Topic: m148 bill of materials?

[it-goes-to-eleven]

The Jensen version of the Reichenbach's in the Aerco are about $60 each, fwiw. From the specs, I guess they are 1:1 windings. I would have thought it would be better to get a little gain from the xformers and the rest from the gain circuit.

I think I have Doug's transformer posts archived.

[Chuck]

The Jensen version of the Reichenbach's in the Aerco are about $60 each, fwiw. From the specs, I guess they are 1:1 windings. I would have thought it would be better to get a little gain from the xformers and the rest from the gain circuit.

I think I have Doug's transformer posts archived.

What is the part number on the transformers in the Aerco and the coorisponding number on the Jensens? Again, this is from memory, but I think the gain in the m148 is all from the transformers. 1:10 is what I remember on the windings to achieve +20db gain.

[Digital Quality]

Ok, now I see, you pick your transformer based on the input impedance of your amplifer circuit. See the little blurb below the selector guide on Jensens site.

So, should we pick the amp to match the transformer we want or the other way around? Which contributes more to the sonic properties??

[RebelRebel]

this site will help..

http://www.diyaudio.com/

http://www.studio-central.com/DIY-projects.htm

http://1176neve.tripod.com/id10.html

gyraf provides excellent products.. http://www.gyraf.dk/gy_pd/g9/g9pd.htm

http://www.seventhcirclestudios.com/SCA/SCA.htm  another popular company..

[it-goes-to-eleven]

So...... Digging through my packrat archive of stuff..  Funny how you still need to save web stuff for later.  You never know when those web pages will suddenly disappear..  Who's your packrat daddy!

Jerry ala AERCO...

"There are two options for the input transformer so you can have 0 - 50 dB gain for rock & roll or 20 - 70 dB for nature recording."

So... To have 0dB of gain as an option, you must have a 1:1 input xformer (or do BS attenutation). Since my Aerco is 0-50 model, it is a 1:1.

Not sure who posted this but it was in regard to the aerco:

reichenbach mb-c input tranformers! (my google search equated these with the jensen jt-mb-c)

I'm sure Jerry would tell you what xformers you might use and he maybe even sell you some. He says the 48v circuit is by far the most complex aspect of the box.


Misc Doug Stuff:

Hi!
The transformers Jensen sells for mics have gain. It is very clean gain with no electronic artifacts as there are no electronics in transformers. Naturally if you add electronics, they can enhance or limit performance. This step is key to good sound or you can use one that needs no electronics. You also avoid the need for capacitors to block the phantom voltage and most caps add a good deal of noise and or distortion. You can use the Jensen JT-110K-HPC without a buffer or op amp for additional gain and it provides an amazingly clean 18 dB of gain. Very good sound that is easy to build.
Add 9 volts batteries for P48, a case with connectors and you have a very good preamp for under 300.00.
Jensen also provides detailed schematics for mic preamp circuits using their transformers that are at or near state of the art.
...Doug

http://www.jensen-transformers.com/mic_in.html
http://www.jensen-transformers.com/apps_sc.html

Hi !
I have built all three of these :
AS018 JT-16-A in Single Stage Low-Noise IC Mic Preamp
AS019 JT-16-A in Single Stage Mic Preamp with Two DC Servos
AS083 Famous Twin-Servo 990 Mic Preamp Basic Circuit
They inspired me to design the M148, which does not use op amps, it uses discreet transistors but does use a Jensen transformer, to my ears the best made. I think the first design (AS018) is very good and a great place to start for a first project. I would NOT use the NE5532, it is great for pushing long cable runs, but most engineers today will not pass their signal thru one. Sub out an AD712 for a much better sound. It is also possible to bias the op amp for single ended operation ( i.e. no negative supply rail needed). Using the same powersonic PS605 batteries I use for the M148 will provide the voltage for the single DC supply op amp and the best possible source for phantom power, true DC. This will blow your mind, it will sound so good and YOU made it !
Enjoy ...Doug

Hi !
Consider using the INA163, Grace, Apogee and a host of others use this newest design from Burr Brown /TI. If you use this chip, you do not want to use the Jensen transformer, this will save you a lot of money. Sounds like you have CAD/CAM capabilities, perhaps even put together a PCB design to post. I know several tapers who built preamps like this, they are not too costly and fairly easy to build and of course, they sound very good. Rane uses this current feedback chip in their low cost mic preamp and they offer a peek inside !
enjoy...Doug

http://www.chipcatalog.com/TI/INA163.htm
http://www.rane.com/note148.html
http://www.rane.com/ms1b.html
http://www.rane.com/pdf/ms1bsch.pdf

[Digital Quality]

Sorry, you can't repeat a karma action without waiting 12 hours.

