jamesmking

the fresh led has a sharper curve than the used ones, I am zoomed in on the curve, If we look at the full curve the LtL-4221nlc is sharper compared to the HLMP-1700. The TLLR4401 looks promising but is also not quite as sharp. I almost feel like putting 2 pin sockets in the D24 position and trying different les to discover which sound best 🙂 Xicon 273 series. Although discoloured they are not burnt. The drift from new was less 140.5K -> 141.5K so not actually that significant. I did place them on the underside of the pcb. This time I'm placing on the top side and I think that will be enough. Although 0.42W through a 0.5W part is still a little close to the limits for my tastes. I have modified my gerbers to include 4mm airflow holes under each pcb. I think one day I will build a second T2 with some modifications built in.

the style of that 6 in the 2sk216 seems a lot different from mine. But maybe they changed font... perhaps its a 7s2sk216 (7 2sk216 is series. in a single package)... 🤪 I just tested a few of mine. Setup on the DY294 : selected NPN gate and source connected to the emitter on the dy294 drain connected to collector on the dy294 and I get around 230V breakdown. spec sheet says 200V.... ----------------------------------------------------------------------- My peak dca75 in identify mode says the following: N-Ch Enhancement mode MOSFET Vgs(on)=0.557V at Id=5.01mA and Ig=0µA Vgs(off)=0.080V at Id=5.3µA gm=25.6mA/V at Id=3.0mA to 5.0mA Rds(on)=6.1Ω at Id=5.0mA and Vgs=8.0V with body diode

I think it might well be thermal. About a month ago I replaced the groove tube el34s with modern production branded mullards and the bases of these run far hotter than the groove tubes so that could also have contributed more heat conduction to the leds... I did match all 6 leds in the amp by curve tracing on a peak dca75. The other 4 leds still work well and have very similar voltage drops meanwhile both the D24 leds (which are positioned close to the El34s) degraded. I did not raise any of the leds off the pcb and I think there was excessive heat conduction from the pcb into the underside of the led. This time i'm using leds from the same batch but have raised them off the pcb and time well tell if they degrade. I carefully de-soldered the degraded leds and curve traced them. As expected their characteristics had considerably changed compared to the rest of the leds in the bag. The D24 led on the left channel which is closest to the EL34 had the most change from new and the lowest voltage drop in circuit 1.4V in circuit, the righthand channel D24 is a little further from the EL34 and in circuit had 1.5V drop and is a little closer to a new led which has a drop of about 1.7V in circuit. To put the change into context I measured multiple leds from the bag and the curves almost superimposed over each other. So the drift in the D24 leds is significant.

testing breakdown voltages would be a good idea. Fingers crossed you have a real ones. Here is some high resolution photos of a known good one from a reliable source- and its brothers are working my T2... Markings are printed not etched and are a greyish cream colour not white. (photo has been colour balanced). Ends of legs are fairly sharp. close up of the circular area in the middle. Lighting adjusted to make the text in the dimple more readable at the expense of the printed markings. Text in the dimple is raised. The starting angle relative to the top of the transistor for the word MALAYISA and the associated number and letters in the dimple varies between the 216s I have.

happy birthday Kevin, thank you for bringing so many diy projects to life and for you advice and troubleshooting help.

