The diyAudio First Watt M2x

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Might want to make it also accept the famous NE5534A opamp. Unlike its cousin the dual ("5532"), the single 5534A is not stable for gains less than 3, unless you add external compensation. Datasheet verbiage attached. Now people can ask and answer the question, how much worse does (candidate XYZ) sound than the 5534? How much better?

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Might want to make it also accept the famous NE5534A opamp. Unlike its cousin the dual ("5532"), the single 5534A is not stable for gains less than 3, unless you add external compensation. Datasheet verbiage attached. Now people can ask and answer the question, how much worse does (candidate XYZ) sound than the 5534? How much better?

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Given what I can find so far:
As a first-order solution, the feedback resistor (100Ω in the vero drawing) can be increased to 10k. In this case I would also recommend increasing the input resistor (22Ω in the drawing) to 100 Ohms.
I did notice that there is a more extensive compensation circuit that is intended mainly for offset-voltage nulling. In our application, we may simply include the output coupling cap(s) to prevent any DC voltage from reaching the Edcor. The links in the TI datasheet to extra documentation proved to be unhelpful in simply compensating for unity gain operation.
 
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I recommend adding the required extra bobs and jiggeys to the board, which externally compensate the 5534A so it will work correctly as a unity gain buffer and function just like all the other M2x daughter cards. In this case "work correctly" means: won't oscillate.

If that's too daunting you could always make a DIP-to-DIP adapter (or SOIC-to-DIP adapter) that uses a 5532 dual which IS unity gain stable, and scrambles the I/Os so it matches the OPA604 single-opamp pinout.

Of course sick baxters like me would reverse bend the appropriate leads of the 5534A DIP so they stick up instead of down. Insert the down pointing leads into the DIP socket and solder bodge components to the up pointing leads.

Crude but effective. Need a high quality DIP extractor tool to swap the contrivance out, though.

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31.94 rupees, qty=1.

8.48 rupees, qty=250.

4403 pieces on the shelf.

See posts #201 and #202 on this thread. Notice that post #198 was written by user manniraj, on the very same day.

Also post #1547 sheds additional light.

Thanks Mark, as I had all the parts in the Mouser cart of US did not want to go to Digikey for ordering only the LEDs. But looks like I have to do that now as shipping to India is prohibitively expensive both on Mouser and Digikey. I also see that you had ordered a bulk of these LEDs post #442, do you have any left overs let me know.
 
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Yes I have 200+ MV5075Cs which I will sell at my cost: ($1 for 8 LEDs). Shipping inside the US: $5 flat rate independent of quantity. Shipping outside the US: $15 flat rate independent of quantity. US Postal Service sets prices, I pay them.

Order in multiples of 8 LEDs. Maximum 96 LEDs per customer. PM for more info.
 
Yes I have 200+ MV5075Cs which I will sell at my cost: ($1 for 8 LEDs). Shipping inside the US: $5 flat rate independent of quantity. Shipping outside the US: $15 flat rate independent of quantity. US Postal Service sets prices, I pay them.

Order in multiples of 8 LEDs. Maximum 96 LEDs per customer. PM for more info.

Thanks Mark much appreciated, sent you PM for a set of 8 LEDs (MV5075Cs).
 
Does an explanation of the schematic in details exist somewhere like a Burning Amp video?
There is some info at Firstwatt but it is very high level?
E.g. diode D1, D2, D3.....this construction looks a bit asymmetrical (everything else looks symmetrical)?
There is also a kind of local feedback from output back to input of mosfets?
Then there is the special optical bias with the two 1.2V voltage references.
Maybe I will find out slowly bit after bit...….
 
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Not in this thread, no. The earlier threads about the First Watt product called "M2" (M2x minus the daughter board options) might contain what you want:

GB Pass M2 Clone Boards with 120mm UMS spacing by Tea-Bag

Official M2 schematic

I don't know of a YouTube video about the inner workings of the M2.

It may help to remember that First Watt sold a bunch of M2s to paying customers for pretty big bucks (like $4000 per amp). It got good reviews in the audio press. Then when Nelson Pass decided to stop selling it, he published the schematic here so that DIYers could make themselves a copy if they wanted to. He might not have felt any urgency to "explain" the amp since (a) we already know it sounds great, nobody disputes this; (b) here is the secret schematic that makes it sound great; (c) if you want an amp that sounds like the M2, do this.

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Marketing people call it Value Priced. I'm building one and with the diyAUDIO store PC boards, 4U enclosure and parts bought from DigiKey and Mouser for 5 of the six daughter boards, less than $700. After I add bling, just under $1000 and will look good enough for me to be proud of the build.
When I'm done, all I have to do is remove the top cover, loosen/tighten 8 little nuts, and I can turn it into one of 5 different sounding amps including the original M2.
I call it a bargain. The hardest part is finding a 37K resistor
 
I forgot to order the 37k but had some 39k...…..which I used together with the 20k pots. I feel confident that this gives enough room for offset adjustment. The boards just looks a bit "messy" now as one resistor is a "normal" Vishay with color bands and all the others are the brown Vishay Dale RN55......will see if I can live with that :)