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
mlloyd1
edit: ok, i just found the patent number:
United States Patent 4220817 http://www.freepatentsonline.com/4220817.html
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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.
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.
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....
Thanks to everyone for your great efforts.
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....
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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Great!! Houston, we have ignition!!
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
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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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.
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.
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
Member
Joined 2009
Paid Member
I don't believe this project can bear the complexity of multiple boards - I'm prepared to stock and pass on boards in North America (EU too if nobody there to pick up the honour) and therefore minimize shipping costs for everyone - but I don't want to have to sort out multiple options
For small runs, the set up charges usually dominate the costs. You have more files to generate and check. More boards to mount onto the chasis. Connectors are potential points of failure.
One board is my preference.
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Joined 2009
Paid Member
I agree with Gareth. It should be one board, double sided only if necessary, all options on the one board. I have decided to go single rail, with regulator, no chokes to save space and weight, and virtual earth to scotch hum, which is a major concern in this project.
Tone controls with IC buffer, defeat switch, DC coupled tone control to amp, switchable crossfeed and output series resistor. Target is 12Vpp output, around 9mW into 2K phones, and much more into 24R. Amp remains as discussed, diode biased, Class A at low levels, shifting to AB at higher levels. This will be a very good headphone amp, one of the best around, should take some beating.
We are very fortunate having the expertise of Nico and Gareth, and I thank them for their valued input.
Thank you all for chiming in to offer support. Collaborative design must be properly communicated to all players, and I appreciate your interest.
Gareth, I grew up on a farm. All I ever ate was mutton, I grew tired of it. I married a Javanese lady and now I eat mostly Asian food, which is very healthy and wards off heart disease..... in the west we all eat too much red meat.
Cheers,
Hugh
Tone controls with IC buffer, defeat switch, DC coupled tone control to amp, switchable crossfeed and output series resistor. Target is 12Vpp output, around 9mW into 2K phones, and much more into 24R. Amp remains as discussed, diode biased, Class A at low levels, shifting to AB at higher levels. This will be a very good headphone amp, one of the best around, should take some beating.
We are very fortunate having the expertise of Nico and Gareth, and I thank them for their valued input.
Thank you all for chiming in to offer support. Collaborative design must be properly communicated to all players, and I appreciate your interest.
Gareth, I grew up on a farm. All I ever ate was mutton, I grew tired of it. I married a Javanese lady and now I eat mostly Asian food, which is very healthy and wards off heart disease..... in the west we all eat too much red meat.
Cheers,
Hugh
Member
Joined 2009
Paid Member
I think I can answer this, the new design is calling for a 10 ohm output resistor and a 120 ohm resistor switchable for different impedance headphones. The 120 ohm should work well for the lower impedance headphones like your ATH-AD700 and the 10 ohm resistor mates up for higher impedance HP's like the Sennheisers or anything with an impedance greater than 250 ohms.
YES, definitely count me in for a board, absolutely...
Stan
Not wishing to belabor a point or offend our NZ mates, but the sheep 'entry' reminds me of the following joke which only makes sense if you can pick the difference between Aussie and Kiwi accents.......
An Australian is driving through New Zealand on holiday when he comes
across a local 'enjoying' a sheep in a paddock.
The Aussie yells "Hey mate, we shears our sheep in Australia!"
The Kiwi replies "No worries mate, but in New Zealand we don't share our sheep with anybody"
Just joking......I don't share my sheep either
An Australian is driving through New Zealand on holiday when he comes
across a local 'enjoying' a sheep in a paddock.
The Aussie yells "Hey mate, we shears our sheep in Australia!"
The Kiwi replies "No worries mate, but in New Zealand we don't share our sheep with anybody"
Just joking......I don't share my sheep either