Longish term modern DIY T2 reliability. I estimate its been used around 8+ hours (and more often than not 12 hours) a day almost every day since I built it. yesterday I took it apart for cleaning. I noticed all four 140K resistor strings connected to the voltage reference in the virtual batteries where somewhat discoloured.... hmmm... on further testing I found the D24 led on both channels did not light up at all not even dimly. :-(. but the amp seemed to work and sounded good. (on the left is a brand new resistor from the same pack as the 140Ks I removed from the virtual batteries.) I checked also psu voltages - good. I measured the voltage across the D24 led- about 1.4V. When the amp was originally built these leds definitely glowed as strongly as the others. All the leds where tested before soldering in and were from the same bag I even hand matched them just for overkill. The D24 leds are part of the circuit that provides base voltage and current to transistors that provide feed into the virtual batteries. I checked the virtual batteries - all were 741V on startup and the adjustment pots could adjust the output. So the batteries look good despite the slightly cooked resistors. I removed the voltage references and tested them in a glden reference LV - all good. The discoloured resistors can be explained by the fact they have about 0.423W flowing through them excluding base current draw from the 2 transistors and are on the underside of the board with little airflow - maybe1W would be better or some airflow holes in the pcb, or mount them to the topside of the pcb. So I decided to de-solder the 140K resistors for measuring and the 140K resistors have drifted slightly but all measure within 141.5K. So a little cooked but probably not the case of the problem. But why are the leds not lighting.... Looking at the circuit diagram the D24 leds should get about 0.5mA current excluding any draw from the bases of the transistors. (560V / (560K *2 resistor string to ground). I used the exact SAME leds for the other positions and it also looks like those leds get about 0.5mA excluding base transistor draw and they glow nice and bright. I de-soldered the leds and tested the D24 resistor string to ground. They spot on resistance and have not been damaged or drifted and so should provide 0.5mA current draw through the led. However the desoldered D24 leds would not glow at all with diode check on my brymen BM869s multimeter but do pass current and are not open or shorted. I tried my keithley 2015 in diode check mode (it has adjustable test current) and got absolutely no glow at 10 or 100micro amp but did get strong glow at 1mA - same situation on both D24 leds. I tested my remaining leds from the same bag and they glow on the brymen admittedly fairly dimly, and glow on the keithley at 100 micro amp again dimly but visibly. (I did test all of them on the brymen before soldering into the amp). So the leds in D24 have degraded over time . I used the same leds in the other places in the amp and they are all fine. This would explain why the batteries are working but the leds are off.... So the plan is to do some more testing on the leds and replace them with another model. But what's causing the leds to degrade in brightness on the -560V rail when the others have not? any ideas? regards and and I apologise for the long winded post James Update: I replaced the D24 leds... they now light brightly with a voltage drop across them of about 1.7V. I replaced the resistor strings with the same resistors but now placed on the top of the pcb, raised from the pcb by about 1cm. After a ten minutes with no lid on the amp the resistors reach 65C on the top and 71C on the sides. So its easy to see how on the underside of the pcb with the lid on they could reach temperatures which could cause discolouration.

water cooled data centre means you can overclock the cpu(s) more....

fantastic. I was about to lose all hope. thank you to everyone involved in getting head-case back online

My megaslow build. Thank you JoaMat for supplying the 3 mosfets I needed for the golden reference psu. The megatron is workingish. This build was a little perplexing. I used groove tube 12ax7, electroharmonix 12au7 (gold pin) and groove tube el34s. I implemented the 12ax7 increased current modification form the outset. I found that I could only get about 220Vrms output before clipping. The clipping was not symmetrical and it was the bottom of the wave on the +O that was clipping only. I started to probe with a scope and found that the voltage drop at the 330K anode resistors on the 12ax7 was only about 19V on the +O side and about 35V on the -O side. Everything else looked fine. I scoped the output of the 12au7 when the amp was fine - no clipping when the output of the amp clipped. I checked all the psu voltages - no problems. It was the output of the 12ax7 was asymmetrically clipping. I took the valves out and measured them and the 12ax7 was only managing about 0.5mA output on one plate and about 0.8mA on the other. The avo manual said I should be expecting about 1.2mA. I was not sure if the amp had damaged the valve or if the valve was weak. So I checked the amp and removed the extra current modification and tried with a stronger 12ax7. Now both the +O and -O clip at approximately the same point but the clipping is still asymmetrical. I'm getting about 35V to 40V across the 330K anode resistors on the 12ax7. The bottom of both outputs clips before the top, and I am getting about 440Vrms output before clipping. I got in an email conversation with watford valves and the proprietor said that almost all new production 12ax7s are only capable of about 0.8mA and that only new old stock could do 1.2mA. So the high current mod might not be an option if you are running new production 12ax7s. I did some frequency response measurements and found the -3db point was only at about 23-24Khz... which seems rather low. Could someone tell me what output voltage rms they are getting before clipping and the -3db point for verification. thanks in advance James

