My Yamaha PM1000 Project

How it all started for me...

Note:  photos mentioned are in the gallery below

January 16, 2006 -- saw local ad on for a pair of stock PM-1000 modules ($100).  So, after seeing all the raves about these, I took the plunge. 

A very brief history--the Yamaha PM-1000 mixing board came in a couple different models with varying number of channels.  They are sometimes referred to as the "Japanese Neve" because of the absence of any ICs (op-amps).  Or in other words, they are all discrete components--which is typical of older, analog equipment.  The PM-1000 mixers appeared in the late 70's to early 80's.

January 17, 2006 - start researching, figure out what parts I need, etc.  Read every single post from previous PM1000 DIY's.  Decided a web page to consolidate much of the info I learned on this journey might be a good idea. 

January 31, 2006 -- finally completed (I think) the bill of materials (BOM) that I need to rack and rework these.  I bought some locally (Fry's electronics) and will probably be back there when i figure out what else I forgot...  Ordered the rest from Jameco, Redco and Digikey.  There doesn't seem to be a one-stop shopping for all of this stuff...  I contemplated Panasonic vs. Nichicon.  Ultimately, it came down to price and availability (Digikey had the sizes I wanted in stock).  Jameco had the best prices on a 48VDC power supply and toggle switches.  I also created a "map" of the capacitor layout on the input module.  I had several schematic drawings, but none showed the actual, physical locations on the board (at least that I found) so I made a map <see photo 1 below>.

This just made me feel better--don't know that it will really help me that much though.  Now I'm waiting on all my parts.  Once I get them I will attempt to wire up the boards and see if they actually work before I go to all the trouble of mounting and re-capping.  When I finish, I plan to finalize the BOM and post it here. 

Here are the original values (I think) of all of the caps in the table <see photo 2 below>.  All values are uF/VDC and Electrolytics unless otherwise noted.  The one I designated as C00 I cannot seem to locate on any schematic...yet there it is on the board...  The EQ section is in red.  Green text designates what I believe to be in the fader section.  Aqua blue (cyan) are in the preamp section.  The remainder, I think are all part of the echo channels which I will not be using so I don't intend to recap them at this time.  I will recap the Electros, Tantalum (with film) and the EQ section (with different values).  change C37 to a 220uF (or larger).

February 1, 2006 - I just got my order from Redco.  It shipped quickly and they were nice (they called me with a question about my order).  I ordered some Mogami mic cable and connectors too so not just stuff for this project.  Anyway, now I've got my 2U cover plate.   The Jameco order is supposed to arrive Friday, and Digikey--well, who knows, I specified USPS Priority -- so no tracking.

February 2, 2006 - WOW!  DigiKey was really fast.  USPS was really fast too.  Minnesota to Texas in 2 days.  Maybe there is some benefit to living right off a major NAFTA thoroughfare.  Too bad I hosed up my order.  The Panasonic .01 poly film caps I ordered (trying to sub for the Wima MKP2 0.01/100/5) were way too big -- HUGE in fact!  I'll have to make an order with Mouser now and try to send these back.  At least I got the diodes and a few other parts I needed so maybe I'll be able to power one up soon.

February 6, 2006 - Well, I got my Mouser order really quick too.  Dallas to Austin and Fedex ground did it in one day, with Saturday Delivery.  Location, Location, Location...  So I've got most of the parts now.  Here's a picture of one of my pre's cut down <see photo 3 below>.  As you can see, I removed the Echo Send 1 pot, and rewired the Echo 2 pot to be the output.  I left the phase switch in and wired an XLR input.  The output jack is soldered now too (pictured loose). 

