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  1. Arrived yesterday and it really opens up every electrostatic headphone that I own. I was looking for an amp that can bring more bass out of my HE90 than HEV90 so I drained my pocket to bid on this and now I am very satisfied. The hev90 has a romantic sound but the t2 amplifies every piece of detail, expand the soundstage to what ever possible with extreme fineness and sweetness. Buying any head-fi gear at this price is ridiculous but considering the previous closing bid I think I got a fair deal. And it is so rare to have T2 being sold alone. I do not need another pair of omega so this deal saves me a lot of money. But this amp's functionality in long run is questionable. I hope my handful of obsolete FETs stock will save me some pain when I need to fix this in the future.
    25 points
  2. Went to my dad's to visit, just me and him. We talked about our family history (still much unknown), and of him playing basketball in Philadelphia growing up (and how basketball was a "Jewish game" early on). I recorded 2 long videos of it, so good to have this info although a lot of the family history is so vague.... I had mentioned he played against Wilt Chamberlain in a school playground basketball court....he mentioned that Wilt's nickname - before becoming Wilt the Stilt - was "Dippy" Chamberlain! 😄 This is pure gold for me, having this on record now. Karen had also done some recordings of her mom before she passed, about her family and what she knew. To be treasured for sure.....
    15 points
  3. I was going to name it 'Double the Carbon, double the voltage, double the fun', but I'm afraid that would be too wordy. Ever since I measured the output swing capability of the Carbon, I wanted to see if it can drive my ESL speakers. To do that, I'd need a beefed-up version that can output at least 1kVrms before clipping. That's 1414V peak, out of a ±750V to ±800V PSU. To simply scale up the Carbon amp and the GRHV PSU without major changes to the PCBs, a few hurdles would have to be overcome. First is the 900-V rated 10M90s in the cascode CCS that bottom out with ±450V PSU. When I was browsing the high voltage FETs at Mouser, I found the UnitedSiC UF3N170400B. It's a 1700V 6.8A SiC JFET, naturally in depletion mode, perfect for the upper device in the cascode CCS. The threshold is about 9V, which helps the DN2540 to get further into the constant current region yet keeps the power dissipation still in check (no heat sink needed even with the TO-92 package). The drawback is the package. The TO268-7 isn't too friendly for a DIY thermal solution. I had a few carrier boards made with aluminum-based PCB. According to simulation, the little board would give me 9 degree temperature difference from the package case to bottom of the board when the FET is dissipating 9W. I chose black solder mask, hoping to get a bit better heat radiation capability. 10 boards cost me about $3 at JLC. They also have copper-based PCB with a special process to have the base copper flush with the top surface for a much, much higher K. Too bad the NRE is about $150, so I chose the cheaper route with aluminum. The insulation is good to 3kV so this board can be bolted directly on the main heat sink without additional insulation. Isn't that great? The next bottleneck is the 600-V rated STN9360 when the PSU voltage reaches ±600V. I replaced them with the 900-V rated 2SA1968s. Thanks to the cautionary words from spritzer, I started cleaning up traces with high voltage differential that are getting too close to each other. I removed the middle pad 'A' in the 10M90s footprint, and re-wired a couple of traces on the back. With the bias changed from 24V to 13V above B-, the JFET can be used as the output device as well. At almost $10 a pop, they are considerably more expensive than the SiC MOSFET they are replacing. So the full-JFET configuration shown below is more of a proof-of-concept than anything else. The feedback dividers are changed from 200k:200 ohm to 440K:470 Ohm to maintain the gain and allow the output swing to double, without having the feedback current overtaking the idle current through the input JFET. Two 10pf 1KV caps are in series as a 5pf cap, since I don't have the proper 2kV rated caps. Not a great idea. I was lucky it didn't blow up. Technically the board is now ready for up to ±850V. I tested the SiC-JFET 'doubled carbon' config with ±400V PSU. The performance is slightly worse than the original Carbon. Is it worth the effort? We'll see. (To be continued...)
