If you have a supplier you trust in China (from the post earlier), why not ask if they can get you a part with the proper specs?
A quick internet search will give you some insights re: key characteristics of COG caps vs. other types. tl;dr - they are very stable to drift due to temperature change and also capacitance drift due to dielectric wear over the life of the cap.
So, why were they picked? I don't know, but Mark does. I can try to guess and work through the question.
The caps specified by Mark were/are +- 5% tolerance out of the box. You may note that the capacitors you posted the specs for are also +- 5% tolerance out of the box. Good match.
I don't see a spec for expected temperature effects / stability over time. COG / NPO generally implies that the capacitance will be stable over the life of the cap and with temperature changes. Polypropylene film caps do not generally share those traits. So, that might be an issue. If the absolute capacitance can vary by as much as 10%, but stability is critical... hmmmm. When Mark chooses a part ... in my experience, it's generally for a good reason. I'd consider the dielectric chosen in this case to be important.
Voltage Rating - The parts Mark chose are 100VDC rated. I'd stick with that or higher unless you know why you could go safely lower.
Cost / Availability / Form Factor and Size / Other considerations - You may note that in the BoM, Mark notes 5mm lead spacing, but that of the parts examples he listed, one has 2.5mm lead spacing. So, as Mark noted, bending the leads a bit within reason won't matter. You don't want SMD parts. Radial termination would be nice, and should not be tough to get. You'll likely see variants with all kinds of bends in the legs. It wouldn't make any difference to me.
So, I'd ask your trusted local person if they can get you any NPO/COG caps of 5% or tighter tolerance. Radial termination, with lead spacing from 2.5mm to 5mm. My guess is that if they're reputable, they'll have a number of options for you.
Others may have differing / better advice, and may offer some corrections and additions, but that's how I'd personally work through the situation at my (uneducated) level of understanding.
Enjoy your M2x! It's a wonderful amplifier, and Mark's additional boards are a treat to play with (Even if I still have two yet to build that are far... far... overdue).
A quick internet search will give you some insights re: key characteristics of COG caps vs. other types. tl;dr - they are very stable to drift due to temperature change and also capacitance drift due to dielectric wear over the life of the cap.
So, why were they picked? I don't know, but Mark does. I can try to guess and work through the question.
The caps specified by Mark were/are +- 5% tolerance out of the box. You may note that the capacitors you posted the specs for are also +- 5% tolerance out of the box. Good match.
I don't see a spec for expected temperature effects / stability over time. COG / NPO generally implies that the capacitance will be stable over the life of the cap and with temperature changes. Polypropylene film caps do not generally share those traits. So, that might be an issue. If the absolute capacitance can vary by as much as 10%, but stability is critical... hmmmm. When Mark chooses a part ... in my experience, it's generally for a good reason. I'd consider the dielectric chosen in this case to be important.
Voltage Rating - The parts Mark chose are 100VDC rated. I'd stick with that or higher unless you know why you could go safely lower.
Cost / Availability / Form Factor and Size / Other considerations - You may note that in the BoM, Mark notes 5mm lead spacing, but that of the parts examples he listed, one has 2.5mm lead spacing. So, as Mark noted, bending the leads a bit within reason won't matter. You don't want SMD parts. Radial termination would be nice, and should not be tough to get. You'll likely see variants with all kinds of bends in the legs. It wouldn't make any difference to me.
So, I'd ask your trusted local person if they can get you any NPO/COG caps of 5% or tighter tolerance. Radial termination, with lead spacing from 2.5mm to 5mm. My guess is that if they're reputable, they'll have a number of options for you.
Others may have differing / better advice, and may offer some corrections and additions, but that's how I'd personally work through the situation at my (uneducated) level of understanding.
Enjoy your M2x! It's a wonderful amplifier, and Mark's additional boards are a treat to play with (Even if I still have two yet to build that are far... far... overdue).
Thanks very much, @ItsAllInMyHead . This explanation was very useful in developing my understanding of relevant characteristics.
The post is a little bit old but I didn't get the answer. If possible I would like to mount an Ishikawa card with this potentiometer
Darek
Being somewhat lazy here I admit - looking for an answer.
I just finished an F6 and am very happy about it. Sounds great and really went off without a hitch. I am happy enough that I want to try another. I had the boards for the M2X and ordered all the parts this weekend. I had expected the transformers to take longer but they've shipped so it could start going together very soon.
