There are many (most?) M2x amps set up like you have done. it’s good because it moves the toroid as far from the input transformer as possible, and is a space efficient location. And you have shielded it well. As the daughter boards are towards the back, having more clearance to change them is good.
I have done this type of build with several amps, Aleph J, SissySIT, and M2x mono blocks.
The IEC module sticks out from the backplane and forces the toroid into the middle of the box, wasting space.
Just be sure to run the wiring (twisted) under the perforated plate from back to front.
I keep forgetting that this amp uses a transformer to couple the sound.
But please don't tell me that maximising the mains wiring length with other amplifiers, which you listed, is a good idea. This is just plain wrong and should not be encouraged. There's also no need to suggest that the transformer will be placed in the middle of an amp.... you just have to carefully plan your build so that the major component placement is done correctly.
My other suggestion about rotating the PS PCB by 180 degrees still stands... even with the M2. It is even more important to keep the DC wiring length as short as possible. The chance the PS will have a constant low impedance spec, at a wide frequency range - rises exponentially the shorter & thicker the DC wiring loom is, especially with FW clones that do not use any form of local power supply rails' decoupling.
But please don't tell me that maximising the mains wiring length with other amplifiers, which you listed, is a good idea. This is just plain wrong and should not be encouraged. There's also no need to suggest that the transformer will be placed in the middle of an amp.... you just have to carefully plan your build so that the major component placement is done correctly.
My other suggestion about rotating the PS PCB by 180 degrees still stands... even with the M2. It is even more important to keep the DC wiring length as short as possible. The chance the PS will have a constant low impedance spec, at a wide frequency range - rises exponentially the shorter & thicker the DC wiring loom is, especially with FW clones that do not use any form of local power supply rails' decoupling.
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The chance of EM filed coupling is reduced.
Also, I played with AP measuring gear for 3 straight years on a daily bases... and I know first-hand how moving the mains wiring loom a few centimetres to the left/right, will influence the THD+noise... You probably can't hear it, but you can definitely see it.
Also, I played with AP measuring gear for 3 straight years on a daily bases... and I know first-hand how moving the mains wiring loom a few centimetres to the left/right, will influence the THD+noise... You probably can't hear it, but you can definitely see it.
You do not have any option with M2... but to place the mains transformer as far as possible from the input transformers, so... yeah... run the mains cables between two bottom plates. Just make sure it is safe. No need to place the wires in a braid or anything like that.
For me, the most important consideration is to keep the wires from the transformer secondary to the rectifiers short and tightly twisted. That's where the high current is (in 230V country, each secondary carries about 6x the current of the primary), and therefore the strongest magnetic fields at 50 / 60 Hz. Therefore, in my builds, I usually put the transformer(s) in the front, and run the tightly twisted mains wiring from the iEC inlet in the back under the perforated bottom inner mounting plate to the transformer in the front. That way, I keep the transformer away from the signal input and speaker output wires and connectors that run from the amp PCBs to the back.
I also tightly twist all wires, also the DC rail wires from PSU to amp board, whereever possible. Here, I twist +, -, and gnd all three together to minimize possible loop area regarding currents flowing.
Best regards, Claas
I also tightly twist all wires, also the DC rail wires from PSU to amp board, whereever possible. Here, I twist +, -, and gnd all three together to minimize possible loop area regarding currents flowing.
Best regards, Claas
Yes, all wires with their corresponding returns to minimize loop area is very beneficial for minimum noise. I see pictures of many builds with no twisted wires, many with only some wires twisted, and only a minority of the pictures show all wires twisted.
So twist these wires:
- AC power
-transformer primary pairs
-transformer secondary pairs
-DC pairs from bridge rectifiers to power supply board
-V+, V-, Gnd from power board to amplifier boards
-speaker+ and Gnd from amplifier boards to output connectors
-signal+ and Gnd from input RCA connector to amplifier board
For preamps with multiple inputs, each input should have its signal+ and Gnd twisted together from RCA to selector switch, signal+ and Gnd twisted to volume control and then from volume control to preamp board, in addition to twisting of signal output and AC and DC power wires.