    13 points
  4. It started with repairing a badly damaged shangri la jr driver 2 years ago, I almost rebuilt the set from the diaphragm to the stators,and of course the dust cover😦 The first thing I discovered is that the 'nano-technology' used by hifiman actually comes from the covering used by indoors aircraft model enthusiasts,the name is OS film and it is still available on ebay or https://www.indoorffsupply.com/shop/os-film-25ft-roll-1 the driver of the hifiman estats is completely glued which is similar to the early stax lambdas, but hifiman glue is significantly worse...after opening the driver i found that they only use OS film for their dust cover, the diaphragm is another PET film ~ a little bit thicker but with much better strength. In order to repair the diaphragm, I found a seller on Alibaba who can provide samples of Toray PET film with thickness below 2 microns at an acceptable price,and use the inner tire stretcher to stretch the film like any other diy estats ,Then test it with a 10" subwoofer and minidsp umik-1 to find proper F0. conductive coating is another serious problem,I've tried quite a few methods including antistatic agents like licron crystal, ANTISTATIK100,floor cleaner,carbon-based coatings such as graphene, and alcohol-soluble nylon, even tried nano-silver wire solution and metal evaporation...Some of them are sensitive to humidity, some arcs,some are ridiculously expensive, some have uneven surface resistance distribution, and some are sensitive to temperature changes. Yah~ finding the proper conductive coating is the most difficult part especially for a layman. unexpectedly, I tried to search for hifiman patents, hoping to find something useful... here's a patent showing that they used some kind of metal oxide nano particles as conductive coating for their estats. emmm,very interesting...🙄 By consulting with chemistry professionals, I decided to try a solution called ATO (antimony doped tin oxide), there are many antistatic agents I have used before have ATO ingredients though. I got some ATO alcohol solution at concentration around 10~15%, it works really well, and coating appearance is somewhat identical to hifiman diaphragm! The last thing is to repair stators. hifimans probably use #150~300 brass mesh and solder their edges to a 2mm thick aluminum base plate PCB board, then glue the rest of middle part. I've tried tensioning those brass mesh with embroidery frame and manual screen stretcher,but it is not tight enough to stretche brass mesh in this way, the mesh itself is too strong to tighten it up... then I found some brass sieves with different meshes on taobao and these machined copper screens are perfect for making DIY mesh stators... after everything's ready,i desoldered OG brass mesh, cleaned the copper foil, applied low temperature solder paste, and carefully soldered the new brass mesh with a heat gun. During the process of repairing shangri la jr, I started planning to make some bigger mesh stator estats... of course,the target is its big brother shangri la SR😈I received a set of the first batch of shangri la sr made in 2016,here is the headphone inside,yap~inherited the tradition of hifiman with such horrible workmanship...😱 however,SR sounds not as technical as the X9000 though,but with more pleasant and passion. SR uses 3mm thick aluminum base plate PCB instead of 2mm on JR version,2 black things in the middle are to prevent the diaphragm from attaching stators,The D-S gap is around 0.7~0.8mm(thickness of glue included) which is identical to JR version,active area is close to 6400mm² ,that is pretty large diaphragm size for a commercial product though,but less 5300mm² of area on stator allows air to pass through. I tried to use the 3mm FR4 board as mesh holder at first time,however,mesh stator disassembly is not an easy job...therefore,I changed to use 1.5mm brass plates as the mesh holder and glued the copper mesh to it , brass mesh is also replaced with higher # red copper mesh for more convenient adhension. I spent most of time adjusting the tension of the diaphragm and finally found the tension needed for F0 similar to OG SR ,the clone driver has a slightly enlarged diaphragm(6839mm²) ,0.73mm fr-4 pcb spacer, and everything is screwed to the housing cover. The frequency response of clone and SR are generally similar,but the sensitivity difference between the two is about 1.5dB actually,SR is more diffused...clone one sounds a bit more clearer. SR has obvious recession between 1-2kHz,it may be caused by a sealing problem in the space between the driver and the earcup.... It's unlikely to be solved without EQ, but it doesn't sound as bad as it looks from the graphics. one more thing... Every shangri la must have a throne , so I made one for my mutation🤣
    12 points
  5. Making Mother's Day dinner for my family, my parents, and the in-laws. Brisket and ribs are looking good. This was earlier this morning.
    12 points
  6. Finally got the whole magic side table together and did a test cut for an upcoming personalized drawer front project. I guess with the new 3HP spindle it needs to be set almost all the way at the top of the clamp to allow the dust boot to actually enclose the bit and suck better. IMG_1923.MOV
    12 points
  7. Actually last week walking in Orkney and Shetland. Orkney is flat with wet pools and quite boring geographically, Shetland is much hillier and nicer to walk. Weather was uncharacteristically superb; the whole area is known for torrential rain and gale force winds, often together. Jarleshof is a Viking trading post on Shetland. The Old Man of Hoy is a famous 450 feet sea stack, and is notoriously difficult to climb. Scara Brea is a stone age settlement on Orkney. Note the stone sideboard! Real Flintstones. And two pics of us.
