This is a nice reference for semiconductor mounting - this looks like a revised version of an old paper from Motorola:
https://www.nxp.com/files-static/rf_if/doc/app_note/AN1040.pdf
Phil
https://www.nxp.com/files-static/rf_if/doc/app_note/AN1040.pdf
Phil
Look for "Tellerfedern" / "Belleville Washers" at your favourite nuts & bolts supplier ... a Google search returned numerous online shops in Germany.
Best regards,
Claas
Hi - I have a question on the RV1 orientation: I see a pins 1, 2 & 3 marked on the resistor and on the PCB, a square solder point and two circular ones. Some resources say orientation does not matter, while some diagrams indicate it does. I do not see anything on the schematic or in the forums which tells me which is true. Is there a direction required for correct installation? Thank you all!
Yes. The Opamp's input topology is inconsequential for this application.
What matters for an audio opamp is good PSRR, good CMRR, internally compensated, unity-gain stable, fairly low noise, and (for a modern opamp) fairly slow slew rate.
I'm sure Mark can explain better, but remember we're just using these as buffers.
What matters for an audio opamp is good PSRR, good CMRR, internally compensated, unity-gain stable, fairly low noise, and (for a modern opamp) fairly slow slew rate.
I'm sure Mark can explain better, but remember we're just using these as buffers.
Hello member darrr,
I think if you check the datasheets you'll discover that OPA1611 has one single opamp in a SOIC-8 package. Its cousin the OPA1612 has two opamps in a SOIC-8 package. You want the OPA1611, you only want one single opamp for the Tucson daughterboard.
The OPA1611's internal cicuitry does indeed have an input stage made of bipolar transistors, not JFETs, as you say. This is not a problem with the M2x circuit, and indeed my "SMD Tucson" boards with OPA1611s have played lots of music through my M2x amplifier. The amp sounds simply wonderful with OPA1611s.
Another M2x input stage daughterboard has bipolar transistors at its input; the one named Austin. You can take a look its schematic if you wish; it is attached to M2x post #1.
Jim/6L6 is exactly right, M2x uses the opamp as a simple unity gain buffer, which is a particularly un-demanding configuration for a high quality opamp. As a result, Tucson+OPA1611 gets vanishingly low distortion, extremely low output impedance, and very precise gain (+1.0000).
If you enjoy comparing datasheets of opamp chips, I think you'll have a lot of fun comparing the "Total Harmonic Distortion" specifications of the OPA1611, against the THD specs of other opamps. When I did this myself back in February 2018, the OPA1611 had the lowest THD of all that I studied. This is very important to some M2x owners, while other owners consider THD specs to be less relevant than other electronic and sonic characteristics. As with many aspects of DIY audio, you have complete freedom to make up your own mind about this.
Have fun with your M2x! -- Mark Johnson
I think if you check the datasheets you'll discover that OPA1611 has one single opamp in a SOIC-8 package. Its cousin the OPA1612 has two opamps in a SOIC-8 package. You want the OPA1611, you only want one single opamp for the Tucson daughterboard.
The OPA1611's internal cicuitry does indeed have an input stage made of bipolar transistors, not JFETs, as you say. This is not a problem with the M2x circuit, and indeed my "SMD Tucson" boards with OPA1611s have played lots of music through my M2x amplifier. The amp sounds simply wonderful with OPA1611s.
Another M2x input stage daughterboard has bipolar transistors at its input; the one named Austin. You can take a look its schematic if you wish; it is attached to M2x post #1.
Jim/6L6 is exactly right, M2x uses the opamp as a simple unity gain buffer, which is a particularly un-demanding configuration for a high quality opamp. As a result, Tucson+OPA1611 gets vanishingly low distortion, extremely low output impedance, and very precise gain (+1.0000).
If you enjoy comparing datasheets of opamp chips, I think you'll have a lot of fun comparing the "Total Harmonic Distortion" specifications of the OPA1611, against the THD specs of other opamps. When I did this myself back in February 2018, the OPA1611 had the lowest THD of all that I studied. This is very important to some M2x owners, while other owners consider THD specs to be less relevant than other electronic and sonic characteristics. As with many aspects of DIY audio, you have complete freedom to make up your own mind about this.
Have fun with your M2x! -- Mark Johnson
It is interesting that the very low THD+N figure mentioned in the data sheet (0.000015) is measured at full output (where the opamp will probably never be used):
http://www.ti.com/lit/ds/symlink/opa1612.pdf (covers both 1611 and 1612)
….at 0.01 Vrms output the THD+N is "only" 0.005 or so...….still very low.
http://www.ti.com/lit/ds/symlink/opa1612.pdf (covers both 1611 and 1612)
….at 0.01 Vrms output the THD+N is "only" 0.005 or so...….still very low.
dB - Happy to see that you've gotten this sorted and that the amp is working per expectations.
I'm curious about your use of the SMPS. Is it the LRS-150-15 pictured in one of your earlier posts? (Or rather two of them, I'm assuming, for pos and neg, and adjusted for 18v)
I ask because I'm thinking of using two of the Connex SMPS500R (http://connexelectronic.com/wp-content/uploads/2017/09/SMPS500R.pdf) power supplies for a dual-mono plus/minus 24v arrangement for my M2. If you're using the Meanwell(s) you've got 10 amps per rail available, and I'd be in that same range. If I'm reading the Connex datasheet correctly.
Looking forward to hearing one of these amps here soon. - Pat
thanks - I was beginning to doubt
just waiting for new heatpads and I will be good to go.
I'm curious about your use of the SMPS. Is it the LRS-150-15 pictured in one of your earlier posts? (Or rather two of them, I'm assuming, for pos and neg, and adjusted for 18v)
I ask because I'm thinking of using two of the Connex SMPS500R (http://connexelectronic.com/wp-content/uploads/2017/09/SMPS500R.pdf) power supplies for a dual-mono plus/minus 24v arrangement for my M2. If you're using the Meanwell(s) you've got 10 amps per rail available, and I'd be in that same range. If I'm reading the Connex datasheet correctly.
Looking forward to hearing one of these amps here soon. - Pat
Yes - those are the exact units I used ( because I had them lying on the shelf ) and I set them to 18V - I connected them as you would any supply to get dual voltage - ie plus for positive and it's minus to ground then the other plus to ground the minus is neg rail giving a 10A dual 18V supply.
The Connex look like they would work in the same manner, except - they are available with dual supply rails, so even simpler.
..dB
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This is my first power amp build and with all the help and guidance here it has been a very pleasurable build, my main concerns are the power supply. I bought a 240V transformer to make life a little easier, I have a couple of bridge rectifer blocks and I bought the v3 psu pcb and am using the filter from that. It should all go to plan, I recently ordered some of the risers for the 4u deluxe case I was thinking of mounting the filter on those. Is the best place to mount the TXFMR at the front? I was thinking of placing it where it balances the weight of the front panel to make lifting easier for balance.
So many questions, sorry.
So many questions, sorry.
Hi Batty, I believe it has been mentioned in a few places on this thread as well as the M2 build thread that the transformer should go at the front as far away from the Edcor transformers as possible to eliminate any electrical interference that may result in a hum on the input of the amp. Some others, including myself have had great success mounting the transformer vertically with the mains and secondary wires facing the front of the case. My M2 is very very quiet with zero buzz coming through the speakers, and it’s a 300mm depth 4u case. Hope this helps, have fun with your build, the M2 sounds great!
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