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The diyAudio First Watt M2x
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Old 11th June 2019, 07:20 PM   #2121
ItsAllInMyHead is offline ItsAllInMyHead
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@RafaPolit - I can't be completely sure, but I am pretty sure the values measured between the pins on the pot won't be the same with the pot in the circuit (on the board). I should have centered it before installation. I did adjust it until the values read across R1 and R2 read roughly equivalent, but I don't think that is quite as close as it should be. Thanks!

@Itsmee - thank you! That makes sense. Apologies for the additional questions. Is it safe and the right thing to do with a bench supply? ~46VDC between "pin 1 and pin 3" on the IPS? Or, must this be done with the IPS board installed on the amp board and in the amp with power from the actual rails? Just for my own sanity -- Is it correct that I'd measure the offset between the junction of R1 and R2 and "Pin 4" (the output)? Based on my extremely limited knowledge, that seems correct, but I'd appreciate a confirmation or any pointers. Zapping my Toshibas would be a sad situation. Mainly I'd just like to keep both channels the same and within fairly normal conditions until I can learn to "tune it" per the recent thread.

On a positive note - Austin boards are in and making beautiful music! 3 down and 2 to test.
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Old 11th June 2019, 07:38 PM   #2122
Itsmee is offline Itsmee  England
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The diyAudio First Watt M2x
Install the IPS into the amp, you need the connection to R2 in the main amp (when adjusting, don't forget to put a short across the amp input socket); your safe from dc offsets due to C1.
Measure between ground (0V) and the IPS R1 & R2 junction.
You can investigate RV1 later with ARTA.
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Old 11th June 2019, 07:59 PM   #2123
ItsAllInMyHead is offline ItsAllInMyHead
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@Itsmee - I would have never figured that out. Thank you for the clear instructions! Greatly appreciated.
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Old 12th June 2019, 09:05 AM   #2124
debk is offline debk  United States
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Just finished building the M2X. So far only tried the ISHIKAWA input stage.

Very nice sounding amp, though the F4 is still my favorite

Debra
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Old 12th June 2019, 01:58 PM   #2125
6L6 is offline 6L6  United States
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The diyAudio First Watt M2x
Heya Doc! Glad to see you are still building stuff.

The various input stages are absolutely worth playing with, this is a fun amp to experiment with.

Last edited by 6L6; 13th June 2019 at 01:49 PM.
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Old 12th June 2019, 08:43 PM   #2126
elwood625 is offline elwood625  United States
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Distortion analysis of my M2X with Mountain View IPS, 2v p-p, 1 watt, 4 ohms. Still learning how to use REW. Once I get good at this, I will perform measurements for Tucson, Ishikawa, and Austin.
Not sure how good or accurate my measurements are, I'm still learning. Taking baby steps for now.
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Old 12th June 2019, 09:13 PM   #2127
MEPER is offline MEPER  Denmark
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I would have expected lower distortion. 0.18% 1W. There are some 120 Hz ripple noise? 50 dB down. There are more 120 Hz noise than 2nd harmonic?
THD+N is 0.35% ….seems a bit high if generated by amp.
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Old 13th June 2019, 12:49 AM   #2128
debk is offline debk  United States
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Quote:
Originally Posted by 6L6 View Post
Heya Doc! Glad to see you are still building stuff.

The various input stages are absolutely worth playing with, this is a fun amp to experiment with.
Too many hobbies, but building electronics is still my first love.
I just got the parts for the rest of the input stages, will definitely have some fun experimenting with them.

Norwood should be fun to build now that I have a surgical microscope in my lab

Debra

Last edited by 6L6; 13th June 2019 at 01:50 PM. Reason: fix typo in quote
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Old 13th June 2019, 01:12 AM   #2129
deafbykhorns is offline deafbykhorns  United States
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Quote:
Originally Posted by MEPER View Post
I would have expected lower distortion. 0.18% 1W. There are some 120 Hz ripple noise? 50 dB down. There are more 120 Hz noise than 2nd harmonic?
THD+N is 0.35% ….seems a bit high if generated by amp.
That is high, i dont recall those numbers when i checked the m2x with my HP and Tektronix analyzer.
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Old 13th June 2019, 12:35 PM   #2130
ItsAllInMyHead is offline ItsAllInMyHead
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@Itsmee – thank you again. Worked like a charm.

I completed the installation, testing, and preliminary listening checks for all the IPSs. My willpower was lacking. I’ll stick to the excuse of having company coming to to help A/B the boards this weekend. So, I had to make sure they all work properly

I listened to Tucson for quite a while over the course of a few days. Some listening was “critical”, but most of my time was spent just enjoying the music. If I did not have the other boards and a severe case of “New DIYer Syndrome”, I could have easily left in Tucson and been a very happy camper.

I swapped out the boards in the following order:
Tucson (3 days)
Mountain View (~1 hour)
Austin (~30 mins)
Norwood (~30 mins)
Ishikawa (Still in)

My only reason for the order was to end up at Ishikawa and leave it in for a while. Because… it’s the “original”. It may not wind up my favorite. Who knows?

It took me ~15 minutes to swap boards. So, I think it stayed fairly warm. I listened to a few tracks that I know well and took a few notes with each, but I was on a tight schedule.

The positive is that there was <20 mins between each board. So I think I could "remember" the sound of the previous board fairly well in comparison to the next.
What did I perceive…? It’s too early to make any judgments, but I’m confident I heard differences. I’m going to give them all plenty of listening time. My best guess is that I’ll probably never pick only one.

The only insight I can offer at the moment is that Norwood is going back in after Ishikawa. Even in a short session, there is something about that board that grabbed me. A blind A/B between them all would be best, but I'm not sure if I can pull that off. A switching mechanism would be ideal. Hmmmmmmm.

It's incredible to have all the options.

Have fun! I am.
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