    12 points
  8. Got one of the cab corner repair panels welded into my father’s ’62 Willys project. As the saying goes, “a grinder and paint makes me the welder I ain’t.” Lower cowl panel in front of the door will be next, then the rocker, and finally lower door repairs. Then lather, rinse and repeat on the other side.
    11 points
  9. Coquille St. Jacques Six-Onion Soup Lamb Chops with goat-cheese grits and a mushroom,apple and baby kale medley with Crème Brûlée for dessert
    11 points
  10. Went to see Wagner's opera Lohengrin last night at the Royal Opera House, Covent Garden, London. This was the final part of my awesome series of birthday presents - this one from my wife, long planned and two months afterwards. It was bloody awesome. Everything was perfect - the setting, the set and lighting, and an Internationally renowned top flight cast of singers. https://www.roh.org.uk/tickets-and-events/lohengrin-by-david-alden-details With various courses of an excellent meal in the intervals. Carole was not a Wagner fan initially - but I've converted her. She was in tears of emotion by the end of the overture to Act 1 (honestly - so was I!). Now Wagner the man was a loathsome individual. Anti semitic, hateful towards his contemporary composers, and impossible to work with - a micromanager from hell. He described Brahms as "That bastard, Brahms", and put it about that Brahms' music was inspired by shooting birds from his balcony with a "Tyrolean bow" (there is actually no such thing) and listening to their dying cries. His dreadful reputation was not helped by Hitler being a Wagner fan, and it representing the pinnacle of music for Nazi National Socialism. Putting the awfulness of Wagner to one side - he was one hell of a composer! You just have to divorce the man from the music.
    10 points
  11. Sorry for your troubles with the magic side table, Jeff. I've been meaning to post another plug for Doug's idea of waiting for a combo jointer/planer. I've been using my Hammer A3-31 in both modes to mill some maple and it is such a joy to use. It is very smooth to operate and the results are fantastic. The minor hassle of converting between modes is worth having both tools in one relatively small footprint. I'm sure it will take awhile to get one but it will be worth it. Speaking of maple, Steve and I have finished the miter saw station gave frames and drawer fronts. Very happy with the station and its functionality. Not measuring most cuts because of the StealthStop works great and is really precise. I also got a hose adapter so I could use the 2.5" hose with the Kapex.
    10 points
  12. i am really glad i didn't buy ls50 wireless in the past... very good chance i will try these at some point https://us.kef.com/wireless/ls60/ls60-wireless.html
    9 points
  13. Well, we decided to add kitty #3. Penelope never really got over losing Koshka a few years back, and while she loves our cats, they didn’t really bond with her. She’s a couple of years older and a little more cat-savvy now, so we thought it’s the right time. 8 month old just up from GA. P and the new addition (name TBD): And the requisite shot of the meezers: Yes, they’re this cute all the time So far Nutella and Marshmallow are intrigued by whatever is behind the door, but they don’t seem too put off. We’ll be patient with introductions to avoid rocking the boat too much. Edit: She’s a doll.
    9 points
  14. One of the fun things that happened early in the pandemic was I got to run a little corp virtual concert with her. She was pretty much outside my radar until then and I have to say she seems like a decent person and a beautiful voice. I'll also say sheltering in place, so having her kids be crew/tech support, has its ah downsides. Well, most of the songs were heard anyway. 😜
    9 points
  15. Learned how to engrave with my milling machine today. It's an original Kevin Gilmore et. Al. DIY T2 amplifier with original parts.
    9 points
  16. "All those moments will be lost in time, like tears in rain... Time to die."
    8 points
  17. Finished up the week at Milo & Otis siding, screen & vent repair, in preparation for what may be an epic paintjob on Mayberry Manor.
    8 points
  18. I think we're done with this particular asshat.
    7 points
  19. I just can't help it. There's something about him...
    7 points
  20. A box with some dirt in it Pre box, pre dirt
    7 points
  21. Since you are getting so close to the Paltauf and understand how the circuit works, why don’t you share with us the details? There is no problem for an unaffiliated user to disclose what he/she can see in plain sight, I assume. What I can see is that sharing is part of the core spirit of this site and what drew us together to begin with.
