The diyAudio First Watt M2x

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#203
As always thanks Jim
I should have mentioned I did search both Mouser and DigiKey but because of my total unfamiliarity with SMD I totally missed the part you suggested.
I am on the road but will answer questins later tonight.
Tuscon is going to be my first board. As withe whammy I have this need to roll op amps.
Best
Bob
 
#212
Got the PCBs today. Great quality. Will build M2C first (as I have a set of Toshiba jfets) and then M2X with one or two of the alternative buffers. Then I can better compare the different different buffers. Could be fun to make a simple tube buffer as well.

Regarding power supply I saw the earlier discussion regarding 18v vs more. However dosent the M2 benefit from larger ( VA ) trafos and caps and/or separate supplies for each channel like other amps?

I also saw in one of NPs articles (possibly the F6 article) that he splits the supply in a way so that half the Rs and one of the 2 caps after the R (in CRC) service each channel of the stereo amp. Would it be beneficial to modify the universal supply in that way? I.e. would one get some of the benefits of a mono power supply?
 
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#213
It's DIY, make the power supply however YOU want. I personally am using a single Antek AS-4218 transformer and Nelson Pass's standard First Watt PSU schematic. The transformer is toroidal, 400VA, 2x18VAC secondaries, with electrostatic shield between primary and secondary. Why? Because the day I tried to order their 300VA 2x18V transformer, Antek was out of stock. So I paid ten dollars more for the 400VA and got immediate shipping.

Remember that Nelson Pass designed M2 to be a Class-A amplifier, and remember that Class-A amplifiers are comparatively easy loads for a power supply to drive. Much easier than a Class-AB amplifier, for example. {INCREDIBLY easier than a Class-D amplifier}. So there's not going to be much noise or hash or signal-correlated Yuck on the supplies to begin with. Thus the benefit of "improving" the supplies is smaller (than on a Class-AB amplifier).

By all means go ahead and experiment with it. Remember this is a hobby in which you hope to be entertained. Do what entertains you!

To those who enjoy simulating M2 power supplies using LTSPICE: see what happens when you create an accurate simulation model of an 0.47 ohm 5W wirewound resistor (instead of a metal oxide resistor), and put that resistor model into your power supply sim. Does anything change? Does it change for the better? Entertaining!
 
#215
I know well that I can do whatewer I want. However I thought there was an interesting difference between the stereo and mono powersupplies in the First Watt F6 burning amp article. I can ask in another thread. Im here to learn.
 
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#216
kbergsson said:
I.e. would one get some of the benefits of a mono power supply?
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It wouldn't make much, if any, difference.

Having 2 PSU in the same chassis will benefit, if you wire properly to elimanate ground loops from channel to channel.

Where going mono really and truly makes the huge, absolutely noticeable differences is monoblocks. Of course the aded expense is nearly double, as you are duplicating the 2 most expensive items in the build, the PSU and chassis.
 
#218
6L6 said:
It wouldn't make much, if any, difference.

Having 2 PSU in the same chassis will benefit, if you wire properly to elimanate ground loops from channel to channel.

Where going mono really and truly makes the huge, absolutely noticeable differences is monoblocks. Of course the aded expense is nearly double, as you are duplicating the 2 most expensive items in the build, the PSU and chassis.
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Thanks 6L6, I have 3 pairs of tube monoblocks and one pair of class D monoblocks so I know there is a difference. The F6 I recently built is so good that Ill probably sell the two pairs of tube monoblocks I did not build my self and the class d monoblocks. I might go for a more modular approach and build two double powersupplies in separate boxes. And use eg active filters and a M2 or F6 for the top and F6 or F5 for bass in my Altec A5s. Withe the possibility to change later only the amp/heatsink modules.
My detailed question regarding the stereo and mono versions of the F6 powersupplies is because I have great respect for mr. Pass and dont think he would propose different stereo mono p.supply designs without a reason/benefit. Somewhere I read that the first C (in CRC) take on the turn-on peak and the largest part of the ripple and that the last C is meeting the main dynamic demand from the amp. If that is the case the stereo design might give one most of the benefits of separate supplies. I don know and I dont know the right terms/terminologi as Im just an amateur. I however have been a user of effective speakers and simple tube amps for decades and know that every component and circuit change in the whole system matters in some way - good, bad or different.
 
#219
kbergsson said:
... and I know that every component and circuit change in the whole system matters in some way - good, bad or different.
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I am interested to learn what sonic differences you hear, when you try out all five input stages in your M2x amplifier. Two of the input stages use ICs. One is all-JFET. One is all-BJT. One uses both JFET and BJT. Three are no-feedback designs. One is single ended. Maybe these very different circuit approaches, lead to audible differences. Or maybe not. Maybe the sound of the M2 is determined by, and dominated by, the Edcor transformer; swapping input stages makes no sonic difference (?)

I'm also interested to learn whether the potentiometer on the Ishikawa JFET board, makes any difference at all in the sound you hear from your M2x. (The other First Watt amps which include this pot, don't include an autotransformer).
 
#220
Mark Johnson said:
I am interested to learn what sonic differences you hear, when you try out all five input stages in your M2x amplifier....
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Maybe you are right ( ie if I read you email right) that all Solid state sounds the same and is different to simple se tube stuff. I dont know yet. I only know tubes, of late, and a couple of different class d amps. Autoformers at least do not provide galvanic isolation. Im am not on any mission and really do not like your relatively aggressive style. I will leave your tread alone.
Regards
Kjartan
 
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