Driver to drive?

>What's wrong with using magnetoresistance for current-sensing?

Nothing except that iirc it isn't a wide-range phenomenon, unlike inductive pickups.

Cheers

Phil Hobbs
 
On Monday, 13 March 2017 08:28:39 UTC, olds...@tubes.com wrote:
I've been looking into buying an Audio Generator (Sine and Square Wave).
I mainly want this to run thru an amplifier to listen to the frequency
repsonse of the amp and speakers. Nothing very scientific, just to see
what these amps and speakers can do.... And on occasion to inject an
audio signal into amp sections to dee if the audio is passing that
stage.

Originally I was looking at some of the old tube gear, such as the Eico
model 377. I also looked at the Heathkit IG-18 a transistorized version
from the 70s. Because I like that old test gear, I'd be happy to get
either of these, or another similar. Both of these are Sine and Suqare
Wave. But what I am finding is the prices combined with high S+H fees,
make these things very costly, and I have not found any of them which
claim to work. Sold as-is, for parts or repair. So, I may end up paying
$60 or more and getting something that dont work, likely needs new caps,
and so on..... If they were $25 or less, I'd take a chance, but not for
that kind of money.

My search on ebay lead me to something called a "Function Generator".
What the heck is that??? And also called a DDS device. (I have no clue
what DDS means). But I carefully looked at this NEW device, sold without
a box (case), but only needs a power module and test leads. They sell
for around $14 from China, but since I dont care to order from China,
I'll probably have to hunt one down from the US, and pay around $5 or
$10 more. But that's ok. These have both the Sine and Square wave, as
well as Triangle wave (what does that sound like?).

While I prefer the older stuff, for around $20 a cheap wal-wart, and a
little work putting it into a box, I'd probably buy one of these, *IF*
it will do what I need..... I have read all the info on the ebay pages,
but I am not 100% sure that this is a modern replacement for the old
audio generators. One nice thing, is that they will show the exact
frequency on the digital readout.

IS THIS WHAT I AM LOOKING FOR?
Is something like this made to really be used, or is it just another toy
that does little and fails in a few months?

And can something like this work to test tube amps, without blowing up
from the high voltages in tube gear?

One last thing that has me puzzled. There are two BNC connectors. One is
labeled DDS, tho other is HS.

I found this in the description.
DDS frequency range: 1Hz-65534Hz, high-speed frequency (HS) output up to
8MHz.

I dont understand how or what the high speed feature does. Why would an
audio frequency be or need "high speed"? And what is the point for this
device to go above 20,000 cps, since we cant hear that anyhow? Going up
to 8MHZ seens senseless, unless this also serves as a RF signal
generator.

Here is the ebay URL.

http://tinyurl.com/h5celuc

Those are proving popular at the bottom end. I gather they're good except near the top of their freq range, when it gets a bit weird. They do audio and much more. But as you say, longevity is another matter. But at $14 it's hard to complain.


NT
 
On Monday, March 13, 2017 at 4:28:39 AM UTC-4, olds...@tubes.com wrote:
> I've been looking into buying an Audio Generator (Sine and Square Wave).

In addition to looking at Ebay , look at AliExpress. Sometimes identical items are much less expensive at Ally or Ebay. Try including diy to find kits.

Solid state equipment is a lot more reliable than vacuum tube equipment. So you are better off buying something new. Getting a replacement vacuum tube may be nearly impossible.

Dan
 
On 2017-03-13, dcaster@krl.org <dcaster@krl.org> wrote:
On Monday, March 13, 2017 at 4:28:39 AM UTC-4, olds...@tubes.com wrote:
I've been looking into buying an Audio Generator (Sine and Square Wave).

In addition to looking at Ebay , look at AliExpress. Sometimes identical items are much less expensive at Ally or Ebay. Try including diy to find kits.

Also search "suite", which seems to be a common miss-traslaion of "kitset"

> Solid state equipment is a lot more reliable than vacuum tube equipment. So you are better off buying something new. Getting a replacement vacuum tube may be nearly impossible.

Electrically, tubes are harder to bust...

--
This email has not been checked by half-arsed antivirus software
 
On Monday, 13 March 2017 16:09:59 UTC, dca...@krl.org wrote:
On Monday, March 13, 2017 at 4:28:39 AM UTC-4, olds...@tubes.com wrote:

I've been looking into buying an Audio Generator (Sine and Square Wave)..

In addition to looking at Ebay , look at AliExpress. Sometimes identical items are much less expensive at Ally or Ebay. Try including diy to find kits.

