Audio Generator or Function Generator? Which to get?

On Wednesday, 15 March 2017 12:10:36 UTC, Martin Brown  wrote:
> On 14/03/2017 13:58, tabbypurr wrote:
> > 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.
> 
> It was never anything like as good as a Wein bridge sine wave but it was 
> good for about 0.5% THD if you trimmed it properly. I suspect 
> manufacturing tolerances made it inconsistent batch to batch.
> 
> Cute chip in its day, but that was a long time ago.

I doubt it managed 50%, let alone 0.5%. It had 3 outputs, sine square & triangle. At some frequencies one output looked more like one of the others should, and the others were just a mess. It was dire, and yes I followed the advised circuit. It might manage 0.5% at some frequency, but as a sig gen it was a real failure. If I ever get the time I'll look at it again one day, it's on a shelf somewhere.


NT

On Wednesday, 15 March 2017 00:51:22 UTC, k...@notreal.com  wrote:
> 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).
snip

> >>> 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

It's certainly way off. Domestic valve gear typically runs a couple of decades before needing a new valve. TVs weren't as reliable, being expensive goods in their time the valves tended to be pushed harder & the TVs ran hot.


NT

On Tuesday, 14 March 2017 23:57:20 UTC, rickman  wrote:
> On 3/13/2017 3:23 PM, oldschool@tubes.com wrote:
> > On Mon, 13 Mar 2017 09:27:50 -0700, Jeff Liebermann <jeffl@cruzio.com>
> > wrote:

> > Thanks to all who replied. I read that WIkipedia article, which
> > explained what these things are, (even though that article was like
> > reading a legal manual).
> 
> Wikipedia often is written by those with a certain level of elitism 
> rather than an interest in explaining topics to all who wish to learn. 
> It is not uncommon for a technical article to be written at such a high 
> level that a reader needs much more than just a casual understanding of 
> the topic.
> 
> In my opinion, this is one of the ways Wikipedia has failed.

Surely that beats a dumbed down retardopedia. Some topics just aren't that simple. There's always the simple-wiki articles aimed more at children. Wiki has its problems, but I'm not convinced that is one of them.


NT

On Wednesday, March 15, 2017 at 8:10:36 AM UTC-4, Martin Brown wrote:
> On 14/03/2017 13:58, tabbypurr@gmail.com wrote:
> > 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.
> 
> It was never anything like as good as a Wein bridge sine wave but it was 
> good for about 0.5% THD if you trimmed it properly. I suspect 
> manufacturing tolerances made it inconsistent batch to batch.
Right that's my memory, I could tweak one up and get the 3rd harmonic down 
below ~1%.. but not by much.  
BTW I've got tubes of ICL8038's if anyone wants to play with some, drop me an
email.  (Well US/Canada... shipping costs.) 

George H. 
> 
> Cute chip in its day, but that was a long time ago.
> 
> -- 
> Regards,
> Martin Brown

On Wednesday, March 15, 2017 at 8:43:39 AM UTC-4, tabb...@gmail.com wrote:

> It's certainly way off. Domestic valve gear typically runs a couple of decades before needing a new valve. TVs weren't as reliable, being expensive goods in their time the valves tended to be pushed harder & the TVs ran hot.
> 
> 
> NT

TV's also had more tubes.  So with the same mtbf per tube, the system reliability was much less.  

                                       Dan

On 3/15/2017 8:46 AM, tabbypurr@gmail.com wrote:
> On Tuesday, 14 March 2017 23:57:20 UTC, rickman  wrote:
>> On 3/13/2017 3:23 PM, oldschool@tubes.com wrote:
>>> On Mon, 13 Mar 2017 09:27:50 -0700, Jeff Liebermann <jeffl@cruzio.com>
>>> wrote:
>
>>> Thanks to all who replied. I read that WIkipedia article, which
>>> explained what these things are, (even though that article was like
>>> reading a legal manual).
>>
>> Wikipedia often is written by those with a certain level of elitism
>> rather than an interest in explaining topics to all who wish to learn.
>> It is not uncommon for a technical article to be written at such a high
>> level that a reader needs much more than just a casual understanding of
>> the topic.
>>
>> In my opinion, this is one of the ways Wikipedia has failed.
>
> Surely that beats a dumbed down retardopedia. Some topics just aren't that simple. There's always the simple-wiki articles aimed more at children. Wiki has its problems, but I'm not convinced that is one of them.

