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Re: Drafted to helo a friend who designs audio amps
wn4isx
The problem my friend is almost certainly facing is the parameter(s) that are driving him nuts aren't standard and aren't specified. I'm sure a process engineer could provide us with a wealth of information but just try and talk to one. They are guarded closer then Roman Vestal Virgins.
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I'm going to check
Hfe at different collector currents, well away from the standard tests levels
Ft at different current collector currents
Actual switching speed at different collector currents
I'm trying to figure a practical way of measuring the collector base, base emitter, and collector emitter junction capacitance under different voltages.
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I once used a 2N???? as an electronic variable capacitor by using the collector base and reverse biasing, so I know transistor junction capacitance varies with applied voltage. I wonder if the audio can modulate the variable capactance of the junction [pretty certain it does] and "Does it have any effect?"
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I'm so far over my head I might drown.
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And a lot of audiophile "Standard of belief" is snake oil and smoke.
The idea a special power cable can improve an AC mains powered amp is silly, consider how many feet of house wiring is between the amp and breaker box, how long the cables from the home to the step down transformer, how many miles of wire between "your' transformer and the substation and how many miles of wire between substation and power plant, add to that the interconnectivity of the various national sub-grids....
? Double blind tests are the only subjective tests I accept. Others are entitled to their own beliefs.
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Re: Drafted to helo a friend who designs audio amps
¿ªÔÆÌåÓýAs others have said, high end audio goes into the realm of non-book theory. What actually happens is not what you¡¯re thought at school. It resembles radio behaviour. All sorts of weird stuff going on everywhere. The smaller the amount of parts, the easier it gets. Add more parts, you get a big headache! I¡¯ve been told that even the direction a wire is connected can make a difference. One reason so many audiophiles like valve amps, is because of the amount of noise generated (lack of, I¡¯ve been told) I¡¯m not an audiophile, my hearing is also affected (army service), but the electronics of amps have been under my scope. Definitely more difficult than microwaves¡ I dealt with different parts specs, by testing a great number of the same batch. Eventually I got a few that were matched. ? Nuno T. ?
? From: [email protected] [mailto:[email protected]] On Behalf Of wn4isx via groups.io ? I've been dragooned to help a friend I've known since the second grade. Jimmy designs and builds ultra high end audio systems, he builds everything up to the speakers. ? Recently he's ran into some odd problems where "identical" transistors behave differently in high end audio. He purchases directly from the manufacturer so the chances of counterfeits is pretty low. ? It's been a life time [1968~1973] since I designed any serious audio amps. I realized my talents lay elsewhere and it was a better value to trade money for decent amps then spend nearly unlimited hours to obtain similar results. ? Note: I do not consider myself an audiophile, I damaged my hearing riding a motorcycle for 35 years and had tinnitus as a young child. ? Sooo, I'm refamiliarizing myself with the issues of high end audio design, theory and reality. ? No amplifier is perfect, they all have artifacts. One thing that is very different today from way back when is moderate priced USB audio I/O 'cards' allow meaningful FFT analysis that actually matches reality, within limits. ? I downloaded this book to start with.... ? Bob Metzler - Audio Measurement Handbook https://convexoptimization.com/TOOLS/Metzler.pdf ? While copyrighted it appears in quiet a few respectable locations, I'm guessing the author has waived copyright issues. ? Rod Elliot of ESP audio has quite a few articles on design and measurement of distortion. ? https://sound-au.com/articles/distortion.htm ? https://sound-au.com/articles/intermodulation.htm#ref ? https://sound-au.com/articles/intermodulation.htm ? https://sound-au.com/project52.htm ? Uses a sound card to measure distortion https://sound-au.com/project232.htm ? Perhaps the single most useful trick shown by Mr. Elliot is his "distortion adder." It allows sanity checks, which, when dealing with audio distortion is necessary. It is way too easy ending up chasing your tail like a puppy or kitten. ? That's why I gave up on amplifier design in 1973. A quasi-comp Sansui AU-555A sounded much better then my best efforts at about 1/2 the cost in material and 1/gazillionth the wasted time. I could have collected sodapop bottle along the highway, turned