    7 points
  22. I somehow managed to copy H and C from HeadCase logo and mill it on the plate. picture in B/W
    7 points
  23. Have made a few test inscriptions on aluminum with CNC machine.
    7 points
  24. I found the tonearm for cheap
    7 points
  25. Couldn't resist posting this - what cats think
    7 points
  26. I have been commuting to work on this since March of last year. I don’t have to worry about gas.
    6 points
  27. We're up in Maine for our anniversary and had to stop to see one of the local celebrities....
    6 points
  28. That’s awesome! I did something similar with my grandmother, dad and mom about ten years ago. I watch it all the time These family stories are priceless.
    6 points
  29. Don't I know it. Still, so much death right next door influences every part of life. That is grammatically an imperative, so, an order. I have no fight with you, Helium, I'm just expressing a little solidarity with a fellow forum participant in my neighborhood. That can't possibly be what passes for hate.
    6 points
  30. Take a breath and stop issuing orders when you are not empowered to do so. I see nothing wrong with the posts here.
    6 points
  31. I just cleared out a bunch of boxes of my momentos, family memorabilia, and files from my parents' house that had been in boxes in front of my main rig for many months. I decided to pick a Jeff Beck album (There & Back) from my high school years to celebrate clearing it away (sadly, just into the basement--sorry Marie Kondo). I still like it, but there is a whole lot of Jan Hammer on this album!
    6 points
  32. Nick Cave and Warren Ellis all morning. La Panthère Des Neiges/Carnage/Ghosteen.
    6 points
  33. Piper started calling her Jelly Bean and it seems to have stuck. Integration is going pretty well. Nutella seems wary of another female, but Marshmallow seems to have accepted her quickly. They play together a lot and Lauren sent me this earlier today. I’m happy to call that a win. And even though she’s still getting settled, there clearly isn’t too much drama. from yesterday…
    6 points
  34. My SME 20/2A which I purchased new in Jan 2002, got around 3000 L.P.'s and still climbing
    6 points
  35. Picked up a gift certificate at a local spa for my wife for Mother's Day. I wanted to give the monetary equivalent of three 50-minute massages ($87 each). The person getting the GC for me asked her co-worker what 3 times the price was, and before she could even pull out the calculator, I told her the amount. They both stared at me in awe, the second one double-checked my "work" and proclaimed I was right. they spent the next few minutes completing the card, and talking about how good I was with math. Scary.... They certainly LOOKED lovely.... 😂
    6 points
  36. A picnic in Sonoma Square
    6 points
  37. Yesterday morning first day mowing on the golf course. 40F to start. 39F four hours later when I finished.
    6 points
  38. Live From the Ryman And More Sheryl Crow 2021 https://album.link/i/1568134877 Example: I had never seen her perform live, and I don't know why. The songs that I like, I really like. Voice and performance very strong. And overall a good recording. It has a Tom Petty jam session vibe - maybe shared a lot of performers.
    6 points
  39. Happy 100th birthday to Charles Mingus!
    6 points
  40. Love my boy....he surpasses me in sarcasm and is almost Bernie-left....but we had this fun exchange when he told me he was going back to Spotify instead of the TIDAL family plan (more selections and features for him and his g/f).