With respect to the daughter boards. I am no electronics expert. I research what I need in advance and try to get that particular task done correctly. Then I move to the next. I see now that the Ishikawa board needs adjustment while connected to a distortion analyzer . I don't have one nor do I have any clue how to use one. Is there another way of attacking this? If not which would be a better board to start with to get up and running. I'd like to move on to learning how to use more tools, but not right now. What would be your recommendation for building this in a way that will do it justice but as simple as possible.
I just finished an F6 and am very happy about it. Sounds great and really went off without a hitch. I am happy enough that I want to try another. I had the boards for the M2X and ordered all the parts this weekend. I had expected the transformers to take longer but they've shipped so it could start going together very soon.
With respect to the daughter boards. I am no electronics expert. I research what I need in advance and try to get that particular task done correctly. Then I move to the next. I see now that the Ishikawa board needs adjustment while connected to a distortion analyzer . I don't have one nor do I have any clue how to use one. Is there another way of attacking this? If not which would be a better board to start with to get up and running. I'd like to move on to learning how to use more tools, but not right now. What would be your recommendation for building this in a way that will do it justice but as simple as possible.
The M2x will make a fine addition to your collection of Pass designed amplifiers. I have built both it and the F6 (pluse a couple others), and appreciate them each in different ways.
The Ishikawa FE boards can be built in a way that allows for adjustment, but I recommend a simpler configuration without the potentiometer. My two favorite M2x front ends happen to be the Mountain View and the Austin. Neither of these requires any adjustment. Together with the Ishikawa, they demonstrate that subtle yet meaningful differences may be heard from simply changing the style of the unity gain buffer that drives the Edcor signal transformer. Surprising, but true.
The Ishikawa FE boards can be built in a way that allows for adjustment, but I recommend a simpler configuration without the potentiometer. My two favorite M2x front ends happen to be the Mountain View and the Austin. Neither of these requires any adjustment. Together with the Ishikawa, they demonstrate that subtle yet meaningful differences may be heard from simply changing the style of the unity gain buffer that drives the Edcor signal transformer. Surprising, but true.
....And now someone should weigh in (me!) saying that their favorite card is Norwood. All system and taste dependent of course—everyone gets to be "right" on this one. After a long stretch with Cedarburgs (and all the cards, including MJ's recent fantastic explorations, over some time and debate and back and forths) going back to Norwood was cool and refreshing. We aren't motivated to swap them at this time (again). SO GOOD!
In short—you need to build them all. (my own opinion, of course, I most certainly have an amp building problem). This not only applies to M2X daughter boards—but amps in general!
In short—you need to build them all. (my own opinion, of course, I most certainly have an amp building problem). This not only applies to M2X daughter boards—but amps in general!
@iplayforme , the Ishikawa boards don't necessarily need a distortion analyzer. If I recall correctly, it would be required if you want to fiddle with the level of 2nd-order harmonic (H2).
Kind regards,
Drew
Kind regards,
Drew
Great, all good news. I can see what pfarrell might mean about an amp building problem. This F6 success makes me want to build them all. That fact along with the world seeming to end has had me buying parts and stocking up with the suspicion that they will either be more expensive or gone soon. Has gotten expensive and I'm just waiting for the live in auditor to catch wind.
Norwood uses the Analog Devices AD744 integrated circuit, designed by diyAudio member Scott Wurcer. It's a JFET input opamp which is also externally compensated -- a combination not found in other monolothic ICs*. That combo, plus the video speed + high current HA5002 buffer chip from Harris / Renesas, are responsible for Norwood's good performance, in my opinion.
*However earlier, non-monolithic opamp Hybrids (multi chip modules) from the early 70s, usually did have JFET inputs and external compensation, for maximum flexibility. Scott Wurcer made a presentation about these prehistoric devices, at the 2013 Burning Amp Festival (link).
*However earlier, non-monolithic opamp Hybrids (multi chip modules) from the early 70s, usually did have JFET inputs and external compensation, for maximum flexibility. Scott Wurcer made a presentation about these prehistoric devices, at the 2013 Burning Amp Festival (link).
A question to the wisdom of the forum. I have built the most wonderful sounding M2x, with the slight problem of some 60Hz hum barely audible at my listening chair. As a test I tried lifting the ground on the amp power cord by using a 3 prong to 2 prong plug adapter at the wall socket. It removed about 80% of the hum, insofar as I can no longer hear it at my listening spot, but is still present within several feet of the speaker. I have started down the path of putting the PSU in a separate chassis and have acquired most of the parts. But I have two questions for the forum:
Kurt
- How risky is it to continue to use the amp with the ground lifted? Some of my vintage tube gear and older solid state amps only use 2 prong power cords. Thats a lot more convenient than building a separate chassis for the PSU.