A couple shots of the chassis in progress too.  I hoped to get it powered up this weekend, but didn't get all the way there yet.  As you can see the <see photo 4 below> has a front toggle switch for power and a pilot light.  You've gotta have some blinky-blink to let everyone else know how much work you put into this project...  Next up is the inside shot.  The PM-1000 is simply laid in there for now.   As you can see I left the bracket <see photo 5> on the pots because I could not for the life of me get them off--they are glued (probably actually beer and smoke)!!  When I put a wrench on them, they spin (no way to grip them from the back side either).  The power supply is wired and I did test it.  The string of diodes (for step-down to 44VDC) is experimental.  this freaked me out a bit because I was expecting the 0.6V drop per diode as specified in the docs, but after 10 diodes I only dropped to 45+V.   But, since I had no load applied (except my voltmeter) I need to try again.  So I bought a 100ohm/20W wire-wound/ceramic resistor from Rat Shack and I'll measure it again before I hook it to the PM1000.  Since this has worked for others, I'm going to try it (instead of going the LM137 method).  Six of the 1N4003 diodes should get me in the +44VDC range.  The fan does nothing--it's just leftover from the Ethernet switch.  I may de-pop some of the components in the areas that will be unused (echo1, echo2) also.   More to come when I find some time.

February 8, 2006 - Got up enough guts to apply power today (beads of sweat...).  Luckily... no smoke and I even got audio on the output.  Whew...  Anyway, next step is to punch all of the necessary holes in the faceplate, then cut down the 2nd module, and finally recapping.  Also realized I need to add a toggle switch for phantom power.

February 13, 2006 - Got the extra switches I needed for phantom power switches.  Also wired in my DI inputs and drilled my faceplate.  Also, started re-capping one module and replaced the NPN transistors.  I have not added 0.01uf Wima's yet, but that's next.  Then same for the other board and hopefully I can mount them in the chassis and be done (or close).

Here are a couple more pictures showing the re-capped module (right) and the chassis with all holes cut.  I could not find a 15/16" hole saw so went with the 1" and that was a mistake.  the holes are a bit to large for the XLR panel mount so I'll have to fill a slight bit with some silicone or something.  I'll figure that out later I guess.

February 18, 2006 -  Good news.  After re-capping one module, replacing the NPN's and adding the bypass caps on the bottom of the board, it still works! My DI input, phase switch, and phantom power all work too so I'm pretty excited.  I had a slight scare after mounting everything in the chassis -- I reversed my string of diodes (which were covered by shrink-tubing so I couldn't see the polarity anymore) and it did not work.  But, a few minutes of troubleshooting, and I figured it out (no +44 to the board).  

Also, a close-up of the NPN Transistors, showing the correct orientation (because it's different than the originals) and a shot of the EQ section.  The small red film caps are Wima's and the big one's are Panasonic.  I couldn't find the sizes I wanted in the same type, so I mixed them up. 

February 21, 2006 - Got my Mouser order for the extra caps I needed (obviously I screwed up the quantities previously).  Mouser also sent me my 3rd huge catalog today.  I hope they stop soon....  Happy Birthday to my new PM-1000's!

They are now fully racked, operational and all I need is something to record.  Hey, no problem, I built these for tracking drums so that's what I'll do.  More on that as I get to know them better.  I used a label maker with a gold on black tape so I could see which knob I was twirling.  Looks a bit ghetto, but not as bad as the back (silver Sharpie marker...).  I promised to post a BOM, so as soon as I clean it up I'll do that too.  I also meant to take a picture of the bottom of one of the boards after I put all of the bypass caps on there.  Oops!  Too late now.

February 21, 2006 -   Ok, as promised... 

<note I used to have a spreadsheet here but I is out of date and my website no longer allows me to attach it>

BTW, the entire project probably cost me about $250 total (including the PM-1000 modules).   Good luck to y'all.  Now get out there and rack it up!

June 22, 2006 - Another birth announcement!   - Ok, had to add my latest.  Looks very close to the first pair, but this one has the output transformers too.  Also tried a few different caps in the EQ section this time as well as used a better power supply.  I also included a close-up of the bypass caps on the backside, and a shot of C9 which was different from my first set.  These used a 0.47 tantalum whereas the first pair had an axial electrolytic here. 

July 6, 2006 - Racked the 3rd pair.  I think I'm done now since I've got enough for all the drums (kick, snare, & 4 toms).  This one was a little trickier.  The input gain on one unit would go dead after I moved the pot to center and beyond.  After measuring voltage (with a voltmeter) across the transistors, and comparing it to the good one, voltages at Q2 looked suspiciously low.  I replaced it with another and voila! problem solved.  so, looks like the "new" transistor I installed initially was bad. whew...

