MA1 GERMANIUM mic pre support thread

[ppa]

do you think that MA1 is conventional?  ;D

 

[KMB-AUDIO]

Haha, well I suppose you have a point  ;D ;D

I'm done building one of two; gonna fire it up tonight.

Hopefully, I'll have the second one done tomorrow, time permitting.

 

[KMB-AUDIO]

Done with both! They are right at home:

I'll hopefully be able to do some recording this week. I'll post some samples if I do.

 

[ppa]

Done with both! They are right at home:

I'll hopefully be able to do some recording this week. I'll post some samples if I do.

thank you so much ! 

 

[Potato Cakes]

Pier,

I've decided to go with the Lundahl 1576 based on your recommendation and I'm trying to determine what R21, R22, and C31 should be. The only thing I have been able to come up with is using the value's from Gyraf's G9 preamp, which would be 470K, 1M, and 10u/63F, respectively. Do you know if these would work? If I contact Lundahl, I'm not sure what it is I would ask them about besides a loading resistor. I usually try to do what research I can before I come here to ask questions, but it seems that my lack of knowledge has caught up with me. Any help would be greatly appreciated.

Thanks!

Paul

 

[ppa]

Pier,

I've decided to go with the Lundahl 1576 based on your recommendation and I'm trying to determine what R21, R22, and C31 should be. The only thing I have been able to come up with is using the value's from Gyraf's G9 preamp, which would be 470K, 1M, and 10u/63F, respectively. Do you know if these would work? If I contact Lundahl, I'm not sure what it is I would ask them about besides a loading resistor. I usually try to do what research I can before I come here to ask questions, but it seems that my lack of knowledge has caught up with me. Any help would be greatly appreciated.

Thanks!

Paul

I would suggest you

R21= 120k
C31= 180pF  polystyrene or argent mica type
R22= 33k


thanks
best regards
Pier Paolo

 

[Potato Cakes]

Thanks! Hoping to get the transformers ordered next week. I'll post some pics when they get finished.

Paul

 

[tonycamp]

this is on the shortlist, has anyone done the Tpad in place of the DI? I'd like to hear some impressions on the sound of hitting this hard.

nice job on this ppa 8)

 

[Potato Cakes]

Pier,

I've decided to go with the Lundahl 1576 based on your recommendation and I'm trying to determine what R21, R22, and C31 should be. The only thing I have been able to come up with is using the value's from Gyraf's G9 preamp, which would be 470K, 1M, and 10u/63F, respectively. Do you know if these would work? If I contact Lundahl, I'm not sure what it is I would ask them about besides a loading resistor. I usually try to do what research I can before I come here to ask questions, but it seems that my lack of knowledge has caught up with me. Any help would be greatly appreciated.

Thanks!

Paul

I would suggest you

R21= 120k
C31= 180pF  polystyrene or argent mica type
R22= 33k


thanks
best regards
Pier Paolo

Could I use a film capacitor instead of polystyrene or mica?

Thanks,

Paul

 

[ppa]

it runs with ceramic NP0 , film , polystyrene and argent mica capacitors but with polystyrene and argent mica it has a bit better sound (a bit). 

 

[Potato Cakes]

Thanks! I'll get some more polystyrene caps ordered.

 

[ppa]

is available a manual in english language made by a GDIY menber krcwell at

http://realgearonline.com/attachment/download/2456


thanks very much to krcwell 

 

[Krcwell]

thanks very much to krcwell 

I must admit, my motivation was somewhat selfish... Pier has some very cool new projects in the works that I am really looking forward to, so I don't want him to have to waste his highly skilled time making a guide!

 

[fragletrollet]

So is this like a crossover between an api312 and something like a chandler germanium?

 

[Potato Cakes]

Hello, friends!

So as I am waiting for a pair of T-pad adapter PCBs from CAPI to arrive to finish up my pair of MA1s, I began to think about uses for the DI input since it won't be used on this round of builds, and an LED is a terrible thing to waste. I'm looking over the schematic and I'm thinking about finding away to make the DI button function as a HPF.  Coming off of the backside of the input transformer (which is a LL1576) , my thought is to jump pin 6 directly to the DI switch with a capacitor in line and pin 5 to the ground on the DI solder pad. Am I missing something?

Thanks!

Paul

 

[ppa]

Hello, friends!

So as I am waiting for a pair of T-pad adapter PCBs from CAPI to arrive to finish up my pair of MA1s, I began to think about uses for the DI input since it won't be used on this round of builds, and an LED is a terrible thing to waste. I'm looking over the schematic and I'm thinking about finding away to make the DI button function as a HPF.  Coming off of the backside of the input transformer (which is a LL1576) , my thought is to jump pin 6 directly to the DI switch with a capacitor in line and pin 5 to the ground on the DI solder pad. Am I missing something?

Thanks!

Paul

It might be added an HPF filter just using the DI's circuit section. I am seeing about it, I will send an email with the istructions, very good idea.
thanks
Pier Paolo

 

[Potato Cakes]

So I finally got the parts in to get finish my MA1. I've only run tone through it to make sure it was working, so I can't say how anything sounds. I went with Pier's recommendation using Lundahl for the input  and Cinemag on the output. I opted to do the T-pad and stepped gain switch from Classic API. The stepped gain switch does not fit without cutting into this beautiful PCB as well as notching out the back half of the Grayhill switch (ouch!). I thoroughly abused the circuit board trying to figure out how to make everything fit. If I do wind up making more I would probably just stick with the variable pot as specified, but the temptation to complicate a pretty straight forward build is hard to resist. I would have a second one done but somehow I managed to get Q2 and Q4 flipped in their orientation and I managed to break one of them when trying to correct it. I was pretty annoyed as now I have to wait till replacements show up before I can complete my sweet little rack. I can't wait to do some tracking with this guy as everyone else here seems to be very pleased with the results.

 

[Potato Cakes]

Another pic.

 

[Potato Cakes]

And one more.


Huge thanks to Pier for developing this preamp and the fantastic support he gives for his products. Also thanks to Jeff at CAPI for making available great problem solving parts for completing builds.


Paul

 

[Potato Cakes]

So just in case anyone did want to do a stepped gain MA1:

I used a dremel tool to cut out the white silk screen where the potentiometer would go straight back to C29. Then I had to make a notch between the solder pads of C29. Also, I put the capacitor for C29 under the PCB to make room for the Grayhill switch.

Also, one should probably determine they want to do this before soldering any components. Using a dremel creates all kinds of dust that is hard to clean in tight spaces!