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Musical Power Supplies, Inc.

Lake St Louis, MO 63367

 

 

Email: matt@musicalpowersupplies.com

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MPS New Projects

Been working on a PT275Mi transformer in the 150mA+ current range.  It's going to use a combination pair of 120Vac mains to allow 120Vac  (parallel connection) or 240Vac (series connection).  I expect the next lot of PT285M and PT330M will go that direction instead of the 115/120V mains combination.

The EI-100 sized OT's are all in stock now- OT19PP, OT22PP, OT33PP and OT42PP.  The EBay offering will be open frame (unshielded) and HC100 bells.  If you need an FM100 full mount end bell version for your project just email us.

Built a couple of PT275.2LD (Laydown versions) recently- one made it to the EBay store.  I epsect to build up a couple of EI112 laydown versions in November.  (likely PT260M/520Vac, PT330M/660Vac & perhaps a PT350P/700Vac on EI-125).

Just PT190.2i (220/240Vac mains to 190-0-55-190) remain from the old CN built stock. 

Starting to think about a 12au7 amp project with the PT190.1 and OT2PP - it could be really 'cute' and small. 


Current new projects include:

OT16PP -     Barebones Push Pull OT.  EI87 (OT20PP derived) with 6600 (CT) ohm input and a single 8 Ohm output.  $27.95 on EBAY, Figure $25.95 if you ask me here for a PP Invoice.  

OT17PP -     Barebones Push Pull OT.  EI87 (OT20PP derived) with 8000 (CT) ohm input and a single 8 Ohm output.  $27.95 on EBAY, Figure $25.95 if you ask me here for a PP Invoice. 

PT Laydown covers -  Picked up some EI-112 and EI-125 covers to work with laydown PT ideas.  Expect to start with a 660V CT version on EI-125 iron.  

PT190.1 (USA)- EI87 Power Transformer-
 This is a small power 20VA transformer the size of an OT20PP USA in VC87 covers.  Specs 115/120Vac Mains & 190-0-190Vac (Approx 250Vdc B+) at around 40mA with a 3.3-0-3.3Vac Heater winding.  It should fit in a pedal......  

PT290.2 (USA)- EI100 Power Transformer- This is a version of the basic PT275.2 (550vac) boosted up to 580Vac.  It will run basic 18W P-P amps with EZ81 rectifier & has a center-tapped mainheater 3.3-0-3.3Vac.  I now have regular production stock on the shelf.  A little less expensive than a PT285M it can also ship more economically to Canada as it weighs in just under the 4# limit for 1st class int'l mail.

OT12PP- EI75 Output Transformer- A couple of customers have had me build a tweed/princeton sized P-P OT at 8K:4/8/16 and really liked the range on this smaller OT.  I'll keep a couple around to see if it cultivates a following.  Kind of a "Fat" Tweed OT. 

PT240.1- EI87 Power Transformer- This is a small power 20VA transformer the size of an OT20PP USA in VC87 covers.  Specs 115/120Vac Mains & 240-0-240Vac (Approx 325Vdc B+) at around 40mA with a 3.3-0-3.3Vac Heater winding.  It might fit in a pedal......  

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

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 ;-)
http://classixaudio.com/nsv6b.htm

 

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

OT22PP (USA)- An oversized 6600: 4/8/16 ohm Push-Pull OT for use up to 30VA.  It's wound on EI100 structure, same as the OT40PP & OT19PP.  It's got a 5 section winding, so a bit bright and british.  Currently I run this to order and will try to keep one or two on the shelf.

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 

OT5PP (China)- This part was offered at MPS until around 2013 when the original stock ran out.  I now have over 100pcs on hand from my last buy lot.  It was designed for a 0.5 to 5W PP amp running 12AU7 in Push Pull and has a high Inductance 29M6 audio grade lam core for low end emphasis at low power. This has been used in the small Fuchs amp & as an upgrade on Vox Lil Night train.  Again, under $20...can't beat that.

Specs: it essentially the same as the OT5PP+ (USA) version in mounting and overal footprint except it uses a 3/4in lam stack instead of 1in found on the OT5PP+- so it typically measures 40H inductance, vs 45 to 50H on the US version.  Otherwise its 22K5 : 4/8/16 ohms ratio and up to 5VA just like the newer model..... just less expensive.

OT8SE (China)- This part was offered at MPS until around 2012 when the stock ran out.  It was designed for a 5 to 8W SE amp running 6V6 or EL84 and will carry about 45mADC nicely thru it's gapped core structure on 29M6 audio grade lams.  It's wound like the OT10SE at 5K/7K : 3.2/8/16 ohms with the "3.2" output being setup for the original Champ circuit for replacement.  This part actually has been used nicely in low power HiFi (see Frequency response curve in my gallery page).  Whether you want something economical for that first amp project or you just like a great sounding Xfmr at an under $20 price.....this is a great offering.

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