Some will say that their amplifier or preamplifier is quiet even though their wires are not twisted. Perhaps their speakers are not very sensitive. Or some may say that they have twisted the wires and their amplifier is still noisy. Unfortunately, although minimizing loop area is a part of minimizing noise pickup, other factors such as component placement and grounding layout can also contribute noise to a build.
A guide that I have found informative is this one by diyAudio member Bonsai:
Bonsai/Hifisonix - Ground Loops
Also this:
Bonsai/Hifisonix - More Guidelines
So twist these wires:
- AC power
-transformer primary pairs
-transformer secondary pairs
-DC pairs from bridge rectifiers to power supply board
-V+, V-, Gnd from power board to amplifier boards
-speaker+ and Gnd from amplifier boards to output connectors
-signal+ and Gnd from input RCA connector to amplifier board
For preamps with multiple inputs, each input should have its signal+ and Gnd twisted together from RCA to selector switch, signal+ and Gnd twisted to volume control and then from volume control to preamp board, in addition to twisting of signal output and AC and DC power wires.
Some will say that their amplifier or preamplifier is quiet even though their wires are not twisted. Perhaps their speakers are not very sensitive. Or some may say that they have twisted the wires and their amplifier is still noisy. Unfortunately, although minimizing loop area is a part of minimizing noise pickup, other factors such as component placement and grounding layout can also contribute noise to a build.
A guide that I have found informative is this one by diyAudio member Bonsai:
Bonsai/Hifisonix - Ground Loops
Also this:
Bonsai/Hifisonix - More Guidelines
I built the Mountain View today, and am about an hour into listening. Wow. I don't find the difference to be subtle. Bass is tighter, and highs are a bit more present. This makes cymbals sound a little different, as well as the attack from woodwinds, brass, and plucked strings.
The three dimensional effect generated by M2x with Ishikawa has changed proportions. The overall effect is, to me, more detail. There's so much, in fact, that I need to focus on particular instruments to better perceive what's being communicated by them.
One thing's for sure: I want to listen much more to it, and build all the other input boards! This is exactly the kind of fun I was hoping to have. You've done a great job, Mark! Thanks!
As a side note, Mountain View revealed an oversight in my build. My power is external, and I didn't ground the chassis with the amp boards in them. Ishikawa wasn't too particular about this. The right channel was generating a random amount of hum. Connecting the incoming DC ground to the chassis floor completely eliminated it.
Side note #2: I'm building the Tucson next, and plan to install a DIP-8 socket and solder the OPA1611 on an adapter which mates with that socket. Will the extra length in the connections make any difference?
The three dimensional effect generated by M2x with Ishikawa has changed proportions. The overall effect is, to me, more detail. There's so much, in fact, that I need to focus on particular instruments to better perceive what's being communicated by them.
One thing's for sure: I want to listen much more to it, and build all the other input boards! This is exactly the kind of fun I was hoping to have. You've done a great job, Mark! Thanks!
As a side note, Mountain View revealed an oversight in my build. My power is external, and I didn't ground the chassis with the amp boards in them. Ishikawa wasn't too particular about this. The right channel was generating a random amount of hum. Connecting the incoming DC ground to the chassis floor completely eliminated it.
Side note #2: I'm building the Tucson next, and plan to install a DIP-8 socket and solder the OPA1611 on an adapter which mates with that socket. Will the extra length in the connections make any difference?
