Which device will provide a 1kHz 14mV signal?

I'm starting out in amplifier repairs and acquiring equipment. The schematic for one of my repairs specifies using a 1kHz 14mV signal for test points. This seems like a pretty small signal to me; what device should I buy (signal/function generator) that will provide this resolution? What specs should I be looking for? Thanks.

Signal Generator?

Assuming you need a sine wave, buy something with a good quality sine wave output, possibly an old analogue second hand one will have better purity. Then, if the signal is too large it is easy enough to make a resistive attenuator.

Keith

Re: Signal Generator?

Thanks. That's a good suggestion.. Yes, it's a sine wave. I suppose I could also incorporate a 10-turn pot in a resistor circuit to gain the resolution I'd want.

Re: Signal Generator?

hi
ICL 8038 and XR2206 is complete function generator chip with sine wave
output

Signal Generator?

Hi SMSAmps,
As Keiths said too; for audio you need a better quality signal, so are some good older audio generators to buy. I would not see for simple function generators, their distortions arent enough low for audio measurements, bu unfortunately it depends from your goals...
A better function generator(I mean less as 0.2--(0.5)% distortion in audio range) is surly usable for general measurements on amps, but i.e. for distortion measurements you must have a dedicated generator & with (i.e.) less 0.001% distortion (abs. minimum less as 0.01%)...
In my opinion you need for an audio workshop a signal/generator with output of 1mV...1V (better up to 10V) & with eventually 50 or even 600 Ohm (best both).
I would not use a helipot (multiturn poti), but its possible, than a switched attenuator is not only speedyer/rasher to set into new values/positions, but its good repeatable, what by multiturn is not so direct to say (even if it has a microdial, is some uncomfortable to use & has a range only of 10x!
A simple 3x switched attenuator as 10/20 & 40 dB solutes your all signal problems_ anyway, a better generator has it built in & delivers on 50 Ohm impedance!
K.

Re: Signal Generator?

That's great advice. Thanks. That gives me some real tangibles to chase after. I'm heading out to look at an HP 3312A this afternoon. I'll see if it meets the specs. I do know that it has 50 ohm output.

Signal Generator?


Otherwise if you need distortion measurements you can self build a good spetial generator too...
K.

Re: Signal Generator?

http://cds.linear.com/docs/LT Magazine/05_03-12-LTC1968-Pei.pdf is a good starting point for a home-brew project

Many high quality audio amplifiers may have distortion specifications below 0.1% THD

Some of the earlier HP function gen's are not that good (0.3 - 0.5%)

Re: Signal Generator?

SMSAmps said:

That's great advice. Thanks. That gives me some real tangibles to chase after. I'm heading out to look at an HP 3312A this afternoon. I'll see if it meets the specs. I do know that it has 50 ohm output.

Click to expand...

That is 0.5% distortion on sine wave so may not be good enough for you, as already mentioned by E-design.

Keith

Re: Signal Generator?

Hameg used to make a very affordable low distortion audio generator HM8037 (<0.01%) https://www.akh.se/hameg/hm80/hm8037-serv.pdf that you may still find from time to time on eBay. Also look at the Krohn-Hite stuff: Model 4200B gives less than 0.1% distortion and often on eBay for little as $30. If you can get hold of a Tektronix SG502 or SG505 at a good price you will be very happy 502(<0.035%), 505(<0.0008%).

Read https://www.diyaudio.com/forums/everything-else/41115-low-distortion-signal-generator.html for some more ideas

Signal Generator?

Yes,
Krohn-Hite is a well knowed audio equipment supplyer, these Tek`s are fine too for your apps.
Im i.e. over longer time on the finding for Krohn-Hite 3232 filter (or similar), some are on eBay for $ 50--100,-, but my/our problem is that these "super low prices" are every times only for "(US) domestic addresses" :-(.. I think so, that E-designs $30 generator would be in the same situation...
For foreigns are often $ 150-300 to calculate, but worser is a delivery price from minimum $70, typically 150-200, but some dreamer wishes at $3-400 too, thier are modern Alcapones/thievs...We can not forget some customs tax too! Thats life.
Jim Williams circuit ideas are simple "GREAT"_ I thinked exactly on the AN 43 from LT if Im writing: "Otherwise if you need distortion measurements you can self build a good spetial generator too... "
I have some from hes circuit colllections adapted or 1:1 buildin in my designs/projects, their are really GOOD & 100% rebuildable.
HM8037 isnt bad too, but if some thing will be rebuild, is a resultat of 10---100 times lower distortion with Jims circuit & similar complexity: for me is clear, that Hamegs circuit won the second place...
@E-design,
Best tnx for the Serv. Man! , btw; I need some HM-scope doc too_if you can help pls?
K.

Signal Generator?

Leader used to make some nice ones. The LAG 126 is 0.005% with 80dB attenuator. You find them in the second hand retailers. I am not sure if they are a peculiarly British make though.

Instek GAG-810 is quite cheap new and is 0.02%.

Keith.

Signal Generator?

Nice discussion about low distortion generators. However, I don't see an indication in the original posters question, that he would need it. Without a THD meter, it's of no use. For audio amplifier functional tests, nearly any sine generator can do.

Signal Generator?

Hallo,
I think you will not say, that an Audio workshop will not need a signal generator with extrem low distortions (too)?
OK, it was not explicit said from OP, bot he didnt make some nagations too.
Than, distortions are with an spektrum analyzer & other ways too to measure, not only with a distortion(THD) meter...
K.

Re: Signal Generator?

FvM said:

Nice discussion about low distortion generators. However, I don't see an indication in the original posters question, that he would need it. Without a THD meter, it's of no use. For audio amplifier functional tests, nearly any sine generator can do.

Click to expand...

Yes, the gen and meter go hand in hand. I use a Tek DA 4084 which is excellent. This was an eBay find at about $150. It is fully automatic, so you don't have to cal your 100% level when you make a measurement. I also have a HP3561A which help analyze the components of distortion.