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jamesmking

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Everything posted by jamesmking

  1. the nearest i can find has no thread for panel mounting but is 3.5mm 4 pole, no switching. https://www.mouser.co.uk/ProductDetail/Kycon/STX-35331-4N-TR?qs=sGAEpiMZZMvlX3nhDDO4ANdBTK25DNHDLDgQvn584hU%3D is a 3.5mm socket, 4 pole (3 signals + ground) smd (the picture shows a thread for panel mounting but the datasheet says no thread)... The datasheet implies there may be a variant with a thread but the STX-35331-4N-TR 4N is 4 pole No thread... datasheet: https://www.mouser.co.uk/datasheet/2/222/STX35331-334673.pdf disclaimer I have not actually used one of these, I just did a mouser search and this might fit your needs.
  2. I have two blue hawaii se (golden reference hv and lv psus) , two joamat mini t2 (with golden reference hv and lv psus) and a diy t2. I only have experience with them using sr007 mk2 earspeakers. The hawaii is very good, far far far better than the stax srm006 or anything modern stax sells. The mini t2 is better still improving bass, micro dynamics and detail. The diy t2 is fantastic its takes the mini t2 strength and improves on it and adds better macro dynamics, even better bass and detail. If you can get any stax amp get the diy t2. As far as I can tell the sr007 needs as much drive as possible to get the best bass and dynamics and the diy t2 has the drive.... (we are still waiting for Kevin Gilmore to design a single ended stax amp which uses 300Bs or 211s or something even more powerful... 🙂 ) In terms of build difficulty the blue hawaii is probably the easiest (there are two version the original uses obsolete components but the modern version only uses transistors which are still available new), the mini t2 amp boards are almost all surface mount (psu is still through hole) and require precision and a good hot air station. For checking a stereo microscope is very useful. It only uses modern components and costs a bit more than the blue hawaii to build. The diy t2 is not difficult to build (if you use resistors that can handle the voltages) it's just big and intimidating. In terms of build costs the diy t2 is by far the highest. (there are two versions of the t2 one which uses almost all obsolete and very expensive nos components and a more modern version which only uses two types of obsolete transistors.). Either way you need to be aware there are many people selling fake nos transistors which will fail and blow up immediately on switch on or if you are "luckier" fail slowly over time. So you either need a trusted source or a transistor breakdown voltage tester and transistor identifier and even then you are taking a risk... (almost every seller of nos transistors on ebay sells fakes or a mixture of fakes and modern "equivalents" relabeled as originals. In terms of size I built the entire blue hawaii in a single 400mm deep case, the mini t2, transformers in one case and the amp and psu in a single 400mm deep case. Diy t2 transformers and psu in one 400mm case and amp in another 400mm case. (I had to modify the diy t2 amp board gerber files for the amp circuit board to make it fit)...
  3. vpi 16.5 with disc doctor record cleaning fluids. I have cleaned my entire classical music collection (1500+ lps) on it. I have two arm wands, one for the cleaning fluid and a seperate one for the distilled water wash cycle. I also use the disc doctor replacement arm wand pads - a lot cheaper than buying a complete new arm wand from vpi. the machine is not that quiet, there are grinding noises from the motor and the vacuum pump is quite loud but it has worked very well for me. I almost had a keith monks. A hifi shop I used to frequent often was closing (the original owner had died some years before and his son taken over but had died) and his grandson was going through the estate. I went through the ex-owners record collection pointing out some of the more rarer and nicer records (they were all played on only high end equipment, cleaned with a keith monks before playing and mint). The grandson was totally clueless about the value of the lps. I assumed he would either sell the collection in parts on ebay or go to a specialist dealer. I purchased a few records myself (I was fairly short of money at the time) and asked about the keith monks. The grandson said it was for sale but had no idea about the price. At the time I did not have enough spare cash to make what I thought would be a reasonable offer i.e. multiple hundreds of pounds. I found out a few days later rather than ebay it the grandson threw it away! He sold the entire record collection I guess about 750+ lps on bulk dirt cheap to a dealer.... sigh A sad end to my favorite hifi shop. I found a while later that someone passing by saw the keith monks in the rubbish skip and took it.... the hifi shop was in a tiny village in the middle of nowhere so I hope it was another patron of the hifi shop. Even sadder (for me) was the ex-owner had made reel to reel recordings over many years of live classical music radio concerts broadcast on BBC radio 3 on agfa pem368 tape ar 7.5 or 15 inches per second, on either a high end teac, ferrograph logic 7 or a tandberg td 20a reel to reels. I asked about these recordings... the grandson said he had erased them all.... sigh
  4. cyberpunk 2077 will be out in 2177, this game allows you to explore the historical setting of .......
