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The Stax Thread III - Page 102

post #1516 of 11566

Hi all, Looking for some feedback regarding the  SRM-007T II.  I currently have a SRM T-1 which is partnered to a Koss ESP-950 and it sound really nice but sometimes seems to lack a little drive on some material.


Would going to a SRM-007T be a big step forward or more of a sideways move, I know both amps share the same 6CG7 type tubes but the 007T has four of them vs the single pair in the T-1. Do they share the same sonic signature ?


Any comments would be appreciated.

post #1517 of 11566

I very much like my 007t/ii with my 009 phones. The slightly rounded, reticent highs I hear in the amp (which was a weakness with the SR007 mk1 phones, making them sort of flat) 

is just what the doctor ordered I sense with the 009s. Bass is very high quality, just not thunderous, about the same amount of bass-power and depth as my HD800s, but with more

bass detail and bass-life. Nice tube signature, with a great inner glow and silkiness in the mids.

Edited by rgs9200m - 2/8/14 at 11:43am
post #1518 of 11566

I agree totally with rgs.  I think he has exactly nailed the sound quality of the 009/007TII combination.  I very much enjoy it.  It's the best headphone sound quality I've ever come across.

post #1519 of 11566

Thanks for that greggf.

post #1520 of 11566

can the bias be changed on an amp like the T1 or srm1mk2 to accommodate something other then the stax pro line?  like maybe a koss 950 or jade?

post #1521 of 11566
The 950 works fine off 580vdc pro bias
post #1522 of 11566
Originally Posted by milosz View Post

2 channel 10 watt class A amplifier - suitable for driving Stax SRD-5. SRD-7  etc.  Also works well with speakers, although power is limited to 10/ channel watts at 8 ohms. 20 watts/ channel at 4 ohms.


Pair of  assembled 10-watt class-A MOSFET   boards from eBay seller jims_audio  CLICK HERE


Power supply board from jims_audio click HERE contact jims_audio via eBay, they will give you a list of the parts needed to stuff this board.


Standoffs  / hardware to mount boards to chassis from eBay click HERE


Neutrik RCA input jacks, 2 needed  MOUSER  click HERE


2A slo-blo 5x20 mm fuse, MOUSER get 2 or 3, good to have spares Click HERE


Four TO-220 transistor mount kits MOUSER  click HERE


IEC  AC input jack w/ fuseholder Parts Express click HERE


On-Off Switch  Parts Express Click HERE


Two  HS-0606-b heatsinks from PAR-METAL  Click HERE


Pick a size  Par-Metal chassis that will fit.  I suggest you buy all the parts first, and then collect them together on a desk and measure how large a space they require, and then order the appropriate size from Par-Metal in your favorite color.  Click HERE


You will also need:


TOOLS - power drill, files, screwdrivers, soldering pencil, small diagonal cutters or nippers, needlenose pliers


OTHER SUPPLIES  - the thinnest 60/40 rosin-core solder you can find, some electrical tape to put around the bare AC line connections inside the amp, some misc screws and nuts etc.  


To mount the heatsinks, place them over the ventilation slots in the chassis, and drill holes from the bottom of the chassis into the heat sinks, then use some sheet metal / self tapping screws to mount the heat sinks to the chassis.  What you want is for air to be able to rise through the ventilation slots on the bottom of the chassis, pass over the fins of the heatsink, and then rise out of the vent slots on the top cover of the chassis. So you want to place the fins so that they have the most exposure to the vent holes possible given the space.


You can also find some fancier chassis on eBay that have heatsinks built in to their sides, if you prefer.



(Stuff I forgot)


5-way binding post output terminals - Parts Express - click HERE


Hook up wire - I suggest using some 18 ga. Teflon insulated wire.  Most hookup wire is 22 ga, but I think here you have a bit higher current on the DC side, so 18 ga might be a good choice.  Probably OK to use 22 ga. wire from the AC power inlet to the on/off switch and from the switch to the primary of the power transformer, but I would use the heavier 18 ga wire for the power supply connections to the amp boards, and for the speaker output wires from the amp boards to the binding posts.  Search eBay for some Teflon insulated wire, you don't need much, perhaps 5 feet.  Teflon is best because the insulation doesn't melt or burn when you solder it. 


You might want an LED pilot light, see Mouser HERE


The power transformer I originally specified might be a little too small.  This one from Mouser would be better, 30 V CT, 150 VA  Click HERE




#1 TIP - DO NOT WORK ON THE AMPLIFIER WHEN IT IS PLUGGED IN TO THE POWER LINE!!!! Close the chassis up before plugging the thing in!


I suggest wiring the power supply first, without connecting it to the amp boards. The close the chassis up, plug the thing in and hit the power switch. If the pilot light LED lights up and stays lit,  then disconnect the power cord, open the amp chassis up and wire the power supply to one channel at a time.....