them in for the deposit and been time ahead. I'd reached a point where I'd lost confidence in my ability to measure differences in slight design variations. ? ? One important issue, I've been playing with several USB sound cards for several years and realizee "The 5V power rail in most USB systems simply suck!" Modify your USB cable and add your own 5V power supply. I went with a LM7805 with the standard design with an added 1uF tantalum (I hate and distrust tantalums but they have the best filtering capacity for size and a 100uF and 1000uF on the 5V out. I'm not convinced the added capacitors were worthwhile but the PCB I used had the pads for them so I decided to toss them in. ? [Be certain to tie your 5V power supply V-/ground to PC USB V-/ground! I spent an hour late one night wondering "Why doesn't this damn thing work!"] ? The residual noise floor was just under 10dB lower with the external supply versus the laptop USB 5V power. ? You mileage will vary because every maker of USB almost certainly has different noise issues.. ? I suspect Jimmy is running into the hard wall of physics, where each device is inherently different even if made at the same time. This is something I have no idea how to verify. ? They don't call it the bleeding edge of technology for nothing. ? Oh, and don't bother trying to test the modulator in your SSB/AM/FM ham rig, they all suck. -- Nuno T. |
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Re: Isolated Power Supplies
wn4isx
'Galvanic' isolation means no common electrical connection, intrinsic means no common electrical connection with a specified safety factor, if unspecified, it would generally mean isolated up to the AC Mains voltage, 120V in the US, 240V most other places. One of my lab power supplies claims an intrinsic isolation of "up to 1,000V AC or DC." [Yea I take that claim with a large block of salt.] ? 'Galvanic' doesn't include any safety factor. It might be safe to 10,000V or only 10V. Intrinsic depends on insulation and creepage distance, the distance electricity might leak across. Buy a cheap switch mode power supply at a thrift store and crack the case,? Trace out the AC inlet, see the isolation zone and then the DC out. ? ? ? |
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Re: Drafted to helo a friend who designs audio amps
wn4isx
I like it, use a super fast, low noise opamp to do the summing and monitor the output.
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By chance did an amp with ungodly high TIM happen to be a Crown DC-300? [What an overrated POS]
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I worked part time in college at an odd specialty electronic shop that did all sorts of custom electronics, everything from stepping relay PBXs to exotic high end audio. We sold an early Haffler integrated ?100?W amp to a biker bar. It was only time in my life when a boss ordered me "Carry your pistol and be prepared to use it." There were 5 of us armed to the teeth.
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It was one of the most frightening jobs I was ever on.
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School got too busy the next semester (trying to carry two majors, EE and physical anthropology was somewhat demanding time wise.....] so I lost track of any follow up. [The bar was still there last June when we drove past.]
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I've often how long the amp lasted before it was stolen, blown up or had beer poured in it.?
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It felt [it was!] like a major sacrilege against everything good in the universe to put such a good amp in such a dive with the best JBL speakers of the time.
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That was the first and last biker bar we did and I still get the shakes.
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Now Johnny Angels was a very different bar...being 22 and naive I had no idea there were gay bars....
They wanted a very fancy disco system. I'd have had to design a light sequencer using a Motorola 6800. [I hated programming, still do.] We passed on that gig.
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Much much later, when I worked at the university we were taking a break from setting up a major production in Lexington's classiest hotel, went to the cafeteria and a very pretty young lady got way too close to me? with some really odd body language.
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A coworker cut her off, "Lady he can't afford you."
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That was the moment I realized she was a working girl.....
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I had to hotwire our work van when we were in Dayton because the supervisor lost the keys. Theory became practice. The van was pre steering wheel lock. My coworkers gave me the oddest look when I said, "Oh no big deal, let me get under the dash." 30 seconds later the engine was running and then I got the really odd looks.