  5. T2 frequency response is at least that good so it's confirmed to be running class AB.... 7K is an awful lot of money that's shop built blue hawaii se with a really nice potentiometer and 0.1% 15ppm resistors. Or two modern full T2s if you go DIY... so its up against the best of the best. 1. does it have interstage coupling caps (bad for sound)? 2. is the signal path cap free? 3. is it using constant current sources? if so where? 4. does it have a 5M ohm resistor on the bias to protect the headphones. 5. does it have 5.1K resistors on the outputs to protect the stax headphones? 6. how quiet are the power supplies? 7. is the B+ delayed on startup? As a speaker amplifier it's interesting, as a stax amp I am not convinced.
  6. that's the integrated amp only 4K
  7. 7K and its BASED on an amplifier that is class AB and has a cheap alps low end pot not even a TKD.... no details of the topology... no photos of the inside.... no details of the voltage swing for the stax... just the bias voltage 0.5% distortion into speakers, ok you might not be able to extrapolate from speakers to stax but... the T2 is much better than an order of magnitude better than that at (0.02% THD) at 575Vrms output. At 600V rms the T2 is starting to clip and even then the THD is still an order of magnitude lower at 0.05% THD and thats over a wide bandwidth of 20 to 50khz... I bet the case is not big enough to fit just the power supply of a full T2 into it.... here is the inside of the amp its based upon https://www.lineartubeaudio.com/products/zotl10-mkii erm where's the power supply transformer?... it has a seperate power supply no details and no photos. "100V / 120V / 240V operation: Auto-switching" ... sounds like a switch mode power supply???? nichicon 85C cap right next to a bunch of valves.... looks legit to me... Wait its a ZOTL design and has no output transformer.... just like the blue hawaii, mini t2, full T2, alpha centauri.... erm just like almost every stax headphone amp... (yes im ignoring the fact its output transformerless into speakers but this is the STAX forum...)
  8. nice electrical isolation... I didn't realise fluke had put prototype micro optical isolators into just some of the input jacks...
  9. Thank you for the feedback Spritzer, yep I am concerned about that. I'm still working on the track routing.... first priority was getting right the pad placement. v1.3 now has isolation slots and the ac lines rerouted further from the secondary output pins.... I also decreased the ac track width from 1.5mm to 1mm just in the area around the transformer solder pads to give a bit more clearance. The transformers have been moved a bit more apart to increase primary to secondary spacing there too. I have also moved the secondary tracks further from the m5 screw hole. All the tracks are on the underside of the board, I could move the secondaries to the top side as long as the transformers are not going to short to them.
  10. The m4/m5 screw hole looks centred in the diagram left to right but not top to bottom... looks like its displaced 2mm bellow centre on the transformer? Slightly larger holes for the transformers and slightly smaller for the 25VA. AC carrying tracks moved further apart. ALL tracks made slightly wider. added transformer windings onto silkscreen. moved mounting holes now centred This zip v1.4.zipcontains the gerber files. The zip needs checking for hole sizes, hole placement etc. Note some isolations slots are 0.5mm. NOTE THIS HAS NOT YET BEEN CHECKED AND VERIFIED.. This needs careful checking to verify pad placement, m4/5 hole placement etc. All tracks are on the underside of the board.
  11. I can make gerbers for you - no cost for something simple. If you can post the measurements, hole spacing, track layout etc. PREFERABLY in mm not inches.
