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Old 15th October 2009, 09:39 PM   #521
mlloyd1 is offline mlloyd1  United States
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Aspen Headphone Amp
btw, if you're still looking at tone controls and you're looking at baxandall type (negative feedback), you could do worse than the clever approach used by tom holman in the apt 1 preamp years ago. basically, he added a unity gain buffer to eliminate interaction with the midrange.

mlloyd1

edit: ok, i just found the patent number:
United States Patent 4220817 http://www.freepatentsonline.com/4220817.html

Last edited by mlloyd1; 15th October 2009 at 10:04 PM. Reason: added link
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Old 15th October 2009, 09:59 PM   #522
Nico Ras is offline Nico Ras  South Africa
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Sheldon,

that is not a thing to say: "if you dare" I was not aware that Carlos has to check something before it is labled acceptable.
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Old 15th October 2009, 10:15 PM   #523
Nico Ras is offline Nico Ras  South Africa
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Every designer, are unique and each one will create a product that has some character of what the he/she perceives as being good and that differentiates one good product from another good product.

Electronics is an exact science. If you cannot produce a stable design then choose another career. Two chefs can cook the same meal consistently but it tastes different.

The fact that Hugh uses a little feed-back from the VAS is one of such things, or the particular ratio he uses for the bootstrap resistors, etc.

If all was equal there would be no artists, it would be paint by numbers.
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Old 15th October 2009, 10:25 PM   #524
kimbo is offline kimbo  Australia
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Default Another Lurker .....

I'm also lurking so I'd better put my hand up too. I have been following this thread with great interest. I'm afraid I'm not knowledgeable enough to make a contribution, but it is very instructive following this wonderful collaborative effort. I'm learning heaps and I'm looking forward to building once the design is finallised.

Just a couple of minor points....

I for one am not interested in tone controls....however I'm sure I could bypass this in the circuit (or add a defeat switch?)

And Nico....
Quote:
Originally Posted by Nico Ras View Post
One final question. This is regarding the headphone impedance, I know of some having a low impedance around 32 ohms, most decent headphones have a much higher impedance around 200 - 500 ohms, why did we select 23 Ohms and why a 1000 uF pass capacitor, anyone though about that? As it stands the frequency is 7Hz, anybody listen to this?
My headphones are AudioTechnica ATH-AD700. Not exactly top shelf, but about as good as I can afford and I'm pretty happy with them. They are 32 ohms and I'm sure there are others out there with something similar.

Thanks to everyone for your great efforts.
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Old 15th October 2009, 10:28 PM   #525
gaetan8888 is offline gaetan8888  Canada
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Originally Posted by AKSA View Post
Folks,

Very quiet here now.

Have people lost interest, or are you merely waiting?

Let's have a show of hands to confirm one way or the other.

There remains a lot of work to be done here, but I'm cool if there is no interest, I can halt the project any time. Please let me know what you want.

Cheers,

Hugh
Hello Hugh

I was waiting.

I am interested in your tone controls.

Thank

Bye

Gaetan

Last edited by gaetan8888; 15th October 2009 at 10:30 PM.
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Old 15th October 2009, 10:32 PM   #526
AKSA is offline AKSA  Australia
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Great!! Houston, we have ignition!!

Quote:
But I'll buy a board for you to send to Carlos, if you dare.
Now, that really made me laugh, Sheldon!! I like a little humor.......

BTW, we will be adding a defeat switch. One of the downsides of Baxandall tone controls is that even set flat, they still have dips and peaks, around 4dB of them, but sufficient to notice. A defeat (even my old car sound system has Rock, Classical, Jazz and Defeat!) is the only way to return a truly flat response.

Thanks to all who are responding...... more design work to follow.

Hugh
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Last edited by AKSA; 15th October 2009 at 10:34 PM.
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Old 15th October 2009, 10:50 PM   #527
Nico Ras is offline Nico Ras  South Africa
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Hugh/Guys,

from the PCB design I would like to highlight some things and ask some questions.

Should the amplifier not rather be modular, in other words I design it so that there are ribbon connectors plug-in from one board to another, thus make each a separate board for example, tone control, amp, crossfeed, psu, etc.

What is the down side. PCB manufacturers charge a set-up cost for every type of board, making a single board with everything on results in a single set-up cost which is a standard cost.

However, the cost of the board is related to real estate and number number of through hole plates. Thus the bigger the board the more expensive.

Smaller boards are cheaper (and the chances of being single sided is better and even cheaper still) but since some people may select not to buy the tone control board or whatever would drive each small board cost up slightly as fewer divide into set-up costs.

How would you guys want me to handle the PCB design.
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Old 15th October 2009, 10:59 PM   #528
Sheldon is offline Sheldon  United States
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Quote:
Originally Posted by Nico Ras View Post
Sheldon,
that is not a thing to say: "if you dare" I was not aware that Carlos has to check something before it is labled acceptable.
I admit that it could have been taken in more than one way, but think Hugh understood my meaning. Carlos is a fan of AKSA, but, shall we say a somewhat of a wildcard? And if there is anyone more inclined than me to mess around with a perfectly good thing, it would be the X man. Who knows what he would do with it. Anyway the offer stands. .

Sheldon
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Old 15th October 2009, 11:08 PM   #529
Nico Ras is offline Nico Ras  South Africa
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I know Carlos liked AKSA 50. I was just worried that everyone does not share the same sense humor. Remeber Hugh is from Down Under.

To them shagging sheep is serious past time, but but you cant tell them that it is wrong just because you don't share the same passion.

Last edited by Nico Ras; 15th October 2009 at 11:11 PM.
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Old 15th October 2009, 11:14 PM   #530
Nico Ras is offline Nico Ras  South Africa
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I think it would be an insult to Hugh if Carlos was to share his sheep.
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