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I always thought it funny when TV/Movies made hot wiring out to be quantum mechanics. I learned how in a junkyard owned by a great uncle at 8. I hotwired an old junker and drove it about 200 feet right into a 100 year old oak tree. My father only laughed. Mom wasn't all that amused and muttered something about her only son is going to end up in prison.? [Not yet]
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Hey you try to steer, work the gas peddle, brake and a clutch you can barely press with short legs and your older sister screaming "We are gonna die!" as loud as she could. Once I got moving I couldn't stop ... well not under control.
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The oddest parts of my work life weren't technical.
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Oh damn, just remembered this device....Sound Impairment Monitor - The Answer?
And
The ESP SIM (Sound Impairment Monitor)
Though this one only monitors the long tailed pair...not sure how accurate it would? be.
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The first unit is based on the Baxandall Subtractive Test Set and appeared in a ?mid 1960s? Wireless world. I should have mine, built it in EE to prove a point. Probably need better opamps, LM301A aren't exactly state of the art.
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I'll try to locate the Wireless World where it appeared. might take a week or so.
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Sorry for the mixed fonts.
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Found my SIM" it! God it is primitive, I used that funny ?Dymo? embossed plastic ribbon label maker. They don't hold up well after 50 years. Now to rebuild it and make new labels! [and a new power supply, zeners don't cut it!]
[I saved each and every piece of test equipment I made in EE then later at various jobs.]?
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I did a quick search and found this paper by David Haffler, he's doing the test very different then I expected.4
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And here is a reprint of the Baxandall audio test scheme.?
This works, it will show the minute differences between units of the same model.
I'd loved to have had a PC based FFT system back then.
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I'm betting if we can find a way to measure the subtle non linearities in Hfe in the transistors, we'll find the problem, then he gets to figure out how to design to minimize those variables. I'll borrow a tektronix curve tracer Monday.
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Now, what to bill him....
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Isolated Power Supplies
Found a few low voltage isolated buck converters on Amazon, 12/24vdc in, 12/5vdc out. While I could make those work, the cost is high. I need something that is able to deliver 12vdc, at least 100w.
Best solution I have found is: Orion-Tr 12/12-9 (110 W) Orion-Tr 12/24-5 (120 W) Both offer 200v 'galvanic' isolation (vs intrinsic?) and should work. Cost is higher at $64 ea, with needed qty of 4. Ultimately the outputs will be connected to individual LFP cells that are already connected 4s. Basically Top charging. Haven't been able to use 'traditional' LFP batteries as I would be pulling ~180A short burst intermittently. Basically is 2nd Battery used only for starting an engine. Current solution is using 12vdc to 120vdc converter, and feeding to an isolated smps that is rated for DC on AC inputs. Repeat 4 times. Lots of underhood space used. While above is very doable, a 500w inverter feeding power supply then LFP single cell chargers through isolation transformers should work as well. Or find isolated versions of the LFP cell chargers. Anyone have suggestions on isolated converters, or isolated single cell LFP charger? My searches at Amazon, Digikey, Mouser, Allied have been kind of dismal. And in case you are wondering: Yes, this abomination would comprise several loads switched by latching relays. ~SD |
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Re: Drafted to helo a friend who designs audio amps
¿ªÔÆÌåÓýHafler, an amplifier engineer/manufacturer came up with a very clever and simple test procedure: Divide down the output with two resistors and sum it with the input signal also using two resistors. If the two signals are 180¡ã out of phase, tweak the resistor ratio so there is no output. Monitor with a scope, headphones ¡¡ Play music through the amp.? If there is any output, it is distortion created by the amplifier. Test with different types of loads. If the signals are in phase, add an inverter to the input signal. ? He demonstrated that most big-name amplifiers had transient intermodulation that never showed up on the specifications and often not understood. His amplifiers were ¡°clean¡±. See: Bertho ? From: [email protected] <[email protected]> On Behalf Of wn4isx via groups.io