it seems like at the moment the only thing in stock is out of stock notices.... 😞 check the height of the 1000uF cap... at 105mm tall its a beast which will not fit into a 2u case. (around 65mm depending upon the height of the standoffs for the pcb is about as tall as you can go for a 2U (80mm tall case)... are you going 120mm tall 3U case? the issues with very large capacitance input caps is that they will create a very large inrush current on switch on so you may need a larger value fuse than you would otherwise. Also the larger the cap the more diode switching noise it will cause because the caps will pull more current for shorter periods of time from the diode bridge rectifier. For the output cap some psu can become unstable if the output cap has a too high (or too low) capacitance. You may want to send a private message to kevin gilmore - the designer of the golden reference psu to get his input. Personally I use 470uF most of the time on the golden reference because I could not find any 680uF caps that would fit into the 2U cases I use.

if you are referring to the high voltage lines on a diy t2 - those psus use two 450V caps in series for double the voltage rating of one cap at the cost of halving the capacitance (except for rails bellow 300VDC output). The golden reference does not use series capacitors like this. the golden reference uses a single input and output cap per rail. So the each cap has to withstand the full voltage by itself. if the output is 400V then 450V is ok for the output cap giving you 10% or so margin. the input cap will need to have a higher rating than this because all regulated power supplies require more input voltage than they provide output voltage so they can maintain regulation. I think, if I remember correctly, the golden reference is about 330VAC input for 400VDC output. 330VAC once rectified through the diode bridge will give 330* squareroot(2) ~ 466Vpeak. Plus main voltage can vary, plus transformers can vary so to be safe you would want at least a 500V input cap. You may be able to get away with a lower input VAC if the golden reference can maintain regulation and your line voltage does not sag. Also consider that the higher the current draw the lower the output of a transformer and visa versa. So if you over spec your transformers current capacity the output voltages can be higher than you expect...

the quick 861dw comes highly recommended its also useful for drying out pcbs after ultrasonic cleaning, removing surface mount components, heat shrink etc.

I did some experimentation and found that low airflow and fairly high air temp worked best for me. I have a quick 861dw hot air station. I set the airflow to 5 out of 120 and set to 360C (the temperature will depend on your solder paste melting point). I hold the hot air nozzle with one hand and with the other I use tweezers to keep the smd part in place. If you do not hold the part in place almost any airflow will send components into low earth orbit. The tweezers I use are curved on the end which makes it easier to place components, keep your hands away from the heat and easier to see what's going on.

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opa134pa is exactly what i am using and is fine the LT1021DCN8-10#PBF is about half the price of the version of the reference your are proposing. The output accuracy is a function of the accuracy of the LT AND the divider network (which sets the output voltage) by taking the output and dividing it down to a nominal 10V. This is fed to the opamp which acts as a comparator between this and the LT. Unless you are going to use 0.1% or better tolerance hand picked resistors for the divider network there is not much point in spending $$$ on a very accurate version of the reference when the divider resistors are 1% and will drown out any extra accuracy a more expensive version of the LT will provide.... If you want high accuracy and don't want to spend $$$ you can always hand measure and match the resistors to get a more accurate output voltage (if you need that level of accuracy).

well my amp boards for the megaslow build finally arrived today. I have decided to use a golden reference HV psu for the +-450V and a second golden reference hv for the +300V. The psus are finished other than I don't have and cant source the pass mosfets.... *sigh* One question. since I will be using a 300V psu do I need to populate the 3*100V series zener string connected from the 300V line down to ground? I assume the zener string is there to stop the 300V line rising above 300V with respect to ground if the 300V line is derived from the +450V line via a dropper resistor.. or is there another reason why the string is there?

