Oscilloscope and HP 3580A Audio Spectrum Analyzer Usage

[@pixelpatter01]

Interesting video, thanks for taking the time to do it. I too am retired and although I never worked in the electronics or technical fields, it has always fascinated me.

[@ElPasoTubeAmps]

Thank you so much for your comments. I am now 62 and retired and I love this stuff - always have and now I have time to "give it away" before I get so old I can't find my oscilloscope... I have two Tektronix plugin spectrum analyzers I need to put on KZbin, 7L5 and 7L12 but for audio the HP 3580A is King. Thanks again and pump out some videos. I also have a web site but KZbin gives me an error when I try to put it in. Oh well.

[@ElPasoTubeAmps]

Yes, the function generator produces a good bit more sine wave distortion than the SG 505 oscillator. Some people use square and triangular waveforms to test amplifiers as it may show anomalies that can easily be seen on an oscilloscope. I think I could do an interesting comparison video on that - Thanks. I stick to sine waves because of my particular test equipment setup. Thanks for your comments.

[@basspig]

Enjoyed your videos greatly. Seeing your modern gear, I was inspired to go shopping on eBay for some of the same Tek modules. My signal generator is going on 60 years old. It served me well, but I decided it's time to get some nicer stuff.. found a Tek TM504 with DM501A, FG501A, PS501-1 for $62. Just spent a couple hours cleaning them up. Have a SG502 on the way ($42) and a HP3580A ($212) on the way this week. Gets my juices flowing again after 30 years away from electronics. Keep em coming!

[@basspig]

@essoterric I'm impressed with the HP 3580A. I bought it in working condition, just needed some cleaning and a few new knobs (still looking for a crank knob), downloaded service manual and did an alignment and it works great. I'm working on getting an AA501 and SG505 next. That 7L5 would have been great when I was working in broadcast maintenance. My buddy has a $30K Anritsu that the FCC uses, but the Tek seems just as good for my purposes designing broadcast gear. Thanks again for these videos.

[@zazzledelacruz6036]

I thought my Audio Precision equipment was old. You've got an excellent collection of 1980's audio test equipment.

[@ElPasoTubeAmps]

+Zazzle Delacruz Thank you - I have always wanted the Audio Precision instrument as I know it was made by some that left Tektronix back-then. I am sure it is an excellent piece of equipment.

[@philipiano001]

Great video, your are a talented educator.

[@MrAletube]

very interesting display of harmonics,i think this could explain much better what is going on in distortion channels of guitar preamps,i think i will purchase a similar device to boost my knowledge in that field,thanks for inspiration!

[@ElPasoTubeAmps]

Ray - I have estimated my costs for all the equipment I have and I have spent only about 5K - there is a site that has all the original specs and costs of new Tek and HP stuff - very interesting to look at - new cost back in the 1980's when this stuff was new would be 100K+ - as for repair of my test equipment, I have to do it, or get another instrument if I can't fix it.

[@gmcjetpilot]

Great video. So the function Gen has more distortion than the audio Gen (sine wave). Are most audio test done with square waves because they are more critical or more sensitive on audio equipment (FM tuners, amps...)? Or do you use all wave forms, saw, square and sine? Thanks

[@oldestgamer]

I sent this to my circuits teacher for the class, loved it!

[@bendec2969]

ElPaso, I've watched many of your videos, love them! I have an HP 8903a because of you all configured with the PMillet software - works great. One of my favorites. Anyway, I really would like to get an audio freq spectrum analyzer and I'm wondering if you have any insight on a CURRENT FFT that would provide a comparable replacement for one of these old HP 3580 or 3582s? I currently have a Siglent SDS 1202-X-E but it really doesn't do it. I saw your comparison with the Tektronix and the ARTA software these seem a bit dated now. Any insight would be appreciated. Thx, Ben.