  12. how is the voltage O- to ground does it behave and vary similarly to the O+? are both channels approximately the same? Unless there is a servo to automatically adjust the offset then you will see some variation with time as the device heats up and reaches a stable temperature. My T2 takes more than 3 hours for the offsets to become mostly stable. Even with a servo there is a tendency for some low frequency oscillation since the servo will alter the current flow and the change in current current flow causes a change in the temperature of the components and temperature change effects the gain and therefore makes the correction over or undershoot - a servo is always chasing its own tail.... Plus unless your valves have regulated heaters, mains voltage varies with time and the variations in the ac heater voltages will affect the valve temperatures and therefore offsets too. You need to put the offset into context. The stax headphones are built to withstand 100s of volts of input. The music signal is going to be far far higher than this offset. For example the T2 is capable of more than 600V RMS output into pro bias headphones... even at very moderate listening levels of say 50Vrms output, 0.1V offset is a tiny fraction of the signal... It's also normal for the offsets to be fairly high (10s of volts) on initial switch on, fairly rapidly decreasing while the valves initially warm up, especially if you do not have a delayed high voltage switch on circuit.
  13. 4K on a 15.6" monitor is not really going to offer much more than 1080p - 4K only really makes sense on large screens e.g. 32" or more Are you using the gpu for anything e.g. rendering? first person games? - there is not a huge performance difference between the 2070 super and 1650TI. if you are doing colour work you need to know the technology of the screen IPS vs TN IPS is generally more colour accurate AND wider gamult. You need to know the colour gamalt and accuracy. if you are doing lots of cpu intensive work the 8 core will give some advantage. my fear with the Dell is that it is not that well balanced, the 4K screen requires more video memory but the dell has LESS than the MSI, 4K requires more gpu and cpu power but the DELL has less cpu power. My feeling is the dell has compromised on the gpu and cpu in order to fit in a 4k display which you will not get any benefit from (in terms of resolution). The DELL might have better colour accuracy and gamult than the msi if its an ips panel or they may have cheaped out and use a low gamult tn panel. In general laptop manufacturers make it very difficult to get meaningful specs on the screen...
  14. low voltage transformer 52mm high 105mm diameter ( I like to run the heaters at a bit under 6.3V AND in my experience the transformers I buy provide a little more voltage than the specs) 2x 4.5A @ 6V for el34s 2x 1.5A @ 6V for 6922s 2x 0.4A @ 15V for balance servo, HV delay circuit and delay relay high voltage 65mm high 125mm diameter (voltages are the same as the psu board silkscreen.) 2x 0.15A @ 260V for +250, -260VDC 2x 0.15A @ 450V for +-500VDC 1x 0.15A @ 465V for -560VDC Both transformers have magnetic shields, electrostatic shields and thermal resettable fuses. transformer manufacturer Mueller rondo in germany http://www.mueller-rondo.com/kontakt.htm With postage and vat slightly under 200 euros for the pair. I like seperate HV and LV transformers so I can run the heaters and LV at full voltage and slowly bring up the HV on a variac when I am doing initial testing. It also offers the chance to easily reuse the LV transformers in other valve amps.
  15. The site did an update and there are issues accessing attachments. The admin know and they think its been fixed now.
  16. I agree about the low temperatures of the GR psus. In my experience the GRHV seems to generate very little heat (compared to the T2 psu whos 3W resistors are inferno level hot), For my blue hawaii I managed to fit everything including a GRLV, GRHV, transformer and amp boards in a single modshop 400mm deep disapante. For the mini T2 I had to go separate box for the transformers but I still managed to fit the dual GRHV, separate GRHV for the 250V, GRLV boards and amp boards in a single 400mm disapante. In both cases the majority of the heat was from the amp boards and the overall GR transistor temperature levels very acceptable.
  17. your not alone, I have the same problem mini T2 thread also has members having issues with attachments in posts that were definitely working previously e.g. bom .xls and gerber .zips.
