Topic: another DIY preamp and some links

[kuuan]

Built another preamp, see circuit: http://sound.westhost.com/project13.htm

I made the figure 2 modified version for 12 Volt, point to point soldering, fit it into a small box and power it with an 'external' 9 Volt battery, see below.
OK, it is not a beauty, I had bought cheap parts in a local shop in Thailand, but it works that well that I plan on building one more once I find a nice metal box. It made lots of fun to build and really is very noise free.

Of course I made two circuits to have stereo and added a 9 Volt plug-in power supply. I simply terminated it with two stereo mini females, one for Mic-in, one for 'out', one power switch, one pot for gain control and one switch to turn on/off mic in power supply ( as the AT822 does not, but the Giant Squids and the coming CMC4s want the 9 Volts )
 
With the AT822 no noise at all noticable, but with the Giant Squids there is some noise.


However I wonder if I had better changed some values of resistors to optimize it for 9 Volts, but I do not know how to calculate them. For the mic-in power I used 6,8 kOhm Res. and 22uF Caps and though it works I am not sure if their value could better be changed.
Anybody here who can answer this questions?
I asked them here: http://sound.westhost.com/phpBB2/viewtopic.php?t=1086 ( answer 3, username kuuan ) but there are no answers yet.

If you only consider ballanced see:
http://sound.westhost.com/project66.htm
a simple unballanced to ballanced solution:
http://www.fivefish.net/diy/balanced2/default.htm resp. http://www.fivefish.net/diy/balanced/default.htm
to understand ballanced: http://www.tangible-technology.com/power/Phantom_Power_connect.html

mixers:
http://www.aaroncake.net/circuits/mixer2.htm
http://home.maine.rr.com/randylinscott/may20.htm
http://sound.westhost.com/project94.htm ( this one I really would like to build, but have many questions - which I posted at the forum of that site in section 'preamp', but no replies yet - somebody here will check it out? )

linkpools:
http://www.izatech.ro/linkuriaudio.htm
http://www.epanorama.net/




http://

[celticrogues]

Cool stuff!
Hof hard was this to build?
I am relatively new to DIY, but have built a couple of mics and was thinking about getting into some preamps next. Thanks!
-Mike

[kuuan]

I found it very easy to build, I even had much fun building it. However some previous experience with soldering electronic parts could be essential. I really recommend making it yourself as it is a lot of fun and doesn't cost much.

I had bought all parts to build one more but this time inside a metal box, and I just arrived in Japan where I know a shop where I can get nice metal boxes. In case I will make that other one I could sell the first one which can be seen on the foto, if interested you could make me an offer.
BTW I also had found a very nice product, an Audio Technica Mic Preamp which is only sold in Japan, see: http://www.audio-technica.co.jp/products/dj-plus/at-ma2.html
I could find the time to buy one and send it to anybody who want one and is willing to pay a small premium for my efforts, e.g. 80 USD plus shipping. For this prize I'd include an external 9 Volt battery box with the right connector soldered to it to power the unit.

[Nick's Picks]

while this project is interesting, I find this more interesting:
"Everything you do through out the day, every thought and every feeling leaves an impression stored inside you.
These impressions create tendencies, their sum total is your character."

[kuuan]

while this project is interesting, I find this more interesting:
"Everything you do through out the day, every thought and every feeling leaves an impression stored inside you.
These impressions create tendencies, their sum total is your character."

Hi Nick,

I am happy you like that quote.

It is a personal abbreviation of contents taken from a small booklet called:
'The Probem is You, the Solution is You' by Swami Dayanand Saraswati. ( A foremost teacher and expounder of 'Vedanta', the essential teaching of the ancient scriptures of the Vedas of India )

The booklet can be ordered for 2 USD here: http://www.arshavidya.org/ at the bookstore section.
Get a good introductory article online clicking 'readings' on the main page.

I hope nobody minds this post for being off topic.
In case the admin. decides to delete this post please be so kind and send it as a PM to Nick first.
thank you.

and: disclaimer: I am not affiliated to the organisation mentioned and personally believe that there is too much sold as the only truth or in other way exclusive to the interested in the spiritual.

[poorlyconditioned]

I found it very easy to build, I even had much fun building it. However some previous experience with soldering electronic parts could be essential. I really recommend making it yourself as it is a lot of fun and doesn't cost much.

