Re: Drafted to helo a friend who designs audio amps

wn4isx

#99357

I meant to add, do not carry the AC Mains ground through to the 5V V-/ground!?

You'll introduce more noise then you'd believe possible.

?

Re: Drafted to helo a friend who designs audio amps

#99356

开云体育

Hafler, 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° 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

?

Show quoted text

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.

?

Drafted to helo a friend who designs audio amps

wn4isx

#99355

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.

Re: aliexpress freq counters views

#99354

开云体育

Some 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:

Show quoted text

I've stayed out of this thread because I post too much.

?

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.

?

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.

?

Another option might be a 10 MHz disciplined oscillator, extract the 10th harmonic with a filter and amp.

?

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.

?

I ended up junking all three counters and only saved the brass hardware. An expensive lesson.

?

Another poster suggested replacing the stock oscillator on the frequency counter module with a precision unit. That would probably work.

??

Re: aliexpress freq counters views

wn4isx

#99353

I've stayed out of this thread because I post too much.

?

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.

?

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.

?

Another option might be a 10 MHz disciplined oscillator, extract the 10th harmonic with a filter and amp.

?

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.

?

I ended up junking all three counters and only saved the brass hardware. An expensive lesson.

?

Another poster suggested replacing the stock oscillator on the frequency counter module with a precision unit. That would probably work.

??

Re: aliexpress freq counters views

#99352

fwiw,i cut a track and fed the rear of the pcb,ie the vhf+ side of things,this now has its own rf feed,it now reads well on 2m vhf and 70cms uhf.

Re: my new psu

#99351

no selinieum in this just a few diodes.

Re: my new psu

wn4isx

#99349

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.

?

Re: Archival data storage

#99348

开云体育

It 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:

Show quoted text

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

Re: Archival data storage

#99347

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

Re: my new psu

#99346

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

File /counter info..pdf uploaded #file-notice

Group Notification

#99345

The following items have been added to the Files area of the [email protected] group.

/counter info..pdf

By: paul larner <quadzillatech@...>

Description:
more info on chinese 8 digit counter moduals inc schematics.

Re: aliexpress freq counters views

#99344

more info inc schematic uploaded to files section.

Re: aliexpress freq counters views

#99343

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

Re: my new psu

#99342

thanks,it has no valves in it,,so dont?know about the 6.3v windings,what is the 5002 you mention?,cheers paul.

Show quoted text

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
they are all a common center tap. I would expect the 6.3v winding to be around 3Amps? Is there just
the single 6.3, or is it split into 5 / 6.3?? In a couple of the pics, 20241129_160556.jpg and
20241129_152617.jpg, the transformer appears to have been stressed.? Appears that there is some
discoloration already, though may just be a light artififact when pic was taken.
Bear in mind that that transformer has a lot of windings on it, and 1 intended (main) to be used at a time.
You draw double the current, and you may end up saturating the core. Not good.

You might get away with drawing greater current at a lower voltage winding, but looks like
you are already connected to the 45v tag. Higher Voltage? No way would I do that as the supply sits.
Pass transistors exhibit wear on cases, hope surface of the mica insulators is not compromised.
1 transistor likely for voltage, other for current. If supply set for 5, and transformer is connected at 45,
with a 1A draw, the voltage pass transistor is going to be dissipating ((45-5)x1) 45 watts of heat.
Doubling that to 2amps and you likely are going way outside design specs and looking at a much
higher junction temperature in the transistor.? Plus, you don't know how close the main caps and such
are in relation to working voltage rating compared to actual voltage.? If a diode has become 'leaky' and
allows excessive ripple to pass, working voltage rating may be exceeded.? Similar for the (National Semi?)
old plastic pill style transistors.? Had a bit of a time dating that power supply, was going to peg it around
1978 to 1980 based on component and wiring styles.? But, I saw that one of the meters has a 0272
date code, translating to 2nd week of 1972 if the meter is original.

Ultimately it comes down to are you willing to stress the supply given its age by exceeding ratings that
are present on at least some of the components?? If it were me, that would be a NO until I can slowly
check it out.

I am quite curious, as to what is connected to the 6.3vac windings? Are they supplying the heater for
a valve rectifier?? If so, got a part number?

The meters are likely going to be a 50uA moving coil variety.? Have you considered scrapping the
internals, then retrofit with off the shelf variable Boost / Buck regulator supplied by a larger transformer,
possibly a 100w laptop power supply (20v @ 5A)?? I would think would be much tighter on output than a
supply that is 52 years old, despite its brethren (like 5002) having excellent characteristics.

~SD

Re: my new psu

#99341

Found your pics in photo section. Labeling on transformer yields 1A across all windings, likely because
they are all a common center tap. I would expect the 6.3v winding to be around 3Amps? Is there just 
the single 6.3, or is it split into 5 / 6.3?  In a couple of the pics, 20241129_160556.jpg and 
20241129_152617.jpg, the transformer appears to have been stressed.  Appears that there is some
discoloration already, though may just be a light artififact when pic was taken.
Bear in mind that that transformer has a lot of windings on it, and 1 intended (main) to be used at a time.
You draw double the current, and you may end up saturating the core. Not good.

