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Found 11 results

  1. Hope you guys don't mind, but I'm taking the liberty to collect some info, links etc. here. 900V floating supplies 350V/us the cole slew (couldn't resist) seems to be happening in bits and pieces in multiple threads on multiple forums and there are some implementation issues which seem to be worth discussing...namely fitting all of this somewhat daunting amplifier into one case. I guess at some point Kevin decided to split the input and output stages- output board output schematic The output stage features the floating supply floating supply fboard floating supply schematic the input/driver board As of today the aim is to fit this all in a single modushop 5U chassis, the floating supplies make it prohibitive to split the build across multiple boxes. Transformer Specs: Supposedly trivial to get an EL34 version of this working but SiC version will be first Just wanted to hopefully direct discussion here instead of dragging it across the kgsshv/GB/headfi threads. I'll update this when I get around to fishing around for the appropriate information. Thanks to Kevin for making the design process somewhat transparent ---------------------------------------------------------------------- Figured I'd put this here too, since Kerry speaks for all of us:
  2. Hey all , so this is my first post here so sorry if its not up to par. Recently i bought a Srm-006t amp 404 signature combo . I loved the sound but it seriously lacked volume . I replaced the tubes with a new set of EH tubes .. but aside from a uptake in tone .. I didn't get any extra volume . I started searching Google for mods to this energizer and came across a post by Kevin about a cascade mod for this amp and mention of an article in Audio Express July 2017 edition by James Lin. In the thread i was reading i saw that a board had been designed (im really not a fan of point to point electronics) and messaged Kevin Gilmore about it , He said he was all out but happily sent me the screens for it and permission to get some more made . So this is the start of this roller coaster of a mod , I've learnt a pile about Stax and I've had some great help from some of the best in the bizz to produce what is a good looking addition to my amp with significant results in both volume and audio quality . So I found a place to make them and got a few made , and then populate the board with the parts listed in the article ( there was a small design change of the board from the article but ill talk about that later ) board completed ( the pot was changed to 5k and the set resister to 390ohm ) This was due to a design change from the article , The original was in series and would get scratchy over time from the current demands on it , The board mounts the resister and the trim pot in parallel meaning only a tiny portion of current is passed through it increasing reliability . So here was the first mistake ... you can't put in the wires that go down to the board after the heatsinks are installed , Also pro tip ... attach the resisters to the heatsinks and fasten them , Then install into the board as a unit .. makes it as easy as just inserting the resisters instead of trying to do paste insulators and bolts up when the back in shrouded with the previous heatsink . However it was all together and it looked great. Now to set the current limit . you can see the wires coming out the wrong way because soldering down in between the heatsink was difficult and i was lazy . So now we clear out the plate resisters , If you have never soldered before of don't know how to remove solder from a connection well ... this is not something you want to do , The boards are a little fragile and success relies on you been able to clean out the holes well . a flux pen and solder wick is your friend . I believe its been said that once you can work on a 5 layer board without damage you can work on Stax . so practice practice practice This picture also shows the 4 wires you will attach 5.1k safety resisters to in series to keep your stax safe and your head safe should the worst happen Next mistake ... mounting HV over the input side , This isnt how kevin designed this to be attached ( i think) but id ordered the standoffs and they were there .. it also worked well with how id run the wires out the top of the board , ultimately in hindsight this was just an epic fail and again i was been lazy ... however this is very unwise when you are dealing with 580v ... don't be lazy .. don't be impatient .. I knew better this this but after weeks of waiting for parts and boards i just wanted to hear what it sounded like . Also .. you cant get to the balance pot to do tube bias so in order to do the bias .. you had to remove the board from the mounting ... did i mention this was a fail in so many ways So this is when it all went wrong . I hung the assembly over the side so i could set bias .... and this is where the little things id done poorly bit me in the arse . The article says just use an insulating pad because the back of the fets are live . So i did that and plastic collets and metal fastenings (no contact to the fets were made and for anything lower volts this would of been fine ... However for 580v .. this was not ok .. it arc's through and made the heat-sink live with MUCH jumpy electrics . Luckily i hadn't touched it with my hands because in my laziness and rush . i didn't connect the earth off the board to the actual earth ... something that incredibly foolish and stupid .. but hey ... i hadn't worked on electronics like this in 20 years so i was a bit rusty in remembering the fundamentals of safety safety safety ALWAYS install your earths . The result was catastrophic the heat-sink arc'd with full force to the body of the unit . I shut it down to assess the damage The result of this was a Amp that no longer functioned , I messaged Kevin and told him exactly what happened and owned the mistake like you should . I guess he took pity on me for been stupid and organized Spritzer to send me a high res copy of the T1 schematic . As well as a few suggestions on where to start as well as the frightening reality that i may have killed the input fet , A part no longer manufactured . So i reinstalled the plate transistors (something you don't wanna be doing on a fragile board in installing and installing parts repeatedly so much care was taken . Obviously my attitude to this mod had changed from smash it through to one of respect for the gear , something i should have had from the start. So now comes the fun part .. tracking voltages and testing on gear that you