The pcb files are in zips with the contents in a format called gerber which can be uploaded to a pcb manufacturer like jlcpcb. The gebers contain all the necessary information for the creating the copper tracks, drilling of holes, silkscreen printing etc. Often there are minimum order sizes of around 5 of each type of board so often people have spares... There are no step by step instructions. There is an assumption that you can read a schematic, are prepared to read through some very lengthy forum threads and do basic drilling for mounting boards to heatsinks etc. the information is a bit spread-out. In general you need: BOM - bill of materials to get the right value and size components. Downloads from the appropriate forum thread for your build (and possibly two threads - the second thread being for the power supply) schematics - for troubleshooting etc in the forum threads and or download from https://drive.google.com/drive/folders/0B7egryukiT7_TFlEQlBRejdVdDQ the gerber files for getting the pcbs made in the forum threads or download from https://drive.google.com/drive/folders/0B_iJFfZStuVhSE5nOHBVdTByR1k the specifications for the transformers. in the forum threads. advice. in the forum threads and ask in the threads. in general the markings on the pcbs takes precedence over the schematic or bill of materials (unless the pcb has a silkscreen error). Some amps have more information than others - the threads grow organically over time depending upon popularity, etc. In general support is available for everything on a voluntary basis. You post questions on the appropriate thread hope for someone to answer. There are some very knowledgeable and helpful people active in the forum for example Kevin Gilmore, Kerry, JoaMat. Often the people who created the design will answer questions in the forum posts or people who have actually built one or even modified one. Unless you have lots of money/luck/ or existing stocks of obsolete components obtained from known good sources, I would stay away from any design which requires no longer manufactured transistors. There are many fakes floating around which can and will fail catastrophically on first switch on and non fakes are rare and there are few trusted sources willing to sell to non friends. I would advise reading the forum threads from start to finish and making notes, that way you can see the different versions/modifications emerge, see issues with certain components for example in the DIY T2 thread the voltages are high enough that some makes of resistor sparked and the insulation broke down.... Look at what people did that worked or did not work and learn from their experience. Finally if you can, give as well as receive. Post what works for you, post pictures, post updated bills of materials etc.

I also have the peak dca75 and several adapters. It can't test at high voltages or currents but its insanely useful for identifying transistor pinoutsand the type of transistor. I have used it several times to identify bad/failed transistors making troubleshooting much easier. The windows software also provides curve tracing which is useful for matching small signal transistors and leds.

Digital-First Retail Limited owns Maplin. the company did not exist prior to 29 June 2018... and has changed the location of its registered office no less than 4 times since then... The original director of the company resigned 6 oct 2020. The accounts only show 2 employees ... so im guessing its a shell company. The accounts is interesting section 476 means no requirement for external audit of accounts, section 477 companies act 2006 exemption from audit and exemption from publishing a full statement.... so the entire financial statement is simply one line current assets, one line creditors amount due and one line net assets. current director is director of 1 other company and previous director of another - all from the same address.

quick heads up KSA1220AYS transistors are now END OF LIFE https://www.mouser.co.uk/ProductDetail/ON-Semiconductor-Fairchild/KSA1220AYS/?qs=ljbEvF4DwOOJTVoo5AYsWQ%3D%3D 😞 mouser is currently out of stock radio spares has stock farnell is out digikey is out