  18. Pars, I entirely agree about the seperate thread for GRHV. Almost all 680uf 550V and even 500V caps are 80mm high - too high to fit into a 2U chassis (for example mouser lists some 500V less than 80mm high but none are stocked items, for 550V 680uF ALL are 80mm) . I also like the kemets for their life expectancy (although they are not cheap). I put 550V into both positions simply because at some point I might reuse the power supply and change its output. If you are budget conscious the output caps can be 450V or 500V for 400V output. This is one of the cases where moar does not always equal better. The kemet caps are very low ESR and so the inrush current from the GRHV quite considerable - with 470uF caps its enough to weaken a 3.15A slow blow fuse to the point where after 10-30 switchons the fuse can fail. 680uF is going to be even worse inrush... This also puts more strain on the power supply transformer. For example, on my mini T2 with GRHV supplies the high inrush chokes the HV transformer and results in it humming for quite some time, I don't get this problem with the kgsshv on my full T2 (despite the fact the full T2 has 25% more idle power consumption) because kghsshv in it has even less capacitance and so less in rush than the GRHV... I have not done a listening comparison between 680uF and 470uF. For me the only considerations was space and reliability.
  19. Seriously, don't run the bias at 645V and dont run bias through a DIN plug....
  20. moar voltage is moar good... everyone uses +580V bias voltage why?... convention, lack of imagination, no willingness to innovate and because its easy! No one knows the origins of this "standard" few dare to question its validity... True leaders and visionaries dare to be different and go that extra electron or two even if it cost more and requires more engineering. 645V is clearly moar than 10% bigger/better than the conventional "standard" everyone lazily adopts. ðŸĪŠ the fact this can be achieved in such a small amplifier is even more testament to next level, next generation engineering effort put into this remarkable amp. Occam clearly stated that perfection is reached not when nothing else can be added but when nothing else can be taken away. Look at the size and complexity of the full T2 (but then it uses valves which are obsolete technology, environmentally unfriendly, dangerous inefficent space heaters) and even the behemoth that is the T2 cant manage to reach the bias voltages of this seeming humble and simple amp. This amp is Occams razor in its purest form. Who else would dare to run bias voltages through a 5 pin DIN plug? they said it could not be done, they said a DIn plug is not rated for more than line level voltages... they were wrong, just as they were wrong about the +580V convention. This amp is just full of innovative and convention breaking, ground breaking, diaphragm breaking and heart breaking design choices. ... and next week a stax amplifier based on a dual 741 opamp with zero feedback powered by energy harvesting the heat from a T2 or megatron..
  21. T2 first listening impressions. wow..... erm.... wow..... erm..... wow The first thing that strikes me is marco dynamics are amazing, on recordings that are not that dynamic the amp does not exaggerate the dynamics, but on dynamic recordings like full orchestra the dynamics are so powerful but not overdone. This is backed up with bass is far more defined, less mushy, more full than my other stax amps but the bass is not not dry or hard or overblown Stereo images are more solid and tangible and more precise than any other stax amp I have, its so close to the experience my Quad 2805 speakers..... Detail is amazing, but the detail is not thrown at you and its therefore not tiring to listen to. But I do notice tape edits, dropped violin bows, musical score page turns more... but it just adds to the experience that tens of musicians in a room can't be totally silent all the time. when music gets complicated there is far less tendency for sounds to just clump together into a messy mushy ball. However you still get the feeling of musicians playing together and the detail is not analytic. The amp just says here is all the detail let it wash over you and you decide how much you want to listen into the detail and how much you want the whole music. This is the first time I have been satisfied with the bass and dynamics from my sr007a mk2. I think it shows that my stax sr007a just need as much drive as they cant get. My journey: stax srm006 (piece of mushy yet bass light and less bass the higher the volume, undynamic, undetailed, poorly constructed, stereo thick soup, gloop with the sweetness of a lemon), hi-amp alpha centauri (improvement in every way over the srm06, its an upgrade but you still feel there is music missing. Overall you get the impression is nothing special and has but poor bass, slightly deeper than the srm006, but mid and upper bass is almost non existent. Bass loss with volume is far less), blue hawaii (murders the alpha in every way but maybe slightly hard sounding for me and a bit of a tiring long term listen. It was a very enjoyable build and a considerable step up from the alpha but I rarely could relax into the music), Mini T2 (better micro dynamics, smoother and more refined more listenable than the hawaii but lacking in some drive and macro dynamics, detail and bass. I still got the feeling with it that it was struggling with the sr007s a bit) and finally the T2 (im sure I will eventually find something wrong with it... that's just the way my brain works but for now im content [which is rare])... So whats next after the T2? (other than building a second one).... Many many thanks to Kevin for the T2 and joamat for the modified T2 and mini T2, spritzer for providing the nos transistors and everyone for their encouragement and help.
