Ok, not what I was thinking of. More like a trumpet which, when you find the right component values (eg single resistor), can just solder and leave in place on the pcb.
Got an email stating mine are shipping out today and I ordered these on the 16th. If anyone else is needing to get these, i'd order them soon just cause they're shipping them out fast. No telling how long this will last
I just cut-to-order from these:
SPL 64: Socket, 64-pin, single row, spacing 2.54, straight at reichelt elektronik
Much more cost-effective
Or, for a JFET or other TO-92 transistor, you can use these:
MPE 006-1-003: Precision socket strip, 2.54 mm, 3 pin at reichelt elektronik
Best regards,
Claas
Here is Nelson Pass's schematic for the power supply he used in the original M2 amplifier sold by First Watt (link to sales page). It calls for a transformer with two 18VAC secondary windings.
Since the M2 amplifier uses Nelson's very clever 4N35 optoisolator circuit to achieve constant current Class-A bias, M2 will draw the same current whether you use a 2x17VAC transformer, or 2x18VAC transformer, or 2x22VAC transformer.
The supply current remains constant, but the supply voltage changes. So the power drawn from the AC mains, also changes. Since M2 is a Class-A design, more than 75% of the power drawn from the AC mains is dissipated as heat by the output transistors. That's why Class-A amplifiers have gigantic heatsinks!
So if you propose to replace Nelson Pass's 2x18VAC transformer by a 2x22VAC transformer (voltage higher by 23%), your amplifier will dissipate 23% more heat than Nelson Pass's original M2 amplifier. And you will need to increase the size of your heatsink by 23%.
It might be easier to buy a 2x18VAC transformer than to buy even bigger, even giganticer heatsinks.
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Since the M2 amplifier uses Nelson's very clever 4N35 optoisolator circuit to achieve constant current Class-A bias, M2 will draw the same current whether you use a 2x17VAC transformer, or 2x18VAC transformer, or 2x22VAC transformer.
The supply current remains constant, but the supply voltage changes. So the power drawn from the AC mains, also changes. Since M2 is a Class-A design, more than 75% of the power drawn from the AC mains is dissipated as heat by the output transistors. That's why Class-A amplifiers have gigantic heatsinks!
So if you propose to replace Nelson Pass's 2x18VAC transformer by a 2x22VAC transformer (voltage higher by 23%), your amplifier will dissipate 23% more heat than Nelson Pass's original M2 amplifier. And you will need to increase the size of your heatsink by 23%.
It might be easier to buy a 2x18VAC transformer than to buy even bigger, even giganticer heatsinks.
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Attachments
Thanks Mark, the reason I asked for 2x22VAC transformer is that I have it as a spare from my VFET2 amp build. As you said the heat dissipation asks for a bigger heat sinks, I will drop that idea. Then I also have a spare 2x18VAC but with 7A current rating dual transformer which makes it to only 250VA compared to the recommended 300VA. Is this fine to go ahead and use for the time being and get a 300VA later on.
Recommended method of discovering substitutions:
Dear community of M2x builders,
I have a problem and would like to ask for your help.
Part AAA is out of stock at all of the distributors
I am able to buy from. So I did a bit of research
and I discovered parts BBB and CCC, which ARE in stock,
and which look to me like acceptable substitutes.
I would like to ask your opinion about this please.
Do you think it's okay to use either BBB or CCC ?
I have made a little table, attached below, showing
the similarities and differences between parts AAA,
BBB, and CCC. After all, why should you have to
dig out these details yourself? I'm the one asking
for help, I'm the one obligated to do the grunt work.
Thanks for any recommendations and opinions!
I have a problem and would like to ask for your help.
Part AAA is out of stock at all of the distributors
I am able to buy from. So I did a bit of research
and I discovered parts BBB and CCC, which ARE in stock,
and which look to me like acceptable substitutes.
I would like to ask your opinion about this please.
Do you think it's okay to use either BBB or CCC ?
I have made a little table, attached below, showing
the similarities and differences between parts AAA,
BBB, and CCC. After all, why should you have to
dig out these details yourself? I'm the one asking
for help, I'm the one obligated to do the grunt work.
Thanks for any recommendations and opinions!
Be sure to use a different fuse in series with the AC mains, if you use a different transformer. For 250VA transformer, I suggest 1.0 amp slow-blow for 230VAC mains, 2.0 amp slow-blow for 115VAC mains.
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Any specific reason Mark to go with 1A fuse with 250VA and does this change if using a 300VA!
manniraj - The larger transformer might pull a bit more current at start-up, but it will be slowed down by the CL-60s, and if there's no great increase in capacitor size it won't make a marked difference.
That said, if you find the fuse is not holding, increase the fuse rating 0.5A at a time until you arrive at a value that survives power-up.
Bob -
GCM3195C1H393GA16D Murata Electronics | Mouser
That appears to be the 2% resistor in different packaging; 0.039uF, 2%, and the 1206 SMD footprint.
As for the NPN transistor, There is no alternative package or whatever in stock... but it shown 50,000 to be arriving in mid-july... which is a long time to wait.
Which board and location is this for?
Also, in the short term to get the amp up and going, build a pair of Tucson boards (the standard opamp circuit). Easy to get parts, totally self-adjusting, and honestly sounds fantastic.
That said, if you find the fuse is not holding, increase the fuse rating 0.5A at a time until you arrive at a value that survives power-up.
Bob -
GCM3195C1H393GA16D Murata Electronics | Mouser
That appears to be the 2% resistor in different packaging; 0.039uF, 2%, and the 1206 SMD footprint.
As for the NPN transistor, There is no alternative package or whatever in stock... but it shown 50,000 to be arriving in mid-july... which is a long time to wait.
Which board and location is this for?
Also, in the short term to get the amp up and going, build a pair of Tucson boards (the standard opamp circuit). Easy to get parts, totally self-adjusting, and honestly sounds fantastic.
ProTip: use DigiKey's Parametric Search engine to find parts, then buy them from whoever you like.
High Voltage, High Beta, NPN
One of them should look very VERY familiar.
Austin's Q5 and Q6 are excellent performing, high beta, high voltage devices with good thermal properties. Since good thermal properties are not an absolute requirement for Q1-Q4, I specified KSA/KSC parts that cost a lot less (in percentage terms!) for Q1-4. If you've got the money to use Zetex parts in all six positions, you'll be very pleased with the results.
High Voltage, High Beta, NPN
One of them should look very VERY familiar.
Austin's Q5 and Q6 are excellent performing, high beta, high voltage devices with good thermal properties. Since good thermal properties are not an absolute requirement for Q1-Q4, I specified KSA/KSC parts that cost a lot less (in percentage terms!) for Q1-4. If you've got the money to use Zetex parts in all six positions, you'll be very pleased with the results.
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And as Mark was making the search for the N-channel devices, I did the P-channel, although it appears that there are bajillion PNP devices in stock everywhere...
Transistors - Bipolar (BJT) - Single | Discrete Semiconductor Products | DigiKey
The Cliff Notes version of the Austin is that the output transistors, the ZTX696B and ZTX795A can happily be used everywhere. It will sound fantastic. They are required in the Q5/Q6 position for thermal reasons. They were not specified in the other positions only because they are 3x the price of the KSA/KSC parts.
Transistors - Bipolar (BJT) - Single | Discrete Semiconductor Products | DigiKey
The Cliff Notes version of the Austin is that the output transistors, the ZTX696B and ZTX795A can happily be used everywhere. It will sound fantastic. They are required in the Q5/Q6 position for thermal reasons. They were not specified in the other positions only because they are 3x the price of the KSA/KSC parts.