Re: Twin Servo Mic Preamp for 500 series * Partial Kit FEELER *
« Reply #20 on: November 05, 2019, 06:09:30 PM »
Wordsushi
One kit
I have a spare pair of Hardy 990c's I'd use
Yes on Transformers/Cinemags


OneRoomStudios

Re: Twin Servo Mic Preamp for 500 series * Partial Kit FEELER *
« Reply #21 on: November 07, 2019, 11:53:25 AM »
Which Cinemag input transformer are you using? Also, do you have a sense of the cost per kit? Thanks!

elskardio

Re: Twin Servo Mic Preamp for 500 series * Partial Kit FEELER *
« Reply #22 on: November 07, 2019, 12:05:22 PM »
Which Cinemag input transformer are you using? Also, do you have a sense of the cost per kit? Thanks!

The Cinemag is the CMMI-2APC. It's not on their website but you can order it directly from Cinemag.

Same thing for the Jensen JT-16-PCJR. You need to contact them directly.

This is the reason I might include the input transformer with the partial kit.

About the price, I'll try to calculate it tonight. It will depend on what's included or not.

Thanks

Fuzz Face

Re: Twin Servo Mic Preamp for 500 series * Partial Kit FEELER *
« Reply #23 on: November 07, 2019, 03:08:45 PM »
I see you’ve built them with Cinemag and Jensen now. I imagine you have had more time with the Cinemag build but do you have any thoughts on differences? I guess they’re both relatively “clean”?

elskardio

Re: Twin Servo Mic Preamp for 500 series * Partial Kit FEELER *
« Reply #24 on: November 07, 2019, 03:48:18 PM »
I see you’ve built them with Cinemag and Jensen now. I imagine you have had more time with the Cinemag build but do you have any thoughts on differences? I guess they’re both relatively “clean”?

The sonic difference between both choice of transformers is very subtle... a lot of audio engineers couldn't tell them apart... but here's my thoughts:

Jensen:
- A tad more Precise in the mid frequencies
- More neutral, true to the source

Cinemag:
- Slightly more coloured
- A little lift in the low-end frequencies

SKJGProject

Re: Twin Servo Mic Preamp for 500 series * Partial Kit FEELER *
« Reply #25 on: November 08, 2019, 07:11:16 AM »
Skjgproject
2 kits
CA-990
Transformers yes
I used to date a blind girl. Her name was ::… ..:.: .:::. .::.. ….: .:.::

Fuzz Face

Re: Twin Servo Mic Preamp for 500 series * Partial Kit FEELER *
« Reply #26 on: November 08, 2019, 08:26:27 AM »
The sonic difference between both choice of transformers is very subtle... a lot of audio engineers couldn't tell them apart... but here's my thoughts:

Jensen:
- A tad more Precise in the mid frequencies
- More neutral, true to the source

Cinemag:
- Slightly more coloured
- A little lift in the low-end frequencies

Thanks, I’ll be happy with whatever option you go with

Vac11

Re: Twin Servo Mic Preamp for 500 series * Partial Kit FEELER *
« Reply #27 on: November 13, 2019, 03:38:26 AM »
Hi Elskardio,

Great work, as usually!

What voltage is feeding the 990 DOAs? +-24V as on geniue Jensen schematic? Or +-16V (500 series srandard)?

Thank you

Best

Milan

Re: Twin Servo Mic Preamp for 500 series * Partial Kit FEELER *
« Reply #28 on: November 13, 2019, 03:51:06 AM »
objectgroup
1 kit
CA-990
with jensen trafos

Re: Twin Servo Mic Preamp for 500 series * Partial Kit FEELER *
« Reply #29 on: November 13, 2019, 02:04:20 PM »
Just curious. What is the biasing procedure for different op amps?


elskardio

Re: Twin Servo Mic Preamp for 500 series * Partial Kit FEELER *
« Reply #30 on: November 13, 2019, 08:01:26 PM »
What voltage is feeding the 990 DOAs? +-24V as on geniue Jensen schematic? Or +-16V (500 series srandard)?

Hi Milan,
+/- 16V
thanks

Just curious. What is the biasing procedure for different op amps?

First we remove the dc servos from the circuit using the onboard jumpers. After you connect your multimeter to the  output of the opamp. The goal is to have the same dc voltage at the minimum and the maximum gain positions. So you go back and forth with the gain knob and each time you adjust using the trimmer until you get close to the same voltage. Once this is done for both opamps, we re-engage the dc servos and voilà ;) This minimize the dc offset and helps the servo works faster.

Rogy

Re: Twin Servo Mic Preamp for 500 series * Partial Kit FEELER *
« Reply #31 on: November 14, 2019, 01:11:47 AM »
Hi Gabriel!

Rogy here, the live sound guy using your excellent EQ's on tour.

Interested in 4 kits.

No need for DOA's, I built eight 990s ages ago that have been waiting for your kit :-)

I'd like transformers included in the kits. Slight preference for the Jensen option to stay true to the original design, but will take whatever option is offered.

Thanks for doing this!

Rogy

Fuzz Face

Re: Twin Servo Mic Preamp for 500 series * Partial Kit FEELER *
« Reply #32 on: November 14, 2019, 09:19:03 AM »
PM’d  :)

elskardio

Re: Twin Servo Mic Preamp for 500 series * Partial Kit FEELER *
« Reply #33 on: November 17, 2019, 08:51:40 AM »
The kits with Jensen are gone.
3 kits with Cinemag left.
Thanks

SKJGProject

Re: Twin Servo Mic Preamp for 500 series * Partial Kit FEELER *
« Reply #34 on: November 17, 2019, 07:53:33 PM »
Too bad i thought you were saving the jensen kits for people who posted....

I take  one jensen when they are available again
« Last Edit: November 17, 2019, 08:10:30 PM by SKJGProject »
I used to date a blind girl. Her name was ::… ..:.: .:::. .::.. ….: .:.::

elskardio

Re: Twin Servo Mic Preamp for 500 series * Partial Kit FEELER *
« Reply #35 on: November 17, 2019, 10:07:20 PM »
Too bad i thought you were saving the jensen kits for people who posted....

The buyers contacted me by PM as requested in my post...

Fuzz Face

Re: Twin Servo Mic Preamp for 500 series * Partial Kit FEELER *
« Reply #36 on: December 05, 2019, 08:54:19 AM »
My kits came in yesterday or before and they look great! The PCBs and metalwork look top knotch. Thanks Gabriel!

Do the component designations match the Jensen schematics?

https://www.jensen-transformers.com/wp-content/uploads/2014/08/as083.pdf

https://www.technicalaudio.com/pdf/Jensen_Transformers/Jensen_OpAmps_990_and_related/Jensen_JE-990_opamp_JAES_reprint_1980.pdf


 

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