JoaMat
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Everything posted by JoaMat
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Happy Birthday!
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and now for something completely different part 3
JoaMat replied to kevin gilmore's topic in Do It Yourself
So, I got myself QuantAsylum QA-403 Audio Analyzer. Now I can make some simple analyses of amplifiers I build. Screenshot – my CFA3smd something with HD800 headphone, 2Vrms into headphone. Probably room for improvements. But I’m satisfied and I’m not competent enough to make it better.
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Not much (nothing) has happened since my post 11 months ago. Here is a schematic, original to the left and lsk389 version to the right. My idea was to replace 6922 tubes with lsk389 and just make necessary changes and else keep the board unchanged. This is a draft - more work is needed. Of course you can use SOIC lsk389, but I prefer TO-71 since I think it fits better in the layout.
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Nice, great news! Did this in 2019 and it has been in sleep mode since then. Maybe UHV-POWER bricks will wake it up. Power transistors plus a few other components on one side and the rest on the other side.
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Happy Birthday!
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and now for something completely different part 3
JoaMat replied to kevin gilmore's topic in Do It Yourself
Like this? Think I got inputs to op amp right.
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and now for something completely different part 3
JoaMat replied to kevin gilmore's topic in Do It Yourself
Have had a new bias servo working with my CFA3smd something for a few days. Schematically it looks like this, and the new thing is in red square. Now I get a good reference point to the servos. Don’t understand why I didn’t figure this out earlier – slow brain perhaps. All four servos are fed from the same point. So, one trimmer and full control over the BIAS of all channels. Diagram for new servo - 6 minutes from cold. and diagram for old servo (in mA for the first 40 minutes from power on) Please have in mind that the graph for no servo is for my CFAsmd something. I guess the original CFA3 have a different and better behavior – where all tripple Darlington and vbe transistors are mounted on heat sink.
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and now for something completely different part 3
JoaMat replied to kevin gilmore's topic in Do It Yourself
What dual op amp are you using? -
happy Birthday!
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Happy Birthday!!!
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Happy Birthday, Kerry!
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Megatron Electrostatic Headphone Amplifier
JoaMat replied to kevin gilmore's topic in Do It Yourself
Great work - more Sort Guld. -
Megatron Electrostatic Headphone Amplifier
JoaMat replied to kevin gilmore's topic in Do It Yourself
Emission Labs 20B and 300B, is that the 4 pins socket or the octal socket with center tap filament? -
CNC metal machinists (for Stax amp cases) unite?
JoaMat replied to jamesmking's topic in Do It Yourself
Impressive! What kind of tool do you use for threading? -
All you need is a forgiving connector. Homemade, 3D printed, socket with “floating” Neutrik pins from NC3FD.
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Happy Birthday!
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A simple way to adjust offset is to replace R73 with a 10K trimmer. Looks like this on my amplifier. Works like a charm.
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Seems your balance servos are working since C and D have same readings. As for right channel where you have unbalance – investigate the R88 – R91, C8 and C9.