    6 points
  41. This is a very niche topic so if you are not planning to buy or write programs for the Keithley 2015 or 2016 thd or p multi-meters then this post will probably not be interesting to you - especially given their skyrocketing prices on ebay and their age. If you are planning to buy one because it has audio analysis built in then there are a number of limitations and issues you should be aware of before deciding to buy. Some of these limitations effect the accuracy and validity of its calculations and are not documented in the manual, some of the limitations effect usability and some effect it programmatically if you access it through gpib or rs232. If you look on the internet there is very little software written for these meters and you may be wondering why. Well now I have written some software for them I think I have a better idea... Here is an example of the "quality" of the manual "The Model 2015/2015-P/2016 can use up to the 64th harmonic of a signal (64 times the fundamental frequency) in the THD measurement, but only recognizes frequencies below 50kHz. Harmonics with frequencies above 50kHz are ignored, therefore acting as an adjustable lowpass filter." What do you mean by use? are the ignored harmonics included in the background noise measurement? or are they simply ignored completely? Well it turns out thd+n included the harmonics as does SINAD. ( I'm still trying to determine for background noise since my calculations do not match the Keithleys). Similarly the statement about the upper frequency is ambiguous for multiple reasons. Bellow 50khz is included and above 50khz is ignored... what about exactly 50khz? more importantly what about a harmonic bin that starts before 50khz but ends after 50khz? or has its centre frequency at 50khz? The 50Khz limit is NOT adjustable and is absolute. There is a separate low pass filter which is configurable and can be switched on and off. Once you dig into the detail the descriptions in the manual leave more questions unanswered than answered. Limitations the in built signal generator goes from 10hz to 20khz only and is flat to within only 0.02db it also has a noise spike at 10khz average noise is about 50uV noise spike is more than 350uV.... thd measurement is limited to a maximum of 64 harmonics. This means if you are measuring the thd a 20hz input, the bandwidth of the thd measurement tops out at 20hz*64 harmonics i.e. way bellow 5khz.. However, Sinad and thd+n not limited to 64 harmonics.... this is obviously inconsistent behaviour and if the harmonics higher than the 64th are large in magnitude then the thd will be underestimated but the sinad and thd+n will be good... it is possible to limit the number of harmonics calculated in the thd to less than 64 using the front panel or programmatically but this does not effect sinad or thd+n calculations. But if you do limit the harmonics and then programmatically ask for all the harmonics any above the limit are not returned - they are lost forever. thd cannot be measured for inputs bellow 20hz or above 20khz all audio analysis is bandwidth limited to 50khz or lower (in some cases the bandwidth limit is 20khz due to the limited number of fft bins) and it is not possible to get the actual bandwidth limit via the front panel or programmatically. If you want to know the upper limit you have to reverse engineer its behaviour - the behaviour is not documented. The fft and harmonics are bandwidth limited to 50khz so if you measure a 20khz fundamental thd is calculated on two harmonics only and one of them is the fundamental! the fft bin width automatically varies depending upon the input signal fundamental frequency for example at 20hz the bin width is 20hz at 1Khz the bin width is 66.6 recurring hz this is not documented and must be reverse engineered to workout the relationship between fundamental frequency and bin width. This is made more difficult when: it is NOT possible to get the bin width displayed on the screen of the keithley or get the bin width programmatically. it is not possible to get the starting or ending frequency of a bin it is not possible to get the number of fft bins used in the thd, thd+n, sinad or noise calculations it is totally unclear from the manual if the rms value for the signal returned in audio analysis mode is the rms value of the entire signal, the signal plus harmonics or just the first harmonic. The manual simply says the result will be different from measuring the ac volts value of the input... Extensive experiments seem to indicate it is the rms of the 1st harmonic. The slowest part of a program communicating with the Keithley is transferring the fft bins especially using rs232. But the keithley does not provide a way for you to obtain the number of fft bins which contain valid data so you have to get all the bins. This increases an fft transfer time by up to 25% (in the case where bandwidth limits the number of valid bins) compared to only fetching the bins with valid data and the situation is far worse if weightings or low and high cut filters are used. you can improve performance across the gpib bus by setting the keithley to transfer floating point numbers rather than number in their text representation however not all measurement returns actually support this so you have special cases all over your program to determine if it should be reading a float or the ascii representation of a float. The manual is also not accurate ascii rather than a float is returned in float mode. If you apply a weighting filter such as C-message which only has a bandwidth from 60hz to 5khz the keithley does not reduce the fft bin width to provide higher FFT resolution. As a result, a 1khz input FFT with C-message results in only 300 valid bins out of 1023 and uses a bin width of 66.66hz when the keithley could have chosen a bin width of 33.33z and doubled the resolution.... or picked