are directing testing on the HV rails and components . i even changed the multimeter to one that was rated for HV rather than just the junker I use that I don't really care about . After a few hours of testing all the resistors around the d3 LED , i moved on to the power section , The great think about this amp its its discrete , so EVERYTHING has a matching part , I was lucky i had only killed one side . Slowly making my way through i found that the STAX schematic had errors in it .. That worried me a lot but luckily its a simple circuit and tracking voltages is easy ... turns out id open circuited a resister named R44 and that was all that was damaged Sadly to rebuild the board it was just easier to strip the old one apart ... and i did that destructive because reality is ... its way safer than putting lots of heat into fets to remove them from a board (10n90s is not available locally it got shipped from mouser usa ) I also could see the Dn2450 has sweated and i had a spare set to just replace them with . So we started again ... much more carefully this time and using 1kv insulation pads and fastenings on the fets [ edit .. going to move up another step to ceramic insulators and peek fastenings, following some good advice , i suggest you do the same ] Using nylon bolts and nuts and installing the fets on the heat-sink before removing the solder to help keep the heat in the fets from that process under control (i was been super careful of everything now ) Yes there is to much paste .. i wiped them down pre installation but the nylon nuts have way less clamp so i wanted to be sure there was substantial contact As you can see the wiring is now coming out the right way , Now back into testing ... and here is where it got interesting , The new batch of 10n90's (bought from Rs components as extras rather than mouser) caused the original 390ohm resister to not allow me to set my current value to .49 volts . My lowest range was .52v (approx 6 mA of draw ) while this might seam like a good idea (a little more current is a good thing ) i was thoughtful of if the transformer could supply more that so i added another 100ohms (making 490ohms) to the set resister and this put .49v set at 4.9mA draw as per the article specs All wired in and ready to mount Mounted and looking good ...... [except this isn't how it should be mounted , as pointed out mechanically the heatsinks need to be vertical so will be remounting ASAP will add updated pics as things are fixed ] Bias set and time to listen The difference this made is ASTOUNDING , It fixed all the things that annoyed me about this amp and its total lack of drive . So this was my little adventure , I hope its helpful to someone wanting to do this and also helps show some of the pitfalls and dangers of doing something that you just don't everyday Also hope it helps someone with the construction order . I really need to give credit to Kevin Gilmore for sticking with me through this and to Spritzer for giving me a high res schematic to work to, Without that i would have been dead in the water come diagnostics time as well. Also James Lin for what is basically a how to article Who should do this mod , Anyone with good soldering skills , A person that respects HV and the dangers of working with it . And also have the expectations that if something goes wrong , if you make a mistake , You COULD brick your amp in a way that makes it unrepairable and that that, is all your own fault . BTW . the guy that says he will do this for you .. is not the guy you want doing this for you . Also note edits and updates... Cheers all Wayne
  3. After a few weeks burn-in period of this little beast, I found it's very relaxing to listen to. I can hear more juices coming out and the STAX 009 just doesn't have that analytical sounding cliché to my ears. It also enhances the soundstage and life-like of Focal Utopia makes it way more enjoyable to hear. This is a push-pull design tube Headphone Amplifier/Preamplifier attempting to achieve the true high-performance of headphones from Dynamic, Planar Magnetic to Electrostatic models. I've gotten a few PM's asking about the schematics and stuff so I decided to open a thread to discuss more here. a few interesting measurements of the amp at R = 6Ω DT-HWT Headphone Amplifier/Preamplifier schematic: DT-HWT Power Supply schematic: ===================== Inputs – it has two sets of RCA inputs. Output – it has different outputs, provided on a number of different connectors. On the amp front is a TRS ¼” unbalanced jack, and balanced headphone outputs on a single 4-pin XLR and a pro bias 5-pin Stax headphone jack. On the amp rear, there are two sets of 3-pin XLR and RCA preamp outputs. Both sets can be used at the same time if desired – for example, you could feed a power amplifier from the XLR connectors, and a subwoofer amp from the RCA connectors. The bias voltage settings on the separate power supply unit are used only with electrostatic ear speakers (> 100K Ω impedance). You can select whichever bias level sounds better to your STAX/HE90 models from 230-500-580 up to 620 V DC bias. Tube complement for the amp unit is: matched pair of EF86/E80F/6D8 & matched pair of 12AU7/5814A/E80CC/E82CC & matched quad of EL95/6AQ5 Tube complement for the power supply unit is: matched pair of KT66/KT77/KT88/6550/6L6/EL34/350B/350A & one 6080/5998/6AS7/6H13C/2399 Look forward to those next iterations/variants from you guys soon... For the meantime, I keep on rolling 11 tubes to find the best combination that suits best for different music genres
  4. Dear fellows, Maybe you can help me with an advice. A friend of mine gave me a Koss head amp E/9B but without the suited headphone. I want to know whether it is possible to play a Stax headphone (normal or Pro Version) through this head amp. If it does not work - it is possible to convert the Koss working with a Stax headphone, maybe by building an adapter? Many thanks in advance. I wish you a great happy new year 2018. Best, Andreas
  5. Thought it might make sense to make a new thread on this so as not to pollute the T2 thread. So this would be limited to the chassis, any potential board run, and any other potential group buys for traffos or transistors (if numbers warrant). I am hoping to move forward by the end of the week. Please keep in mind, if you are in and make your deposit, you are committed and will not back out unless you find someone to take your spot (so if you are not well established, then paypal gift only). Please express interest here or by PM. I have also included a link to the results of the first group buy:
  6. Arthrimus

