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Old 4th August 2018, 09:36 PM   #461
Mark Johnson is offline Mark Johnson  United States
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The diyAudio First Watt M2x
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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The diyAudio First Watt M2x-edcor-png

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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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Old 16th August 2018, 02:51 PM   #468
indra1 is offline indra1  Indonesia
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From the Official M2 thread.
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Originally Posted by Mark Johnson View Post
If I ever decide to do that, it would probably be sometime after the diyAudio Store starts selling M2x boards. Certainly I'd wait until a few members have built and auditioned all five input stages on the Store PCBs, and shared their listening impressions & preferences. I'd probably post in the other thread, the one about M2x itself.
No problem Mark, I was actually curious about your view on not taking output of the AD744 from pin 5 which has some single ended negative phase K2 signature.
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Old 20th August 2018, 05:44 AM   #469
RafaPolit is offline RafaPolit  Ecuador
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This is probably a stupid question, but I am going to shield myself behind 6L6's nice YouTube conference where he claims that 'the only stupid question is the one not asked'.

The BOM lists nicely most of the MOUSER part numbers, but the resistors are just 'named'. Put a 1K resistor. I know that for most of you, that is enough... but if you go here to an electronics store, you really get the lowest possible parts made in bulk with the lowest possible standards.

So, if I were to order resistors to stuff this incredibly tempting M2x (or any other PCB for that matter), what are the recommended:
- Power Ratings for those with un-listed power ratting? (I assumed 1W, but I could be so off I am asking nonetheless)
- Recommended type (or types)? There are options for Carboon Film, Ceramic Composition, Metal Film, Metal Oxide, Thick Film, Wirewound
- What is the recommended tolerance? Obviously the less, the better, but also more expensive. Is there a 'sweet spot' most folks prefer to rely upon? Or is this just a: "as low as you can afford it" type of scenario?
- Does voltage ratings matter or even apply?
- Finally, is there any 'preferred brand' that has proven to be more reliable or that just 'plays better' with this sort of amps?

Again, I know this is probably knowledge 101... so please be gentle!

Best regards,
Rafa.
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Old 20th August 2018, 06:52 AM   #470
kbergsson is offline kbergsson  Iceland
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Hi RafaPolit,
Im also new in the game and have no component preferences. I have used Vishay/Dale metal film and some Vishay / Beyschlag thin film in posisions where spesific components have not been recommended. I have several amps on hand for reference and my F6 and M2 sound great with those components.
There are general component guidelines in many of Nelsons First Watt articles.
Kjartan

Last edited by kbergsson; 20th August 2018 at 06:55 AM.
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