Solid state equipment is a lot more reliable than vacuum tube equipment.

It _can_ be more reliable, but making it so is a challenge most equipment fails. If 50 year old valve kit is working it has proven itself, and any new electronics has a very low chance of lasting that well. So in practice old valve kit is on average more likely to last better.


> So you are better off buying something new. Getting a replacement vacuum tube may be nearly impossible.

it's not. On the rare occasions it is, boost the heater voltage, if it's not physically broken.


NT
 
Martin Brown wrote:

These days DDS is probably the way to go since it can do so much more.
Testing power amps it is wiser to use frequency shaped noise rather than
pure sine waves since you can hit mechanical resonances and damage
acoustic drivers with quite modest power levels of pure sine wave.

** Giant HUH ???

Testing amplifiers does not involve speakers AT ALL !!!

Sine waves are the primary and still most revealing method.

BTW,

any speaker that cannot survive short term sine wave testing is not worth owning.

You could not be more WRONG.



.... Phil
 
On Monday, March 13, 2017 at 8:43:24 PM UTC-4, tabb...@gmail.com wrote:

Solid state equipment is a lot more reliable than vacuum tube equipment..

It _can_ be more reliable, but making it so is a challenge most equipment fails. If 50 year old valve kit is working it has proven itself, and any new electronics has a very low chance of lasting that well. So in practice old valve kit is on average more likely to last better.


NT

I do not agree with you. A fifty year old valve kit that is working does not prove that it is a reliable gear. There may have been 50 thousand of those produced and all have failed except for one.

Way back in the 1960's the mean time to failure for some transistors was 1500 years.

Dan
 
On Tuesday, 14 March 2017 09:22:05 UTC, Martin Brown wrote:

There used to be old school analogue function generator chips that made
a triangle wave and then applied diode shaping to get a pseudo-sine
wave. HP made one design implementation that was surprisingly good.
Intersils 8038 was the poor mans alternative for DIY.

http://www.intersil.com/content/dam/intersil/documents/icl8/icl8038.pdf

I built one of those decades ago. What a car crash. The wave forms were hopeless. I don't remember the details to know why, I presume the problem was the 8038 though.


NT
 
On Tuesday, 14 March 2017 13:46:23 UTC, dca...@krl.org wrote:
On Monday, March 13, 2017 at 8:43:24 PM UTC-4, tabby wrote:

Solid state equipment is a lot more reliable than vacuum tube equipment.

It _can_ be more reliable, but making it so is a challenge most equipment fails. If 50 year old valve kit is working it has proven itself, and any new electronics has a very low chance of lasting that well. So in practice old valve kit is on average more likely to last better.

I do not agree with you. A fifty year old valve kit that is working does not prove that it is a reliable gear.

It proves the design is capable of great longevity

> There may have been 50 thousand of those produced and all have failed except for one.

There's always a 1 in 50k chance of that. Statistical conclusions are only a reflection of the data fed into them.

> Way back in the 1960's the mean time to failure for some transistors was 1500 years.

And the mean time to failure for soldered connections, electrolytics, bits of plastic, switch contacts and all other parts?


NT
 
On Tuesday, March 14, 2017 at 10:02:05 AM UTC-4, tabb...@gmail.com wrote:


Way back in the 1960's the mean time to failure for some transistors was 1500 years.

And the mean time to failure for soldered connections, electrolytics, bits of plastic, switch contacts and all other parts?


NT

On the stuff I was designing there were no bits of plastic, switches , or soldered connections. The electrolytics were the biggest problem and we used mostly dry slug tantalum caps ( as I remember it, It was a while back )

It was somewhat after someone at MIT or Harvard built a difference analyser with something like 50,000 tubes. The tubes had a 50,000 hour average life . Se it would fail about every hour. To find the bad tube took something like two hours It was not a success.

Dan
 
On 3/14/2017 10:51 AM, dcaster@krl.org wrote:
On Tuesday, March 14, 2017 at 10:02:05 AM UTC-4, tabb...@gmail.com wrote:


Way back in the 1960's the mean time to failure for some transistors was 1500 years.

And the mean time to failure for soldered connections, electrolytics, bits of plastic, switch contacts and all other parts?


NT

On the stuff I was designing there were no bits of plastic, switches , or soldered connections. The electrolytics were the biggest problem and we used mostly dry slug tantalum caps ( as I remember it, It was a while back )

It was somewhat after someone at MIT or Harvard built a difference analyser with something like 50,000 tubes. The tubes had a 50,000 hour average life . Se it would fail about every hour. To find the bad tube took something like two hours It was not a success.

