Cooking an M2X
Hello members,
the M2X is playing music first time!
Thanks to Mark Johnson, 6L6, Nelson Pass and all other involved persons
giving us this beautiful soundmachine!
The first run is with cheap speakers (JBL Control 1). I wanted to be careful.
My first run is with the austin boards switched in.
Will avoid to use the Norwood yet. Thanks Mark Johnson for the tip.
Last second I read it. Perhaps I would have got fire in my 'soup'
Now I am testing / listening. Will report back.
Have a good night!
Dirk
Hello members,
the M2X is playing music first time!
Thanks to Mark Johnson, 6L6, Nelson Pass and all other involved persons
giving us this beautiful soundmachine!
The first run is with cheap speakers (JBL Control 1). I wanted to be careful.
My first run is with the austin boards switched in.
Will avoid to use the Norwood yet. Thanks Mark Johnson for the tip.
Last second I read it. Perhaps I would have got fire in my 'soup'
Now I am testing / listening. Will report back.
Have a good night!
Dirk
Attachments
Good you have some sound. Do you use 2x500VA toroid's for the project. Can you hear hum pickup from the Edcor's?
I have a couple of 500VA 2x18V underway as I want to make psu that can be reused for various power amp projects. I think 500VA can be "started" directly on the 230 VAC mains without softstart. …..the primary fuse "just" have to be a 5A slow fuse or so pr trafo? ….a short on the secondary should be able to "burn" it....of course. Will have a closer look on that…...maybe a good thing to have soft start so a "smaller" primary fuse can be used. Also a good thing for the capacitors not to be "chocked". Do you use a NTC for softstart? …..between 2x115 VAC primary windings?
I have a couple of 500VA 2x18V underway as I want to make psu that can be reused for various power amp projects. I think 500VA can be "started" directly on the 230 VAC mains without softstart. …..the primary fuse "just" have to be a 5A slow fuse or so pr trafo? ….a short on the secondary should be able to "burn" it....of course. Will have a closer look on that…...maybe a good thing to have soft start so a "smaller" primary fuse can be used. Also a good thing for the capacitors not to be "chocked". Do you use a NTC for softstart? …..between 2x115 VAC primary windings?
answer to MEPER
Hello Meper,
the transformers are from SEDLBAUER AG, Germany:
POLYTRONIK Rinkerntransformator - RSO 825046
2 x 18V / 250VA each
sec.windings in parallel - 18,0V and 13,89A each trafo
primary windings in line (2 x 115V = 230V) - inbetween the 2 primary windings of each trafo is one CL60 inrush current limiter.
These Trafos have shielding between the windings (primary - secondary)
and a Thermoswitch (120°C).
I have some very light hum. I am still testing. I have also a small metalcase
to shield the EDCORs. Wanted to try first without.
Greets
Dirk
Hello Meper,
the transformers are from SEDLBAUER AG, Germany:
POLYTRONIK Rinkerntransformator - RSO 825046
2 x 18V / 250VA each
sec.windings in parallel - 18,0V and 13,89A each trafo
primary windings in line (2 x 115V = 230V) - inbetween the 2 primary windings of each trafo is one CL60 inrush current limiter.
These Trafos have shielding between the windings (primary - secondary)
and a Thermoswitch (120°C).
I have some very light hum. I am still testing. I have also a small metalcase
to shield the EDCORs. Wanted to try first without.
Greets
Dirk
MEPER,
My understanding is that for the M2 clone a single 300VA Transformer with 2 x 18V windings is enough, so single 500VA should be more than enough.
Also, the M2 by design takes some time (close to a minute?) to start up, so no speaker thump is audible when powering on, and a separate "soft start" can be avoided.
More expert builders can add more comments and suggestions.
cubicincher,
Congratulations on your build.
If you would not mind sharing, what are the dimensions of your chassis?
Congratulations!
No, that's a mistake. "C0" on the M2x main board is optional, and Nelson Pass did not include "C0" in the original M2 amplifier sold by First Watt. This is called out on the M2x schematic AND in the Notes For M2x Builders at the top of the M2x thread.
Ccomp1 on the Norwood board is a compensation capacitor and is mandatory for proper circuit function.
_
Attachments
answer to Mark Johnson
Hello Mark Johnson,
that was my mistake. I should not interchange informations about the Norwood inputboard with infos about the mainboard! Exact reading is a necessity.
Thanks for your attention and your good eyes!
I add the Ccomp on the Norwood - I already purchased it with all the other parts.
Greets
Dirk
Hello Mark Johnson,
that was my mistake. I should not interchange informations about the Norwood inputboard with infos about the mainboard! Exact reading is a necessity.
Thanks for your attention and your good eyes!
I add the Ccomp on the Norwood - I already purchased it with all the other parts.
Greets
Dirk
MEPER,
My understanding is that for the M2 clone a single 300VA Transformer with 2 x 18V windings is enough, so single 500VA should be more than enough.
I will build an universal PSU for Firstwatt power amps. For this I have ordered two 500 VAs where each has 2x18 V secondary. It will be external PSUs that can be reused (dual mono). The nice thing with DIY is that you can "overdo" things a bit. But these large transformers probably like to have a kind of softstart. Either a thermistor in primary or a dedicated circuit which makes a well defined delay with reduced current. The thermistor solution looks almost too simple.....does it really work? ….why do people built boards with 555 timers, relay, regulator etc. etc. when it can be made that simple using a thermistor in the primary?
answer to MEPER
Hello MEPER,
Nelson Pass is using the CL60 in a lot of his amps as an inrushlimiter.
You also can use the softstartboard from the diyAudio Store.
There is also a thread where Mark Johnson recommends another part /
substitute for the CL60.
There are many roads which lead towards rome - some are stony ways,
some are easy roads - like with the CL60.
Greets
Dirk
Hello MEPER,
Nelson Pass is using the CL60 in a lot of his amps as an inrushlimiter.
You also can use the softstartboard from the diyAudio Store.
There is also a thread where Mark Johnson recommends another part /
substitute for the CL60.
There are many roads which lead towards rome - some are stony ways,
some are easy roads - like with the CL60.
Greets
Dirk
It probably also depends if it is the small 20mm fuses or some larger ones which can be made "more slow…..or Träge" for the same amount of current?
It would be nice if a 2A5T in 20mm version can be used…….then the NTC resistor to limit the current has done a very good job. It is very visible if the fuse blows…...can see the light though the black plastic holder and all metal has coated the inside of the glass of the fuse...….don't have to use a DMM to check the fuse......
It would be nice if a 2A5T in 20mm version can be used…….then the NTC resistor to limit the current has done a very good job. It is very visible if the fuse blows…...can see the light though the black plastic holder and all metal has coated the inside of the glass of the fuse...….don't have to use a DMM to check the fuse......
Douglas Self discusses this in his power amp book.
I also made a post about this myself, stating six reasons why somebody might decide NOT to use a simple inrush current limiter in the primary: LINK
But as 6L6 points out, there are many paths and they all take you to the same destination. Choose the one that appeals to you, for the reasons YOU think are important. Don't let it wound your self-esteem if someone else chooses differently.
What current is needed for an inrush limiter for an amp like this? I haven't done much with solid state, preferring tubes, but am SLOWLY thinking about a Pass option. I've used CL150 in the secondary in tube amps (4.7A I think) where steady state current needs are decidedly lower than that. So what is a turn-on current rush in a Pass amp with honkin' big PS caps? And why put the limiter on the primary? I suppose current might be the issue but will it function as well there? Hmmm. Love to hear peoples' thoughts.
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