Topic: need help for DIY preamp - wiring

[kuuan]

Just bought this DIY kit for a preamp ( together with a very cool case )
This is in Japan, and all instructions are in japanese which I cannot read. Maybe somebody here can help me out.

l1st attached image shows the schematics, 2nd the wiring.




I am using stereo mini for in and out. So I connected the 'grounds' and run the 'S' ( uuh, they are difficult to see, will post better fotos later. The 'S' are the conncections on the in and out which are not ground ) on the input schematics to the middle and front contact of the stereo mini.
Same I did for the 'out', grounds connected together to the ground of the stereo mini, and the connection named 'S' for left and right channels to the middle and tips of a stereo mini.

On trial I ran into a problem: only one channel is showing.

what's my mistake?

please also have a look at the 3nd and 4rd schematics:
the 3rd shows how to conect a potentiometer as gain selector. Here I am lost. The square shown to the left is the preamp, the middle the battery, but what is the big square on the right side with many words inside?



the 4th image shows two samples of two different mics connected, the first with two cables, the other with 3 cables which shows a resistor has to be added. For which kind of mic is that added resistor necessary? ( right now I am connecting an AT822, later an SP-CMC4 )


Generally: what do you think about this circuit? Worth while?
The opamp used says: GO15A ( or CO15A ) but I also bought another which says: G001B ( or C001B )
should I replace it?

[kuuan]

After soldering everything it works fine, both channels there.
The pot shown in the graph of the 3rd foto is put in between the preamp and another full amp it seems, so I will not use it.
The additional resistance on the mic-in on the foto 4  must be applicable for ballanced wired mics only so it won't apply for me.

Two more question I have though:

1: If I want to have adjustable gain., which pots do I have do use? Do I have to use 1 for each channel, simply attenuating the hot wire? Or is there one I could use for both channles. If so, which pot and how to wire it?

2: If I want to add a low cut, which condensers to add where?

[lordbelial]

Just a question...

Where did you buy this preamp? And how much did it cost to you?

[kuuan]

I bought ths kit at an DIY electronic parts shop in downtown Osaka.
The DIY kit costs about 9 USD. I bought the already soldered unit for about 18 USD. However I needed to buy all the connectors, switch, pot, case, battery holder, a better opamp to replace the stock opamp asf and then the total came to 37 USD.
It works very well, exactly what I need for my iriver ( Setting the gain to - 6 on the iriver and going line-in I get a very good, noiseless signal )

[lordbelial]

I bought ths kit at an DIY electronic parts shop in downtown Osaka.
The DIY kit costs about 9 USD. I bought the already soldered unit for about 18 USD. However I needed to buy all the connectors, switch, pot, case, battery holder, a better opamp to replace the stock opamp asf and then the total came to 37 USD.
It works very well, exactly what I need for my iriver ( Setting the gain to - 6 on the iriver and going line-in I get a very good, noiseless signal )

Wow, could be interesting to know that Osaka Part shop URL... 

[kuuan]

I tried to find the shop's internet site, but unfortunately it does not have any. Even if they had chances are that it would all be in japanese only, and if there was an email adress and you wrote them in English that you never would get any reply ( speaking from experience contacting japanese shops in English )

Once I realized that this preamp is working very fine I really wished that I would have had more time in Osaka to go back to the shop and buy some more of them in case somebody at tapersection wanted to have one resp. to take orders and send them off. Well, I am planning to do that when next time in Osaka, but that will be next year only!

I still have to learn how to add a gain selector though. As I am living in an hotel room in Shanghai now I do not the possibility to experiment soldering ( that shop in Osaka certainly would have sold me all I'd have needed ) Here in this thread also nobody yethas given me any advice on that.

I am still curious how more knowledgeable people view this preamps specs.

Still, if there are more people interested and willing to pay some premium I will try to make it avaiable ( with the help of my japanese friend...won't be easy..she is an artist, certainly reluctant to travell 3 hours + to spend 20 USD train fees to go to the shop )

But so far there was not much reaction, besides yours.




 

[poorlyconditioned]

I tried to find the shop's internet site, but unfortunately it does not have any. Even if they had chances are that it would all be in japanese only, and if there was an email adress and you wrote them in English that you never would get any reply ( speaking from experience contacting japanese shops in English )

Once I realized that this preamp is working very fine I really wished that I would have had more time in Osaka to go back to the shop and buy some more of them in case somebody at tapersection wanted to have one resp. to take orders and send them off. Well, I am planning to do that when next time in Osaka, but that will be next year only!

I still have to learn how to add a gain selector though. As I am living in an hotel room in Shanghai now I do not the possibility to experiment soldering ( that shop in Osaka certainly would have sold me all I'd have needed ) Here in this thread also nobody yethas given me any advice on that.

I am still curious how more knowledgeable people view this preamps specs.

Still, if there are more people interested and willing to pay some premium I will try to make it avaiable ( with the help of my japanese friend...won't be easy..she is an artist, certainly reluctant to travell 3 hours + to spend 20 USD train fees to go to the shop )

But so far there was not much reaction, besides yours.




 

This is pretty similar to the little circuit I posted a while back.  Well, I copied it from someone else, so it is by no means original .  My guess is you could sell it for something like $50 or so and people would buy it.  But Chris Church is already selling stuff pretty cheap on here (this is like his lowest preamp, with fixed gain, I think), so I'm guessing people will just buy that.

But thanks for providing the (detailed!) info..

  Richard

[kuuan]

This is pretty similar to the little circuit I posted a while back.  Well, I copied it from someone else, so it is by no means original .  My guess is you could sell it for something like $50 or so and people would buy it.  But Chris Church is already selling stuff pretty cheap on here (this is like his lowest preamp, with fixed gain, I think), so I'm guessing people will just buy that.

But thanks for providing the (detailed!) info..

  Richard

Would you think 50 USD for a DIY kit to solder oneself, a soldered unit but without casing and plugs or for an all assembled unit incl metal box., all plugs etc.?

BTW the number 2114 might specify the opamp I used to substitute the "stock" 4558 opamp to boost it's gain much better than the number I gave before.

The shop had an incredible selection of stuff, electronics, cases, connectors etc. and I believe also better circuits and opams.

I really would like to do this, best make a preamp all assembled with adjustable gain, maybe a clipping light, custom made with the connections wished, and all in a black metal box...and not for the big bucks, if I think of all the effort going into it I'd really be more just fun and curiosity.
I wished I was still in Japan..

[kuuan]

BTW the pot shown in the picture above ( 10 kO A ) works perfectly to adjust the gain. Simply wire ground to the left pin and the hot wire goes into the pot in the right pin and out in the middle before going to the 'out' plug. You need two, one for each channel, or a double one ( is it called differently then, not 'A'? ) if you want only one pot for both channels.