Dan

Still in use by the DMV.



---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
 
On Tuesday, 14 March 2017 15:51:30 UTC, dca...@krl.org wrote:
On Tuesday, March 14, 2017 at 10:02:05 AM UTC-4, tabb wrote:

Way back in the 1960's the mean time to failure for some transistors was 1500 years.

And the mean time to failure for soldered connections, electrolytics, bits of plastic, switch contacts and all other parts?

On the stuff I was designing there were no bits of plastic, switches , or soldered connections. The electrolytics were the biggest problem and we used mostly dry slug tantalum caps ( as I remember it, It was a while back )

Most testgear of course is built to nothing like those standards.

> It was somewhat after someone at MIT or Harvard built a difference analyser with something like 50,000 tubes. The tubes had a 50,000 hour average life . Se it would fail about every hour. To find the bad tube took something like two hours It was not a success.

A killer problem with valve computers. At least they were better than relays. A sig gen with a few valves is a very different proposition. Basic maintenance every 16k hours of use, typically several decades, is quite acceptable.


NT
 
On Tuesday, March 14, 2017 at 11:31:50 AM UTC-7, rickman wrote:
On 3/13/2017 4:26 AM, oldschool@tubes.com wrote:
I've been looking into buying an Audio Generator (Sine and Square Wave).
I mainly want this to run thru an amplifier to listen to...

I haven't read all of the posts in this thread, but I see a lot of
confusion of the terms "function generator" and "audio generator".
Audio simply refers to the frequency range of the signal generated
without saying anything about the manner in which it is generated. But
most signal generators output a sine wave and perhaps a square and
triangle wave.

That's incorrect; most inexpensive signal generators output a square and
triangle (hey, it only takes two op amps); adding a sinewave is complicated.
To do a GOOD sinewave, the old HP20x units had matched pairs of adjustable
capacitors, which are VERY pricey items.

So, the iCL8038 and XR2206 and some other IC generators (which dominate
the market at the low-cost end) distort and/or filter the triangle wave to make
a "sinewave". The sinewave outputs are dreadfull.

For audio test purposes, a CD with test tracks is a pretty good sinewave source. Digital
sythesizers are good, too. Neither is convenient for a test bench, though.
 
dca...@krl.org wrote:

I do not agree with you. A fifty year old valve kit that is
working does not prove that it is a reliable gear.

** It proves that someone has been keeping it running.


Way back in the 1960's the mean time to failure for some transistors
was 1500 years.

** Which only means that the unforced failure rate is one in 1500 per year.

Says nothing about the typical lifespan and it sure as HELL ain't 1500 years.



...... Phil
 
Prickman wrote:
I haven't read all of the posts in this thread, but I see a lot of
confusion of the terms "function generator" and "audio generator".

** There is no such confusion here.


Audio simply refers to the frequency range of the signal generated
without saying anything about the manner in which it is generated.

** But an "audio generator" has a particular meaning NOT the same as "function generator".

FYI, terms mean what people men when they use them.


...... Phil
 
On Tuesday, March 14, 2017 at 5:52:48 PM UTC-7, rickman wrote:
On 3/14/2017 8:23 PM, whit3rd wrote:
On Tuesday, March 14, 2017 at 11:31:50 AM UTC-7, rickman wrote:

So, the iCL8038 and XR2206 and some other IC generators (which dominate
the market at the low-cost end) distort and/or filter the triangle wave to make
a "sinewave". The sinewave outputs are dreadfull.

So they *do* produce a sine wave?

Not a sinewave suitable for a set of test results that can be easily analyzed. The
"sinewaves" have all the harmonics of a triangle wave, but at lower amplitude, and this
is accomplished with hand-tweak adjustments.

If/as you want to test an amplifier for distortion, that 'sinewave' is not pure enough to use.

For audio test purposes, a CD with test tracks is a pretty good sinewave source. Digital
sythesizers are good, too. Neither is convenient for a test bench, though.

I'm not clear on what you consider inconvenient, but you don't need much
space to create a decent sine wave.

What is inconvenient, is that one cannot dial the frequency with an analog knob, while
listening for room resonances or speaker-crossover blips. A DDS solution will have to
be programmed to do a sweep, and reprogrammed if you want to check that one
part of the range that sounded odd... or at least, that was how the old Agilent DDS
worked.
 