Sent: 7 December, 2024 8:08 To: [email protected] Subject: [electronics101] Drafted to helo a friend who designs audio amps ? I've been dragooned to help a friend I've known since the second grade. Jimmy designs and builds ultra high end audio systems, he builds everything up to the speakers. ? |
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Drafted to helo a friend who designs audio amps
wn4isx
I've been dragooned to help a friend I've known since the second grade. Jimmy designs and builds ultra high end audio systems, he builds everything up to the speakers. ? Recently he's ran into some odd problems where "identical" transistors behave differently in high end audio. He purchases directly from the manufacturer so the chances of counterfeits is pretty low. ? It's been a life time [1968~1973] since I designed any serious audio amps. I realized my talents lay elsewhere and it was a better value to trade money for decent amps then spend nearly unlimited hours to obtain similar results. ? Note: I do not consider myself an audiophile, I damaged my hearing riding a motorcycle for 35 years and had tinnitus as a young child. ? Sooo, I'm refamiliarizing myself with the issues of high end audio design, theory and reality. ? No amplifier is perfect, they all have artifacts. One thing that is very different today from way back when is moderate priced USB audio I/O 'cards' allow meaningful FFT analysis that actually matches reality, within limits. ? I downloaded this book to start with.... ? Bob Metzler - Audio Measurement Handbook https://convexoptimization.com/TOOLS/Metzler.pdf ? While copyrighted it appears in quiet a few respectable locations, I'm guessing the author has waived copyright issues. ? Rod Elliot of ESP audio has quite a few articles on design and measurement of distortion. ? https://sound-au.com/articles/distortion.htm ? https://sound-au.com/articles/intermodulation.htm#ref ? https://sound-au.com/articles/intermodulation.htm ? https://sound-au.com/project52.htm ? Uses a sound card to measure distortion https://sound-au.com/project232.htm ? Perhaps the single most useful trick shown by Mr. Elliot is his "distortion adder." It allows sanity checks, which, when dealing with audio distortion is necessary. It is way too easy ending up chasing your tail like a puppy or kitten. ? That's why I gave up on amplifier design in 1973. A quasi-comp Sansui AU-555A sounded much better then my best efforts at about 1/2 the cost in material and 1/gazillionth the wasted time. I could have collected sodapop bottle along the highway, turned them in for the deposit and been time ahead. I'd reached a point where I'd lost confidence in my ability to measure differences in slight design variations. ? ? One important issue, I've been playing with several USB sound cards for several years and realizee "The 5V power rail in most USB systems simply suck!" Modify your USB cable and add your own 5V power supply. I went with a LM7805 with the standard design with an added 1uF tantalum (I hate and distrust tantalums but they have the best filtering capacity for size and a 100uF and 1000uF on the 5V out. I'm not convinced the added capacitors were worthwhile but the PCB I used had the pads for them so I decided to toss them in. ? [Be certain to tie your 5V power supply V-/ground to PC USB V-/ground! I spent an hour late one night wondering "Why doesn't this damn thing work!"] ? The residual noise floor was just under 10dB lower with the external supply versus the laptop USB 5V power. ? You mileage will vary because every maker of USB almost certainly has different noise issues.. ? I suspect Jimmy is running into the hard wall of physics, where each device is inherently different even if made at the same time. This is something I have no idea how to verify. ? They don't call it the bleeding edge of technology for nothing. ? Oh, and don't bother trying to test the modulator in your SSB/AM/FM ham rig, they all suck. |
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Re: aliexpress freq counters views
¿ªÔÆÌåÓýSome of these are supposed to have tcxo mine had an unmarked
Plain xo. Replacing it with a cheap aliexpress 0.5ppm tcxo made an enormous difference
And checked against my gpsdo is rock solid at 10mhz and 100mhz and within 0.5ppm. Its not particularly sensitive but good enough for my needs.
Dave
Get
On 6 Dec 2024, at 21:45, "wn4isx via " <hotmail.com@groups.io target=_blank>[email protected]> wrote:
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Re: aliexpress freq counters views
wn4isx
I've stayed out of this thread because I post too much.
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Anyway I tried several of these modules and found them to be useless for any thing resembling precision.
I had 3, one in each color, and all drifted...drifted really bad. I tried a insulated case with a clear lexan window, tightly regulated power supply.
Before spending too much effort, get a known frequency reference, 100MHz is gooed, connect it and monitor the displayed frequency for an hour or so.