July 14, 2006 - edited this page a bit to make it load faster (too many pictures...)

October 16, 2006 - Dang it!  I bought a couple more strips so I'll be racking up another pair and may end up putting it up for sale cause I don't really need more right now...

October 27, 2006 - This is the fourth pair I've racked now.  This unit was sold to a TapeOp'er.

November 29, 2006 - Oops, I did it again...  Here is number 5.  This unit was sold to a local studio!

December 02, 2006 - I must be crazy but I did another.  Number 6 front and rear view.

January 21, 2007 - I got a pair of PM1000 master modules, and after a bit of schematic reading, rewired them as preamps.  So here is Number 7.  And yes, that's a strip of Red Oak on the front panel (just for variety). 

March 9, 2007 - Here is a picture of Number 8.  This time I figured out how to replace those crappy slide switches with rotary switches.  Much cleaner!

March 14, 2007 - Here is a picture of Number 9.  This is yet a different flavor, constructed from two talkback modules (which incidentally had different circuit layouts).  It seems to have lots of gain!

April 25, 2007 - I forgot to mention this earlier.  I took the 3rd unit and added some output transformers.  I heard about the Altran transformers and decided to try a pair.  The specific model I tried is the C-4000.  This is a 200:600 ohm, however they also make a C-2780 which is a 600:600.  Anyway, I definitely noticed a thicker presence in the low end (compared to the unbalanced out).  In my opinion they sounded very comparable to the original Yamaha/Tamuras.  So, if you cannot find the originals, the Altrans may be good alternative.

May 26, 2007 - Here is Number 10 almost complete (made a few changes after the pictures).  These are from a pair of master/monitor modules and have the original input/output transformers.  Added the input and output gain/level pots for more flexibility.

September 24, 2007 - Found a full 16-channel PM-1000 mixer for sale, although I had to drive a couple hours to get it.   These are big, heavy and a bit impractical for my use so looks like I will be racking a few more modules.  

October 15, 2007 - Pictures of old and new rack projects will now be in the photo gallery page.

November 10, 2007 - check out the "PM1K mini" in the gallery.  Arguably the smallest 2-channel PM1000 ever!  I built it for my toms.  It has a single gain control for each channel but does have transformer in and out.

December 20, 2007 - I'm up to 20 now... .

March 1, 2008 - Wow, I'm up to 26 of these now.   Finally getting close to the end of the parts though so then I hope to take a long break and get back to making music!

March 23, 2008 - Earlier this week I gutted the PM1000 chassis and took the bare-bones, wood shell out to the curb for garbage pickup.  It felt kind of weird but not much else you can do with them.  I do have a few miscellaneous parts I will be selling (VU meters, metal parts, arm rest, a few pots, knobs, etc) so if you need something, feel free to email me and see if I have what you are looking for.  NOTE:  I do not have any of the channel strips or transformers available...

December 27, 2011 - See the gallery link for pictures.  I still have a few small parts for sale (VU meters, knobs, screws, bolts) but no strips or transformers and I am not racking any more units at this time.

July 16, 2013 - Hey!  its been awhile...  Check out the new PM1000 FAQ.


PM1000 Project FAQ

To answer some questions...

 I have gotten so many questions over the years that I finally decided to put together this Frequently Asked Questions (FAQ) page.   Enjoy...

1.  How do I wire the DI jack?  

Use a switched 1/4" jack (like the Neutrik NMJ4HC-S or NYS2122).  The DI should be wired between the input transformer and the input to the board.  When there is no jack inserted, the circuit flows normally through the switched jack (like its not there at all).  When a 1/4" jack is inserted, then the switch "cuts off" the input transformer and the circuit flows from the 1/4" plug, through the jack and into the board.  

2.  What are bypass caps?
In theory, electrolytic caps are slower and therefore don't handle high frequencies as well as other caps.  By placing a high quality Polypropylene cap of very small value (~0.01uF) in parallel (in parallel, capacitance values are added together...) across the electrolytic cap, we can help it handle the higher frequencies.  In theory this might add more "air" to the sound or allow for better (faster) response of transients.  
Tip:  soldering them on the backside of the board is a whole lot easier.