a bin width of 20hz and triple the resolution. The weighting filters have brick wall filters attached which is not documented in the programming and user manual. However a promotional document for the keithley does have graphs for the weightings but the actually implemented brick walls are not consistent with the promotional material graphs for CCIR and CCIR/ARM. Experiments show the brick walls are at: CCIT low cut 50hz high cut 5khz CCIR low cut 31.5hz high cut 20khz - this is not consistent with the keithley promotional documentation which shows the weighting graphs and shows CCIR extending to 30khz CCIR/ARM low cut 31.5hz high cut 20khz - this is not consistent with the keithley promotional documentation which shows the weighting graphs and shows CCIR extending to 30khz A weighting low cut 20hz high cut 20khz C message low cut 60hz high cut 5khz It is not possible to get the rms value of a harmonic or fft bin - the only option is to get the result in dbc relative to the first harmonic/fundamental frequency rms value. there is a limit of 1023 fft bins as well as a bandwidth limit of 50khz which means some measurements are only performed on around 735 bins because the bin width is large for example 68hz and more than around 735 bins exceeds the 50khz bandwidth limit - the keithley does not try to minimise the bin width to maximise the resolution and the algorithms used are not documented. As a result at input frequencies bellow 50hz you run out of bins before you reach 50khz and above 50hz you run out of bandwidth and lose bins. The bin width behaviour is very dependant upon the fundamental frequency and so two frequencies close to each other can result in radically different bin widths. you can manually set the bin width BUT if the largest input frequency is not a multiple of the bin width the FFT analysis produces poor results. for input frequencies bellow 61hz the bin width equals the input frequency i.e. all fft bins are harmonics so measuring the noise is impossible since there are no noise bins... However, at least with my firmware, the keithley reports a bogus noise value for frequencies of 60.8 to 61hz even though all bins are fundamantals. there are multiple features which you can only access programmatically: noise measurement (only for input frequencies above 61hz) fft bin values low and high cut filters The keithley has a programmable capture window for acv measurements. A too long window results in slow readings, a too short window results in errors in calculating the frequency of the signal. This capture time is NOT programmable in audio analysis mode and is set to a too short value for low frequencies and results in frequency measurement errors at 20hz to about 30hz resulting in incorrect ffts and high distortion values The signal generator is not particularly low noise or low distortion - about 50uV noise at 1V output and about 0.02% distortion (1khz 64 harmonics). My pc sound card analogue output managed almost an order or magnitude lower distortion when measured by the keithley. The programming manual is misleading and varies in quality and detail from section to section. For example equations are provided for thd, thd+n and sinad but not for its noise calculation or its weightings e.g. A, C-message, CCITT etc. Nowhere does the manual mention fft bin width or number of bins varies with fundamental frequency or provide the equations to work out the number of fft bins or fft bin width for a given fundamental frequency - and reverse engineering this was complicated the algorithm changes 3 times over the frequency range 20 to 20khz... For thd, thd+n and sinad I implemented the equations in the user/programming manual and came up with identical answers to the keithley to around 8 significant digits - the rest being rounding errors. For noise I assume all valid non harmonic bins are noise but my calculations do not match the Keithley... I get around a 1% underestimate so the keithley is finding extra noise from somewhere! But my thd and thd+n calculations match the keithley. If I calculate THD+n - thd should just be the noise and this matches the value I get from calculating on all valid bins minus the harmonic bins and still does not match the keithley. If the keithley was finding noise from somewhere then my thd+n calculation should not match the keithley. I.e. the keithleys (thd+n - thd) and noise calculations are not consistent with each other. Sinad also takes into account noise and again my sinad calculations match the keithleys. The keithley has built in averaging but can only apply this to the thd measurement and NOT noise, sinad, thd+n, fft or harmonic measurements. The keithley uses the SAME command to inform it of the fundamental frequency as it does to set the fft bin width (if you choose to hardwire the binwidth)! This has the effect that if you hardwire the bin width the keithley thinks that value is also the value of the fundamental frequency! it is also not possible on screen or programmatically after the fact to separately get and disambiguate the set hard wired bin width from the fundamental frequency - again the same command is used to get both! if a low or high cut filter cut off frequency is part way into an fft bin the fft ban is not excluded. This is not documented. However possibly my biggest issues with the keithley is that it appears that it does not store raw measurement values and then apply filters, weightings sinad, thd thd+n calculations. Instead it stores the final processed values so there is no way to undo a setting or examine how a setting effects the result. For example if you set a low or high cut filter this effects all calculations. Harmonic bins and fft bins excluded by the filters are lost forever and can not be recovered... changing absolutely any setting invalidates the current reading and requires a new measurement to be taken! i.e. you cant