load and it held up a 325Vdc B+ thru my diode bridge (using "120" inputs) and 340Vdc B+ putting 120 actual onto the "115" inputs.  I center-tapped the heater .... just because Hammond doesn't and I can.  I'm not yet seeing why I can't offer this somewhere around the OT20PP USA price level.

PT190.1 (USA)- a small HiV PT with it for 12AU7-ish circuits running at 1W to 5W.  It is the same size as the OT20PP USA in VC87 bells & on the bench I dropped it into my 20VA resistive load and it held up a 260Vdc B+ thru my diode bridge (using "120" inputs) and 285Vdc B+ putting 120 actual onto the "115" inputs.  I center-tapped the heater 

New Projects Incubating.......

OT5PP+ variants built this week for HiFi.  They turned out really nice with super nice inductance and low leakage inductance due to the 5 section winding interleave.  This is a nice little OT.  I can feel an "OT12PP" 12VA push pull OT coming out of this.

PT290.2i - smaller 220/240Vac mains int'l type Power Transformers just under 4Lbs shipping.  These will fit in the 4Lb USPS Int'l Flat Rate package and ship for a reasonable cost (~$26USD).  I can tweak the PT275.2i to operate anywhere from 190-0-190 (120MA)  to about 325-0-325 (80mA).  

USA built OT19PP, OT20SE and OT40PP can be provided in the FM-100 full mount covers
OT3SE in the EI-62 material set. It's an over-sized 3/4" stack with a gap.
OT18.2PP 8000Ohm :4/8/16 EI100 x 1.4in stack w/5 Layer winding interleave. 4 Lbs of sonic goodness. What do you have inside your amp????
OT18.2PP PLUS- EI112 x 1.7in stack. 5 Lbs of heavy goodness. 8000Ohm: 4/8/16 Ohms and 35VA.
PT290P USA Laydown Power Transformer