3.  Do the bypass caps really make a big difference?
Your golden ears will have to answer that for you.  It adds a little expense in parts and labor to the project and if there is any difference its probably very subtle.  You have to decide if its worth the additional time and money.

4.  Hey, can you rack some modules for me?
No, sorry.   This is a great project when you can do it yourself.  You save money and you can say "look what I did!".  If I were to charge a decent rate for time (labor) and parts, the overall costs starts to get pretty close to some of the modern boutique preamps that sound really good too.  So only if you can do it yourself, do I encourage trying it. 

5.  Can you update that Bill of Materials?  I can't find part xyz anymore.
No, sorry.  Admittedly that BOM is several years old now, but you should be able to find a similar part fairly easily if you check the Mouser or Digi-Key websites.   Parts and inventories can change frequently and I just don't have time to keep up with it.  This BOM is really meant to just help you get started.

6.  Where can I get schematics for the PM1000?
Look on the Yamaha support site.

7.  Do I need a knowledge of electronics to do this project?
Yes.  You should understand basic circuits and it helps to understand the components used in these circuits.  You also need decent soldering skills and unsoldering skills (if you intend to recap).

8.  Speaking of re-capping, should I do that?
Yes.  The PM1000 line was manufactured in the mid to late 1970's.  My math says that's well over 30 years going on 40 now.  Electrolytic capacitors tend to have a lifespan that is less than that.  The dielectric will dry up and they either a) create an open or b) short out.  If they open, then they stop doing their intended job.  If they are filter caps, then you get noise.  If they are in the audio path, you get no audio!  If they short out they might blow a fuse, or blow off the board...  or if they are in the audio path, they stop serving their purpose (which might be to block DC).  So at a minimum, replace the electrolytic caps.

9.  What about swapping the other caps?
As noted on other pages, it's recommended to replace the tantalum caps with polypropylene to improve the sound.  Also increase the size of the input cap (3.3uF is a good value) and also of the output cap (an electrolytic -- 220uF works nice).  Optionally you can replace the EQ caps if you want to change the EQ center points.  If you don't then leave those as is.

10.  What input and output transformers should I use?
If you can get the original input and output transformers, then those are a great match for the boards.  If not, then you can experiment.  The original input transformer is spec'ed at 600:600 ohm and the output transformer the same.  If you can't get the original type, then use a high quality transformer (Jensen, Cinemag, Altran, etc.) of similar specs, you will probably be happy.

11.  What does the PM1000 sound like?  Is it really as good as a Neve 1073? or an API 312?
Really - that question again?  OK, here's the deal...  if money was not a concern would you be trying to rack some old channel strip hoping it sounded like the one you really want or would you just buy the real thing?  Yeah, I thought so...   So the answer is no.  They do not sound just like a Neve 1073.  They don't sound just like an API 312 either.  They sound like a...  Yamaha PM1000.  Yes, that's a pretty accurate description.   Yamaha was definitely trying to compete with some of the other popular brands at the time and I'm sure design considerations were made based on that...  Now I happen to think the PM1000 sounds pretty good and it's definitely in that "thick" or colored sound arena.  They work well on drums and I like the DI on bass guitars.  Frankly I've used them on all kinds of stuff (vocals, guitars, percussion) and never had any complaints.  But face it, if you have unlimited cash, I'm sure there is better sounding stuff out there (modern and vintage).  Go get it.   I just can't see paying over $1000 (a 1073 is more like $3K and up today...) for one channel of preamp when there are so many great options (including the PM1000) far below that.  That's why my personal studio has other preamps too.


the Subkick Mic Project

Subkick prototype


 One of the major drum companies offers a "sub-kick" product that is designed to capture the extreme low end thump of a kick drum.  It's packaged in a fancy drum shell and has a fancy stand and a fancy price tag too (over $250).  Luckily, you can make one really cheap.  All you need is a woofer-- 6-8" works great--some wire, an XLR jack and something to prop it up. 