I managed to get my M2X free of noise. One reason to built it as mono blocks was to place the noisy AC-parts as far as way from amp-board as possible. Especially the secondary wires from transformer. In my case they could theoretically be shorter but it works well "as-is":
I put the last set of filter caps relative close to amp board (CRCLC PSU). For safety reason I use rail fuses (4A F as far as I remember). Also good to have the input signal wire from RCA connector as short as possible. The Edcor has a mu-metal foil wrapped around it. Later I also built a small mu-metal case to put over the Edcor just to be sure as I had some spare mu-metal sheets. I have exactly same -+ voltage (numerical value). This is a good indication of perfect symmetry in PSU. Any asymmetry can e.g. cause mechanical hum from the toroid transformer......and I am the must hum-sensitive person in the world......
I use 94 dB speakers.
I put the last set of filter caps relative close to amp board (CRCLC PSU). For safety reason I use rail fuses (4A F as far as I remember). Also good to have the input signal wire from RCA connector as short as possible. The Edcor has a mu-metal foil wrapped around it. Later I also built a small mu-metal case to put over the Edcor just to be sure as I had some spare mu-metal sheets. I have exactly same -+ voltage (numerical value). This is a good indication of perfect symmetry in PSU. Any asymmetry can e.g. cause mechanical hum from the toroid transformer......and I am the must hum-sensitive person in the world......
I use 94 dB speakers.
so i started the psu to try to measure it. it kicked up to 25v and then started to slowly drop. I checked the fuses and they both were blown. They are slow ceramic 1.25A. Im running a cl60 in series. 230V and 500VA transformer. Maybe i need to go up a little on the fuses?
In my experience, with a Toroidy 500VA transformer, 2A or 2.5A fuse should do it. Try 2A fuse first.
Best regards, Claas
Best regards, Claas
Didnt have any larger but tried again and the fuse didnt blowe so probably im close to good value so ill try 2 A. But anyways i have a working psu so i can now continue. though i had 26.5V and -26.5 on the dc. Is this ok or little to much?
That is a very interesting approach. Can you share the CRCLC circuit and BOM? Also, what is the make/P/N for the bulkhead mounted AC entry? I run completely horn-loaded speakers and I, too, spend alot of time on addressing noise and hum sources!
The IEC filter is just a standard Schurter 230V 1 or 2A type I already had. The low A types have "better" filter (thinner wire --> more mH and space for more chokes). They can take the input current "kick". M2X does not draw much current from Mains during operation.
The transformer is a Toroidy 400 VA type. The PSU board is the one from DiyAudiStore. I used 33mF low ESR type caps of good quality.
I tried several types of bridges/dioders etc. and ended with heavy IXYS Schottky types (DSK80-0045B) in my case. Those give very low forward voltage drop at "M2X current consumption". They are double diodes and are paralleled by the PCB layout. Then a filter choke which is probably a Hammond 159ZL (10A, 2.5 mH). After the choke I used a 4-pole 33mH cap I already had. Brand is Danish "Jensen" but factory is closed now but they where made by a German factory after specs. from Jensen. Same factory which makes Mundorf e-caps (Fischer & Tausche which is also just called F&T. There are much more E-cap brands than factories 🙂 ) I also use a heavy DC-filter (Sjöström Audio) and a PS-Audio Powerplant (a small 300W type).
I play my VFET amp in the moment so M2X mono blocks takes a lot of space in my small home-office.
I guess they will go into service again some day. They are very nice amps and can drive low impedance better than VFET amp.
https://www.ftcap.de/en/products/custom-versions/
65% of production are customized.
DiyAudio could get its own "private" versions.......we just need some who can make the specifications.
Everything with "Audio" label on is 10x more expensive than without.....
65% of production are customized.
DiyAudio could get its own "private" versions.......we just need some who can make the specifications.
Everything with "Audio" label on is 10x more expensive than without.....
Sorry, the deal went in 5min. I have some other built boards. Perhaps I will announce the later.
I would install speaker protection on the amp if i were you. Rail fuses and no DC protection is playing russian rulett whit your speakers. One blown fuse and you get full railvoltage DC offset. Even whitout the railfuses i would use DC protection on all single outputpair amps.