My guide to golden reference high voltage (grhv) variants Here is my attempt at documenting some of the different GRHV board variations. (this will be work in progress for sometime) feel free to private message me with any additions comments, corrections etc. please note the schematic for version 1.5 has been reverse engineered by me from the gerbers and may contain error(s). location of the gerbers: https://drive.google.com/drive/folders/0B_iJFfZStuVhSE5nOHBVdTByR1k golden reference filename naming guide fat - boards which are wider and have less height than the non fat variants L bracket mounting only same as the non fat variants. fat with S as the last character of the filename - boards which are wider and have less height than the non fat variants and the height is about 6.3mm less than the fat variant. these boards also feature more screw hole options for the mounting the pcb to the case including an option of not using an L shaped bracket and mounting the transistors directly to the vertical face of a heatsink/side of the case. a silkscreen cut line is included to guide removal of the L bracket mounting roles to facilitate direct transistor to heatsink mounting. dual - has both positive and negative hv supply with additional bias and both positive and negative low voltage supplies on a single pcb left - has a single negative hv rail and both positive and negative low voltage supplies right - has a single positive hv rail and bias no new in the filename version - 1.5 boards high voltage starts instantly board has high voltage VAC power. Topology is much simpler then version 1.7 and 1.8 and therefore not considered golden reference. new in the filename actual golden reference boards with extensive post pass transistor regulation. new without sw in the filename- version 1.7 high voltage starts instantly board has high voltage VAC power. new with sw in the filename - version 1.8 or later boards same topology as 1.7 but high voltage will not start until dc power supplied to the cpc1117n no dual and no fat in the filename - minimal width and quite high. NOTE placement of the screw terminals for input VAC can vary considerably depending on if the board is a fat, fat S or non fat. Overview of the versions It is the extensive post pass transistor regulation that marks the golden reference out from the other power supply designs as such version 1.5 and earlier not classify as a golden reference since they lack any post pass transistor regulation. No details of versions before 1.5 or version 1.6 could be found in the gerber archives. Apparently pre 1.5 versions had on board heatsinks and ground lanes but there gerbers and not available in the google drive archive. No schematic could be found for version 1.5 although after reverse engineering it was found that the circlotronps.pdf is similar in topology but modified to support 900V output. No bill of materials could be found for version 1.5 and it is not certain what is the power rating for the larger resistors. All versions have the pcb tracks on the underside with no tracks on the top. All versions have no ground plane ALL versions have bleed resistors to help discharge the high voltage caps although version 1.5 and a few variants of 1.7 use a single high power resistor and the rest two 1/2W resistors in series. All versions have the same basic voltage regulator based low voltage positive and negative supplies All versions have the same bias supply although v1.5 has different resistor values. ALL versions use a LT1021-10 voltage reference All the versions 1.5, 1.7 and 1.8 use a C2M1000170D pass transistor All the versions use a 10M90S pre regulator although version 1.5 controls it with a zener string and 1.7 and 1.8 control with a DN2540. 1.7 and 1.8 are almost identical in topology although 1.8 does not automatically start the high voltages. DC must be applied to the CPC1117N to start. note 1.8 does not have provision for screw terminals for the DC to switch on the cpc1117n. versions 1.7 and 1.8 have more post regulation using a second 10m90s (which is not present in version 1.5) after the 1N4007 protection diode. version 1.5 uses a 10ohm current sense resistor and versions 1.7 and 1.8 use 5.1ohm by default. version 1.5 uses a 10K resistor to ground in the 3 series resistor chain to decide the output voltage, 1.7 and 1.8 use 20K to get 400V output. The other 2 resistors in the chain are the same for version 1.5 and version 1.7/1.8 version 1.5 uses two stn0214 which are replaced by two KSC5026M in v1.7/1.8 version 1.5 uses two stn9360 which are replaced by two BC557B in v1.7/1.8 Known non golden reference boards which are variations or predecessors to version 1.5 and golden reference variants NOTE These have not been looked at in detail by me or fully reverse engineered. The cyclotron power supply series follows a similar evolution to the golden reference. earlier cyclotron psus (circlotronps.PDF) use a variation of version 1.5 topology with modifications to bring the output up to 900V. However since it lacks any post pass transistor regulation it can not be considered a golden reference these psus do not have new in their name. The later cyclotron power supplies have the words new or newver in their name on quick inspection of the gerbers appear to be modifications for 900V of the version 1.7 power supplies, have post pass transistor regulation and may be considered golden reference variants. The filename conventions follows the guide above with dual, single, S and SWS versions available. circlotronhvpowerdualnew.zip appears to be derived from the version 1.7 topology with a similar complement of transistors. On the underside of the pcb there are two additional stn0214 transistors compared to the version 1.7 plus 3 mount points for a total of 500V worth of smd zeners. circlotronhvpowerdualnewer2.zip ditches the zener string and introduces another stn3960 and includes sw and sws variations. The kgsshv8g.pdf power supply appears to be an predecessor version of version 1.5. There are very close similarities in topology including no post pass transistor regulation. Current sense is still controlled by a 2n3904. The pre-regulator is 10m90s controlled by a zener string and a quad of transistors like the version 1.5. However the pass transistor is two parallel fqpf8n80c. The control transistors are 2sa1486 instead of stn9360 and 2sc3840 instead of stn0214. Both types of control transistor