Thanks Nick, good to know for a baseline. I was using some crap phones and would guess that at the volumes I had it turned up to it would be ear-splittingly loud.
I’ll try to take D-Gnd voltage measurements for all JFETs tonight. I don’t question the providence of any of them... 2SK369s are from teabag; 2SK170s came from a GB here years ago.
I do know that R13 is dropping 26.x Vdc across it on either channel.
I’ll try to take D-Gnd voltage measurements for all JFETs tonight. I don’t question the providence of any of them... 2SK369s are from teabag; 2SK170s came from a GB here years ago.
I do know that R13 is dropping 26.x Vdc across it on either channel.
I checked with an old analog scope and the signal looks the same in both channels.
I took some measurements:
Code:
board 1 2
Q1 8.42 8.41
Q3 4.54 4.32
Q4 11.51 11.28
Q5 11.42 11.24
Q6 23.61 23.36
TP1-TP2 3.25 3.47
Rail 35.51 35.22I then looked at the outputs with a scope and with a DMM on AC mV. Scope showed a waveform:
board 1: 4.6 div @ 0.1V/div or .46V. Period was 8.3 @ 2mS, or 60Hz. DMM read 90mV
board 2: 4.5 div @ 50mV/div or .23V. Period the same. DMM read 45mV
Thank you, and thanks for the design and support! This thing certainly looks the business 
Just as a further test, I powered this from my bench supply instead, and scope was showing the same thing. My scope is a Tek 465b, probably needs a recap, and my probes suck. They did however show me oscillation at 70Mhz in a Gilmore Dynafet I had previously never gotten working, so it isn't worthless...
Just as a further test, I powered this from my bench supply instead, and scope was showing the same thing. My scope is a Tek 465b, probably needs a recap, and my probes suck. They did however show me oscillation at 70Mhz in a Gilmore Dynafet I had previously never gotten working, so it isn't worthless...
A very possible hum culprit that electrical field nearby source or there is some oscillation with the third party supply and this load so check the rail is thin, steady & flat, free of riding AC patterns.
Code:
ref des type 1 2
Q1 2SK369BL 12.41 12.41
Q2 2SK369BL
Q3Z 2SA970BL 657.1 655.6
Q4 2SK170BL 8.37 8.34
Q5 2SK170BL 7.77 7.78
Q6 2SK170BL 8.37 8.56
Q7 2SK117GR 5.69 5.71When I posted them initially, you agreed
this is a 5mV MM configuration with 90.9R R2, 5.6K 1W R13, 1.82K R4, and using the PRP 6.754K R5.
I'll try to bring the board and the Fluke up to the kitchen on Saturday and see what the mV AC reads there.
Best,
Chris
Last edited:
Hi Joztom,
Analogue meters generally do not have the frequency response needed to do much over 400 Hz. The wideband meters use a "true RMS converter chip", same as the digital meters do (HP 3400 - excellent meter). For even higher frequencies I'll go to my HP 437B witch is good to GHz and is digital, or my 436B - same response. If you're talking about a VTVM, you have to check them. Newer digital bench meters are better though.
You can't make general comments like you did. They are often not true.
About your last post ...
This is out of topic here. Open a thread for it.
-Chris
Buy a new bench meter from Kiethley, Fluke or Keysight. Fluke really does their best work with hand held meters.
Analogue meters generally do not have the frequency response needed to do much over 400 Hz. The wideband meters use a "true RMS converter chip", same as the digital meters do (HP 3400 - excellent meter). For even higher frequencies I'll go to my HP 437B witch is good to GHz and is digital, or my 436B - same response. If you're talking about a VTVM, you have to check them. Newer digital bench meters are better though.
You can't make general comments like you did. They are often not true.
About your last post ...
This is out of topic here. Open a thread for it.
-Chris
Hi Joztom,
-Chris
We'll agree to disagree then. I normally use a spectrum analyser for that job. About the only thing an analogue meter does better than a digital one is to show trends. However, if you look at the current Keysight meters (and a few others), they have addressed that in their DVMs. I like using analogue meters for some things. However, they are no longer better than a digital meter at all. About the only meter I don't have right now is an HP 3400. I would like one for sane money, just because.
-Chris
Spectrum analyser cost a lot, it is not for DIY scene. I have Fluke 17 DVM, Phywe analog instrument for fast detecting oscillations at first start, HP1701B oscilloscope (old battery type for Boeing servicing). For calibration and measuring 3-way analog filters is analog instrument the law.