I had bought all parts to build one more but this time inside a metal box, and I just arrived in Japan where I know a shop where I can get nice metal boxes. In case I will make that other one I could sell the first one which can be seen on the foto, if interested you could make me an offer.
BTW I also had found a very nice product, an Audio Technica Mic Preamp which is only sold in Japan, see: http://www.audio-technica.co.jp/products/dj-plus/at-ma2.html
I could find the time to buy one and send it to anybody who want one and is willing to pay a small premium for my efforts, e.g. 80 USD plus shipping. For this prize I'd include an external 9 Volt battery box with the right connector soldered to it to power the unit.

Did you buy that preamp?  Can you take a picture of the insides?  I might be interested in getting one.  Please PM me a price *without* the battery box to power it (I would do this myself).

Thanks!
  Richard

[Chuck]

Yeah, that pre-amp interests me too. Like Richard, I'm not interested in the battery box option either.

[kuuan]

Richard and Chuck,

Are you interested in the AT-AM2
or the DIY preamp I had mentioned in the beginning of this thread?

If it is the AT-AM2:

• I have one which I could send you right now from Japan, but it would come without the 110 Volt DC adapter
• I could send you 'mine' including the 110 DC adapter after about 10 days from Austria ( where I had left the DC adapter ) note: it as as much as new, bought abt. 3 months ago, but the paint of the screws has come off somewhat as I had opened the box to have a look inside
• Or I could go to downtown Osaka tomorrow to get two new AT-AM2s and send them to you directly from Japan ( I will go downtown tomorrow anyway to get some electronic parts, and if it was getting two AT-AM2 it would be worthwhile the extra detour I'd have to take )

here is a Pic of the AT-AM2's inside:
http://i39.photobucket.com/albums/e190/kuuan/IMGA2558.jpg

If it is the DIY preamp:
You could get the one in the foto http://i39.photobucket.com/albums/e190/kuuan/IMGA2584.jpg which consists of two of those: http://sound.westhost.com/project13.htm circuits with an added 9 Volt Mic-in powering function which can be switched on/off
or I could make a new one considering personal preferances of it's finishing ( connectores etc. )

Please let me know soon ( max. 20 hours from now ) as tomorrow  is my last chance to go downtown Osaka before leaving Japan to either get the AT-AM2 or the parts to make the DIY preamp.

[Chuck]

Richard and Chuck,

Are you interested in the AT-AM2
or the DIY preamp I had mentioned in the beginning of this thread?

If it is the AT-AM2:

• I have one which I could send you right now from Japan, but it would come without the 110 Volt DC adapter
• I could send you 'mine' including the 110 DC adapter after about 10 days from Austria ( where I had left the DC adapter ) note: it as as much as new, bought abt. 3 months ago, but the paint of the screws has come off somewhat as I had opened the box to have a look inside
• Or I could go to downtown Osaka tomorrow to get two new AT-AM2s and send them to you directly from Japan ( I will go downtown tomorrow anyway to get some electronic parts, and if it was getting two AT-AM2 it would be worthwhile the extra detour I'd have to take )

here is a Pic of the AT-AM2's inside:
http://i39.photobucket.com/albums/e190/kuuan/IMGA2558.jpg

If it is the DIY preamp:
You could get the one in the foto http://i39.photobucket.com/albums/e190/kuuan/IMGA2584.jpg which consists of two of those: http://sound.westhost.com/project13.htm circuits with an added 9 Volt Mic-in powering function which can be switched on/off
or I could make a new one considering personal preferances of it's finishing ( connectores etc. )

Please let me know soon ( max. 20 hours from now ) as tomorrow  is my last chance to go downtown Osaka before leaving Japan to either get the AT-AM2 or the parts to make the DIY preamp.

kuuan:

Thanks for taking the photo. After seeing the interior, I'm no longer interested in that pre-amp.

Chuck

[poorlyconditioned]

Richard and Chuck,

Are you interested in the AT-AM2
or the DIY preamp I had mentioned in the beginning of this thread?

If it is the AT-AM2:

• I have one which I could send you right now from Japan, but it would come without the 110 Volt DC adapter
• I could send you 'mine' including the 110 DC adapter after about 10 days from Austria ( where I had left the DC adapter ) note: it as as much as new, bought abt. 3 months ago, but the paint of the screws has come off somewhat as I had opened the box to have a look inside
• Or I could go to downtown Osaka tomorrow to get two new AT-AM2s and send them to you directly from Japan ( I will go downtown tomorrow anyway to get some electronic parts, and if it was getting two AT-AM2 it would be worthwhile the extra detour I'd have to take )

here is a Pic of the AT-AM2's inside:
http://i39.photobucket.com/albums/e190/kuuan/IMGA2558.jpg

If it is the DIY preamp:
You could get the one in the foto http://i39.photobucket.com/albums/e190/kuuan/IMGA2584.jpg which consists of two of those: http://sound.westhost.com/project13.htm circuits with an added 9 Volt Mic-in powering function which can be switched on/off
or I could make a new one considering personal preferances of it's finishing ( connectores etc. )

Please let me know soon ( max. 20 hours from now ) as tomorrow  is my last chance to go downtown Osaka before leaving Japan to either get the AT-AM2 or the parts to make the DIY preamp.