  22. try not to kill the user until AFTER they have finished paying for it Equal rights for electrons! they should be allowed to travel freely and not be constrained by insulation... If they want to travel through your heart it just their way of being loving and friendly.... they are so misunderstood.
  23. listen to it? if you check my todo list nowhere does it say listen to it... measure it yes... listen to it? why would I do that? 🙃 latest update, internal signal wiring done (silicone not cardas - I need to buy more cardas chassis wire) and front panel completed. Both channels powered up at the same time for the first time. No drama so far. The heatsinks around the el34s runs a bit hotter than joamats mini T2. I not done any temperature checks look good. All transistors seem ok and so do the high power resistors. .6922 heater voltage is a little high at 6.35V so I will need to add some dropper resistors. All other voltages are spot on. El34 heaters are at 6.1V which is about the same level as my mini T2. I found my first issue, the DC balance between + and - halves of a channel is fine <50mv BUT the DC offset to ground started at -85V and even adjusting the offset pot all the way I only got it down to -33V. Exactly the same on the other channel due to close matching of components and matched valves. So I will need to replace the dc offset adjustment trimmers with something 2-3x the range. Anyway I know you have been waiting for the money shot: glowing leds and heaters so enjoy: Im currently going for an extended power on idle test and will be periodically checking voltages and temperatures on both the amp board and psu. If that passes it will be time to feed it some test signals... I hoping for more detail in the square waves, more dynamics in the triangle waves and smooth fatigue free sine waves. Here are the first measurements. Distortion 1Khz input Total Harmonic Distortion to 49Khz is around 0.0063% unweighted (average of 20 measurements) 2nd harmonic is around -90db and third slightly higher at -87db. The other harmonics are very low all less than -105db. total harmonic distortion plus noise is better than 0.018% (im not using shielded cables for this test AND the amp and psu do not have top lids and the cases are not grounded so the amplifier is almost certainly has better thd+n than I am measuring in this setup. At around 575V rms 5th harmonic starts to rise and at 600Vrms output all harmonis increase and odd order are higher than even order harmonics. NOTE this measurements where taken with around 35V DC offset so it is possible clipping may occur a little later with less offset... Noise, THD, THD+N and level of distortion harmonics at 575V RMS, 1Khz output: Noise, THD, THD+N and level of distortion harmonics at 600V RMS output 1Khz: The THD up to 49Khz is still less than 0.05% The amp runs quite a bit hotter than the mini T2, heatsinks near the EL34s run at 40C and power consumption is close to 205W. The mini T2 is around 153W. The power supply is also is less efficient than the golden reference HV, the 3W resistors between the ksa1156es and ksc5026 run close to 90C and dont have a lot of room around them, on one side there is a large 0.1uF 1KV film cap and on the other 5 closely packed transistors... So the T2 needs good heat sinking and the psu boards could do with lengthening a little to give the 3W resistors a little more air flow around them and drill holes under them. Update DC offset fix, The 5K pot in parallel with the 510 ohm emitter resistor gives a minimum resistance of about 461ohm which still gaves me ~ -33V offset. With the 5K pot in the middle you get around 423ohm combined resistance and ~ -85V offset. So I replaced the 510ohm with 604ohm and this gives enough adjustment range to get <1V DC offset. (I would have implemented joamats suggestion but I did not have any 10K pots)