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I used a local FM station on 98.1 MHz as my reference.
I used a dipole, a narrow pass RF filter, two ganged FM boosters, with another narrow pass filter between them and a home made high gain amp, with another narrow pass RF filter between the output of the last booster and final amp. I had ~1 V 98.1 MHz signal, a spectrum analyzer showed the FM stations nearby in frequency were way down.
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Another option might be a 10 MHz disciplined oscillator, extract the 10th harmonic with a filter and amp.
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I ended up going with a Jackson Harbor pre-scaler kit
And a Tektronix CF250 100 MHz frequency counter a friend gave me.
My combo counts to 1500 MHz with the expected last digit bobble.
It is a lot larger but extremely accurate after replacing the 3.58MHz reference with a reference derived from a GPS disciplined oscillator.
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I ended up junking all three counters and only saved the brass hardware. An expensive lesson.
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Another poster suggested replacing the stock oscillator on the frequency counter module with a precision unit. That would probably work.
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Re: my new psu
wn4isx
If the power supply in question has selenium rectifiers they need to be changed.
They weren't great to begin with, very high internal impedance, and they don't age well.
If the paint protecting the selenium crinkles from age or heat, the selenium will degrade!
Replace with silicon rated at 4 times the current and at least 2 times the voltage.
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Re: Archival data storage
¿ªÔÆÌåÓýIt will leak eventually, but the drives are hermetically sealed, so the leaks are VERY slow. Donald. On 12/6/24 10:49, Roy J. Tellason, Sr.
via groups.io wrote:
On Thursday 05 December 2024 10:51:16 pm Charles R Patton via groups.io wrote:2] A more modern problem is the use of helium in the hard drives in order to fly the heads closer to the disk.? Helium leaks significantly in any system with soft (elastomer) gaskets that will be a feature of any hard drive.? I don't know what the number is today, but I suspect that number is in the 20 year frame also.I've heard of that. I only hope that I can find out about it before I purchase anything like that. It strikes me as a really bad idea... It doesn't matter what you put it in, helium *will* leak. And, it's not a renewable resource. Once it's gone, it's gone. -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, ?a critter that can be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin |
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Re: Archival data storage
On Thursday 05 December 2024 10:51:16 pm Charles R Patton via groups.io wrote:
2] A more modern problem is the use of helium in the hard drives inI've heard of that. I only hope that I can find out about it before I purchase anything like that. It strikes me as a really bad idea... It doesn't matter what you put it in, helium *will* leak. And, it's not a renewable resource. Once it's gone, it's gone. -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, ?a critter that can be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin |
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Re: my new psu
The 5020 is s Zaurie power supply model that was heavily pushed / reviewed in early 1970s. I got mine in 1978, used, from a garage sale. Heavily abused, and if memory serves, used a selenium stack for rectifiers. May be getting mixed up with another supply. Hard to remember 40+ years ago.
How many 6.3 windings are present on transformer? Mine had 3, i think, and were used to make an aux high voltage output. ~SD |
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File /counter info..pdf uploaded
#file-notice
Group Notification
The following items have been added to the Files area of the [email protected] group. By: paul larner <quadzillatech@...> Description: |
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Re: aliexpress freq counters views
Has anyone tried cutting tracks to separate the high and low inputs?
This shows a conventional preamplifier for each channel paralleled at the input, each channel using a
dual gate MOSFET as a preamplifier followed by a buffer stage (CH L) or divider/buffer (CH H). The
buffer transistors in each channel are used to obtain a TTL level. This somewhat "agricultural"
approach suggests that the low channel is likely to be excessively loading the higher channel, and that
is precisely what we see in the French sensitivity results
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Re: my new psu
thanks,it has no valves in it,,so dont?know about the 6.3v windings,what is the 5002 you mention?,cheers paul. On Fri, Dec 6, 2024 at 5:59?AM SheldonD via <68696465=[email protected]> wrote: Found your pics in photo section. Labeling on transformer yields 1A across all windings, likely because |
Bertho