Thanks for the generous offers, but I'm not interested either.

But, if you want to upgrade this yourself, you could add your own opamp there.  One obvious choice would be something like OPA2228.  This will improve the sound quite a bit.  There are lots of other opamps to try if you can't get that one.  Even the NJM2068 would be an improvement over what is in there now.

Why don't you put a socket in that sucker and try out some different opamps?

Thanks again!
  Richard

[kuuan]

Chuck, as you could tell only from the foto this is not a high quality but a simple preamp.

However it is of a sturdy built and has some nice features like it's on/off switch of mic-plug-in power, mono/stereo switch, gain selector and even a clipping light. As it is quite small, operates with a single 9 Volt battery and certainly is way better than the built-in preamp of e.g. the iRivers it does make a quite useful tool for somebody who owns an iRiver and wants a cheap, very portable and reliable preamp solution which also powers mics! - like the SP-CMCs. ( a battery box only costs not much less $$ )

Richard, thank's a lot for the suggestions. I shall try to get the opamp(s) you mentioned just for the sake of experimenting and playing.

I slightly prefer my selfmade preamp mentioned in the beginning of this thread which does without any opamp for being even smaller and because it's sound is cleaner, it's self sound almost zero.

[Church-Audio]

Chuck, as you could tell only from the foto this is not a high quality but a simple preamp.

However it is of a sturdy built and has some nice features like it's on/off switch of mic-plug-in power, mono/stereo switch, gain selector and even a clipping light. As it is quite small, operates with a single 9 Volt battery and certainly is way better than the built-in preamp of e.g. the iRivers it does make a quite useful tool for somebody who owns an iRiver and wants a cheap, very portable and reliable preamp solution which also powers mics! - like the SP-CMCs. ( even a battery box alone usually sells for more $$ )

Richard, thank's a lot for the suggestions. I shall try to get the opamp(s) you mentioned just for the sake of experimenting and playing.

I slightly prefer my selfmade preamp mentioned in the beginning of this thread which does without any opamp for being even smaller and because it's sound is cleaner, it's self sound almost zero.

Try the OPA2227A as well thats a nice sounding opamp, I use this one for some of my preamps.

[kuuan]

thank's a lot everybody, also Chris for your additional opamp suggestion.

How would you Guys, who can read electronic circuits and have a lot of experience, qualify the DIY preamp?
Certainly also nothing for pros, but what's your take?
Maybe you even could tell me how to optimize it for the operation of 9 Volts? ( it was built for 12 Volts )
and if the 6,8 kOhm Res. and 22uF Caps I chose for the Mic-plug-in power are correctly chosen?

- and I did have some problem with the gain control and had changed it's design to make it work -
if someone wants to help I'll elaborate.

[Church-Audio]

thank's a lot everybody, also Chris for your additional opamp suggestion.

How would you Guys, who can read electronic circuits and have a lot of experience, qualify the DIY preamp?
Certainly also nothing for pros, but what's your take?
Maybe you even could tell me how to optimize it for the operation of 9 Volts? ( it was built for 12 Volts )
and if the 6,8 kOhm Res. and 22uF Caps I chose for the Mic-plug-in power are correctly chosen?

- and I did have some problem with the gain control and had changed it's design to make it work -
if someone wants to help I'll elaborate.

I like 10k for bias and 10uf for decoupling caps on a preamps front end. I don't think you need to go to 22uf I think this circuit will run on 9 volt no problem. As far as telling what its going to sound like its very hard I have seen the most stupid schematics for a preamp design sound great. So you can not tell by looking I don't like all the electrolytic caps in the circuit so it would not be a design I would consider just for that reason. That is not to say its a bad preamp. Never judge a preamp by its schematic, or cover listen first judge second.

[kuuan]

thank's a lot Chris.

I don't think you need to go to 22uf

better to substitute them with 10 uF?

