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Old 30th June 2018, 04:29 AM   #421
6L6 is offline 6L6  United States
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The diyAudio First Watt M2x
Art of the Ground Round. The song you speak of is the first of that cut.

Here's the whole thing, listen to the intro, it's Professor Schickele giving some "Historical Context" (Lol...)

YouTube
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Old 10th July 2018, 02:44 AM   #422
RafaPolit is offline RafaPolit  Ecuador
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We are waiting, pop corn in hand, to know how the different input gain stages are performing! What are the sound characteristics of each and what differs from one to the other?

Please, share your experiences for those of us watching from the audience!

Thanks, best regards,
Rafa.
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Old 10th July 2018, 03:11 AM   #423
chat72 is offline chat72
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Quote:
Originally Posted by RafaPolit View Post
We are waiting, pop corn in hand, to know how the different input gain stages are performing! What are the sound characteristics of each and what differs from one to the other?

Please, share your experiences for those of us watching from the audience!

Thanks, best regards,
Rafa.

My experience are the following;


Austin: Sound too warm and too thick for my system, least prefer.

Tucson: Good, better than Austin, it sound like ISHIKAWA but less refine.

Isikawa it's M2 so you know what it's like.

MOUNTAIN_VIEW This is definitely the best, the sound is big, full and still maintain good separation and details and it's runs real hot!

The differences for all input stage are quite obvious, you can notice them immediately.

As always, these are my opinions, YMMV.

My system
Rega Apollo-R
Pre Cat sl1 clone
BA3 clone
6n8s Aikido

Spk Diy 2-ways TL 92db
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Old 11th July 2018, 07:46 PM   #424
jwjarch is offline jwjarch  United States
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For the Mountain View input stage, is any matching or measuring of the J112's and Q1-Q3 helpful?
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Old 11th July 2018, 08:51 PM   #425
Mark Johnson is offline Mark Johnson  United States
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The diyAudio First Watt M2x
The Mountain View circuit has no opportunities for device matching. It is after all a single ended class-A amplifier; single ended means there aren't any pairs of devices that work together in push-pull to generate an output.

While I was testing Mountain View on the lab bench, and tweaking its response at high frequencies, I discussed the circuit a couple of times on the phone with John Curl. John slightly prefers using hand-selected J113 JFETs rather than any-old-J112-that-rolls-off-the-manufacturing-line. But I didn't think diyAudio members would be ready, willing, and able to hand-select JFETs so I didn't follow his suggestion. Besides the circuit as-is sounds GREAT, with any old J112 that rolls off the manufacturing line. So the official Mountain View schematic shows J112, the official Mountain View BOM shows J112, and I don't recommend using anything else unless (a) you really know what you're doing; and (b) you're a crazy person willing to do anything for that last microgram of goodness.

If so then select a J113 that satisfies this inequality: (9mA < IDSS < 12mA). Measure at Vds=9V, i.e., use a battery and a DVM. If you don't know what "IDSS" means then it's probably true that you don't meet criterion (a) above

I gotta warn you, not very many J113s will fall into this IDSS range. So you may need to buy 100 parts and test many/most of them, to guarantee that you'll find two J113s in this IDSS range. Fortunately Mouser's qty=100 price is only $0.12 per part. These two hand selected JFETs for a stereo pair of Mountain View boards, will cost you less than the Toshibas for a single Ishikawa board. {if the time you spend in the lab measuring IDSS is assumed to cost nothing}

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Old 11th July 2018, 09:08 PM   #426
jwjarch is offline jwjarch  United States
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Thanks for the detailed response Mark. I think I'll stick with the "any old J112 off the line" since the amount of time I would need to match 100 JFETs is a bit hard to come by these days.

Interesting you bring up the J113's. I was just browsing an older thread about replacements for the 2SK170/2SJ74 in the F5 circuit. You might be familiar with this thread already, Mark. The J113's seem to have some merit in this regard. Good reading if you're into that sort of thing.

how about using J111 J175 Jfets in F5
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Old 17th July 2018, 08:00 PM   #427
Blk Dynamite is offline Blk Dynamite  United States
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I have a rookie question regarding the Tucson Boards. In the provided literature Mark states "When substituting, make sure you choose opamps rated for at least 30 volts of total supply (VCC minus VEE)". Does that mean if the DIP-8 or SOIC-8 says +-18, this would fall within the safe guidelines since the total supply would be 36 total supply?
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Old 17th July 2018, 08:03 PM   #428
6L6 is offline 6L6  United States
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Correct
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Old 17th July 2018, 08:03 PM   #429
Blk Dynamite is offline Blk Dynamite  United States
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Originally Posted by 6L6 View Post
Correct

Coolio, thank you
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Old 17th July 2018, 09:18 PM   #430
Mark Johnson is offline Mark Johnson  United States
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Remember that miserable math class in school where they talked about negative numbers? Here's a chance to finally use them in your everyday life.

If VCC=+18 and VEE=-18 then (VCC) - (VEE) = (+18) - (-18) = +36.

Since 36 > 30, it ought to work fine in a Tucson board. As you expected.
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