Please suggest a high rail voltage (160V) amplifier - Page 2 - diyAudio
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Old 29th April 2012, 03:48 PM   #11
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by KatieandDad View Post
Here's one.

It does use split rails again though.

http://www.elektropage.com/images/ci...r_Shematic.jpg
Thanks for the link. I like the circuit but I forget to mention that I will use N-channel device only, preferably mosfet in ISOTOP case (their relatively high Ciss makes it even more difficult to work with most circuits).
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File Type: gif isotop mosfet.GIF (62.5 KB, 179 views)
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Old 29th April 2012, 04:03 PM   #12
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Are those isotops STE47N50's ? I have twelve of those that i was planning to build a stereo amp with, i built a ugly prototype which can be seen here: NMOS amp in stereo - YouTube

The plan is to use six fets per channel, it'll need some hefty drive though, bit since this amp is not intended for hifi, i am not really worried about frequency response.

Schematic of the test amp in the video: http://i.imgur.com/z7i8h.png
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Old 29th April 2012, 05:05 PM   #13
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Use a second transformer of the same to cut the voltage in half again...
Either for the supply, or as an output transformer. Latter choice could
make an all N-CH solution easier... You are at a voltage where triodes
in the front end could also make sense.

Last edited by kenpeter; 29th April 2012 at 05:09 PM.
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Old 30th April 2012, 12:40 AM   #14
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by Tekko View Post
Are those isotops STE47N50's ?
I have at least six models. In front of me I have E110NA20. But I think I have also STE47N50.

Quote:
Originally Posted by Tekko View Post
i built a ugly prototype which can be seen here: NMOS amp in stereo - YouTube
Hi, I have downloaded the schematic the day you posted it, even if imho such topology will not give good sound. Even if these isotops have high Ciss, they can still sound good. Of course it needs relatively high current.

Quote:
Originally Posted by Tekko View Post
The plan is to use six fets per channel
With around 6000pF of Ciss, I think the ISOTOP is comparable to 3 to 6 "ordinary" mosfets. So 3 pairs is a lot. One isotop is capable of very high current, so 3 pairs is feasible only if very big power is expected.
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Old 30th April 2012, 03:15 AM   #15
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by kenpeter View Post
Use a second transformer of the same to cut the voltage in half again...
Good idea. Not perfect (efficient) but if nothing else it is a solution I can use, especially when the VA rating is too low for a working amplifier circuit.

Quote:
Originally Posted by kenpeter View Post
Either for the supply, or as an output transformer. Latter choice could make an all N-CH solution easier...
This output transformer thing is new to me

Quote:
Originally Posted by kenpeter View Post
You are at a voltage where triodes
in the front end could also make sense.
Yes, TubeCad DotCom has such thing but with no gain. Actually I already have a solution but I think people might have better idea because imo this is a frequent common situation where people get in touch with step-down transformers. Well, of course not in US or Japan.
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Old 30th April 2012, 09:05 AM   #16
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The alternative is separate drivers for each output pair.

What kinda topology do you have in mind ?
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Old 30th April 2012, 11:12 AM   #17
AndrewT is offline AndrewT  Scotland
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Use 160Vdc single ended PSU. This could potentially give ~300W into 8ohms.

Build the amplifier with AC coupled input and AC coupled output.
This alone will save a lot of cost in capacitors. 200Vdc capacitors are not cheap.
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Old 30th April 2012, 11:45 AM   #18
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Something like the QSC or whoever it was topology might be worth a try, wheres the amp output is grounded and the speaker output is the center point between the two rail capacitors.

The all NMOS output as you say is not a very good topology, in fact it simulates really poorly no matter what, but some of the ppl doing mosfet amps seem to prefer NMOS output over complementary output as there is no good match between the N channel and P channel vertical mosfets.
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Old 3rd May 2012, 07:26 PM   #19
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by Tekko View Post
Something like the QSC or whoever it was topology might be worth a try, wheres the amp output is grounded and the speaker output is the center point between the two rail capacitors.

The all NMOS output as you say is not a very good topology, in fact it simulates really poorly no matter what, but some of the ppl doing mosfet amps seem to prefer NMOS output over complementary output as there is no good match between the N channel and P channel vertical mosfets.
Thanks I will check the QSC. I forget the schematics but as far as I can remember it is not applicable. I think it was the complementary type.

Quote:
Originally Posted by Tekko View Post
The all NMOS output as you say is not a very good topology, in fact it simulates really poorly no matter what, but some of the ppl doing mosfet amps seem to prefer NMOS output over complementary output as there is no good match between the N channel and P channel vertical mosfets.
Yes, I know. Quasi is chosen for economical reason only, not P-N matching reason. But for PA usage, the simulation performance is more than acceptable imo. Don't know with reliability as there is that trade-off.
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Old 3rd May 2012, 07:32 PM   #20
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by AndrewT View Post
Use 160Vdc single ended PSU. This could potentially give ~300W into 8ohms.

Build the amplifier with AC coupled input and AC coupled output.
This alone will save a lot of cost in capacitors. 200Vdc capacitors are not cheap.
Yes I used AC coupling (Cap at output) as there is no other (better) options, right? I don't have issues with caps availability tho.
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