I don't like all the electrolytic caps in the circuit

could I substitute them with ceramic caps and would that improove the it's performance?

about the gain selector problem I had:
In the circuit drawing it shows the symbol of a simple resistor but as it should be adjustable I used a potentiometer instead. I connected line from between R1 and C1 to the Terminal 3 of the pot., terminal 2 went to the output, and I connected terminal 1 to ground. However it did not work propperly, therefore I tried all other possible connections but it never worked.
In the end I simply connected the 'output' of the circuit to the terminal 3 of the pot and terminal 2 became the new 'output'. ( and terminal 1 I connected to ground, though leaving it without connection also worked )

Why would the pot with the original wiring not work? or more imprtantly, is my 'work around' OK?

[Church-Audio]

thank's a lot Chris.

I don't think you need to go to 22uf

better to substitute them with 10 uF?

I don't like all the electrolytic caps in the circuit

could I substitute them with ceramic caps and would that improove the it's performance?

about the gain selector problem I had:
In the circuit drawing it shows the symbol of a simple resistor but as it should be adjustable I used a potentiometer instead. I connected line from between R1 and C1 to the Terminal 3 of the pot., terminal 2 went to the output, and I connected terminal 1 to ground. However it did not work propperly, therefore I tried all other possible connections but it never worked.
In the end I simply connected the 'output' of the circuit to the terminal 3 of the pot and terminal 2 became the new 'output'. ( and terminal 1 I connected to ground, though leaving it without connection also worked )

Why would the pot with the original wiring not work? or more imprtantly, is my 'work around' OK?

Not ceramic ceramic is for transistor radios not Audio polypropylene or metal film or stacked metal film but never ceramic. I may use monolithic in some circuits, but that is as low as I go. I also use Tantalum * I know some people think they suck* but I have seen tantalum in many top end preamps like Neve, so they must be good for something.  As far as the gain pot problem it sounds like you had the pot in backwards, term 1 should be N/C, term 2 should be going to r1 and term 3 should be going to c3. This sets the feedback loop resistor, I would also think that no connection would be unity gain try that and see if the circuit design is good it should be very stable with out a feedback loop resistor. You could use a rotary switch with resistors to set gain, use metal film and the more positions the better.

I like 0.5 db increments anything more is no good, many preamp makers use 1db I think that's not enough .5 db is much better. These rotary switches can be cheap in the surplus electronics market. I don't really like pots in the feedback loop unless they are very high quality, because more often then not they introduce more noise. This preamp circuit that your looking at is very simple. It should be a a breeze to build.

[kuuan]

thank's once again Chris.

decided it was time to learn about capacitors and found this site good:
http://www.uoguelph.ca/~antoon/gadgets/caps/caps.html
( more good info on this site, e.g. about opamps: http://www.uoguelph.ca/~antoon/gadgets/741/741.html,
resp. links to circuits on the main page: http://www.uoguelph.ca/~antoon/circ/circuits.htm )

term 1 should be N/C, term 2 should be going to r1 and term 3 should be going to c3.

thank's for looking that deeply into the circuit. I shall try this, but I with a new preamp that I am going to build, I do not want to open the first one I had succeeded fitting into this tiny box and which is working fine.

I don't really like pots in the feedback loop unless they are very high quality, because more often then not they introduce more noise. You could use a rotary switch with resistors to set gain, use metal film and the more positions the better. I like 0.5 db increments anything more is no good

Will try to find a rotary switch with 0.5 db increments.
Metal film for what? Does this refer to the resistors, or is there a metal film rotary switch?

This preamp circuit that your looking at is very simple. It should be a a breeze to build.

Well, I already had built one, you can see it here: http://i39.photobucket.com/albums/e190/kuuan/IMGA2584.jpg
however I used cheap materials bought in a local store in Thailand, but still I really like it's performance!
I shall build one more with better materials and incorporatring your suggestions, specially the rotary switch. ( those cheap pots I had bought sucked big time anyway, I had to buy 3 until I had gotten one which was not noisy when turning )

[Church-Audio]

thank's once again Chris.

decided it was time to learn about capacitors and found this site good:
http://www.uoguelph.ca/~antoon/gadgets/caps/caps.html
( more good info on this site, e.g. about opamps: http://www.uoguelph.ca/~antoon/gadgets/741/741.html,
resp. links to circuits on the main page: http://www.uoguelph.ca/~antoon/circ/circuits.htm )

term 1 should be N/C, term 2 should be going to r1 and term 3 should be going to c3.

thank's for looking that deeply into the circuit. I shall try this, but I with a new preamp that I am going to build, I do not want to open the first one I had succeeded fitting into this tiny box and which is working fine.

I don't really like pots in the feedback loop unless they are very high quality, because more often then not they introduce more noise. You could use a rotary switch with resistors to set gain, use metal film and the more positions the better. I like 0.5 db increments anything more is no good

Will try to find a rotary switch with 0.5 db increments.
Metal film for what? Does this refer to the resistors, or is there a metal film rotary switch?

