This amp is totally fantastic!! Kind of remind me of a transistor Class A amplifier but with the spaciality of a Single Ended Tube amplifier. Really impressive!!!
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As you can tell, I'm really excited about this amplifier.
Hi Do,
I'm happy you're liking it
Post some pics, please
One thing for sure this amp needs the most transparent attenuation possible
Yes, a good attenuator and/or preamp, as transparent as possible, is a must to enjoy the full potential.
I suggest no less than the chinese type 21 smd pot or, for cost no object performance, TKD pots.
I would avoid Alps RK27, too much dark and veiled.
K71-4
I have many amps to compare it too and My_Ref FE is extremely good in many if not most sound aspects. It is also really transparent, better than most amps I've listened to but I doubt changing the input cap will make it as transparent as the Goldmund Telos. And this is actually not a bad thing at all, I like it the way it is, I like the tube like spaciality that transistor amps can't usually do but My_Ref FE exceeds in doing.
So far, with the tests I've done, I would rate this amp my favorite along with my Telos but for different reasons... Now I still have the VSSA, nx Amp, etc, to build and test so things could change in the future...
I will post some pictures but I'm mostly like many here, my project is not in a chassis yet...
Transfo is a custom made SumR with 4x secondary @ 21Vac and shielded (driving 4 Ohms load).
Close Up view!
This is my JC-2 Clone Preamp with Sigma 22 PSU. Don't worry, those cables won't stay there... It is all prototypes and tweaks still have to be done and chassis added.
Ciao!
Do
National show in detail how to calculate the heatsink size.
But they assume that the device is @ the maximum allowable junction temperature.
This high a junction temperature will trigger the temp compensated protections built into the chipamp.
I always recommend that you double the size as given by the National datasheet.
If they tell you that at 25degrees C for one chip operating from +-38Vdc into a 8r0 resistor should be 3.6C/W, then use a 1.8C/W for each chipamp.
If you put two chips on a common sink then that becomes 0.9C/W sink.
Look up the heatsink section and use the charts to determine your sink requirement for your operational conditions.
If the sink is internal to the chassis, it will run in air that is hotter than the room's ambient air temperature. Sometimes very considerably hotter.
But they assume that the device is @ the maximum allowable junction temperature.
This high a junction temperature will trigger the temp compensated protections built into the chipamp.
I always recommend that you double the size as given by the National datasheet.
If they tell you that at 25degrees C for one chip operating from +-38Vdc into a 8r0 resistor should be 3.6C/W, then use a 1.8C/W for each chipamp.
If you put two chips on a common sink then that becomes 0.9C/W sink.
Look up the heatsink section and use the charts to determine your sink requirement for your operational conditions.
If the sink is internal to the chassis, it will run in air that is hotter than the room's ambient air temperature. Sometimes very considerably hotter.
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James,
Without knowing the details, those heatsinks sound like they would work.
As Andrew says, there is a lot of info on the National website. In addition to the charts he is recommending, I remember that they have a spreadsheet for the 3886. You put in your power supply and load and it calculates the power out and required heatsink transfer rate, deg C/W. In general, that is a good guideline for a MyRef.
That said, MyRef works a little differently than the standard chipamp with the voltage gain in the 318. I think it is fair to say that the MyRef is a little lower heatsink requirement and that a heatsink designed to work on the chipamp will be fine on the MyRef.
Jac
Without knowing the details, those heatsinks sound like they would work.
As Andrew says, there is a lot of info on the National website. In addition to the charts he is recommending, I remember that they have a spreadsheet for the 3886. You put in your power supply and load and it calculates the power out and required heatsink transfer rate, deg C/W. In general, that is a good guideline for a MyRef.
That said, MyRef works a little differently than the standard chipamp with the voltage gain in the 318. I think it is fair to say that the MyRef is a little lower heatsink requirement and that a heatsink designed to work on the chipamp will be fine on the MyRef.
Jac
I try to simulate the design of lm317 for positif and negative power supply using software called circuit maker. the positif is OK,but the negative resulted error simulation. I still doesnt know what is bc639 and bc640 used for.is this transistor can make current more higher? what is the effect if the zener 14v replaced with 15v. I think LM318 still working normally with 15v
BC639 and BC640 are shunt transistors, they reduce the output impedance of the regualtor by the Hfe.
You have a PM
I just start learning about audio-electronic things, still beginner, needs help from master / senior engineer for give better understanding about what will happen if I change some component like R or C value from the original schematic, because sometimes I cannot get the same R or C value in my local store.
the original value of C12 is 220pF and R12 is 3K3 ohm, if I change C12 to 330pF, is it correct for R13 must change to 2K2 ohm?
because I found tutorial :
An externally hosted image should be here but it was not working when we last tested it.
fc = 1/(2*pi * R * C),and using C12 and R12 from original schematic will get fc = 219133 Hz