what value of resistor you have in Iron Pre, in position Gate-to-GND, at buffer signal input Gate?
say that 100K is good for volume pots up to 10K
for higher valued pots, go to 330K or even 470K
in fact, I think it's safe and wise to alarm @ItsAllInMyHead to change that position to 330K, for good
say that 100K is good for volume pots up to 10K
for higher valued pots, go to 330K or even 470K
in fact, I think it's safe and wise to alarm @ItsAllInMyHead to change that position to 330K, for good
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220k in all schematics and kits provided since 2021 boards... nice compromise in between. In all guides we show / will show 10k pots. If boyz want to change... they can, if they have skillz. That's what's staying in kits. If boyz have special situation with wimpy source or tubez in OS of source etc., and don't know how to adjust ... MZM will give exceptional advice per usual. 🙂
10K Alps werent available when I ordered so I grabbed 20K instead, thinking it would be OK...oops.
I used the Iron Pre balanced kit, which shows 220k for R27 and R28. Will bump them to 330K or 470K...whichever I have 🙂
That said, I don't understand how that resistor relates to frequency response.
Thank you for the help guys!
I used the Iron Pre balanced kit, which shows 220k for R27 and R28. Will bump them to 330K or 470K...whichever I have 🙂
That said, I don't understand how that resistor relates to frequency response.
Thank you for the help guys!
On second thought...those resistors are really tucked in there and very well attached. 10K pots are available now. Just gonna buy a couple of those instead.
I have a bunch of Milpitas boards from a large JLCPCB order I put together. I got them for super cheap so passing along that deal to anyone interested. I've confirmed I can ship in a standard envelope in the US with a non-machinable stamp, so two boards shipped in the US is $2 total. See the swap meet if you want to see all the boards I grabbed in bulk.
Hey all.. Wanted to say "Thank you" to everyone who's contributed to this thread, answered so many questions, and provided guidance. My M2X is pretty much finished up! Monoblocks obviously, and very happy. Have only listened to Norwood so far, but have Ishikawa, Austin, Milpitas and Cedarbug all finished up and ready to play with.
My build went pretty smoothly, with the exception of some smoke that emitted from a short caused by the Mumetal transformer box. First one was too tight, and contacted one of the pins of the transformer (oops). Replaced the board, and all components on it. I did have to do the "blasphemous heresy" mod. Still have some interesting behavior from the left channel. It takes much longer than the right channel for the DC offset to stabilize, and when I power it up the next day again, it stabilizes at a slightly different number. Right channel is at about 2 mv. The left will zero out (well, close to zero.. 2-4 mv, then after power cycling and letting it come back up, it may settle in at 10-12. I replaced the RV this week, checked for cold solder joints everywhere.. It sounds great, and is super quiet, so I'm inclined to allow this to be a test of my OCD and move on!
Anyway, thanks again all, especially Mark Johnson and a super thanks to 6L6 and PFarrell for being so great about answering all of my dumb questions! Cheers all..
My build went pretty smoothly, with the exception of some smoke that emitted from a short caused by the Mumetal transformer box. First one was too tight, and contacted one of the pins of the transformer (oops). Replaced the board, and all components on it. I did have to do the "blasphemous heresy" mod. Still have some interesting behavior from the left channel. It takes much longer than the right channel for the DC offset to stabilize, and when I power it up the next day again, it stabilizes at a slightly different number. Right channel is at about 2 mv. The left will zero out (well, close to zero.. 2-4 mv, then after power cycling and letting it come back up, it may settle in at 10-12. I replaced the RV this week, checked for cold solder joints everywhere.. It sounds great, and is super quiet, so I'm inclined to allow this to be a test of my OCD and move on!
Anyway, thanks again all, especially Mark Johnson and a super thanks to 6L6 and PFarrell for being so great about answering all of my dumb questions! Cheers all..
That looks fantastic! The wire dress is very nicely done.
I think this build checks every single box for going the extra mile and making the Ultimate M2x. You’ve got;
- True Monoblock (Separate chassis and separate PSU per channel)
-Power transformer in the shield can
- Softstart / switch controller from @Mark Johnson
- @rhthatcher snubber boards on the bridges
- scratch built mu-metal shield on the signal transformer
- Norwood
I can’t think of anything more to add… seriously well done!!
😎
👏 👏 👏
I think this build checks every single box for going the extra mile and making the Ultimate M2x. You’ve got;
- True Monoblock (Separate chassis and separate PSU per channel)
-Power transformer in the shield can
- Softstart / switch controller from @Mark Johnson
- @rhthatcher snubber boards on the bridges
- scratch built mu-metal shield on the signal transformer
- Norwood
I can’t think of anything more to add… seriously well done!!
😎
👏 👏 👏
Ahem, ... ... it may possibly happen that someone might ask @6L6 whether the rumor is true, that he put a certain set of IPS daughter cards into his own M2x two years ago, and has left them installed there ever since. Without even the merest glimmer of a thought to try any other card. I don't know whether this inquiry will arise or not. It is difficult to make predictions, especially about the future.
@SkyPirate That's a very inspiring build! I think an M2x build is in my near future. Might I ask how you built those lovely signal transformer mu-metal shields? I'd like to follow your inspiring build as I get going on mine.
Thanks for sharing!
Thanks for sharing!