[@ElPasoTubeAmps]

Hi Ben, The one I have that I like is TrueRTA. Here is the link. trueaudio.com/rta_down.htm I think it is worth the price for the license beyond the free version because it prints beautiful images with your name exactly as you put it in when you install it. Another one is SpectraPlus but it is very expensive. Here is a video where I use it and show the very nice printouts. kzbin.info/www/bejne/m4aZY3icfLyBfsk There is another one called ARTA as seen in this link below but they just went out of business as of March 2024. kzbin.info/www/bejne/eHO0qqJ-qNKqgpo Hope I got these right... Thank you so much for your kind words. It makes all this effort worthwhile. The 8903A and Pete's software was a challenge.... but it still works. I had a leak in my shop a few years back and it leaked water on one of my PCs and I lost one of my most important PCs but fortunately was able to move the hard drive into another PC. Now I get constant - this is not authorized software - or something like that - from Microsoft but it does work. I just keep that PC off the Internet. I still have my 3580A also as it is such an icon of a SA. As you know, it is brutally slow on low frequency signals. As I searched for FFT software, it seems like much of it is going away. What is our world coming to? 🙂 In another 20 years, it seems there won't be many of us that like to do this stuff, still around. Lastly, I forgot to mention about the first software I listed - you need and external USB sound device but I am sure I show it in some of my video. Again, thanks for contacting me. I don't do many videos anymore. Time is sneaking up on me and it is hard to get the energy to do them. Best wishes to you, always. David Beard

[@bendec2969]

@@ElPasoTubeAmps David Thanks for the quick reply. Please don't quit making videos. I've learned so much from your material and many others refer to your work. Blueglow electronics mentioned your HP 3580 and I've had several conversations with other hobbiests who also have pointed to your work.

[@bendec2969]

In my quest for Spectrum analyzers I could use some insight from you. Currently I have an HP 8590a which I received first very cheap and supprisingly it work great. Then I got an HP 8560a (not so cheap) which goes down to 50hz and up to 2.9 ghz. I was thinking that these might cover both some audio work and RF work which I'd like to do soon as I get the courage to start aligning am and fm receivers. But I'm not sure either of these will really work properly. The 8590a only has an RBW of 3k which I learned does not allow me to zoom in enough. The 8560a is a much better spec going down to 50 hz and an RBW of 10 hz but to get the span down to see that resolution it is almost a crawl. Do have the opportunity to return the 8560a for a full refund so I need to make a decision. (the 8560 does not perform as nice as the 8590a, the image is a little choppy and blurred but its good enough for the RF work not sure of the audio work. The HP 8560a came to $470 with shipping. I'm wondering if my money would be better spend on another better solution. I know you have a similar device I can't remember the model but I remember you trying to calibrate it. What do you use your for? Any insight on if I should keep or return this HP8560a 50hz to 2.9 ghz and pursue another solution I'd appreciate it. I might sell the 8590a too but it is so damn nice...

[@ElPasoTubeAmps]

@@bendec2969 I went that path also trying to get an RF SA to work at audio and it is not a good choice. The old style analyzers like the HP 3580A, utilize a technology based on swept-tuned heterodyne receivers rather than the Fast Fourier Transform (FFT) approach used in modern digital spectrum analyzers. I love my HP RF analyzer, works great up into the GHz range, but for audio the PC based FFT analyzers are far better - in my opinion - although the 3580A is an icon of a swept-tuned SA. With that said, I have to thank you for reinitializing my interest in my PC analyzers. After your comments from last night, I got my TrueRTA program going again - had to look back for a few years in my email to find the code to make it work properly and then "reinvent" how to make the USB sound cards work again - I have always disliked PC's but know I need them nowadays. I am planning on making an audio video using a stereo amplifier - a Williamson design - and making measurements with one channel using 6L6 beam power tubes and the other channel using EL34 (pentodes) and try to document the harmonic profile of the so-called, British sound, of the EL34. Supposedly, the EL34 has more pronounced high order harmonics and gives it that bit of a "rougher" sound of the amplifiers like the Marshalls vs the smoother Fender. I figure it is time I give some attention to my audio fans. I will break out my 3580A and hope it still works. Thanks again. Stay safe.

[@bendec2969]

David, I'm glad I got you going again. Looking forward to seeing that. I recently acquired two EICO HF-22 Monoblocks for a song!! But they are in rough shape right now but have everything. The original tubes test marginal but they'll do for now. Currently they use the 6L6 and I was wondering if I could upgrade to EL34 since there is a similar model that uses the EL34. I didn't consider the performance details just the fact that I have EL34's seem more available and I have several since I use them in an old Traynor Bass amp. Get that video out!!! I think I'm going to watch some of your videos on my 75" TV right now!

