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Old 4th August 2018, 09:36 PM   #461
Mark Johnson is offline Mark Johnson  United States
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Default 250 pieces MV5075C LEDs have arrived; selling at cost

Arrived today; photo below. Some M2X builders have already ordered and paid.

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Originally Posted by Mark Johnson View Post
I just ordered qty=250 pieces of the MV5075C LED from an authorized distributor and I'm confident these are not counterfeit. I paid USD 0.122 per piece, which is almost exactly 8 LEDs per USDollar.

These are used in the "Mountain View" input stage daughter card of the M2X amplifier.

I'd be glad to let other hobbyists have some of these at my cost, including my cost of postage and mailer envelope. If anyone wants to be a local re-distributor in parts of the world where Mouser doesn't sell the MV5075C (so far we know that Portugal and Finland are on this list), that would be a wonderful thing. Otherwise, small quantities only please. PM me with your needs and to get my PayPal info.

I estimate that shipping within the USA costs $4.50 and shipping outside the USA costs $14.50. Throw in the envelope and its 5 & 15.
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Old 5th August 2018, 09:22 AM   #462
Juntuin is offline Juntuin  Finland
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Thank you ZM! R13 and R14 must be gate resistors.
Made a mistake here by just assuming. R8 and R9 are gate resistors.
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Old 9th August 2018, 04:25 PM   #463
Mark Johnson is offline Mark Johnson  United States
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Default Edcor transformers for M2x: my order was shipped IMMEDIATELY

This morning I ordered eight of the Edcor PC600-15K transformers, for use in M2x amplifiers. To my surprise and delight, they emailed me back 90 minutes later (the same day! today!), to let me know that my order has been filled and shipped. Wow.

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Old 10th August 2018, 06:54 PM   #464
scott wurcer is offline scott wurcer  United States
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First of all thanks to Mark for the transformer samples.

My attempts to measure model parameters have met with difficulty due to the large variation of primary inductance with signal level. I am using our Digilent Analog Discovery USB module in network analyzer mode and even down to 10mV the numbers change. I ended up using a rule of thumb (600 Ohm and -3dB point) to get close and then measured series resistance and inter-winding capacitance with a Beckman handheld impedance meter.

Surprisingly both 15dB and 21dB auto-transformer modes match sim vs measurement fairly well, with the biggest difference being less peaking at 20kHz or so. An appropriate R/C damping network could probably make both very flat at the top end.

The 21dB connection comes with a 4x increase in drive requirement but I also wanted to try something that came closer to a normal PA gain structure. The gain variation with level is mostly below 20Hz (this would obviously come with an increase in distortion vs level) and probably is borderline on audibility. I must say I have listened to and measured an inductor based equalizer where this behavior extends well into the audible frequency region and it is clearly a serious coloration (that some may like).

EDIT - For those that have not done this before the coupling factor K was empirical. The sensitivity to it is surprising at first, 1 is ideal but seemingly tiny deviations below this make big differences.
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Last edited by scott wurcer; 10th August 2018 at 06:58 PM.
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Old 10th August 2018, 09:17 PM   #465
jacco vermeulen is offline jacco vermeulen  Netherlands
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Quote:
Originally Posted by Nelson Pass View Post
the need for
hi fi equipment to take up large segments of living space.D
So do horses. Getting bitten by a daze that came from one of too many stables of my neighbors today reminded me.

(I have to cover up in some way that I'm reading Mr. Wurcer's posts)
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Old 10th August 2018, 10:32 PM   #466
scott wurcer is offline scott wurcer  United States
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This is a nice diversion to the "compelling" need for -160dB THD measurement capability.
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Old 11th August 2018, 12:02 AM   #467
Mark Johnson is offline Mark Johnson  United States
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Yes it makes you appreciate Nelson Pass's remark: "The purpose of building this equipment is entertainment. The customer's, and also my own." M2 seems to entertain many people very well, despite >200 ppm distortion (-74 dB). Oh the humanity.

What's worse, the variant with 8-legs blasphemy is just as entertaining as the one without, according to people who have tried both.
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