Thanks a ton! Google has some Cached pages too but it's tricky finding the right one. WTG!!

Thanks Teddy and all too!

[Chuck]

So...... Digging through my packrat archive of stuff..  Funny how you still need to save web stuff for later.  You never know when those web pages will suddenly disappear..  Who's your packrat daddy!

Jerry ala AERCO...

"There are two options for the input transformer so you can have 0 - 50 dB gain for rock & roll or 20 - 70 dB for nature recording."

So... To have 0dB of gain as an option, you must have a 1:1 input xformer (or do BS attenutation). Since my Aerco is 0-50 model, it is a 1:1.

Not sure who posted this but it was in regard to the aerco:

reichenbach mb-c input tranformers! (my google search equated these with the jensen jt-mb-c)

I'm sure Jerry would tell you what xformers you might use and he maybe even sell you some. He says the 48v circuit is by far the most complex aspect of the box.


Misc Doug Stuff:

Hi!
The transformers Jensen sells for mics have gain. It is very clean gain with no electronic artifacts as there are no electronics in transformers. Naturally if you add electronics, they can enhance or limit performance. This step is key to good sound or you can use one that needs no electronics. You also avoid the need for capacitors to block the phantom voltage and most caps add a good deal of noise and or distortion. You can use the Jensen JT-110K-HPC without a buffer or op amp for additional gain and it provides an amazingly clean 18 dB of gain. Very good sound that is easy to build.
Add 9 volts batteries for P48, a case with connectors and you have a very good preamp for under 300.00.
Jensen also provides detailed schematics for mic preamp circuits using their transformers that are at or near state of the art.
...Doug

http://www.jensen-transformers.com/mic_in.html
http://www.jensen-transformers.com/apps_sc.html

Hi !
I have built all three of these :
AS018 JT-16-A in Single Stage Low-Noise IC Mic Preamp
AS019 JT-16-A in Single Stage Mic Preamp with Two DC Servos
AS083 Famous Twin-Servo 990 Mic Preamp Basic Circuit
They inspired me to design the M148, which does not use op amps, it uses discreet transistors but does use a Jensen transformer, to my ears the best made. I think the first design (AS018) is very good and a great place to start for a first project. I would NOT use the NE5532, it is great for pushing long cable runs, but most engineers today will not pass their signal thru one. Sub out an AD712 for a much better sound. It is also possible to bias the op amp for single ended operation ( i.e. no negative supply rail needed). Using the same powersonic PS605 batteries I use for the M148 will provide the voltage for the single DC supply op amp and the best possible source for phantom power, true DC. This will blow your mind, it will sound so good and YOU made it !
Enjoy ...Doug

Hi !
Consider using the INA163, Grace, Apogee and a host of others use this newest design from Burr Brown /TI. If you use this chip, you do not want to use the Jensen transformer, this will save you a lot of money. Sounds like you have CAD/CAM capabilities, perhaps even put together a PCB design to post. I know several tapers who built preamps like this, they are not too costly and fairly easy to build and of course, they sound very good. Rane uses this current feedback chip in their low cost mic preamp and they offer a peek inside !
enjoy...Doug

http://www.chipcatalog.com/TI/INA163.htm
http://www.rane.com/note148.html
http://www.rane.com/ms1b.html
http://www.rane.com/pdf/ms1bsch.pdf

Thanks Freelunch, that's the thread at the Oade site I was thinking about. +T
From that , it sounds like Doug uses a transistor stage after the transformer.

[Chuck]

Well, I've been doing some thinking... dangerous , I know...
Anyway... I'm going to start with the phantom power supply first. Since a very clean phantom power supply is very useful on it's one...

I'm thinking that (5) of the 9 v DC (actually 9.6 v nominal) NiMH batteries would work well to supply the phantom power and the juice the active part of the circuit will require. The problem is... If I wire them all together in series... how to charge them correctly... I'm waiting from a response from Thomas Dist. as they sell the batteries I am looking to use.