The hardest part of this build will be cutting the rectangular hole in the chassis to mount the IEC power inlet/fuseholder.  My suggestion for this is to make a cardboard template the proper size, and trace around it with a pencil onto the chassis where you want to mount the power cord. Now, drill the largest holes you can drill that fit inside the outline.  After these are drilled, use a file or a chassis nibbling tool to enlarge and square the hole. (see http://www.parts-express.com/nickel-plated-nibbling-tool--360-022 )  The AC power inlet is press-fit. You push it in to hole until the thing snaps in place.


This => http://makezine.com/2006/04/10/how-to-solder-resources/  is a soldering tutorial. Practice a little before you build, if you're not used to soldering. 


In wiring the AC line,  connect the hot lead from the AC input socket to the fuse and then to the power switch in series with the HOT lead going to the power transformer's primary; and don't forget to connect the power cord's safety ground wire to the chassis.  See http://www.ampmaker.com/pp-18-chassis-wiring-part-3-1043-0.html


The output transistors of the amplifiers need to be bolted to the heatsink, but the transistors must not make electrical contact with the aluminum metal of the heatsink- that's why you use the TO-220 mounting kits. ("TO-220" is the standard designation for this type of rectangular, tab-mount transistor)  See http://www.turkiyefagor.com/semi/pdf/rultiris.pdf  for instruction on how to mount the transistors.


Note that this is a POWER AMP; if you want to add a volume control to it, I suggest a 50k audio-taper stereo pot like the Alps Blue Velvet, available on eBay for about $16 if you shop around ( like THIS ) - and although the Blue Velvet has a reputation for quality, reliability and close channel balance, it is perfectly acceptable to use a less expensive pot like THIS one from Parts Express for $2.40;  you'll need some kind of knob for the volume control like THIS budget one from Parts Express or THIS nicely machined one from Mouser.  ( or pick one out from THIS selection guide from Mouser; be sure it will fit the 1/4" shaft of the volume control.)  HERE is a tutorial on how to wire the volume control.


You might want to get a book like Circuitbuilding Do-It-Yourself For Dummies from your local library if you've never built any electronics.  It's really not that hard to do, but there is a bit of craft involved.

Thanks for the in depth directions.. Since you took the time to put in so much work for me I will definitely be tackling this project.. Thanks again

post #1523 of 11566
Originally Posted by Keithpgdrb View Post

can the bias be changed on an amp like the T1 or srm1mk2 to accommodate something other then the stax pro line?  like maybe a koss 950 or jade?

You can run the Koss ESP-950 right off an SRM-T1, no problem. No need to change the bias.  I do it all the time.  You just have to have the right connector on the Koss / or an adaptor.


You can also drive Stax "pro" bias headphones right off the Koss amp, even though the bias on the Koss is a bit higher.  Again, what's needed of course is an adaptor for the headphone plug.

post #1524 of 11566
And there is absolute no reason to convert your Stax headphones to be driven off the stock Koss amp.
post #1525 of 11566

there is if the E/90 is the only ES amp in the house and you have Stax earspeakers


true, chopping cable would be non-optimal


but it was easy to solder up a 2" long adapter out of some pins and sockets that fit and pot in 10 minute gel epoxy

Edited by jcx - 2/10/14 at 5:21am
post #1526 of 11566
Originally Posted by barid View Post

Honestly the fear of channel imbalances has been the biggest deterrent to ordering a 009.  Would be the most expensive gear I've bought....and could fail apparently.  I kind of think that's unacceptable for the price of them.

Just for the record, I've had a few staxes over 15 yrs, 009s for 2 years, and never had an imbalance, and for me, that would not be a factor in a purchase decision.

(There were no other defects either.)

I did however buy them new from stax usa or usa dealers.

(One of my Koss 950s had a whine.)

Edited by rgs9200m - 2/10/14 at 5:44pm
post #1527 of 11566
Originally Posted by rgs9200m View Post

Just for the record, I've had a few staxes over 15 yrs, 009s for 2 years, and never had an imbalance, and for me, that would not be a factor in a purchase decision.

(There were no other defects either.)

I did however buy them new from stax usa or usa dealers.

(One of my Koss 950s had a whine.)

I have had mine since the late eighties (LNB) and have never had an issue...FWIW

post #1528 of 11566

Selling off my Stax rig and going dynamic, If anyone is interested I have listed the SR-009 for $3,650.00 (30 hours max on them) and purchased from an authorized US dealer.

post #1529 of 11566

Why? Also, what amp did you use with it?

post #1530 of 11566
Picked up some lambda pros for cheap on ebay a couple weeks ago. Very enjoyable. Pretty buzzed at the moment, but right now id say im liking them more than the hd800's i just had on:)

U know the bells hopslam and troegs nuggest nectar finally got shipped to dc:) good beers and stax work well together.
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