You might get away with drawing greater current at a lower voltage winding, but looks like
you are already connected to the 45v tag. Higher Voltage? No way would I do that as the supply sits.
Pass transistors exhibit wear on cases, hope surface of the mica insulators is not compromised.
1 transistor likely for voltage, other for current. If supply set for 5, and transformer is connected at 45,
with a 1A draw, the voltage pass transistor is going to be dissipating ((45-5)x1) 45 watts of heat.
Doubling that to 2amps and you likely are going way outside design specs and looking at a much
higher junction temperature in the transistor.  Plus, you don't know how close the main caps and such
are in relation to working voltage rating compared to actual voltage.  If a diode has become 'leaky' and
allows excessive ripple to pass, working voltage rating may be exceeded.  Similar for the (National Semi?)
old plastic pill style transistors.  Had a bit of a time dating that power supply, was going to peg it around
1978 to 1980 based on component and wiring styles.  But, I saw that one of the meters has a 0272
date code, translating to 2nd week of 1972 if the meter is original. 

Ultimately it comes down to are you willing to stress the supply given its age by exceeding ratings that
are present on at least some of the components?  If it were me, that would be a NO until I can slowly 
check it out.

I am quite curious, as to what is connected to the 6.3vac windings? Are they supplying the heater for
a valve rectifier?  If so, got a part number?

The meters are likely going to be a 50uA moving coil variety.  Have you considered scrapping the 
internals, then retrofit with off the shelf variable Boost / Buck regulator supplied by a larger transformer,
possibly a 100w laptop power supply (20v @ 5A)?  I would think would be much tighter on output than a
supply that is 52 years old, despite its brethren (like 5002) having excellent characteristics.

~SD

Re: oscilations in my amplifier ruins my PLL

#99340

Oscillations in a closed loop system are almost always caused by excessive loop gain.? Try reducing the gain in your feedback amplifier.? You should also ensure that your system is linear over the frequency range of your desired operation.? Gain instability can also be caused by amplifier non-linearities.? Check the gain on your EFC since this is a high Q device you may need to attenuate the output before sending it to the YIG mixer.

Sam

Re: Archival data storage

wn4isx

#99339

One trick used in high density hard files is two layers of magnetic media with a thin neutral layer between them, each later is magnetized oppositely which is supposed to element room temperature self erasure.

The high density high speed hard files I installed in the digital video edit suites were made this way.

I have no idea how well it works, the people I installled the systems for sold their business to a national chain with their own tech support.

?

It seems as though the neutral layer was 3 or 4 atoms thick.

?

All media fails in the long run.

?

Re: Archival data storage

#99338

开云体育

two additional failure modes:

1] Tape as described was the older plastic bases, but in addition there is a failure mode of the tape and hard drives self de-magnetizing due to room temperature thermal effects.? Essentially all magnetic media uses magnetic particles with a certain coercivity. The smaller the particle as for higher the bit density, the easier it is to self demagnetize unless the particle is of higher coercivity, but the harder it is to magnetize it.? This properties are balanced in the design/production to some number of years.? As I recall floppy disks and tape of that era the lifetime was about 20 years.

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.

Regards, Charles Patton

On 12/5/2024 9:33 AM, David Slipper via groups.io wrote:

Show quoted text

A contact of mine in the archive business recconed that computer tapes would need to be converted to a standard format (7 or 9 iso) (from DECTAPE and 12/6 track and other odd formats ... you cant find the hardware) and copied with a verify 2 or 3 yearly (think of the number of tapes produced by a big company per year!!)? CD's are a problem too. Hard drives have a limited number of stop/starts I believe. Add to that papertape, film, video and you have a nightmare. Dave

On 5 Dec 2024, at 16:39, "wn4isx via " <hotmail.com@groups.io target=_blank>[email protected]> wrote:

A friend has a production company with an audio studio. He switched from reel to reel tape to hard files in the mid 1990s.

?

He called me in panic yesterday when he couldn't access one of his original archival hard files.

?

I went over and was able to "wake the drive" by tapping the hard file with the handle of a large screwdriver, I'd have used a plastic mallet if I'd had one.

?

NOTE: Do not do this until every other trick has been tried! Some hard files have glass platters and I had to tap pretty damn hard and could easily have shattered glass platters. [How hard? Like driving a nail in concrete.]

?

We were able to copy all the audio to a new drive but that raised a question...

?

I've always said there are two types of hard files, those that have died and those that will.

?

I warned him about the various ways hard files die, CD/DVD ROM rot, how audio tape can have the binder (glue) that holds the magnetic material (fancy rust) and become unusable.

?

"Other then clay tablets with cuneiform, all media degrades over time."

?

He also collects "tombstones". Not literally, he's a member of a local history group and they make paper tracings of the information on tombstones.

?

I asked "How many are barely legible?"

?

"Quite a few of the older ones."

?

?

I have no idea what he's going to do, he's 78, well off financially and may decide to retire. That would be suboptimal for former clients but he is facing a nightmare in time alone to back up all the hard files. Since each client's data is on their hard file(s), I suggested he contact them and give them the hard files with the suggestion "Back this up today!"