On Tuesday, March 14, 2017 at 8:51:22 PM UTC-4, k...@notreal.com wrote:

Solid state equipment is a lot more reliable than vacuum tube equipment. So you are better off buying something new. Getting a replacement vacuum tube may be nearly impossible.

Electrically, tubes are harder to bust...


Weeks? MTBF of 336 hours? You can't aford a tube's filament current?
GMAFB I guess you never turn on a light bulb, either. Heaven forbid
that you would make diner!

When I was in the Navy I had a mk 37 gun fire control system to maintain. The radar used a fair number of vacuum tubes. When the 5 inch 38 guns were fired the radar would go down after about two salvos because some tube had failed. So the system had a MTBF of about 5 minutes or less.



Dan
 
On 3/13/2017 2:59 PM, Jasen Betts wrote:
On 2017-03-13, dcaster@krl.org <dcaster@krl.org> wrote:
On Monday, March 13, 2017 at 4:28:39 AM UTC-4, olds...@tubes.com wrote:
I've been looking into buying an Audio Generator (Sine and Square Wave).

In addition to looking at Ebay , look at AliExpress. Sometimes identical items are much less expensive at Ally or Ebay. Try including diy to find kits.

Also search "suite", which seems to be a common miss-traslaion of "kitset"

Solid state equipment is a lot more reliable than vacuum tube equipment. So you are better off buying something new. Getting a replacement vacuum tube may be nearly impossible.

Electrically, tubes are harder to bust...

No they aren't. Just leave one on for a few weeks and the filament
will go out, if it hasn't busted your wallet on the electric bill.

--

Rick C
 
On Tue, 14 Mar 2017 19:43:52 -0400, rickman <gnuarm@gmail.com> wrote:

On 3/13/2017 2:59 PM, Jasen Betts wrote:
On 2017-03-13, dcaster@krl.org <dcaster@krl.org> wrote:
On Monday, March 13, 2017 at 4:28:39 AM UTC-4, olds...@tubes.com wrote:
I've been looking into buying an Audio Generator (Sine and Square Wave).

In addition to looking at Ebay , look at AliExpress. Sometimes identical items are much less expensive at Ally or Ebay. Try including diy to find kits.

Also search "suite", which seems to be a common miss-traslaion of "kitset"

Solid state equipment is a lot more reliable than vacuum tube equipment. So you are better off buying something new. Getting a replacement vacuum tube may be nearly impossible.

Electrically, tubes are harder to bust...

No they aren't. Just leave one on for a few weeks and the filament
will go out, if it hasn't busted your wallet on the electric bill.

Weeks? MTBF of 336 hours? You can't aford a tube's filament current?
GMAFB I guess you never turn on a light bulb, either. Heaven forbid
that you would make diner!
 
On 3/14/2017 8:23 PM, whit3rd wrote:
On Tuesday, March 14, 2017 at 11:31:50 AM UTC-7, rickman wrote:
On 3/13/2017 4:26 AM, oldschool@tubes.com wrote:
I've been looking into buying an Audio Generator (Sine and Square Wave).
I mainly want this to run thru an amplifier to listen to...

I haven't read all of the posts in this thread, but I see a lot of
confusion of the terms "function generator" and "audio generator".
Audio simply refers to the frequency range of the signal generated
without saying anything about the manner in which it is generated. But
most signal generators output a sine wave and perhaps a square and
triangle wave.

That's incorrect; most inexpensive signal generators output a square and
triangle (hey, it only takes two op amps); adding a sinewave is complicated.
To do a GOOD sinewave, the old HP20x units had matched pairs of adjustable
capacitors, which are VERY pricey items.

So, the iCL8038 and XR2206 and some other IC generators (which dominate
the market at the low-cost end) distort and/or filter the triangle wave to make
a "sinewave". The sinewave outputs are dreadfull.

So they *do* produce a sine wave?


For audio test purposes, a CD with test tracks is a pretty good sinewave source. Digital
sythesizers are good, too. Neither is convenient for a test bench, though.

I'm not clear on what you consider inconvenient, but you don't need much
space to create a decent sine wave. I produce a board with a stereo
CODEC and during test it produces a sine wave that I can't visually
detect and defects in at any resolution. If I removed the application
specific items and gave it a useful PC interface it could sell for maybe
$50. It would have perhaps $20 worth of parts and could fit in an
Altoids tin easily. I believe there are similar products on eBay which
sell for less.

--

Rick C
 

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