Did I miss it in the initial bom? I was going by the part number not the mouser number - was ordering things from digikey. Did I just miss it by not looking up the mouser number?
Anyway thanks!
So for the ishikawa board, the fets 2SK170BL / 2SJ74BL - I would want to order 1 quad from matched-jfets in the store right? Does it matter for 6-8MA vs 8-11MA? What is that bit about? $40 vs $45 - what is that extra $5 doing?
Another question while I'm in the store. The opamps from jfets-mosfets-opamps-tubes in the store could also be used on the Tucson boards right? The ones in the BOM are not the only / sole opamps right?
-- edit --
actually in looking those are dual opamps the TI specd are single so those are different arent they?
-- edit --
actually in looking those are dual opamps the TI specd are single so those are different arent they?
You definitely need a single op-amp for the Tucson board. I happened to have a pair of Sparkos Labs SS3601 discrete op-amps removed from a previous project that works great on the Tucson board. I could not find the recommended singles in my stash of 8 legged bugs.
BTW, just finished building a stereo M2X, from the boards and Edcor transformers I bought a few years ago (too many other projects got in the way). Built up a pair of the Ishikawa boards and the above said Tucson boards as input. Used an Antek AS-4220 transformer I had in hand, a nice compact dual rail decoupled power supply board from Randy Thatcher populated with 47000uF/35V CDE elcaps. Nothing special or innovative, just took advantage of the experience of all the participants in this thread (whom I collectively thank!), including tips on layout and Mu-metal shielding. As a result, the amp worked perfectly on first powering, +/-24V rails, very low and stable offset voltage (after adjustment and warmup), and AC noise of under 2mA at the outputs. Very quiet on 91dB/1W speakers. Breaking in, but is sounding really nice.
First impression is the Ishikawa boards are a bit soft sounding on the bottom and a little closed in, but put in the "Sparkos Tuscon" and they were tauter on the bottom and had a larger presentation and therefore tend to prefer that in the amp. I plan on building a pair of the new Milpitas boards to try as well. I will have to get the "Cedarburg" boards to try since I have a few AD797 op-amps around.
David
BTW, just finished building a stereo M2X, from the boards and Edcor transformers I bought a few years ago (too many other projects got in the way). Built up a pair of the Ishikawa boards and the above said Tucson boards as input. Used an Antek AS-4220 transformer I had in hand, a nice compact dual rail decoupled power supply board from Randy Thatcher populated with 47000uF/35V CDE elcaps. Nothing special or innovative, just took advantage of the experience of all the participants in this thread (whom I collectively thank!), including tips on layout and Mu-metal shielding. As a result, the amp worked perfectly on first powering, +/-24V rails, very low and stable offset voltage (after adjustment and warmup), and AC noise of under 2mA at the outputs. Very quiet on 91dB/1W speakers. Breaking in, but is sounding really nice.
First impression is the Ishikawa boards are a bit soft sounding on the bottom and a little closed in, but put in the "Sparkos Tuscon" and they were tauter on the bottom and had a larger presentation and therefore tend to prefer that in the amp. I plan on building a pair of the new Milpitas boards to try as well. I will have to get the "Cedarburg" boards to try since I have a few AD797 op-amps around.
David
Attachments
Thanks for confirming!
Out of curiosity what did you do with the edcor? Is that just a diy shield around it? What, other than Kapton tape, are you using there? How necessary is it?
The Kapton tape is holding the DIY Mu-metal cover together and provides electrical insulation from the autoformer terminal pins. I bought a sheet of 0.01" thick Mu-metal on Amazon and cut out/bent a box covering the Edcor using the plans posted in this thread (a number of times). I have linked a recent post concerting this shield, but do a search and you can find alot of discussion concerning this (recommended).
As far as whether it is necessary, you can follow the discussion and experience others have, it helps to reduce hum pickup by the autoformer induced by the power transformer magnetic field. I installed mine from the start, so cannot really say how much it helped. Power transformer orientation and shielding also helps. I did not shield my power transformer, other than the vertical mounting bracket and belly band shield on the ANTEK transformer.
David
As far as whether it is necessary, you can follow the discussion and experience others have, it helps to reduce hum pickup by the autoformer induced by the power transformer magnetic field. I installed mine from the start, so cannot really say how much it helped. Power transformer orientation and shielding also helps. I did not shield my power transformer, other than the vertical mounting bracket and belly band shield on the ANTEK transformer.
David
Hello bilsch,
I also made covers over the EDCORs (post #1580 in this thread). I made them out of 1mm thick copper and MU-metal (0,1mm) inside.
I think it would not have been strictly necessary in my build, because I had no audible hum at listening position.
I would build your M2X without the shielding over the EDCOR and would listen. Is there audible hum?
Then you can check where it comes from. PSU, groundloop, shielding of EDCOR...
Cheers
Dirk
I also made covers over the EDCORs (post #1580 in this thread). I made them out of 1mm thick copper and MU-metal (0,1mm) inside.
I think it would not have been strictly necessary in my build, because I had no audible hum at listening position.
I would build your M2X without the shielding over the EDCOR and would listen. Is there audible hum?
Then you can check where it comes from. PSU, groundloop, shielding of EDCOR...
Cheers
Dirk
To the extent the shielding may have helped in my case, I have no audible hum with my ear right next to the woofer or the rest of the drivers (no buzzing either). It is as dead quiet as any of my other builds. So if you DO have an issue, adding the shield will likely work if hum pickup is the problem.
David
David
@bilsch , In my case, is is unnecessary: https://www.diyaudio.com/community/threads/the-diyaudio-first-watt-m2x.321925/post-7648213
For some of us, having no shielding around either the audio transformer or the power transformer causes no issues.
Kind regards,
Drew
nice thanks!
Yea for now I'm focusing on getting all of the parts ordered ( last of the stuff I need for power supply and ishikawa/mountainview arrive by mid-week next week ). Getting the power supply built / mounted is my current focus.
Going to be a little bit before I can actually listen to anything! For now I'm just going without shielding - if I hear the hum I'll revisit. I've got bigger things to worry about right now! I'm also trying to read through the thread - I'm on page 50 of like 350+ so I got a good bit of reading to do yet!
Appreciate the responses though!
Yes, slogging through the posts for these popular designs is the price we have to pay for amazing sound. 😉
Kind regards,
Drew
Kind regards,
Drew
At first i was sorta grumpy about it but now that I’m going through the posts I’m happy to be doing it. There are some good threads in there
I do wish there was a consolidated state so i doing have to slog through it all. I think it could be helpful - the list is only going to grow. Links to interesting things are gone, products are gone etc. At the end it the day even the documentation I’m wishing existed would go stale so I’m not sure it really matters that much at the end if the day
But learning a lot which was part is my goal with this
When I built this many moons ago I used a 300VA antek toroidal, and although It was quite far from the edcor the interference was audible. Not as a hum but the sound was week and spineless. I first grabbed a piece on 0.8mm sheet metal from the home store and built a couple of shields to be placed around the edcor that improved things quite a bit (posted pictures a million years ago). The purchase a round cover for the transformer that improved things even more. Based on my expereince, I would definitely make provisions to magnetically shield the edcors.
It’s on my list for sure but i want to get things assembled first.
I’m thinking in my head in it but building a plastic box shaped and sized to shroud the edcor and then make the shield around - then take the case to the board and tape it into place. I already have kapton tape - I’ve assembled multiple 3d printers so that whole process will take very little time.
Apply the KISS principle. Try to find the pics I posted earlier this should not take more than 15 min to make and cost two dollars.
It needs to be iron.
It needs to be iron.