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Re: Audio Generator or Function Generator? Which to get?

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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:
>
>> 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:
>
>
> 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.


> When I descibed this thing, I actually had looked at several of them
> from China, which all looked identical. One of them said it goes to
> 8mhz, using the BNC connector labeled HS. Either way, that dont much
> matter, since I have my old Eico tube signal generator, for RF use.
>
> I probably am doing this backward, but I really was not looking for
> something like this. I was looking for an old tube based audio
> generator, such as the Eico 377. But you know how ebay tends to show a
> hundred other things that are similar, and these function generators
> came up. I had to spend a good amount of time reading about them, since
> I was not familiar with them at all.
>
> I am somewhat aware about using a computer with software to act as a
> signal generator, oscilloscope, etc. I'll have to read up more on all of
> that, but in all honesty, I would not even consider connecting my laptop
> computer to anything other than and audio input connector on a tube amp.
> I said I also want something for testing interstage circuits, and that
> means applying a test probe to a spot inside a device that may have 400
> or more volts on it. Even with a capacitor and other protection, there
> is no way in hell that I am gonna risk destroying an expensive and
> fragile laptop computer. And while I have several spare deshtop
> machines, I do not keep them in my shop. I dont have the space and I
> dont want to be distracted by computers when I'm soldering. If I do take
> any computers in my shop, it's my laptop, and I only do so to view a
> schematic on the screen.

How exactly would a computer distract you while you are soldering??? 
That is very unclear.

If you want to deal with tube circuits you need a buffer between any low 
voltage equipment and the tube equipment.


> In all honesty, what I really want to buy is still an old tube type
> audio generator. That is what was made for the gear that I mostly work
> on, and that old tube stuff is built to hold up, as well as being easy
> to repair if it breaks. The problem is that this old tube stuff is
> selling for way too much money on ebay. Heck, some of those old Eico
> 377's are asking as much just for shipping as I am willing to pay for
> the whole thing, and one of them looks like it went thru a war, and is
> being sold For PARTS.....

Maybe there's a reason why tube equipment isn't made much anymore?


> Which reminds me, does anyone know of other sources for buying that old
> tube test gear, besides ebay? There must be other sources....
> It's NOT Amazon, I checked, even though I have never cared much for
> Amazon. They just dont sell old stuff like this.

Try connecting with a Ham club.  They often use old equipment.


> I might still buy one of these DDS devices, just for the heck of it. For
> $15, I'm sure I'll have some fun with it..... I actually found some of
> them (identical( located in the U.S. for $17. (I dont buy from China
> because it takes too long to get the stuff). I also found another one in
> the US that comes with the matching wall wart for $23. (Which I'd
> probably buy, or I will just end up having to spend another $5 or more
> to order that wart separately.

The problem with buying wall warts is getting one that does what it says 
it does.  If  you type in 5v, 1A for a wall wart on ebay, the first 
hundred or so units have the same picture, are priced within a nickle of 
each other and contain a single transistor for the entire active circuit!


> So, the bottom line is that I may buy one of these DDS devices, but I
> will still continue to look for the tube type audio generator which is
> what I really want in my shop for testing my old tube gear.


You could just insert a tube amp between the DDS and the gear you are 
testing...

-- 

Rick C

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Thread

Audio Generator or Function Generator? Which to get? oldschool@tubes.com - 2017-03-13 02:26 -0600
  Re: Audio Generator or Function Generator? Which to get? Colin Horsley <horsley-spam@westnet.com.au> - 2017-03-13 20:20 +1100
  Re: Audio Generator or Function Generator? Which to get? Jasen Betts <jasen@xnet.co.nz> - 2017-03-13 09:32 +0000
    Re: Audio Generator or Function Generator? Which to get? Martin Brown <'''newspam'''@nezumi.demon.co.uk> - 2017-03-14 09:22 +0000
      Re: Audio Generator or Function Generator? Which to get? Phil Allison <pallison49@gmail.com> - 2017-03-14 03:14 -0700
        Re: Audio Generator or Function Generator? Which to get? "pfjw@aol.com" <pfjw@aol.com> - 2017-03-14 05:13 -0700
  Re: Audio Generator or Function Generator? Which to get? Ralph Mowery <rmowery28146@earthlink.net> - 2017-03-13 10:13 -0400
  Re: Audio Generator or Function Generator? Which to get? "pfjw@aol.com" <pfjw@aol.com> - 2017-03-13 07:54 -0700
  Re: Audio Generator or Function Generator? Which to get? Jeff Liebermann <jeffl@cruzio.com> - 2017-03-13 09:27 -0700
    Re: Audio Generator or Function Generator? Which to get? oldschool@tubes.com - 2017-03-13 14:23 -0500
      Re: Audio Generator or Function Generator? Which to get? "pfjw@aol.com" <pfjw@aol.com> - 2017-03-13 12:33 -0700
        Re: Audio Generator or Function Generator? Which to get? oldschool@tubes.com - 2017-03-13 15:03 -0500
      Re: Audio Generator or Function Generator? Which to get? Ralph Mowery <rmowery28146@earthlink.net> - 2017-03-13 16:28 -0400
      Re: Audio Generator or Function Generator? Which to get? rickman <gnuarm@gmail.com> - 2017-03-14 19:57 -0400
  Re: Audio Generator or Function Generator? Which to get? amdx <nojunk@knology.net> - 2017-03-13 13:43 -0500
    Re: Audio Generator or Function Generator? Which to get? amdx <nojunk@knology.net> - 2017-03-13 14:01 -0500
    Re: Audio Generator or Function Generator? Which to get? oldschool@tubes.com - 2017-03-13 14:33 -0500
      Re: Audio Generator or Function Generator? Which to get? amdx <nojunk@knology.net> - 2017-03-13 14:51 -0500
      Re: Audio Generator or Function Generator? Which to get? rickman <gnuarm@gmail.com> - 2017-03-14 20:02 -0400
  Re: Audio Generator or Function Generator? Which to get? "Benderthe.evilrobot" <Benderthe.evilrobot@virginmedia.com> - 2017-03-13 21:15 +0000
  Re: Audio Generator or Function Generator? Which to get? rickman <gnuarm@gmail.com> - 2017-03-14 14:31 -0400
  Re: Audio Generator or Function Generator? Which to get? jurb6006@gmail.com - 2017-03-15 00:22 -0700

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