    DIY Stax self bias conversion?

    Hello all, I'm working on a little project with my old SRD-6 energizer and a cheapo TA2020 amp. I'm trying to put together a compact transportable setup for my SR-5s. I have done a few modifications to this box already, such as wiring the transformers directly to the speaker taps on the back of the box and directly to the Stax socket on the front, completely bypassing the bias board and the loudspeaker switch. Those mods have done great things in terms of sound quality, but what I'm interested in now is modifying the bias circuit to operate as a self biasing one. As I understand it, Stax accomplishes this by tapping some of the output signal from one of the transformers, then passes it through a small transformer to step it up some more before sending it to, more or less, the same bias circuit as in the standard models. This seems pretty straightforward, but in my search for information, I've been unable to track down solid details about what type/values of transformer is used, and if there are any other important components in the self bias circuit (resistors, capacitors, diodes, etc.) that I'm not aware of. Any advice would be greatly appreciated. My ultimate goal is to have a system that runs solely off of 12v dc so it can be run off a battery if need be. Thanks!
  7. Hello My little amplifier for my Stax headphones. First stage is based on ECC82. One triode per channel as cathodyne phase inverter. The second stage is 6N1P-EW with CCS, and power stage is with E80CC with CCS too. It was designed to work with my PC to drive Lambda Pro. So output voltage is not so big 308 V peak-peak, but it is enough for Lambda Pro.
  8. Stex

    STAX SR-5 ??? dilemma

    I recently acquired a set of SR5N earspeakers, with white color. I am asking that how can one's decide if it is a gold editon or not?
  9. Due to my impending move at the end of the month to a new and bigger house it is time to have a moving sale. All the amps I have in stock (so not the KGSSHV Carbon as I can't make enough of them) are included plus all the special items I have as well. They are all discounted by 15% and free shipping worldwide is included. See the News section of my site for a complete list of everything included or just click here. The sale will run from noon today (UTC) to midnight on Sunday the 17th. Everything is in stock and ready to go so shipping is expected a week from final payment. Could be less, just depends on how busy I am. Now I'll get back to packing...
  10. 4tray

    Stax SR Lambda making noise

    hi all, i am a new owner of a lambda SR. i found it cheap on craigslist, was not expecting to see one, went and snatched it up for cheap. it looks fairly dirty on the inside and i have been looking at some guides where people describe cleaning lambdas but the process is a bit intimidating... it looks like there is a lot of dirt inside. i wasn't aware dirt was so hard to clean off of them before i bought them, and there are 2 visible specks of dirt on the left driver on the inside. that driver usually buzzes a bit, sometimes not too bad but sometimes a bit louder. when you look down into the driver housings you can see lots of dirt that looks nasty and gross. i am using a new SRM 323S i bought from Stax USA website. i do not have any other stax headphones to use with the amp but since i can see the headphones need a good cleaning. where do i go from here? i am not scared of working on electronics, this is just such a precision device i am scared i'll damage something. p.s. how do you remove a lambda headband? the headband on this is very gross and i wish to wash it off a bit. (edit: didn't notice there was a stax thread like a big idiot, tried to delete this thread and re-post my message there but please remove this thread if necessary)
  11. I've got a Studer amp to keep my Stax menagerie under control via the SRD-7 Spritzer. It has always had quite marked mechanical hum when run at 240V (Australia's mains voltage). I have a 240 -> 110V transformer and the Studer is able to be configured to almost any possible mains voltage via a rotary switch and with a change of fuse. Did that. NO FREAKIN' HUM! $2.50 for 2 new fuses! Love it.