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Old 13th September 2012, 04:04 PM   #101
1audio is offline 1audio  United States
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Compressor schematic attached

I had a BSR spectrum analyzer thing that sort of worked.Jjust a bunch of LED bar graphs. There is a description of the filters and how they work in the manual. The key is translating the noise in the spectrum to a root/Hertz value. This is where the noise generator comes in. The inductors are for narrowing the bandpass in the low frequencies. You could just connect the output to an FFT via a PC. The only confuser will be the 4 KHz agc signal which should be notched out.
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Old 13th September 2012, 04:11 PM   #102
klewis is offline klewis  United States
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Quote:
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Compressor schematic attached

I had a BSR spectrum analyzer thing that sort of worked.Jjust a bunch of LED bar graphs. There is a description of the filters and how they work in the manual. The key is translating the noise in the spectrum to a root/Hertz value. This is where the noise generator comes in. The inductors are for narrowing the bandpass in the low frequencies. You could just connect the output to an FFT via a PC. The only confuser will be the 4 KHz agc signal which should be notched out.
Thanks for the schematic! Just looked at the LED spectrum analyzers, my meters are working pretty well, just looking for improvements or assurance that I have it right. I've used my spectrum analyzer with the output of the 2173 to validate my calibration and the meter readings at 10 and 1khz. Just wondering about the width of the bandpass filters for the low frequencies (100 and 1khz). The 10hz is know because that portion of the schematic is complete. I also see and know about the 4 khz agc signal. The notch filter in the 2173 doesn't complete notch it out (I've adjusted the notch per the specs as well as double checking with the spectrum analyzer). My current 1 khz bandpass slope takes care of the residual 4khz signal.

Ken
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Old 13th September 2012, 04:42 PM   #103
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I also have a 5173. Did you get any of the socket adapters? Mine came with one and I built another. My manual has no documentation on the adapters. I would really like to figure out one for dual transistors but I see no way to implement it in the box.
I have an IC Adapter (shown below) and the transistor adapter:

Click the image to open in full size.

I wonder if Scott has a good copy of the manual -- mine is a repro -- not that i would want to duplicate what they've done.

I wonder whether the state of DSP wasn't sufficiently developed for quick cross-relation of FFT's on an HP35670 at the time.
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Old 13th September 2012, 11:53 PM   #104
klewis is offline klewis  United States
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since we're sharing photos, mine are older than yours
Order left to right, 2173c, 420 noise generator, 2181 self made into old Harris lab supply chassis.
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File Type: jpg 2173.jpg (476.5 KB, 205 views)
File Type: jpg 420.jpg (357.2 KB, 197 views)
File Type: jpg 2181.jpg (455.7 KB, 191 views)
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Old 9th October 2012, 03:02 PM   #105
klewis is offline klewis  United States
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Thought I would post an update on the progress with the quantech 2171c. I made replacement boards for the Amp 1 - (similar to schematic in post 78 except next newer of the 2173c) I used a 2sa1015 for Q1108, a 2n5089 for Q1109, a 2n3906 for Q1110 and a 2n3904 for Q1111.

The spectrum for each looks similar. I measured the noise for each at 1kHz with the input terminated with a 50ohm BNC. (I can't find a 0 ohm BNC terminator) I divided the noise by the gain - measured the gain separately for each -
The original with the carbon resistors replaced by dale RN55's = 3.47nVsqrtHz self noise.
The new version 2.77nVsqrtHz.

I purchase replacement caps for the power supply and will implement the JFET switch next.
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File Type: jpg 2012-10-09_06-06-56_490.jpg (514.5 KB, 149 views)
File Type: jpg 2012-10-09_06-07-24_633.jpg (393.7 KB, 37 views)
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Old 29th October 2012, 04:06 AM   #106
RNMarsh is offline RNMarsh  United States
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Has anyone looked at the super low distortion oscillator used by JanasCard.cz? They include circuit. Doesnt seem too hard to make. Measure incredible distortion numbers. [They also have articles on <1nv noise circuits]-RNM
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Old 29th October 2012, 04:48 AM   #107
RNMarsh is offline RNMarsh  United States
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JanasCard --- see the article in Test & Measurement World (TMW) May 3 2012. >-140

-RNM
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Old 29th October 2012, 05:58 AM   #108
1audio is offline 1audio  United States
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It came up earlier in this thread. Its very similar to Viktor's oscillator. The drawings have some issues and there was some discussion around getting it stable. The AGC uses the led-LDR. The problem with the LED-LDR is that the distortion increases with level across the LDR. A 1V it can be quite high in these terms. At 40 mV it may not be a problem but they don't get to 68 Ohms very easily if at all. And they are not as fast as a FET or 4 Q multiplier so stabilizing the loop may be an issue.
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Old 10th May 2014, 12:52 PM   #109
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...
The Boonton 1120 I use has the monitor output, which I connect to both a scope and an FFT box
...
Hello 1audio

Here Andrea from Italy, i'm subscribed at this forum because i saw this your old post about the 1120.
I'm looking at a Boonton 1120 for my private DIY audio experiment, seems to me a great machine except for the fact i was not able to understand how and if it's possible to take an output in order to display the distortion figure with an oscilloscope like we do at the work place with the Sound Technology.
In the rear there is a BNC that say "Monitor" but my boss made a quick try to connect there a scope and we was not able to display nothing.
Can you please tell me more about this?
Thanks so much.
Andrea
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