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The diyAudio First Watt M2x
The diyAudio First Watt M2x
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Old 10th December 2019, 03:52 PM   #2661
TungstenAudio is offline TungstenAudio  United States
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Yes, it's those little details...
Anyway, it does seem that the Diamond buffer is doing well as the input stage to my F6. Using 10 Ohm base resistors and 10 Ohm emitter resistors on the output devices seems to be adequate. The Toshiba TTC004B and TTA004B transistors barely get warm, and I like having the CCS circuits that drop 10V off the rails for the front end devices.

I believe much of what I'm hearing with my new amp may be attributed to the sonic characteristic of this input stage. As I mentioned a while back, the Austin boards sound great in my M2x. I still like playing with the input JFets in my Mtn View vero prototypes, but that's mostly because I like to tinker. If I had to pick one of the canonical M2x input stages, the Austin has the best balance of characteristics for my ears.
Given my recent experience with the F6, it would be tempting to try higher voltage and current levels with the M2x. This version of the diamond buffer can support that. Perhaps someone with better KiCad-Fu could layout such a PCB which fits the M2x mounting scheme...
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Old Yesterday, 06:19 PM   #2662
scranton is offline scranton  United States
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The diyAudio First Watt M2x
Been listening to the LT1122 in the Tucson Board. Great sound. Reinstalled the Diamond Board and I am knocked out by it.I think that is my favorite with LT1122 and OPA1611 following. It's like having three amps After 6L6 mentioned Tidal I have been discovering so much new music, Lars Danielsson and Cecilie Norby on the "Just the Two of Us" album and the song "Both Sides Now". Danielson is amazing bassist and the Diamond handles it amazingly. The Vet discount on Tidal is a great deal.
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Old Yesterday, 06:45 PM   #2663
Mark Johnson is offline Mark Johnson  United States
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The diyAudio First Watt M2x
Have you tried M2x with the Red Norwoods I sent you on Feb 5th? Many people love, Love, LOVE the sound of that composite pair.
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Old Yesterday, 08:09 PM   #2664
MEPER is online now MEPER  Denmark
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Yes, Norwood is a step-up compared to Tucson OPA604. It may have something to do with better drive capability to drive the Edcor?

I made distortion measurement using Focusrite and REW software when Tucson was installed and will be fun to measure amp with Norwood to see if there is any change in harmonics.

Few days ago I made a small interface box from power amp to Focusrite so level match and I don't burn the Focusrite input by a mistake. Same I used for first measurement (unboxed with long wires). It is nothing special and "quick and dirty" made.....but it seems to work. My theory is that I will get less noise pickup with shorter wires and mounted in a metal box.
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Old Today, 12:29 PM   #2665
unixdeveloper is offline unixdeveloper  United States
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The diyAudio First Watt M2x
Quote:
Originally Posted by TungstenAudio View Post
I’m using a pair of Antek AS-3222 transformers with SLB power supplies in my F6. I used a different set of transistors in the CFP, which reduced the dropout voltage from 3 Volts to 2.1 Volts. The output voltage of each supply is +/– 26.4 Volts while providing 1.4 Amps to the channel board. The nature of of the SLB as a “ripple eater” makes the final output voltage somewhat difficult to pin down. A single SLB powering a typical M2x might end up at 25 Volts. This is at the upper limit of some of the canonical input stages that come with the M2x PCB set.
That’s a long way of saying it would be easier to build a more conventional supply using a transformer with 18V secondaries. Unless you’re willing to modify the input stages and/or the SLB so they are compatible with each other.
While waiting for the AS-4218 to show up from Antek, I was thinking if I can power the input stages from a smaller transformer and M2X with AS-3222. Have a bunch of 18VAC 50VA toroids which could be used.

Regards,
Subbu
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Old Today, 04:35 PM   #2666
TungstenAudio is offline TungstenAudio  United States
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Quote:
Originally Posted by unixdeveloper View Post
While waiting for the AS-4218 to show up from Antek, I was thinking if I can power the input stages from a smaller transformer and M2X with AS-3222. Have a bunch of 18VAC 50VA toroids which could be used.
...
While that sounds possible, I think it would be a lot of work to do it properly, such that there was no hum. The IPS boards would have to be connected to the main board in a way that isolated the power connections, but allowed the IN and OUT connections. The input stage power supply would need to be very clean and low impedance.
I have another suggestion, which is to build a power supply like the F6 Power Supply (Stereo) as presented in Nelson Pass’ F6 BAF article. This separates the second bank of capacitance for each channel for better separation. I also recommend adding high quality smaller value caps ~1000 uF to the second bank.
The choice of bridge rectifier will have a significant impact on the final rail voltage, and even the audible ripple. The LT4320 based synchronous rectifiers have shown better performance in all the amps where I have used them. The next best choice would be a set of FEP30 diodes, or the LVB2650 bridge.
Even though the M2x uses a transformer for the gain stage, it still needs the best PSU that you can manage for the best sound.
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Old Today, 05:20 PM   #2667
unixdeveloper is offline unixdeveloper  United States
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The diyAudio First Watt M2x
Quote:
Originally Posted by TungstenAudio View Post
While that sounds possible, I think it would be a lot of work to do it properly, such that there was no hum. The IPS boards would have to be connected to the main board in a way that isolated the power connections, but allowed the IN and OUT connections. The input stage power supply would need to be very clean and low impedance.
I have another suggestion, which is to build a power supply like the F6 Power Supply (Stereo) as presented in Nelson Pass’ F6 BAF article. This separates the second bank of capacitance for each channel for better separation. I also recommend adding high quality smaller value caps ~1000 uF to the second bank.
The choice of bridge rectifier will have a significant impact on the final rail voltage, and even the audible ripple. The LT4320 based synchronous rectifiers have shown better performance in all the amps where I have used them. The next best choice would be a set of FEP30 diodes, or the LVB2650 bridge.
Even though the M2x uses a transformer for the gain stage, it still needs the best PSU that you can manage for the best sound.
Thank you James for the feedback. I will go through the article and try it out.
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Old Today, 06:36 PM   #2668
Mark Johnson is offline Mark Johnson  United States
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The diyAudio First Watt M2x
I'm using individual 10A 100V Schottky diodes in a PSU for chip amps. Chip amps operate class-AB so the current drawn from the power supply is highly variable, unlike the current drawn by class-A amps like M2x. Still, when I connect the chip amp PSU to an electronic load and draw 4 amps DC from V+ and another 4 amps DC from V-, the Schottky's low Vfwd is quite a bonus. The diodes run cool, which means they don't bake the nearby electrolytic capacitors, which is nice.

Schematic and thermal images here

If you think you ought to feel some sort of nervousness about the 100V diode rating, the superdelightful components MOV1 and MOV2 might provide reassurance. They perform double duty; besides lightning arrestors, they also operate as across-the-trafo capacitors in the C+RC snubber networks.
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Old Today, 07:09 PM   #2669
scranton is offline scranton  United States
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The diyAudio First Watt M2x
Quote:
Originally Posted by Mark Johnson View Post
Have you tried M2x with the Red Norwoods I sent you on Feb 5th? Many people love, Love, LOVE the sound of that composite pair.
I did listen to them but I was in the mode of trying out a couple of others. Not sure when I replaced the Whammy with the Korg B1. The pleasure of this amp is being able to tinker so easily. Tho I do have to give a second thought flipping around the 35 lb beauty. I did listen to my Aleph J for a couple intervening weeks and was pleased with that but your LT1122 recommendation was encouragement enough to move on. Now I'll have to go back to the Norwoods for further audition. Thanks again.
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