are no longer in production and hence the conclusion this is older than version 1.5. Apparently these boards are classified as KGSSHV ------------------------------------------------ Version 1.5 boards ------------------------------------------------- predecessor to the golden reference with no post pass transistor regulation the board uses a single high wattage bleed resistor for each cap uses multiple stn9360s, stn0214s uses a serial zener string for to control the 10m90s pre regulator. LT1021-10 voltage reference based single sided board kgsshvpssicfetdual2.zip this has both positive and negative rails, a simple voltage regulator based low voltage positive and negative supply and 580V for stax headphones bias board size approx. width 152.7mm height 165mm silkscreen revision 1.5 kgsshvpssicfetsingle2.zip this has a single rail identical to the kgsshvpssicfetdual2 in topology and 580V for stax headphones bias board size approx. width 76.5mm height 165mm silkscreen revision 1.5 ------------------------------------------------ Version 1.7 boards ------------------------------------------------- considered the first known golden reference board version (given the lack of information on version 1.6) has extensive post pass transistor regulation. the board uses two serial bleed resistors for each cap uses a single stn9360s and multiple BC557B and KSC5026M uses dn2540 and 10m90s for stage early voltage control for the input to the c2m1000170D LT1021-10 voltage reference based double sided board kgsshvpssicfetdual2new.zip this has both positive and negative rails, a simple voltage regulator based low voltage positive and negative supply and 580V for stax headphones bias board size approx. width 152.7mm height 165mm silkscreen revision 1.7 kgsshvpssicfetsingle2new.zip this has a single positive rail identical to the kgsshvpssicfetdual2new in topology and 580V for stax headphones bias board size approx. width 76.5mm height 165mm silkscreen revision 1.7 single bleed resistor for each cap kgsshvpssicfetsinglenewleft.zip this has a single negative rail identical to the kgsshvpssicfetdual2new in topology and has a simple low voltage positive and negative regulators based supply board size approx. width 76.4mm height 165.3mm silkscreen revision 1.7 kgsshvpssicfetsinglenewright.zip this has a single positive rail identical to the kgsshvpssicfetdual2new in topology and bias supply board size approx. width 76.4mm height 165.3mm silkscreen revision 1.7 kgsshvpssicfetsinglenewleftfat.zip this has a single negative rail identical to the kgsshvpssicfetdual2new in topology and has a simple low voltage positive and negative regulators based supply board size approx. width 138.7mm height 103.1mm silkscreen revision 1.71 kgsshvpssicfetsinglenewrightfat.zip this has a single positive rail identical to the kgsshvpssicfetdual2new in topology and has a 580v stax bias supply board size approx. width 138.6mm height 103.1mm silkscreen revision 1.71 kgsshvpssicfetsinglenewleftfatS.zip this has a single negative rail identical to the kgsshvpssicfetdual2new in topology and has a simple low voltage positive and negative regulators based supply has more mounting options for the pass transistor, 4 holes for mounting to a case and can be used with or without an L shaped bracket board size approx. width 138.7mm height 98.6mm (slightly less height than the fat non S version silkscreen revision 1.71s kgsshvpssicfetsinglenewrightfatS.zip this has a single positive rail identical to the kgsshvpssicfetdual2new in topology and has a bias supply has more mounting options for the pass transistor, 4 holes for mounting to a case and can be used with or without an L shaped bracket board size approx. width 138.7mm height 98.6mm (slightly less height than the fat non S version silkscreen revision 1.71s ------------------------------------------------ Version 1.8 boards ------------------------------------------------- same topology as version 1.7 making this a golden reference board adds a cpc1117n and 600ohm resistor to control high voltage startup the high voltage will not start-up automatically. This negates the need for a external relay for delayed start-up and just requires dc power to be supplied to the cpc1117n (not present in earlier versions) for the high voltage to start-up. if you want the board to power up instantly simply omit the 600ohm resistor and cpc1117n and it will act just like the version 1.7 instant start boards. boards same size as the equivalent version 1.7 pcbs silkscreen 1.8 there does not seem to be a dual version of this board kgsshvpssicfetsinglenewleftSWS.zip this has a single negative rail almost identical to the kgsshvpssicfetdual2new in topology and has a simple low voltage positive and negative regulators based supply board size approx. width 76.4mm height 165.3mm silkscreen revision 1.8 kgsshvpssicfetsinglenewrightSWS.zip this has a single positive rail almost identical to the kgsshvpssicfetdual2new in topology and has a bias supply board size approx. width 76.4mm height 165.3mm silkscreen revision 1.8 kgsshvpssicfetsinglenewleftfatSW.zip this has a single negative rail almost identical to the kgsshvpssicfetdual2new in topology and has a simple low voltage positive and negative regulators based supply board size approx. width 138.7mm height 103.7mm silkscreen revision 1.8 kgsshvpssicfetsinglenewrightfatSW.zip this has a single positive rail almost identical to the kgsshvpssicfetdual2new in topology and bias based supply board size approx. width 138.7mm height 103.7mm silkscreen revision 1.8 kgsshvpssicfetsinglenewleftfatSWS.zip this has a single negative rail almost identical to the kgsshvpssicfetdual2new in topology and has a simple low voltage positive and negative regulators based supply has more mounting options for the pass transistor, 4 holes for mounting to a case and can be used with or without an L shaped bracket board size approx. width 138.7mm height 98.6mm (slightly less height than the fat non S version silkscreen revision 1.8 kgsshvpssicfetsinglenewrightfatSWS.zip this has a single positive rail almost identical to the kgsshvpssicfetdual2new in topology and has a bias supply has more mounting options for the pass transistor, 4 holes for mounting to a case and can be used with or without an L shaped bracket board size approx. width 138.7mm height 98.6mm (slightly less height than the fat non S version silkscreen revision 1.8

