Audio Generator or Function Generator? Which to get?

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

On 13/03/2017 19:26, oldschool@tubes.com wrote:

> 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).

https://en.wikipedia.org/wiki/Direct_digital_synthesizer

Col


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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 2017-03-13, oldschool@tubes.com <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 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. 

Any reason you've not looked at PC software?

> 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).

look it up on wikipedia. it means that inside there's some sort of computer
generating a digital wavform, that gets converted and comes out the output

> 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?). 

you can probably buy he same thing from china on ebay, for about the
same price, most large scale vendors are present in multiple
marketplaces.

> 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?

it will probably last longer than a few months, especially if you put
it in a good case.

> 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.

it's probably a square wave at 128 times the DDS output frequency.
it might be useful for other purposes 

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In article <vaicccta9pdjea9abbc1074l06705f6677@4ax.com>, 
oldschool@tubes.com says...
> 
> 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.
> 
For the price you might as well get a function generator.  Most of the 
audio type signal generators put out sine waves and some square waves.  
The function generator can put out those and many other waveformes.  I 
have one of the China function generators that lets me hook it to a 
computer and any kind of waveform I can draw on the computer screen, the 
generator will put out.  

The one I have will go  from below audio to about 25 MHz. They make some 
other models that only o to about 6 MHz for a few dollars less. It is 
dual chanel so you can put signals into a stereo if you want to.  Each 
chanel can be set sperate.  It includes a frequency counter so you can 
input a frequency and see what it is. I am not sure how accurate it is 
above the audio range.  There is no difference in audio and RF as far as 
to what you get out, just the range of frequencies, so you can use it as 
an rf signal generator if you want.  They are not shielded being in a 
plastic case.

The waves other than a sine wave starts to degrade above about 1 MHz.  
There is a modification that is on youtube that I made to mine to help 
that out.  You probably would not want to try that as it involves 
changing about 6 or 8 of the SMDs, but the parts were less than $ 20 
from one of the larger companies.  I did it mainly to see how it would 
work and am learning how to work with the SMDs.

There are some vidios on youtube about this one and probably others.

http://www.ebay.com/itm/DDS-Dual-channel-Signal-Source-Generator-
Arbitrary-Waveform-200MSa-s-25MHz-W9U7-/162074779152?
hash=item25bc68de10:g:CwgAAOSw74FXOayX

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 Mon, 13 Mar 2017 02:26:56 -0600, 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 the frequency
>repsonse of the amp and speakers.
>Here is the ebay URL.
(...)
>http://tinyurl.com/h5celuc

That DDS generator only goes up to 65KHz, does not have a built in
frequency sweep feature, and does not have a sawtooth output or built
in detector suitable for displaying a frequency sweep on an
oscilloscope.  To sweep an audio amplifier with a DDS, you will need a
sine wave generator feature, and an up/down counter or frequency
modulator to sweep the frequency range.  

First look at a real function generator.  Next, build a checklist of
the features you need.  Then, go shopping using the feature list.
You're doing this backwards.

Note:  You can use a PC sound card as a swept audio source and
function generator:
<http://www.daqarta.com/dw_gen.htm>
<http://www.instructables.com/id/PC-Sound-Card-Signal-Generator-Interface/?ALLSTEPS>
etc...

Most of the PC based oscilloscope and spectrum analyzer programs have
built in generators.  I use Visual Analyzer:
<http://www.sillanumsoft.org/prod01.htm>
and Spectrum Lab:
<http://www.qsl.net/dl4yhf/spectra1.html>
Both have built in generator functions, including two tones for
intermodulation measurements.

This scope program has a tolerable white/pink noise generator.
<https://www.zeitnitz.eu/scope_en>

Hint:  Buy a higher resolution USB sound card that will do 24 bit  96
KHz, 192 KHz, or if you have money to spend, 384 KHz clock rate.  The
common 44/48KHz devices don't make very good test instruments.
External USB is better because sound chips built into a PC or laptop
pickup noise from everywhere.

However, I must admit that $15 test equipment is lots of fun to play
with.  I have LRC meters, function generators, DDS RF generators,
return loss bridges, noise generators, etc most of which cost about
$15.  


-- 
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

On 3/13/2017 3:26 AM, oldschool@tubes.com wrote:
> I've been looking into buying an Audio Generator (Sine and Square Wave).

   If you have any interest in building one, look up the XR2206. It is 
an old but a pretty cool chip. It will do many functions up to 1 Mhz.
  Lots of info available, I even see one Arduino controlled unit.

                                             Mikek


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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...

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On 3/13/2017 1:43 PM, amdx wrote:
> On 3/13/2017 3:26 AM, oldschool@tubes.com wrote:
>> I've been looking into buying an Audio Generator (Sine and Square Wave).
>
>   If you have any interest in building one, look up the XR2206. It is an
> old but a pretty cool chip. It will do many functions up to 1 Mhz.
>  Lots of info available, I even see one Arduino controlled unit.
>
>                                             Mikek
>

Ebay has a XR2206 kit for $9 with a case.

> http://www.ebay.com/itm/171999013818

Here's a 4 part video of assembly, part 4, you can find 1,2 and 3.

> https://www.youtube.com/watch?annotation_id=annotation_1309899397&feature=iv&src_vid=n9sbUxz92uM&v=sKRbb0rJzOE

                                Mikek




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