FINALLY Measuring the Distortion of an SG505!
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- Опубліковано 9 лют 2025
- Link To Shahriar’s (The Signal Path) in depth video on the QA403 - • TSP #234 - QuantAsylum...
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I have been getting asked if I would work on some AA501’s and AA501A’s from viewers. I have been hesitant to take on some of these units in the lab as I have not been able to really checkin the distortion specs for the SG505’s They are speced to 0.0008% which is an incredibly low distortion metric. But after a video from the signal patch linked above I have found a unit that will reassure it RAW. This is fantastic as it allows me to check the spec and be able to have confidence in the SG units when working on equipment for others.
** Repair exposes the Tech to mains electric and should only be done by trained personnel. Errors can be fatal. **
I want one of those QA machines. Watched Signal Path’s review again last night and now you are using it today. Cool
Yeah i got one of them too after TSPs video. It's a nice instrument.
Excellent analysis video! Thanks.
Hi, this QA403 is an amazing tool, I wanted to buy it just to measure THD in home audio repairs, I ended up buying a Keithley 2015. I don't do these audio repairs often and at this point a 6.5 digit multimeter would be more useful 🤔 maybe sometime in the future I'll save money on QA.
Nice day 🙂 Tom
That is one amazing little box. Looks like I will have to start putting some pennies aside. Working in audio, the Quint FFT display will be quite useful to me. When I use my SG505 option 2 to drive single ended, I always plug the dual banana adapter horizontally,across the 2 hot nodes, not diagonally between one hot and GND lug. Can you please try both orientations to see which produces the best numbers?
Great looking instrument, it would be nice to see the loop back performance in place in your lab I would like to know how good the Output of the quad is !...cheers.
Great video, thanks. I want a QA403!
hi truly great video and thank you very much for it
at 11:18 i see peaks on the left of the 1kHz peak Could it be power supply noise coming from the signal generator ? are you aware of signal generator powered by batteries ?
This is most likely caused by a slight imbalance in the transformer winding. This does have a bit of an in depth explanation but this is WAY down in the noise. The unit still meets its specifications so nothing to worry about. The power frames used for this testing was NOT a switching supply. The TM 500 power frames are linier supplies and the TM 5000 frames are switching so the power supply should be able as quiet as is realistic in a lab with a mix of modern and vintage gear.
I am not aware of a ultra low distortion generator that runs on batteries that get this low in the distortion range.
The output of the tested SG505 was an option 2 unit so it has a transformer coupled with a center tap for ground ref to get the fully balanced output for differential signaling.
@@ZenwizardStudios thank you very much again A very good signal generator all considered But also the one in the QA looks wonderful I would like to start some measurements only on line preamp for curiosity I am trying to learn something
Two questions: how long did it take you to receive it? I purchased it along with the QA451 programmable 4/8 ohm load. I had been holding off for the QA404, but decided not to wait any longer. I’ll grab one when they’re released and maybe sell the 403. I paid four days ago and I know they said there was a back order again, but that US and EU markets (I’m US) should have availability in the first week of December. My order still says order placed, not being impatient, just trying to get an idea of how long until it ships.
Second: would you be able to show with a video or tell how you hooked it up to your laptop. I’ve been told you need a really good sound card and I’ve been told using an external USB device like the Focusrite Scarlett is all you need.
When I ordered it was in stock so it took about a week shipping. For the Q403 there is a generator and analyzer built in to the unit. So no sound card is needed. The only hookup to the Q403 is a single USB cable and a software install.
I picked up a DA4084 in the shaved down TM5003. I would really like to add an SG505. My question is, how hard is it to make the shaved TM5003 into a full up 5003. I've heard you can add a connector and the the pass elements. But what is really involved and is it worth it?
I don't know how they "shaved down" the TM5003 however there are many TM5xxx power frames available on secondary markets I have grabbed 6 bay power frames for less then $50.00. The 4 and 6 bay units have the high power port on the right. I do prefer the TM 5xxx power framed over the TM5xx units for the additional cool for everything but audio work. for my AA501A and SG505's I have them in an TM503 frame to get the linier power supply runs a little hotter but the power rails are even more quiet.
@@ZenwizardStudios I can't thank you enough for responding. They put the DA4084, military version of the AA5001 in a TM5003 that has no 3rd port on the left, but does have a circuit board blank to take the connector. The DA4084 has the same THD+noise as the AA5001 But has SINAD instead of IMD. It was my understanding that you could add 2 more pass elements and a connector and have a full up TM5003. Sounds like a pain. Most TM5003's I see are 200+ bucks. I'll keep looking. Of course the DA4084 will not work in a 500 series power supply.
Those connectors can be north of $30.00 for the connector. The good news is a 5xx plugin for the most part will work in a 5xxx frame however the 5xxx plugins will not work in a 5xx frame. As it is derived from the AA5001 I suspect that it will need a 5xxx power frame.
Why you did not connected common wire from BNC to SG505 in differential mode?
Also I see some 60/50Hz spikes in spectrum beginning. Does power supply in SG505 is ok? Filtering caps?
On the BNC version of the 505 there is not a common wire to connect. Return is through the shield of the coax. The output of the SG505 can be set floating or ground referenced on the unit.
The power supply is totally fine for the SG505. There is a chirp that some times happens in the lab. At the time of this videos recording I did not have it nailed down. I do have that 100% figured out now and there will be a video on what it is out soon.
Where did you get the price of "a couple hundred dollars" from? They're 600 dollars, not 200.
I was patient and waited. They come up about every 6 months or so. But I agree for $600 I would rather have the QA 403
@@ZenwizardStudios You've confused me. The IS a QA 403, and they are $600.
That might be my mistake sorry for the confusion. The base video was on the SG505 which can ALSO go for $600 in the secondary market. The SG505 is ONLY the signal source for distortion analysis an AA501 is ALSO needed which also tend to go for around $700 to $1000 but I have seen as low as $200 - $300
The AA501 is a more robust unit being able to take 200 Vac on the input but also does not give the spectrum analysis capabilities of the QA 403. But within its limits the QA404 is an amazing piece of gear for $600 and is purpose bult for audio distortion analysis. Similar equipment will be several orders of magnitude higher in terms of cost especially new. Especially when considering that source and measurement are built in to the same unit. It replaced BOTH the SG505 and the AA501
Zen
That was off the hook. I have to temper my instrumentation to my budget. Haven't afforded a Tek distortion system. I drool every time I see one.
When are you getting in an Audio Precision APX555 🤣
You couldn't purchase one for the longest time, dac factory burned down then corona caused shortages.