I have been justly informed that I have been posting in the wrong thread. My bad. Anyway the boards are here and I hope to have all shipped this week. If you asked for boards and were sent an invoice please pay now. By this time next week if all are not paid for I will let those waiting in line have a chance to purchase them. There are at this time 9 boards allotted but not paid for. I hope someone needs an odd number.
Advanced circuits has done a marvelous job with the pcb's. I am very happy with the results and the final invoice price. It seems they always add on some obscure charge which throws my money numbers all out of wack. If you did not get a chance to see the pictures I posted on the wrong thread I will post one here which shows the new board in comparison to the previous 10 transistor version.
Tad
Advanced circuits has done a marvelous job with the pcb's. I am very happy with the results and the final invoice price. It seems they always add on some obscure charge which throws my money numbers all out of wack. If you did not get a chance to see the pictures I posted on the wrong thread I will post one here which shows the new board in comparison to the previous 10 transistor version.
Tad
Attachments
They are all shipped. The international stuff takes about 10 days door to door. The domestic U.S. boards should be at your location this week.
Total postage was over 260.00. Now we know who makes all of the money.
Does anyone remember when a stamp was 5 cents?
Remeber to check the Priority shipping envelope when you clean it out. The small diode boards are taped to the inside of the envelope. One small diode board per pcb. Getting 8 of these monsters in one envelope is a chore.
Tad
Total postage was over 260.00. Now we know who makes all of the money.
Does anyone remember when a stamp was 5 cents?
Remeber to check the Priority shipping envelope when you clean it out. The small diode boards are taped to the inside of the envelope. One small diode board per pcb. Getting 8 of these monsters in one envelope is a chore.
Tad
Ed,
With this many outputs we should also be able to have a substantial class A bias. What is needed voltage wise to achieve 400/8 something like 95 volts and a regulated frontend.
All of you out there will be making these choices soon. The 30 sum odd white envelopes should be circling the globe by now. I sure am glad that project is out of the way. Keeping up with all of the different names is rough.
My sweet wife is due an atta-boy for her efforts. Thanks Cherie.
Tad
With this many outputs we should also be able to have a substantial class A bias. What is needed voltage wise to achieve 400/8 something like 95 volts and a regulated frontend.
All of you out there will be making these choices soon. The 30 sum odd white envelopes should be circling the globe by now. I sure am glad that project is out of the way. Keeping up with all of the different names is rough.
My sweet wife is due an atta-boy for her efforts. Thanks Cherie.
Tad
A 6pair 1943/5200 output stage cannot reliably provide 400W into 8ohms, even with a big heatsink.
A 6pair 4281/4301 output stage can drive an 8ohm load @ 60degree phase angle to 400W if Tc<=50degC and we use the full 100ms SOA.
It will also drive 28.2Apk, 73.5Vpk into 2r6 within the Tc=50degC DC SOA.
A superb result.
I guess it would need 88Vdc on the supply rail from 750VA transformer with 50mF of smoothing. This will fall to about 84Vdc under full load testing.
Re=0r33 and Vre=25mV (~optimum ClassAB) gives output dissipation of ~78W (=a very big or fanned heatsink to keep Tc<=50degC.)
Maximum ClassA current ~900mApk giving 3.2W of ClassA, or about -21dB ref max power.
I have not checked this Re=0r33 for compliance with Bob Cordell's BJT stability test. Re might have to be a little higher for supply rails at this much voltage.
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I received my boards today. Very nice. I have one question. Looking at this figure, am I correct in which is T1 and T13?
An externally hosted image should be here but it was not working when we last tested it.
Tad - I got my boards today and I could not be happier with the end product.
Thanks a lot to you and Jens for making this project possible for all of us.
Cheers!
Wow, I built my Leach Double-Barreled amp in the 80's and I have to laugh at it now! It is massive TO-3 output transistors everywhere and Wakefield monster heatsinks sure look frankenstein compared to this elegant PCB design. The good news is this amp is outstanding and still in service today.
Andrew,
Could you please explain to me why the 4281 output transistor would provide more output. Also, If the power supply was upped to 1.5kw would the rails still sag as much. I know that regulated or separate frontend supply helps with overall output and would likely use this type of frontend on this amp.
So it would seem to successfully achieve in excess of 400watts/8ohms I would need 9 pairs of outputs. I could easily remove the last 3 outputs from 2 boards and connect them in to the 6 pair pcb's. This is something I have been looking at. The traces line up very nicely and would come together in a neat layout. That re thing could pose a problem.
Having a plethora of 60-100 watt amps I have been wanting to build a really monster unit. For no other reason than to just build it. More parts, more metal, more wire, more everything --- isn't that what being able to DIY is about. It is like quantum horsepower no one really needs it they just want it. And DIY audio is safer and cheaper than DIY monster automobiles.
My wife does not understand this, She is always saying don't you already have two of those. No, This one is slightly different. Go figure.
Tad
Could you please explain to me why the 4281 output transistor would provide more output. Also, If the power supply was upped to 1.5kw would the rails still sag as much. I know that regulated or separate frontend supply helps with overall output and would likely use this type of frontend on this amp.
So it would seem to successfully achieve in excess of 400watts/8ohms I would need 9 pairs of outputs. I could easily remove the last 3 outputs from 2 boards and connect them in to the 6 pair pcb's. This is something I have been looking at. The traces line up very nicely and would come together in a neat layout. That re thing could pose a problem.
Having a plethora of 60-100 watt amps I have been wanting to build a really monster unit. For no other reason than to just build it. More parts, more metal, more wire, more everything --- isn't that what being able to DIY is about. It is like quantum horsepower no one really needs it they just want it. And DIY audio is safer and cheaper than DIY monster automobiles.
My wife does not understand this, She is always saying don't you already have two of those. No, This one is slightly different. Go figure.
Tad
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