?

Most of us don't give much thought to preservation of archival data but maybe we should.

?

Here are two links that look at the issue

?

?

NOTE: I've avoided Apple products and have no idea what magic key strokes he's describing...and I'm happy to remain ignorant.

?

Several friends have contacted me over the last 20 years with I-Omega zip drives with "Data I have to recover!"

I wished them luck and told them I have zero experience with zip drives and intend to keep it that way.

?

I have had CD-R/DVD-R fail and 1 early commercial CD music disk lose 2 tracks. I was a bit irritated but found a new CD and tossed the old one.

?

I have a large "archive." [if such a mess of unorganized data can qualify as an archive.] I haven't lost a drive, yet. I'm in the process of pulling the most important data to new hard drives. Since I have several Exabytes of data...yea it's a lot of unfun.

?

I inherited 3 NTSC digital video editing systems after helping upgrade a local production house upgrade to digital. Digital video editing requires very fast RAID hard files, older hard files that were perfect for NTSC won't work. Not needing any video editing systems, I salvaged the drives and sold the stripped carcasses. The 'unlimited' storage allowed me to save anything online I found the least bit interesting. I'm having a difficult time separating the wheat from the chaff.

?

What to save and what to let nature take her course....

?

or just erase it all...

?

Re: Archival data storage

wn4isx

#99337

One of my wife's cousin is a bean counter.

Yea I know the shame of it. She was down to finalize my deceased mother in law's estate. [Don't die, it is a mess]

?

I mentioned storing and backing up data archives.

Part of her duties is to serve on a committee that decides "What do we archive?" and "What archival media do we transfer?"

?

She explained there are 4 primary costs to data archives.

?

1) A space to store the archive, space isn't free and archives typically require climate control and access security.

?

2) The cost of backup hardware and media, which may be extensive. Let's say for some insane reason you just discovered 1000 5.25 and 8 inch floppies, even worse the 8 inch are about 50/50 hard and soft sector.

You'd have to locate working drives, I don't think there are any 8 inch drives that read both hard and soft sector.

?

[They ran into this and decided none of the data was worth transferring, it was I-Omega Zip drives and a bunch of floppies.]

?

3) you'd have the cost of the backup media.

?

4) There is the labor costs of actually doing the backups, and a space to do the transfer.

?

So, you have to ask yourself, "Is the data worth the time and expense to transfer?"

?

Most of my archive probably falls under "Why in the hell did I print that webpage to PDF?"

?

Consider....

MTV/Paramount deleted ~30 years worth of old programs.

https://www.usatoday.com/story/tech/news/2024/06/26/mtv-news-archives-deleted/74225789007/

?

A youtube video on the subject

https://www.youtube.com/watch?v=yLdi7Kp62bU

?

Do a net search "youtube deleted 30 years of video" for more stories then you'd believe.

?

[Some people are upset because the early history of hip-hop has been lost. I'm so unsad I can giggle.]

?

I worked in a media center with several tens of thousands of hours of film, slides, photos, shellac phono records, various audio tape formats and various formats of video.

?

I worked with video so I'm way too familiar with the problems of video tape.

?

Our oldest video tape was Japanese 1/2 EIJ, open reel to reel video recorder. By the time I was hired in 1979 we couldn't locate a working machine to transfer the video tape. EIJ tapes suffered from striction.

?

Our film chain died in 1995, a projector for NTSC TV has a pull down of 5 per second instead of the standard 4. We couldn't locate repair parts and the campus machine shop tried but couldn't fabricate a replacement part with the required accuracy.

?

We had several hundred hours of Ampex 2 inch quadraplex. The tape heads were good for a few hundred hours and then had to be sent off for a rebuild. The only company that did the rebuilding went out of business and we faced the tough decision "Which tapes do we transfer?"

?

We drew up a priority list and copied just over 70 tapes to U-matic 3/4" and Betacam (not home Beta!). This disrupted our normal operations for over a month.

?

Then they nuked the entire media department and we shut everything down per written orders. "Everything" meant the HVAC. The archive was destroyed by the first frost. The room the archive was in would reach temperatures of 130 without HVAC.

?

So they had no issue with "What do we save?" because it was all ruined.

?

I attended a meeting 6 months after they shut us down, I charged them big time, and it was decided "We should have kept the TV department open until we backed up valuable media and transferred it to the official university archive."

?

It would have taken the entire engineering staff 6 to 12 months to transfer the most important videos.

?

Since they were in a severe budget crunch, was the lost video worth preserving?

?

Don't ask me, I was an engineer and my opinion was irrelevant. ?

?

I hope I've made it clear backing up data is important but not cost free and not all data needs to be archived.

?

I'm a bit OCD and still have report cards from elementary school. The comments by my teachers are high humor.

?

My wife wonders why some of my teachers didn't just strangle me. They did not approve of my enjoyment of 'bail out.' That's where you swing as high as you can, release and land in a paratroopers roll. I was school camp. Which is hilarious given my fear of heights.

?

[We so won't go into Terry's cryptography that tried to pass as proper writting.]