- Given the results of the reduced hum with the ground lifted, does that suggest I will not gain anything by building the PSU in a separate chassis to move the toroidal transformer as far from the amp boards as possible? Maybe I have a ground loop issue somewhere else in my system that will persist with a separated PSU chassis.
Kurt
NIce! Have you tried (not specific to 60hz per se):
—Rotating the transformer (there will be a quieter orientation—flipping it over and trying as well)
—Mumetal shields on Edcors (BIG difference)
—Run your AC leads under the perf grid panel in the amp
—"chopstick" the amp to eval lead dress issues
—Ferrite bead on primaries (Small but notable difference)
—Steel shield for Antek (won't fit in my builds—wish I would have made room from the start)
—Cheap line conditioner like Tripp Lite (Small, but audible difference)
—External cable dressing—separating AC from signal leads (Big difference)
—No LED lighting in vicinity (100% buzz, computers and phones too)
—Moving each external component to isolate if a component might be causing the issue, volumes on preamps maxed for eval. or just speaks and poweramps.
Each of these made a difference in my setup—some small, some large—cumulative overall leading to an exceptionally quiet noise floor, if any, into 92bd speaks. All the amp work I did was with headphones plugged into the outs—stethoscope style. Separating AC from signal between components was big. My amps are considerably tighter spaced inside than your build, not a lot of space. I have large external crossovers on my speakers—they like room too.
A product like HumX that "safely" lifts ground is reported to be good—but others can advise...My thought on this is solve the underlying issue—but IDK.
—Rotating the transformer (there will be a quieter orientation—flipping it over and trying as well)
—Mumetal shields on Edcors (BIG difference)
—Run your AC leads under the perf grid panel in the amp
—"chopstick" the amp to eval lead dress issues
—Ferrite bead on primaries (Small but notable difference)
—Steel shield for Antek (won't fit in my builds—wish I would have made room from the start)
—Cheap line conditioner like Tripp Lite (Small, but audible difference)
—External cable dressing—separating AC from signal leads (Big difference)
—No LED lighting in vicinity (100% buzz, computers and phones too)
—Moving each external component to isolate if a component might be causing the issue, volumes on preamps maxed for eval. or just speaks and poweramps.
Each of these made a difference in my setup—some small, some large—cumulative overall leading to an exceptionally quiet noise floor, if any, into 92bd speaks. All the amp work I did was with headphones plugged into the outs—stethoscope style. Separating AC from signal between components was big. My amps are considerably tighter spaced inside than your build, not a lot of space. I have large external crossovers on my speakers—they like room too.
A product like HumX that "safely" lifts ground is reported to be good—but others can advise...My thought on this is solve the underlying issue—but IDK.
Thank you @pfarrel, good ideas. I appreciate your inputs based off your experience. What is meant by "chopstick" the amp? I do have mumetal sheeting laying around and had considered using it on the Edkors, however I was concerned about shorting something. There's not a lot of room there. Any input on how to avoid causing shorts with mumetal?
Here's a starting point for shields (pdf). I covered the parts that might contact with kapon tape—and used a nylon standoff and post at the one location you can see, if you look at the pdf, to anchor it.
Chopsticking is to use an actual chopstick—being non conductive—actually I use these nylon dental style tools because they have hooked ends and you can easily maneuver wires... to move leads about with the amp live—and see/hear what might be making noise in terms of lead dress. I've gotten pretty serious about this since I've been making some high gain guitar amps and lead dress is super critical to a quiet amp—perhaps less so in hifi as a rule due to circuit boards, but still—I've been surprised. So this is really about your secondaries and AC lines perhaps...BUT one can also suss out cold solder joints...
Chopsticking is to use an actual chopstick—being non conductive—actually I use these nylon dental style tools because they have hooked ends and you can easily maneuver wires... to move leads about with the amp live—and see/hear what might be making noise in terms of lead dress. I've gotten pretty serious about this since I've been making some high gain guitar amps and lead dress is super critical to a quiet amp—perhaps less so in hifi as a rule due to circuit boards, but still—I've been surprised. So this is really about your secondaries and AC lines perhaps...BUT one can also suss out cold solder joints...
