[DESIGN] Original(?) mike-amp design

[gyraf]

[quote author="henk"](..) Further i would like to put some stuff on a server/ftp site , who knows a site where i can put things for this forum and other forums?[/quote]

We have a GroupDIY upload area:

http://groupdiy.twin-x.com/index.php

Jakob E.

 

[tk@halmi]

[quote author="Gus"]does any one know what is inside the Grace preamps?[/quote]
The INA103, but the output is taken from the Gain Drive pins as I understand. Then some video opamps, the AD844 if I recall right, are use to send a balanced signal out. It also uses stepped gain control and some nice input caps.

 

[henk]

Dear Admin

I thy to do that but could not find any upload thing , could not find a button to upload things or so.
Have asked kubi the same , he is willing to serv the things i have scanned and hope he will explain it to me.

 

[Guest]

All you do for the upload site is register, then you get the upload buttons after logging in.

 

[Kev]

[quote author="gyraf"] We have a GroupDIY upload area: [/quote]

:thumb:
at last

I hope you guys are ready for an indexing method ... cos this is gonna get big fast. ... :green:

 

[henk]

Trying to put something on in , hopefully it works.....
The first part of an nice piece of engineering from Mr Barry Porter.

 

[henk]

Have tried to get something on that server , have login done get the upload page , put in the files and press continue.

Than nothing happens , or what should happen????

 

[henk]

Dear Admin

Have tryed to put on the site but the time is to short to put a nice file on it and in these days of GigaGiga... only 2Mb??
Cant that border of 2Mb not go to 10Mb or so?? or even bigger.
Because when i put something on it , it must have a quality that i like and something that i cant read or so , you better can have files that are "big" but give you all the details you like to have , so you dont have to ???? what is there.

 

[henk]

Have send my things to KUBI on CD , hoping he show it to us.
If it it not there , just look an other time.

 

[tmbg]

Did this design ever get finished? Did it move to a thread in the drawing board?

PRR, did you abandon it due to noise issues?

I was rereading it, getting into it, and BLAMMO, it ended

 

[rafafredd]

I think PRR abandoned the idea after he found it to be not good enought. Noise problems if I recall... :?: :?:

 

[PRR]

> did you abandon it due to noise issues?

Yes. The signal-to-noise in the thread got too bad to think.

The low-gain noise isn't "bad"; just not nearly worth the insane dissipation.

I did do one more drawing that I did not post. It is right off the simulator, not a practical implementation. If you try it, do note my comments about heat and low-inductance/ohmic paths.
Image

Yes: 110mA at 48V, and 0.75Ω gain-set. This is heroic design, not good design.

There is another variant with a 22-tap output transfomer, but I can't analyze the noise, nobody could afford the winding, and I have a bad feeling it could spot-weld mike connectors.

 

[Guest]

[quote author="PRR"]
Yes: 110mA at 48V, and 0.75Ω gain-set. This is heroic design, not good design.
[/quote]
Why??? Microphone is low impedance input and
adequate amp (designed from only low noise figure view)
must have adequate many input transistor in paralel
and adequate high current dissipated by its collectors.

From other view, we use transformers only for reducing dissipated power in
input amp,
(Mainly, in the ribbons some 100 Watts, you writes it in some old thread )

I do not mean, that 100 mA consumption for preamp is much,
ic could be O.K.,
You can try genetic algorithms and design optimal input amp,
mr. KOZA, help !!!!
I mean, that current which it dissipate would be very near.

xvlk

 

[Rossi]

Hi PRR, I just dug up this thread again (which I think is one of the best ever). I have a couple of questions regarding the last version.

Q15 and Q16 are darlington transistors (right?). Are they supposed to be monolithic devices (if so, what part number?) or would you rather build them from two transistors each.

Why did you abandon current sources instead of R20 and R21?

And thanks again for this instructive lecture! :thumb: :thumb:

 

[henk]

For everyone that renember that i had the articals of Mr Barry Porter about audio is put on the server of Savefile


Part 1
WWW.savefile.com/files/7727611
/6628231
/4034619
/7922053
/6067082
/8330812

Part 2
WWW.savefile.com/files/8385440
/5472963
/5501635
/2189437

Thanks Mats that he told me to load up on this server otherwise it would still in a dark place outside this nice forum.

 

[TedF]

Looking at these sorts of threads one constantly questions what's serious and what's a wind up.
Is there really a market for a super mic preamp? And if there is, what are the parameters?
PRR started with the 48V single rail option; which must be good.
I have to be just a little cynical.... there are a handful of designers who could produce a mic pre that will do anything you can think of, perfectly. The reality is that if it ain't there in the marketplace, then there isn't the demand!

I throw down the gauntlet....
Make a good enough case for a high tech. front end... and I will produce it at a sensible price; or give a very good reason why not.
Ted Fletcher

 

[[silent:arts]]

for comercial products you are right, Ted.
but while this is DIY, we don't have to think about the market.
or am I missing something ?

 

[Guest]

Ted, let me preface this reply by stating that I am just an old fart with very limited knowledge, but I do have some, so I will desagree with your market analogy. Some good marketers can, and do create demand for products that have little practical use (mood rings, pet rocks,etc). Many telented folks make brilliant products and can't sell anything. Demand is NOT created by consumers in nearly all cases. It is in fact, the rare exception.

I am very glad you propose to make something "high tech" if someone can make a case for it. I know I sure can't. I am just now beginning to look seriously at transistors. I bet you could sell a few too, but again, I am just an old fart so I don't know how good a marketer you are, I suck at it myself. I just wanted to state my disagreement with the your premise that the market is consumer driven. A quick look at oil prices in the US will dispell that pretty quickly.

Now, back to your regularly scheduled program.

 

[bcarso]

Yeah---I don't think this forum is about markets that much, although some may get ideas and attempt to do a bit of business. I can tell though that most who comment on existing equipment, and marvel over how much money is asked, probably haven't attempted to run a manufacturing operation. They would quickly realize how much is involved besides the costed bill of materials, and as well, why people may be reluctant to purchase equipment from a small startup.

I was curious as to what was desired in a mic pre a while back, thus started a thread and got a number of items on a wish list. Paul Stamler's criteria were by far the most challenging. This might have spawned a design, and I did do some work before I started to get busy with some paying biz again, but the primary purpose was to find out what people wanted, and to that end find out if there were any design issues yet to be addressed that would be challenging.

The primary motivation is to have fun. And I have fun solving design problems.

 

[TedF]

As long as you all appreciate that this is all for fun....

Audio is not a business to make money.... If I wanted to be rich, I would have stuck to civil engineering!

But I was serious; is there a spec for a mic amp that would be an 'ultimate'? I have my own view, but I'm not set in my ways enough yet to really believe that I'm always right!

There's no intentional 'business opportunity' here.... If we come up with an interesting design, I would be delighted to share it!