[@rpbale]

Just picked up a 3580A. Will be arriving soon to go with my Tek and other HP instruments. My collection is very much like yours. I've learned a lot from your videos. Question for you. I expected only 1Vrms on the SG505 in the 0db output level. Mine is at 1.7vrms. I think I saw yours at 1.14 in this video. Do you know what the calibrated or close to it output should be.

[@ElPasoTubeAmps]

The SG505 requires a 600 ohm load on the output for the dB scale to be accurate. Without the load the voltage will be double what it should be (into a high impedance load like a meter or oscilloscope). Zero dB into 600 ohms is calculated as: E = Sqrt(P*R) which comes out to be Sqrt(0.001*600) = 0.7746 volts. Also, make sure the variable control is clicked into cal on the dB knob.

[@rpbale]

That explains everything. I couldn't calibrate it down either because I didn't 600 ohms on it. I will modify my 50 ohm to 600 ohms per your earlier video and let you know how it worked out. Thanks!

[@ElPasoTubeAmps]

Good. If you want the proper level for 0 dBm at 50 ohms from the output of a 50 ohm signal generator, you do the same thing, E=Sqrt(0.001*50)=0.2236 volts

[@ElPasoTubeAmps]

The 3580A is a beautiful instrument. You do have to wait for a while for it to plot a 20 Hz signal, (as slow as 50 seconds per division) just so you will know that it is OK, but it is the lab instrument that virtually every vintage vacuum tube amplifier we enjoy today was judged by a few decades ago. Plotting 1 KHz and above is fast enough and the range is 80 dB but in reality, these (supposed?) dynamic ranges of 140 dB... that run on PC's... I am not too sure about. Not to say that technology doesn't advance, as it surely does but, to me, there is a real satisfaction in understanding the technology at a deeper level using the older instruments than just getting a digital number off of a modern day inexpensive instrument. I hope you enjoy your new instrument.

[@rpbale]

I'm looking forward restoring it. It looks like it's had a rough life. It was only $85 but has a trace. I have a HP3562A for a faster analyzer if this is a bust repair. I spend more time playing with the lab equip then I do on the amps. It's addictive. Your video even made me find a GenRad 722-MD cap box. Sheesh. What's next :) As for the 600 ohm termination, I have a HP350D that I thought I tried before with the SG505 but I don't recall that I got the reading I was expecting like with the make shift 600 from the Dekabox earlier. I'll try it again now that the SG is calibrated. The 350A is a little confusing because I don't have the manual. I believe it can present the input with one impedance and the output with another. So I would assume I'd set the input to 600ohms and the output to what the meter calls for. Ill have to look back through your videos to see if you went over your HP350A for an audio lab. I'm usually running the SG505's into a Leader LAV-192 millivolt RMS meter, the TM506's plugs DC501, AA501, DM504; and the HP8903A and HP3562A, and finally the scopes, on the line simultaneously. I suppose they'd all prefer the 600 ohm termination since most of these can report in db.

[@kgsalvage6306]

Thanks!

[@robzecc]

16:00 that's a sub harmonic at 500hz on the left

[@jamesguillebeau9093]

Thank you! You must have 20K invested in Tek and HP test gear. If you have any of this equipment serviced then who do you let repair it. Ray

[@cgrassi2439]

Hi! I have a HP 3580A Audio Spectrum Analyzer and I need some information about it... Maybe you can help me. Do you have some email contact? Thank you. Camilla.

[@ElPasoTubeAmps]

You can contact me directly at, [e-mail]

[@ElPasoTubeAmps]

The HP 3580A is a high-end spectrum analyzer that goes from 5 Hz to 50 KHz, but have you looked into the ARTA and SpectraPlus software that works with a PC and a USB sound card? These programs do an amazing job basically all the way down next to DC and are accurate to 5 KHz or better and display the low frequencies almost instantly whereas it will take the HP 3580A several minutes to plot a 5 or 10 Hz signal.