change the weighting filter, cant change the low or high cut filters, can't change the measurement type from thd+n to sinad or vice versa, can't change the number of harmonics included in the thd calculation can't even change the returned thd and thd+n values from db to percent or visa versa. Absolutely any setting change results in you needing to make a new reading. To summarise The signal generator is poor, audio analysis is difficult to control, difficult to understand how it works under the hood, has multiple low frequency measurement limitations, only saves processed values is missing multiple commands for getting useful information about fft bins and has poor documentation on the detailed workings and interactions between settings - especially when multiple settings effect a calculation. Conclusion The keithley hardware is not an audio percision on the cheap. I don't know if any of this will ever be useful to anyone, but I have said it now - perhaps this is more or a rant because of the amount of time and effort I have had to go through to reverse engineer its behaviour and algorithms. If you are insane enough to want to write program(s) for the Keithley I can provide you code for calculating the bin width vs fundamental frequency, number of expected valid bins returned vs fundamental frequency, etc. P.S. AC current limitations the 2015 and 2016 also only have two ac amps ranges 1A and 3A so they are not great choices for low current ac measurement. In contrast the older and more humble keithley 197a has a AC current ranges from 200uA to 10A! here is the frequency response of the keithley signal generator100 frequencies log sweep 10 measurements per frequency. notice at 20hz the standard deviation is almost 1mv on a 1v output and varies by 0.015db over the 10 readings . This is not the signal generators fault - it is a issue with the way the keithley measures frequencies bellow 30hz in audio analysis mode. If you measure in ac volts mode almost all of this variation is gone here is the total thd vs frequency for the inbuilt signal generator. Again notice the disproportionally high thd at 20hz (10 times that of 1khz) and large variations in the 10 measurements min reading at 20hz 0.07% max at 20hz 0.14% at that frequency: The+n looks simular and other signal generators feed in to the keithley also show high 20hz thd and thd+n results. and the harmonic analysis of the 20hz measurement: and the noise vs frequency with the 10khz noise spike:
    5 points
  42. I'm finally able to put a closure on this pentode experiment, sorta. What finally improved the THD figure between 300V and 500Vrms output is the driver transistor. I replaced the PZTA42s with TTC004Bs when trying the original GG circuit with EL34s, while the PZTA42s remained in the left channel. With SiC FET as the output device, the driver transistor has a pretty steep load line, so the nonlinearities on the upper left portion of the curve didn't matter that much, as long as the idle Vce is chosen to be high enough to avoid that area. With the GU50 tube as output device, the driver transistors not only need to swing current, but also swing voltage (about 10Vpp), so the load line is more flat. The nonlinearities of the transistor becomes more problematic. The PZTA42s have to go. The KSC2690s I have on the left channel have higher hFE than the TTC004B on the right. The two channels ended up having very close THD+N curves. The 2nd harmonic is more prominent than the 3rd in the left channel with the KSC2690s, not sure if that's consequential. The hum is 110dB below the 100Vrms mark, with the 12.6V filament transformer CT simply tied to B-. I'm quite happy with the sound on my SR-009. It has the basic characteristics of the Carbon with a very slight touch of tube softness, yet not losing resolution or immediacy. I searched up and down but didn't find another pentode more suitable for this role, at least on paper. If some day I manage to put this into an enclosure, the ugly 'hats' would surely be sticking out.
    5 points
  43. This cloud 7 vs. cloud 9 stuff is a little confusing to me, but a Google search on cloud 8 seems it’s at least a little easier to understand.
    5 points
  44. Have you considered this Blend? Google lens translation "GEMINI RUSSIAN WARSHIP GO FUCK YOURSELF CREMA HOUSE, 250 (g) Natural roasted ground coffee, in airtight packaging. Sort of GOST 6806-07 Net weight 250r (g) 23% Minimum shelf life: 18 months from the date of storage Conditions to store in a dry cool place Method of cooking method manufactured is indicated on the number Manufacturer and addresses of production facilities TOB Compfood in Ukraine 07406. Chiysk region. Brovary, P02 str +380 (44) 250 55 88 TM Gemini Hanexans TOB-Kounais ya las 28.03.2022 408201561430096" via: "The flavour has been described as "bold and defiant, while still smooth and satisfying" "Striking"
    5 points
  45. The Freddie Mercury Tribute Concert
    5 points
  46. We’re launching a new company – Eksonic – along with our new amplifier called Aeras. Launching an audio company is something I’ve had in the back of my head for many years and I’m proud to be able to bring a passion to market. I've been building my own version of the DIY T2 for quite some time now and have long hoped to capture the spirit of the beast in a smaller single chassis design that's more accessible to many. We think we've accomplished that with the Aeras. Aeras is the result of endless hours of circuit design and analysis, brainstorming and many iterations of prototyping and testing. Our initial users have had great things to say about this new amp. We’re going to be launching the company formally at the NYC CanJam later this month. We’ll bring our DIY T2 along with the Aeras so people can hear them side by side. I hope to see some of you at the launch
    5 points
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