This preamp circuit that your looking at is very simple. It should be a a breeze to build.

Well, I already had built one, you can see it here: http://i39.photobucket.com/albums/e190/kuuan/IMGA2584.jpg
however I used cheap materials bought in a local store in Thailand, but still I really like it's performance!
I shall build one more with better materials and incorporatring your suggestions, specially the rotary switch. ( those cheap pots I had bought sucked big time anyway, I had to buy 3 until I had gotten one which was not noisy when turning )

Metal film 1% or better 1 watt resistors even though you dont need 1 watt i like the fact that they will not break down over time.

[kuuan]

...but have built a couple of mics and was thinking about getting into some preamps next. Thanks! -Mike

Mike I am VERY interested in building mics!
Can you help me? How to do that? - Any advice, or introductory site you can point at?
( e.g. I had bought this very cheap Panasonic copy mic in China recently. It's a shotgun with a very long body. I'd love to use this body but repalce it's capsule and fet/amp but do not know WHERE should get WHICH parts for this job )

But, if you want to upgrade this yourself, you could add your own opamp there.  One obvious choice would be something like OPA2228.  This will improve the sound quite a bit.  There are lots of other opamps to try if you can't get that one.  Even the NJM2068 would be an improvement over what is in there now.

Try the OPA2227A as well thats a nice sounding opamp, I use this one for some of my preamps.

They did not have any of the three mentioned at the local store, bought a socalled OPA2604AP instead. Anybody knows about this one?

Metal film 1% or better 1 watt resistors even though you dont need 1 watt i like the fact that they will not break down over time.

thank's again for your valuable suggestions. The store did not have a rotary switch as you described, and I opted for <1% resistors, the 1 Watt res. looked too big for me as I want the amp to be small.

[kuuan]

I was very happy with this preamp because it is 'quiet' but I have been hoping for more gain.
Just now, very much delayed because of delivery problems, I received th SP-CMC4s I had bought at the yard sale a while ago.
And surprise, surprise: The level with them is much higher then with my AT822, no need for more gain, I am very happy with this preamp! ( talking the DIY preamp, not the AT )

[Church-Audio]

I was very happy with this preamp because it is 'quiet' but I have been hoping for more gain.
Just now, very much delayed because of delivery problems, I received th SP-CMC4s I had bought at the yard sale a while ago.
And surprise, surprise: The level with them is much higher then with my AT822, no need for more gain, I am very happy with this preamp!

Cool I will have to check it out you should put in a gain pot instead of the feedback resistor and see how that works out so you can change the gain of the feedback loop.

Chris Church

[kuuan]

Not ceramic ceramic is for transistor radios not Audio polypropylene or metal film or stacked metal film but never ceramic. I may use monolithic in some circuits, but that is as low as I go. I also use Tantalum...

so those are all different types of caps? and you recommend audio polypropylene or metal film or stacked metal film? or monolytic and tantalum?

... you should put in a gain pot instead of the feedback resistor and see how that works out so you can change the gain of the feedback loop.

You could use a rotary switch with resistors to set gain, use metal film and the more positions the better.

I would also think that no connection would be unity gain try that and see if the circuit design is good it should be very stable with out a feedback loop resistor.

Your truth finally dawned on me. time to get a metal film rotary switch ( if I can ) and above all connect it correctly.
Or could no connecting = unity, be my best option?


edit:
no metal film rotary switch to be found.

how about what they call 'Drahtpotentiometer' in german, translated 'wire-potentiometer' with 10 steps branded 'Vishay' which only can be had in mono.
 
the best stereo pot I have found is branded 'Alps', model number: RK27112 50KBX2CC

how about this:
substitute the 50k pot with a 470k resistor, and a 10k log pot in the out section ( somebody had suggested this )

[kuuan]

Cool I will have to check it out you should put in a gain pot instead of the feedback resistor and see how that works out so you can change the gain of the feedback loop.

Chris Church

Finnaly put the gain pot in correctly as you had explained. I can't make out any change of performance though.

Questions:
1: more gain:

• Can this circuit be modified to add more gain? another transistor gain loop?
  
• Or could I even simply put two of this circuit in series? 

2: Now I want to build a mic mixer:

• Can anyone recommend a circuit?
• If going mic > DIY preamp > line mixer could I also take a line mixer? E.g the one Chuck is trying to build, see: http://taperssection.com/index.php?topic=75397.0;all, - drawing attached.