I may not be an expert in various areas of electronics and computers, 
but I am far from a novice.  There are various electronics related pages 
on Wikipedia that I can't read without going to the references and 
studying.  That is ridiculous.

When only the experts in a field can even read and understand an 
encyclopedia entry I'm not sure that's any better than a "retardopedia". 
   It essentially becomes the same thing, a web page that conveys very 
little information to very few people.

I think the editors end up being full of themselves trying to be 
"expert" or "professional".  In the end they become irrelevant.

-- 

Rick C

On 3/15/2017 8:24 AM, amdx wrote:
> On 3/14/2017 9:21 PM, Jasen Betts wrote:
>> On 2017-03-15, rickman <gnuarm@gmail.com> wrote:
>>> 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?
>>
>> curved:  yes
>> a sin(2 pi f t + phi ): no.
>
>   Under 1% distortion when tweaked.
>
> I don't think our op would notice.

He wants to do a listening test.  You know, with the ears.  How many of 
us can even hear 0.1% distortion?

-- 

Rick C

On Wednesday, 15 March 2017 14:30:05 UTC, dca...@krl.org  wrote:
> On Wednesday, March 15, 2017 at 8:43:39 AM UTC-4, tabby wrote:
> 
> > It's certainly way off. Domestic valve gear typically runs a couple of decades before needing a new valve. TVs weren't as reliable, being expensive goods in their time the valves tended to be pushed harder & the TVs ran hot.

> TV's also had more tubes.  So with the same mtbf per tube, the system reliability was much less.  

again mtbf was not the same. This was common knowledge in the valve tv era.


NT

On Wednesday, 15 March 2017 16:37:05 UTC, rickman  wrote:
> On 3/15/2017 8:46 AM, tabbypurr wrote:
> > On Tuesday, 14 March 2017 23:57:20 UTC, rickman  wrote:
> >> On 3/13/2017 3:23 PM, oldschool@tubes.com wrote:
> >>> On Mon, 13 Mar 2017 09:27:50 -0700, Jeff Liebermann <jeffl@cruzio.com>
> >>> wrote:
> >
> >>> Thanks to all who replied. I read that WIkipedia article, which
> >>> explained what these things are, (even though that article was like
> >>> reading a legal manual).
> >>
> >> Wikipedia often is written by those with a certain level of elitism
> >> rather than an interest in explaining topics to all who wish to learn.
> >> It is not uncommon for a technical article to be written at such a high
> >> level that a reader needs much more than just a casual understanding of
> >> the topic.
> >>
> >> In my opinion, this is one of the ways Wikipedia has failed.
> >
> > Surely that beats a dumbed down retardopedia. Some topics just aren't that simple. There's always the simple-wiki articles aimed more at children. Wiki has its problems, but I'm not convinced that is one of them.
> 
> I may not be an expert in various areas of electronics and computers, 
> but I am far from a novice.  There are various electronics related pages 
> on Wikipedia that I can't read without going to the references and 
> studying.  That is ridiculous.
> 
> When only the experts in a field can even read and understand an 
> encyclopedia entry I'm not sure that's any better than a "retardopedia". 
>    It essentially becomes the same thing, a web page that conveys very 
> little information to very few people.
> 
> I think the editors end up being full of themselves trying to be 
> "expert" or "professional".  In the end they become irrelevant.

I don't recall seeing such pages. There are some idiotic ones, wiki certainly has its problems with wallies thinking they're experts. But for an encyclopaedia I don't know a better one.


NT

On Tuesday, March 14, 2017 at 8:27:11 PM UTC-7, rickman wrote:
> On 3/14/2017 9:24 PM, whit3rd wrote:

> > 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 ...

> You mean like this?
> 
> http://www.etc.sk/index.php/en/products/auxiliary-equipment/control-panels/item/136-control-panel-for-usb-oscilloscopes.html

It looks good, doesn't it?  The Agilent had a knob, that controlled one digit at a time of the
frequency (so it would give you a step on dialing).   The multipurpose 'knob' of a DDS
gets so  many functions assigned to it...  just spend a minute or two in the  menus, and
you can attach the knob to the 'frequency' attribute.   First, though, just a minute or
two in the menus, and you cn attach it to the 'amplitude' attribute.   Before that, of course,
you gotta power the gizmo up and give a few seconds to boot, and squint at a few
menus to make sure it's not simulating heartbeats, 'cuz you want a sinewave.

On a test bench, you want to power ON, adjust volume to see a meter move, or hear the
speakers sound off.   Then you check the frequency range, and turn the F dial... 
all of which takes four seconds.  Total.