  24. It might be a little premature but I think I now have a working T2 using a modified version of joamat's staxt2nc3fdh7 amp files and kgsshv dc supplies.... Initial startup looks good. Channels started up seperately. Heater transformer running at full voltage. High voltage transformer on a variac. virtual batteries within 100mV of 740V before any adjustment. DC balance between + and - sides of a channel <1V without any adjustment, all 3 leds lit on both channels. once my hands stop shaking I will take a few photos... I have been dreading switch on... in the meantime here's a few build photos of a finished amp channel top and bottom, the amp and psu I modified the delay circuit on one of the psu boards to use a relay instead of the now unavailable solid state relay. I modified the amp boards so that 1. they fit into a 400mm deep chassis, hifi 2000 dissipante chassis. 2. they have screw terminals for all connectors on the top.. (less neat but easier for testing and rebuilding) 3. all resistors of 1W or more go on the top of the pcb with a drill hole under for increased airflow 4. groundpane is between 1.1mm and 1.3mm from any solder point 5. pcb is cut in half so each channel can be built, tested and mounted independently, 6. solder points for pot and input jacks removed and replaced with screw terminals. 7. silkscreen has instructions for adjustment of pots 8. mpsw06 transistors replaced with mpsa06 9. small standalone heatsink for Q34 FJPF2145 in the 20mA current source darlington pair has drill holes in the pcb by the fins for enhanced airflow. 10 all components have schematic numbers included in the silkscreen 11 leds and adjustment pots mounted on top side of pcb like the original T2 12 removed the bias input and 5.1M resistor (since the kgsshv psu already has the resistor in the bias section) I will be happy to release the gerber files of my modification once I am certain the amp is reliable For the build: wima film capacitors, mixture of koa cm1/2 and xicon 273 series 1/2W resistors, for higher wattage vishay pr02 and pr03 All resistors, diodes, zeners raised from the pcb. pcb 2mm with 2oz traces. All 1/2W resistors matched to 0.1% or better at 1khz on a good LCR meter between + and - sections of an amp board AND between left and right channels. all non psu and psu decoupling caps matched to better than 1% at 1KHz on a LCR meter between + and - sections of an amp channel AND between left and right channels. (except for the pF caps which are just too small to measure accurately). all leds and mpsa06 transistors matched on a dca75 curve tracer between + and - sections of an amp board AND between left and right channels. all zener diodes matched to within 1% or better between + and - sections of an amp board AND between left and right channels. separate umbilical cords for AC heater power and DC voltages all internal wiring 1KV silicon all signal wires will be cardas chassis wire volume pot tkd 2500 series left to do install rca signal wiring, volume pot and stax output socket test with signal generator and measure distortion etc collapse from T2 build anxiety drill top of case for valve sockets clean up wiring pray to the god(s) of electronics sort out grounds on psu post moar pictures Here is the schematic for the staxt2nc3fdh7 NOTE this is my reverse engineer based on the pcb and the original T2 schematic and has not been checked by anyone. ( as far as possible component labels reflect the original T2 component labels. In the case of 2 components replacing a single component in the original T2 the components are now labeled Xpt1 and Xp2. In the case of additional components no present in the original T2 they start with the number 9XX. In addition both batteries are shown and the the components labeled with a Xp for the O+ side battery and Xn for the O- side battery. Note the 140K resistors in the virtual batteries dissipate 0.423W each and I found xicon 1/2W 273 series discoloured and drifted by about 1% after about 6 months heavy use when placed on the underside of the pcb. So you may want to think about 1W resistors or place the resistor on the top side of the pcb. psu low voltage, bias, +500V -500V and hv delay reverse engineered from pcb and original schematic. not checked by anyone. psu +250V, -260V and -560V reverse engineered from original schematic and pcb not checked
  25. The headphones are only made of organic materials and grip the head well, however they do have a tendency to slide around a bit and my ears got fairly slimy rather quickly. I am concerned about long term life expectancy and batch to batch consistency. I may have received a faulty pair, connecting them up to my blue hawaii resulted in the drivers crisping up very quickly. The ear cups are also quite fragile and have a tendency to crack if dropped.
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