1. part of the headcase experience is trawling a massive number of posts in one thread e.g. the carbon to find out about the grhv. Having a dedicated thread is seen as cheating. 🙂 2. to build a grhv you need C2M1000170D which are out of stock just about everywhere with little hope of being back in stock anytime soon... this is one of the issues delaying my megatron build. I can't comment on any sound quality differences, but there very few options if you want a 680uF cap that is 550V and will fit in a 2u case, i.e. be about 65mm in height or less. 450V or better 500V would be fine for the output cap with 400V output. The + lead of the input cap is connected to the centre pin of the large C2M1000170D. Output cap + lead is connected to the cathode of the IN4007 protection diode that is directly inline with the 5.1ohm 3W current sense resistor.

I get mine from https://www.ebay.co.uk/itm/Stax-socket-5-pin-Pro-Bias-WHITE-Teflon-custom-made/184601921523?hash=item2afb21c7f3:g:CHcAAOSw2ENf7Jyy

great in the winter time to keep hands warm. not so sure about the utility in the summer and i hate lugging around the batteries.

(I would like to try NOT using my headphones or my ears or any other part of my anatomy) stax amp using multiple parallel push pull ef86 valves.... called the maxi minitron stax amp using push pull 211 valves called the ouch stax amp using push pull 101D valves called the almost-inplausible joking aside, a T2 using golden reference HV supplies (capable of the required +-500V and -560V) and only modern components.