Which is one reason why the other four input stage daughterboards exist.
They let you build and listen to your M2x, using current production (non obsolete) semiconductors that don't require matching, while you slowly and carefully scour the globe for matched pairs of obsolete Toshiba JFETs. You can buy the parts today from Mouser or DigiKey or Arrow or Avnet. They're on the shelf, waiting for you.
They let you build and listen to your M2x, using current production (non obsolete) semiconductors that don't require matching, while you slowly and carefully scour the globe for matched pairs of obsolete Toshiba JFETs. You can buy the parts today from Mouser or DigiKey or Arrow or Avnet. They're on the shelf, waiting for you.
Toshiba 2SJ74 + 2SK170 LAB MATCHED QUAD to 0.03mA AND 4mV (10ma range) | eBay
Found 'em.
(Yes, they are genuine)
For comparison purposes here is today's OCTOPART.COM price sheet for the amplification devices used in the M2x "Mountain View" input stage daughter card. That's the stage whose circuitry is single ended Class-A, and which does not use any Toshiba JFETs at all.
To build a stereo pair of Mountain View boards, you need to buy a total of 2 pieces of J112, and 6 pieces of KSC3503. I am amused by the money numbers.
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To build a stereo pair of Mountain View boards, you need to buy a total of 2 pieces of J112, and 6 pieces of KSC3503. I am amused by the money numbers.
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Understandable situation given scarcity of impressions, lack of measurement of performance and hazy understanding of design choice on alternate input modules. For me at least, I would prefer something that I can adjust to yield a negative phase H2 for which there exist no discussion on alternates while original design will allow for a certain matching of input parts and an addition of a P3.
After making this you might abandon the quest for j74/k170.
So you feel that the Mountain View input is that good? I think I’ll definately try that set of boards out when I finally get my project started.
I'm aware of your generous offer, Mark. However, I'll still have to fork out about US$18 to get it to my country by courier - the only reliable way unfortunately. 18 Dollars may not sound like much if you're paying in US$, but to us it's not cheap.
I may be onto a local supplier, though. Awaiting their answer now on minimum order quantity.
Edit: Just received an answer; As expected, they can't supply just 10 LED's! The joys of DIY.
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By all means, feel free to do that! You will be pleased that the layout of the Ishikawa PCB, makes your modification particularly simple and straightforward. No cuts, no jumps, no new drill holes. Just calculate new component values, stuff, and solder.
However ... ... ... ...
I should point out that the original M2 amplifier, sold by First Watt, did not have any "negative phase H2". The owner's manual (.pdf file) is still available on their website, and it includes the snippet attached below, on page number 5. I added the markings in red myself; if they are annoying I apologize.
You are free to modify the sound of YOUR M2, as you see fit. Nobody is forcing you to slavishly make an exact copy of the First Watt M2 circuitry or the First Watt M2 sound. Want H2 when the original amplifier built by Nelson Pass had none? Go right ahead, it's YOUR amplifier. This by the way is the same pep talk I give to people who like the sound of other, non-Ishikawa input stages, more than they like Ishikawa. It's THEIR amplifier, they can drop in whatever sounds best TO THEM. The originality police won't come throw you in jail.
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Certainly Mark, we are in DIY PASS subforum after all.
I still hope to discuss the possibility of a simple mod to one of the offered alternates to have a similar effect with you. But as you said previously, you may only entertain such discussion (if ever) after more builders have their say first. I respect your wish.
Hopefully builders in general will understand a bit better after more sharing of impressions, discussions and measurement of the alternates and ease the demand of a certain item from a wise seller in Sacramento.
If neg H2 is your goal, I suggest that this really isn't the amplifier for you. The current offering that is neg H2 beauty queen would be the ACA, run bridged mono through the RCA. (Monoblocks, you'll need 2, obviously...
) It's a clever circuit with an incredible sound and I highly recommend it.