N-channel amp.

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Joined 2002
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I'm in the middle of a N-channel project (4 x), (Aussieamps)
-and need to source the degenerative resistors (0R33-5W).

Can anybody please suggest the quality for these,
soundvise, and the source (link please).

Should I use metal-film / wire-wound / in alu-housing / ???
Would the different resistor-types have a "sonic signature"?

Arne K
Joined 2002
Paid Member
More Q...

I have searched thru all forums, and printed most about this amp,
And it only leaves me more confused.
I have tried to e-mail Mr. Holton, but some mail buonces,
and I have not managed to get a reply. (Holiday/Travel???).

Quote from e-mail:


I have been assembling the N-channel boards,
and I have a few questions:
(Comparing w. shematics, March-2001)

On the PCB: (dated Jan2001), I cannot find marking/holes
for more than 2 x Zener-diodes.

And marking/holes for C5-470pF is missing.

- marking/holes for C1 and E1 (470nF/470uF) is missing.

- marking/holes for E6 (10uF) is missing.

A 47uF is indicated on PCB but not on Bill of Material, which also has other errors...?

Please tell me where these (on PCB) missing components are supposed to be
mounted, (a drawing/picture would be great), and if there are other errors I should be aware of.

I would also like to see a picture of the PCB with reference to component no. instead of value, as I find it much easier to find the part compared to schematics.


Arne Karlsen


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If you use wirewounds, make sure they are the non-inductive type. Some of those metal clad ones come in both types, i.e. you can specify which one you want. Some amplifiers will oscillate if the source resistor is inductive, the resistance wire inside them is wound up like a coil.

Have you tried searching on this Forum. I have posted quite a bit about this amplifier. I have working modules. I used 3 x 1 Ohm 1 watt resistors for the output stage. This amp simply does NOT oscillate. Perhaps, it is because I used my own PCB design. I repeat, search the Forum.

Previously I had posted a photograph of a fully populated board.

The sound quality of this amp is excellent. I am investigating placing a buffer stage before the driver mosfet for even better resolution.
Joined 2002
Paid Member
I think it's sorted now...

Hi, all...thanx

I did get an answer from Mr. Holton, and I think I'll manage to
sort it out.

Yes, I have read a lot of old treads, and some of the same issues
was mentioned, but not fully explained.

I really want this amplifier to be GREAT, and will spend money
(whitin reason) on those parts that have most sonical influence.
And I'm building it as a balanced amp. with 4 boards for 2 channels.

Arne K
Hi All

Whether you use metal film, wire wound or Carbon film, makes no difference to the objective performance of the n-channel amplifier.
It will not oscillate.
However Carbon film or Metal film if available could help the subjective performance.

Nice to see they is quite a few working n-channels out there.
I for one use mine everyday. I love the sound of Asymmetrical o/p stages.

If you have any questions, you can get me via this forum.


Anthony Holton

For bridging, I would just insert 470 Ohm resistor at the node of Q2,R24 and R27 in series with a 2.2uf cap and use this as the inverting i/p on one amplifier module only, then ground the i/p of R22 1k Ohm to signal ground, leaving out C3 2.2uf cap
It would also be a good idea to remove R27 and E1,C1 on this module.
The other module is used as normal, but the o/p's of each amplifier are of cause connected across the 8 Ohm load.
The schematics can be found at this link below.


Anthony Holton
i wonder how my n-channel will do powering 2 10" i also wonder if i should put the subs into a config to make it 8 or 4 ohms anthony said that the amp has no problem powering 4 ohms but i dunno if that is a good idea.. ill be building one more of these when i get some cash to send to get another board i will since i doubbled the parts for the first now i have enought to build another..
Greetings Eric

I haven't ever loaded the N-channel amplifier to 2 Ohms, However with the right number of O/P devices it could be achieved. But the Phase Splitter driver stage does have its limitations on how many it can drive. I would suggest no more than 16 devices in the O/P stage.
Advanced Power Technology do make some very interesting Power MOSFET devices, which are made for Linear operation and they would work very well in this design. Maximum case dissipation @25 degress C of 500 watts per device and a minimum of 325 watts @60 degress C.
Gate C of around 7000pf though, Ouch!:D

The sound of the n-channel, mmmh... Well its midrange or its ability to reproduce the Human voice would be the best I have heard from any transistor amplifier I have heard. Very very smooth.... Bass is tight and very musical. The High end could be improved, but it holds it own quite well.
I guess the best way to express how its sounds is, its very very detailed in the sound stage. Its not very hard to place instruments in space at all and even at high power levels it doesn't hurt your ears. In fact you don't realise how loud it is until you try to talk to someone next to you...

I hope this not so good explaination on how it sounds, gives you some idea. Perhaps you should just build one, I can say you will not be dissappointed.


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