I think another builder went for a PNP pair of the MJE1503x series TO220 drivers. They are are probably the ultimate, affordable, high current drivers still readily available. Well, they would be my first choice, as long as they proved stable on the 'scope.
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I ought to correct post #286. The regulator resistors are the same in the 606 and 909, its the BOMs that are wrong - again.
There are three 6V8 zeners;
D12 is fed with 10K
D1 is fed with 5K6
D2 is fed with 3K3
There are three 6V8 zeners;
D12 is fed with 10K
D1 is fed with 5K6
D2 is fed with 3K3
I would be intrigued to see what Rolls Royce mods have ever been done to the original 606.
Reading through these posts, one of the big ones is to replace IC1 from TLC271 to something like an OPA 627AP. This is only a servo amp so it would make very little difference to the design.
Reading through these posts, one of the big ones is to replace IC1 from TLC271 to something like an OPA 627AP. This is only a servo amp so it would make very little difference to the design.
It lives and breathes
Despite the wrong transistors, the test amp is now living and breathing.
All I've changed are the wrong NPN transistors for the correct PNP ones. OK, I've changed the horrible 5W 560R resistors for some that fit the board.
I'm still waiting for the high current 4.0uH coil.
It's producing nice quiet music into my test speaker with zero DC output offset.
I'm going to let it soak just in case there is some underlying damage before releasing it onto my main speakers.
The other channel is still virginal and has never seen an electron, well not a fast moving one that I have fed it.
Despite the wrong transistors, the test amp is now living and breathing.
All I've changed are the wrong NPN transistors for the correct PNP ones. OK, I've changed the horrible 5W 560R resistors for some that fit the board.
I'm still waiting for the high current 4.0uH coil.
It's producing nice quiet music into my test speaker with zero DC output offset.
I'm going to let it soak just in case there is some underlying damage before releasing it onto my main speakers.
The other channel is still virginal and has never seen an electron, well not a fast moving one that I have fed it.
Attachments
During testing everything is staying reasonably cool. TR7 seems to be the main source of the heat. It's not unbearable, probably only about 50 degrees C. Is this normal with an output power of only a few watts ?
The main sinks are staying relatively cool, its just the case of TR7 that is hot to the touch. TR7 has a mica washer between it and the main sink, unlike the main O/Ps which are cool and have thermasil pads. (yes it does have thermal goo).
The main sinks are staying relatively cool, its just the case of TR7 that is hot to the touch. TR7 has a mica washer between it and the main sink, unlike the main O/Ps which are cool and have thermasil pads. (yes it does have thermal goo).
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I would highly recommend this as a DIY clone. The only awkward components are the coils and they are not too difficult to DIY. Boards readily available, PSU is not too critical.
What is the Tc to Ts temperature difference for TR7?
This difference may indicate good thermal coupling, or poor thermal coupling.
This difference may indicate good thermal coupling, or poor thermal coupling.
It will get hot because TR7 is the Class A section of the amp. It sees 50 volts (rail voltage) across C-E as it feeds two series 560 ohms to the -50 volt rail. So that's 50v * 0.045ma, 2.5watts. Hot ! If your rail voltage is higher then its more.
The tab of TR7 is as cool as the heatsink, it's just the plastic body which is a bit warm.
But as it is the Class A element, it is only to be expected.
But as it is the Class A element, it is only to be expected.
Post the schematics,amplifier and power supply, pdf pcb. for easy access in the same post.
That looks like the 8A RMS rated ferrite baby in this Coilcraft list:
Coilcraft Power Inductor Finder (You'll need to dial in a 4uH value and say, 10amps current to see the parts on offer.)
Maybe you just like experimenting but I wouldn't touch high current density ferrites for audio applications. The history of these is a litany of distortion problems in speaker crossovers, power supply filters and output coils going back to the 1970s. Some of the large composite core material inductors may well be fine, as I mentioned earlier.
I guess I needn't add that audiophiles will convulse and die in their thousands if you mention ferrite and audio in the same sentence. 😀
Coilcraft Power Inductor Finder (You'll need to dial in a 4uH value and say, 10amps current to see the parts on offer.)
Maybe you just like experimenting but I wouldn't touch high current density ferrites for audio applications. The history of these is a litany of distortion problems in speaker crossovers, power supply filters and output coils going back to the 1970s. Some of the large composite core material inductors may well be fine, as I mentioned earlier.
I guess I needn't add that audiophiles will convulse and die in their thousands if you mention ferrite and audio in the same sentence. 😀
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Now, you've got me thinking. The air cored 0.4mm wire coil does get warm but not hot under duress. I haven't pushed it to full volume but I have had it running at VERY LOUD.
This cropped up earlier in the thread, I'll have a re-think about a DIY air cored inductor with heavier gauge wire.
This is the only problematic coil as it does have the full output current passing through it.
This cropped up earlier in the thread, I'll have a re-think about a DIY air cored inductor with heavier gauge wire.
This is the only problematic coil as it does have the full output current passing through it.
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Looking at the photos of original boards there is no way that they are air cored.
Just using simple maths the wire needs to be 1.92mm diameter which makes the coils quite meaty. OK it's highly unlikely that the amps will ever run at 160W RMS, I'm not sure of the derating figure to get the wire down to a reasonable gauge.
Just using simple maths the wire needs to be 1.92mm diameter which makes the coils quite meaty. OK it's highly unlikely that the amps will ever run at 160W RMS, I'm not sure of the derating figure to get the wire down to a reasonable gauge.