Papa - a query. I'm adding the additional parts for the revised board to a Digikey cart and in your explanation of the additions to the original board (post 686) you cite 33pF as a starting point for the C6 lag compensator value. The C6 Kemet part number you later posted in post 795 shows up in Digikey as 33uF. Shouldn't that cap be 33pF?
Goes without saying I blame ZM....😛
Goes without saying I blame ZM....😛
The Kemet P/N at post 795 is a 3u3 PP film cap for C1, C2, and C3. For the optional, and situational dependent capacitor C6, I would choose a COG/NPO or a silvered mica part there.
Probably does not matter, but this is Polyester, not Polypropylene (PP) film cap.
Here is a polypropylene 3.3uF by Panasonic. I have them in my DIY FE.
Panasonic 3.3 uF Polypropylene cap
Panasonic 3.3 uF Polypropylene cap
You are quite right. My bad. Too many late nights. For which I blame ZM. Still.
I guess "suitable" is whatever you deem that value to be. With my room, my speakers, my source, my ears, etc. I like about 20-23dB of gain in the power amp portion of my audio system. An M2 has 15dB of gain as designed. In "my" situation I would probably be sticking something in front of it with maybe ~6dB of gain..
I like a gain setting that allows a large range of preamp volume control. In other words, volume knob about 1/2 way up on the the potentiometer at normal listening levels. Can't stand a system that is makes your ears bleed at a quarter turn on the volume.
I say build it, try it out, and change it if the gain is too much. Purchase a variety of resistor values beforehand, to have them available.
That is the beauty of DIY. 🙂
That is the beauty of DIY. 🙂
I started with +12dB (which is R3 & R4 = 40kohm) on my MoFo. I like to socket things until I settle on a permanent value,
When I'm happy with the value, I remove the socket then solder in permanently.
BTW, these are my own PCBs with Texas Instruments JFE2140 as the long tailed pair. Can also use LSK389 SOIC or TO-71.
I got a little impatient waiting for boards to be stocked in The Store.
When I'm happy with the value, I remove the socket then solder in permanently.
BTW, these are my own PCBs with Texas Instruments JFE2140 as the long tailed pair. Can also use LSK389 SOIC or TO-71.
I got a little impatient waiting for boards to be stocked in The Store.
HiI started with +12dB (which is R3 & R4 = 40kohm) on my MoFo. I like to socket things until I settle on a permanent value,
When I'm happy with the value, I remove the socket then solder in permanently.
BTW, these are my own PCBs with Texas Instruments JFE2140 as the long tailed pair. Can also use LSK389 SOIC or TO-71.
I got a little impatient waiting for boards to be stocked in The Store.
View attachment 1186813
what are the Current Source Transistors in this build ? is it J113 and if so how did you select the correct J113 as I have bought 30 of them and all of them have more than 6mA and most of them above 10mA. Do you have extra PCB's as I want to use JFE2140 as i have those.
thanks
kannan
Maybe someone might want to create a PCB which allows builders to use Nelson's DIY Front End 2022 circuit, as a front end for the First Watt M2x (?). It would be a daughter card, just like all the other daughter cards which the Store ships in the M2x board set ("Ishikawa" , "Tucson" , "Mountain View" , etc.). Images below.
I doubt that I'll do this myself. Three years ago I laid out and released Gerber CAD files for the "IPS6" daughter card, which is quite similar, and I'm not too interested in a do-over. But there may be someone who wants to hear Nelson Pass's 2022 front end circuit (daughter card) playing through the M2x output stage. They might decide to lay out a board and publish their Gerbers here. That would be fun, that would be fugly.
_
I doubt that I'll do this myself. Three years ago I laid out and released Gerber CAD files for the "IPS6" daughter card, which is quite similar, and I'm not too interested in a do-over. But there may be someone who wants to hear Nelson Pass's 2022 front end circuit (daughter card) playing through the M2x output stage. They might decide to lay out a board and publish their Gerbers here. That would be fun, that would be fugly.
_