BTW, using the 9v NiMH batteries is about 50% less expensive than buying the eight 6 v cells Doug uses in the M148. They don't have the storage capacity (about half) but they can be cycled more times and are smaller and lighter in the end. I'll post again when I get the charger circuit figured out...

[it-goes-to-eleven]

I don't know anything about combining nimh batteries.. But I thought internal resistance was a problem with wiring in series?  Or is that with lions?

Jerry at Aerco made a comment that straight battery 48v can suffer from low frequency noise due to variable chemical reactions.  I'm not sure how significant that is or how it varies between battery type. My gut says lead would be more stable than nimh.

[Chuck]

Hmmm... Those issues never crossed my mind... I wonder if they are valid concerns?
I guess I could look at lead, but there is a reason they call "the Brick" the Brick. Also assembling a charging circuit for lead batteries is easier...

[mhibbs]

You're not moving to the dark side are you?

I'm supposed to be getting a FedEx today.  I broke about a day before they started showing up on the yard sale. 

I'm not really trying to duplicate the brick as much as work on something with quality components and play around with some different discrete topolgies. I saw the talk of $200 Jensens but it didn't look to me like the $200 ones were as applicable for a pre as maybe for direct in or ground loop boxes.

If this thread is seen by enough people, someone will know the transformers he uses. I may have that info at home. If you do find the right materials, I'd like to work on it with you. I have an idea for a transformer based pre-amp that also has two line inputs that can be blended with the transformer outputs. A very simple design. It would work as a high quailty pre-amp on it's own, or a line . mic mixer when needed. The line inputs could be passive or possibly switchable to keep noise out of the circuit. I was starting to put together a MarkerTek order for the chassis parts, maybe I'll hold off. We could save on shipping etc... if we buy all the stuff together...

Search the Oade forum (old and new) and you should be able to find the part number on the Jensen transformers.  They were out there at one point...I've seen it...but I can't remember what they were.  The only thing I've never seen any part number info on is all of the stuff on the board covered up by the goop.  That design is what is so closely guarded, the transformers are fairly common knowlege.  I'll try to search around and see if I can find them too.


mitch

[Church-Audio]

A true taper.

Good luck with everything man.

Oh yea, my life is a 3 ring circus right now,, it's all good though. Thanks for the kind words.


Edit: Only one at a time, thanks!

I love it when people try to reverse engineer products, but why don't you ask him what he uses for a transformer? Tell him what you want to do. Maybe he will say yes, maybe he will tell you to get lost. But I would be upset if I knew someone was reverse engineering my designs with out asking me. Just my two cents.

[Digital Quality]

Not reverse engineering the m148. Only curious which transformers were used but thanks anyway.

[RebelRebel]

Doug wouldnt tell anyway, dont believe. I also asked him if hed train someone up on how to build them as he couldnt anymore, but he said no.

I like the 148 a lot, but the fixed gain is a deal killer for me. I found that the Neve Portico sounded nearly identical (not in silk mode, but normal) but of course had variable gain..if I was still doing rock concert taping, id have the Portico. I love that sound and that of the brick.

A true taper.

Good luck with everything man.

Oh yea, my life is a 3 ring circus right now,, it's all good though. Thanks for the kind words.


Edit: Only one at a time, thanks!

I love it when people try to reverse engineer products, but why don't you ask him what he uses for a transformer? Tell him what you want to do. Maybe he will say yes, maybe he will tell you to get lost. But I would be upset if I knew someone was reverse engineering my designs with out asking me. Just my two cents.

[Church-Audio]

Doug wouldnt tell anyway, dont believe. I also asked him if hed train someone up on how to build them as he couldnt anymore, but he said no.

I like the 148 a lot, but the fixed gain is a deal killer for me. I found that the Neve Portico sounded nearly identical (not in silk mode, but normal) but of course had variable gain..if I was still doing rock concert taping, id have the Portico. I love that sound and that of the brick.

A true taper.

Good luck with everything man.

Oh yea, my life is a 3 ring circus right now,, it's all good though. Thanks for the kind words.


Edit: Only one at a time, thanks!

I love it when people try to reverse engineer products, but why don't you ask him what he uses for a transformer? Tell him what you want to do. Maybe he will say yes, maybe he will tell you to get lost. But I would be upset if I knew someone was reverse engineering my designs with out asking me. Just my two cents.

I called him and he told me but I am not allowed to tell anyone