I DIY because I want to make things that are better than what I can buy.
Things that are not commercially viable.
Just making carbon copy is not interesting for me.
But that is just me.
Patrick
Spot on
You will get them. You are high on the list.
> Apogee stage, 3 ohms.
Then correct choice.
And if I were you, I would lower rails to 20V and increase bias to say 1.5A for each device.
And I would use 2SK3497 for the SRPP, as already mentioned earlier.
Save the Semisouth as life-time spares.
Patrick
> Apogee stage, 3 ohms.
Then correct choice.
And if I were you, I would lower rails to 20V and increase bias to say 1.5A for each device.
And I would use 2SK3497 for the SRPP, as already mentioned earlier.
Save the Semisouth as life-time spares.
Patrick
It got more interest than I thought so I opened a GB thread (GB "long and skinny" FirstWatt J2 clone PCBs). I've added your name.
Cheers,
Jeff.
Cheers,
Jeff.
EUVL, I see you say it is safe to run each device at 30W (+-24V 1.2A).
The Semisouths are rated at 1.1c/w per juction to case so at 30W they will be running
at least at 60C ++?
But the First Watt J2 is rated at 200W so Nelson run each device at 50W, right.
And that in a chassis that may be comparable to the 4U Deluxe at diyaudiostore.
Though with probably better heatsink and fins.
There is still a big difference between 30W and 50W... Do Nelson run these devices
hotter? A large stash of the semisouth may prompt one to take more risk?
I am trying to decide for dual chassis monoblocks or single chassis, and how big
chassis should be.
The Semisouths are rated at 1.1c/w per juction to case so at 30W they will be running
at least at 60C ++?
But the First Watt J2 is rated at 200W so Nelson run each device at 50W, right.
And that in a chassis that may be comparable to the 4U Deluxe at diyaudiostore.
Though with probably better heatsink and fins.
There is still a big difference between 30W and 50W... Do Nelson run these devices
hotter? A large stash of the semisouth may prompt one to take more risk?
I am trying to decide for dual chassis monoblocks or single chassis, and how big
chassis should be.
FW J2 dissipates 200W of energy not that power at the speakers.
There you have 30W into 8Ohms per channel or 20W into 4 Ohms per channel.
The heatsinks need to dissipate all the 200W but NP likes to run his amps hot, typical 50ºC at the outside of heatsink.
But if you live in a warm climate, as is summer here is Portugal, ambient temp is way over 30ºC normally and many days over 40ºC so these 50ºC become much more than that.
It seems that will not be an issue to you , reference is usually 20ºC ambient temp, for us southern folks a good solution is the "babysitter" that ZM has made popular here ie: a base with fans for the amplifier, these can be run at low voltage just to move the air through the fins, this is very efficient and can be made to look really nice as the base of the amp.
There you have 30W into 8Ohms per channel or 20W into 4 Ohms per channel.
The heatsinks need to dissipate all the 200W but NP likes to run his amps hot, typical 50ºC at the outside of heatsink.
But if you live in a warm climate, as is summer here is Portugal, ambient temp is way over 30ºC normally and many days over 40ºC so these 50ºC become much more than that.
It seems that will not be an issue to you , reference is usually 20ºC ambient temp, for us southern folks a good solution is the "babysitter" that ZM has made popular here ie: a base with fans for the amplifier, these can be run at low voltage just to move the air through the fins, this is very efficient and can be made to look really nice as the base of the amp.
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