@Plott That’s a great question! I’m glad you asked, as yes, IPS 6 has been in my M2x for quite some time and I’ve been too lazy to replace it… or perhaps unwilling to try anything else, as it sounds fantastic and I’m happy as a clam using it.
https://www.diyaudio.com/forums/pass-labs/321925-diyaudio-watt-m2x-post6316096.html
This would be a great opportunity to order some PCB and make it!
https://www.diyaudio.com/forums/pass-labs/321925-diyaudio-watt-m2x-post6316096.html
This would be a great opportunity to order some PCB and make it!
Thank you, Jim. Way to kind, and I can't thank you enough!That looks fantastic! The wire dress is very nicely done.
I think this build checks every single box for going the extra mile and making the Ultimate M2x. You’ve got;
- True Monoblock (Separate chassis and separate PSU per channel)
-Power transformer in the shield can
- Softstart / switch controller from @Mark Johnson
- @rhthatcher snubber boards on the bridges
- scratch built mu-metal shield on the signal transformer
- Norwood
I can’t think of anything more to add… seriously well done!!
😎
👏 👏 👏
Birdbox!
Thank you for the kind words.. The MuMetal boxes were a bit of a challenge. I made a few practice versions to get the hang of it. The one in the pic above was not as pretty as the other. In any event, I bought the MuMetal from Amazon, as well as Kapton tape. PFarrell was kind enough to send his template which is attatched. I think he posted this in the thread somewhere. You'll want a good pair of shears, I think the MuMetal will smoke a pair of scisors pretty quickly. My suggestion is to be sure the box "floats" over the transformer.. My first one was a tight fit and caused big problems! Be sure to wrap the entire box inside and out with the Kapton tape. I ran a piece around the outside of the transformer as well, just for good measure. The box does cut down an amazing amount of noise however.. Much more than rotating the main torid, ferrite ring, etc!
PS. I also got a package of nylon M3 screws to attach the box to the standoff.. Afraid of a metal screw in that spot.
So, better late than never, I am expecting M2X boards from the store today, and have ordered the other input boards from the fab house.
A question, perhaps @Nelson Pass or @Mark Johnson could answer; is it feasible to add one or two pair of output transistors with the goals of sharing load per MOSFET, biasing at higher currents, and/or increasing power output (assuming higher rail voltages)?
Several decades ago I built some guitar effects circuits using optocouplers, but their use in this circuit for biasing leaves me wondering if changes to the current part selection would be required, or some other change to the bias circuit? Just thinking it would be neat to be able to scale up the amp a bit if that is possible and reasonable.
Thanks!
A question, perhaps @Nelson Pass or @Mark Johnson could answer; is it feasible to add one or two pair of output transistors with the goals of sharing load per MOSFET, biasing at higher currents, and/or increasing power output (assuming higher rail voltages)?
Several decades ago I built some guitar effects circuits using optocouplers, but their use in this circuit for biasing leaves me wondering if changes to the current part selection would be required, or some other change to the bias circuit? Just thinking it would be neat to be able to scale up the amp a bit if that is possible and reasonable.
Thanks!
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Unless you fundamentally change the amplifier's biasing scheme, the ratio
(power dissipated by output transistors) / (maximum power that can be delivered to the loudspeaker load)
will remain constant. To double the output power, you must double the heat dissipation. This might require much larger heatsinks than anyone is using on their existing M2x amplifier.
I sorta half-remember that Modushop has thermal resistance data on their site, for the various heatsinks they ship. You might require the very biggest one they sell: 5U x 400. Run the numbers and see.
(power dissipated by output transistors) / (maximum power that can be delivered to the loudspeaker load)
will remain constant. To double the output power, you must double the heat dissipation. This might require much larger heatsinks than anyone is using on their existing M2x amplifier.
I sorta half-remember that Modushop has thermal resistance data on their site, for the various heatsinks they ship. You might require the very biggest one they sell: 5U x 400. Run the numbers and see.
I've currently got a 4U/400, and it is already populated with a pair of AS3220 transformers and associated rectifier/filter boards. In an identical chassis/PS, I'm running an Aleph 30 with 3 outputs per channel, but it sounds like this circuit biases the devices higher. Do you think there is any benefit to going with two pairs per channel, keeping rail voltages the same, and with the existing biasing scheme, or am I trying to change a leopard's spots?
Thank you.
Thank you.
To increase the maximum possible output power by a factor of 2, you need to do two things:
... if you increase the rail voltages but don't increase the output stage bias, you will not affect the max power into 8R ; it will be limited by current
... if you increase the bias current but don't increase the rails, you will not affect the max power into 8R ; it will be limited by voltage swing
- increase supply voltage rails by a factor of sqrt(2) = 1.414X
- increase output stage bias current by a factor of sqrt(2) = 1.414X
... if you increase the rail voltages but don't increase the output stage bias, you will not affect the max power into 8R ; it will be limited by current
... if you increase the bias current but don't increase the rails, you will not affect the max power into 8R ; it will be limited by voltage swing
Thank you for that very concise reply, Mark! You have answered my original questions.
That leaves me with one more, if you don't mind; leaving rail voltages and bias the same, is there any benefit to running 2 pairs of outputs per channel (e.g. lower distortion)?
Thanks very much.
That leaves me with one more, if you don't mind; leaving rail voltages and bias the same, is there any benefit to running 2 pairs of outputs per channel (e.g. lower distortion)?
Thanks very much.