Subkick side view


First, I bought an 8" foam-surround woofer on eBay for about $10.   Next, I wired an XLR(M) jack to the speaker.   I wired (+) to pin 2 and (-) to pin 1.  I used some old scraps to make a bracket, and used some old rubber plumbing washers as gaskets (to isolate it a bit from the mount).  I used a PVC T fitting to connect the bracket to the mic stand.  Then I cut down a cheap MF mic stand and mounted it.  It is actually plenty stable, and fits right up next to my kick drum.

The cost of mine was probably under $40 although I didn't actually keep track and many of the parts were just laying around anyway.

Subkick in a drum shell?


I got an old 10" drum shell ($10), stripped the hardware off and mounted the speaker (mic) in it.  This can prevent the sound from reaching the back of the speaker and causing phase issues (or cancelling some frequencies).  I stuffed some foam in the back to reduce the potential of any "ringing" inside the shell. 

subkick in action


I usually use it with an Audix D6 inside the kick. 

Side view


I got emails about the attenuator, and even though I tried to explain that my resistor choices were non-scientific, everyone still seems interested in it.  The fact is, you may not even need it depending on what kind of mic pre you are using.  At the time I was using one of the built in pres on a Digi 002r and it did not have a pad and the signal was too hot.   I was actually wiring it as unbalanced, so that may have had something to do with it.  Anyway, I did some experimenting with an H-Pad Calculator (google it), and came up with a more scientific choice to try to match the impedance as best as I can.  A mic would usually present a load of around 150-200 ohms and a speaker is typically around 8 ohms.   So, by plugging in the following values:

Input (the speaker)

--  9 ohms

Output (the XLR)

--  205 ohms

Pad (-dB)

--  19

we get an R1/2 = 0, and R2 = 10 and R2/3 = 100.  I chose these values because then you can build this with off-the-shelf parts easily attainable, even at Radio Shack and it's pretty close to what might be ideal.  In effect, you place a 10R across pins 2 & 3 and then the 100R goes from pin 2 or 3 to the cable you attach (that go to the speaker).  And now I am running it as a balanced signal as well.   I used some shrink tubing on mine before I closed it up again.

It doesn't sound much different than it did before - but at least now we can all sleep better knowing our preamps are happy with their input loading.



It sounded really great but the signal was REALLY hot, so I built an attenuator pad into the XLR jack.  I created a simple "L pad" by placing a 10K ohm resistor in series with pin2 and a 1K ohm resistor (shunt) across pin's 1 & 2 (I didn't get very scientific with the resistor sizing, so this probably is not the optimal impedance matching - but hey, it works!).  This drops the signal around ~20dB and helps so it doesn't overdrive my preamp.   You may or may not need it.  Try it first.

Bass Traps Project

finished bass trap


 There are several manufacturers that sell ready-made bass trap products, but since I like building stuff (and I'm cheap ) I decided to have a go at it myself.  

Inside of bass trap


 I constructed a 2' x 4' frame (of 1"x4" pine), with some bracing (3/16" x 2") on the back.  I used a table saw to bevel (45degree) the front edge of these boards.  I squeezed 2 of the 2" thick SAFB batts in each frame, then stretched cloth across them and stapled it on the back.  I used a couple of cup hooks and eye rings to hang them in the corner. 

Cotton batting


If you can find it this stuff is so much nicer to work with than fiberglass.  Your lungs and skin will thank you.

With Insulcot - front


so yeah, the insulcot batting worked nicely

With Insulcot - rear


a little chicken wire to help hold it in

Well hung...


a really old picture from when I was first setting up a home studio -- I've since built a separate studio --

Mic Mods

Modding these mics


Nady  SCM900 and GXL2400 mics

GXL2400 - replace caps


the larger red caps are the new .47uF film caps

Modding the grill


Removing the inner players of mesh - grab a hold and pull.  Bear careful you don't cut yourself though.  it can be sharp.

SCM900 Cap Mod


Replace the stock .22uF ceramic caps with  0.47uF Panasonic film caps

Nady SCM900 - cap mod


Replace the stock ceramic 1000pF cap across the capsule with a  Xicon Polystyrene of the sam value

Replace this cap


This is what the stock ceramic cap looks like in the GXL2400 - replace it with polystyrene for a smoother top end