Whoops

Re: [BUILD] 1108 DIY project and PCB layout
« Reply #220 on: May 12, 2020, 06:00:01 PM »
Neve 1290 (the preamp circuit on the 1073) uses +24v.
And there's a lot of modules based on this preamp  for the 500 series .

Check the schematics for those and see how they implemented the +16v to +24v

https://groupdiy.com/index.php?topic=41147.0

https://groupdiy.com/index.php?topic=33492.0


Saying this, there's much more simple projects to pursue for someone with your experience so chasing this one for the 500 series might be too much.
There's already a lot of amazing preamps for the 500 series, with pcbs already made and the project well documented


Re: [BUILD] 1108 DIY project and PCB layout
« Reply #221 on: May 12, 2020, 06:13:57 PM »
Thank a lot for those. I'll study them

I hear you man. I built an 1176 rev D a few years ago and love using it as a pre amp so I'm pretty set on the 1108 so I'll keep at it for some time.

Another question: My rack (Radial workhourse 8) has a TRS omni port on the back for each channel that corresponds to pin 7 and 9. Would it be possible to send 24 volts through the omni port via another power supply or is this insane?

Re: [BUILD] 1108 DIY project and PCB layout
« Reply #222 on: May 12, 2020, 10:21:43 PM »
So I studies the don classics nv73 converter circuit from the schematic. Given my limited knowledge  it looks exactly like what I need but am unsure after playing around in lt spice (for the first time). I would be willing to pay someone to help me figure this out. Hopefully this is an appropriate post... please remove if not.

Whoops

Re: [BUILD] 1108 DIY project and PCB layout
« Reply #223 on: May 13, 2020, 12:47:08 AM »
So I studies the don classics nv73 converter circuit from the schematic. Given my limited knowledge  it looks exactly like what I need but am unsure after playing around in lt spice (for the first time). I would be willing to pay someone to help me figure this out. Hopefully this is an appropriate post... please remove if not.

as this thread is for another 1108 project, not the one you're after, I think you will be better in doing a new thread for a 1108 project in the 500 series format, to gather some help and have the relevant info compiled there

Re: [BUILD] 1108 DIY project and PCB layout
« Reply #224 on: May 13, 2020, 01:03:57 AM »
Ahh, will do. Thank you much, for your responses.

louder

Re: [BUILD] 1108 DIY project and PCB layout
« Reply #225 on: June 28, 2020, 07:35:18 AM »
Hello
Long time no see.
After reading the whole thread one doubt... J309 it's out of production... Beside eBay where can I get some?
Best regards

TwentyTrees

Re: [BUILD] 1108 DIY project and PCB layout
« Reply #226 on: June 28, 2020, 07:59:26 AM »
Cricklewood Electronics in London seems to have them in stock:
https://www.cricklewoodelectronics.com/J309.html

Hello
Long time no see.
After reading the whole thread one doubt... J309 it's out of production... Beside eBay where can I get some?
Best regards

louder

Re: [BUILD] 1108 DIY project and PCB layout
« Reply #227 on: June 28, 2020, 09:22:54 AM »
Thanks
Regards

Whoops

Re: [BUILD] 1108 DIY project and PCB layout
« Reply #228 on: June 28, 2020, 03:47:45 PM »
Hello
Long time no see.
After reading the whole thread one doubt... J309 it's out of production... Beside eBay where can I get some?
Best regards

Mouser has J309 in stock:

https://www.mouser.com/ProductDetail/InterFET/J309?qs=OxRSArmBDfxFLq%252BlAKFMwA%3D%3D

Probably any of this would work well also as a replacement:

2SK170
LSK170
2SK370
2SK117
2SK369
2N5457
2N5486
BF862

louder

Re: [BUILD] 1108 DIY project and PCB layout
« Reply #229 on: June 28, 2020, 06:15:26 PM »
Thank you.
Obrigado


JerryPbury

Re: [BUILD] 1108 DIY project and PCB layout
« Reply #230 on: January 04, 2021, 01:51:23 PM »
Wouldn’t this work, connection to 5, E and ground?

JerryPbury

Re: [BUILD] 1108 DIY project and PCB layout
« Reply #231 on: January 04, 2021, 01:58:02 PM »
I also have a few UTC A-10’s to try this:

Title: Re: UREI 1008 Mic Preamp Schematic
Post by: Bill Wilson on May 13, 2010, 01:14:51 PM

For the input transformer a UTC A-10 would do very nicely. It has a winding ratio of 1 to 10 & has the necessary taps on the primary. The secondary impedance is 50k ohms & will take +15dbm before the core saturates. The freq response is down only 1 db @ 30cps & .5db @ 20kcps,
(oop's hertz), forgive me but I cut my teeth on tubes back in 52.

The A-10 will work for the 1008 & 1108 as they are to single grid & single FET; it will not work for 1016 as it is a balanced circuit configuration & requires a split primary. A UTC HA-114 will work well as the output xfmr. for the 1016, it is 30k ohms split primary w multiple secondaries covering all the pro output impedances & will handle +23dbm. It is perfect for a 12AY7/6072 in push pull. Freq. response -1db 30hz to 40khz. Input trafo. for 1016 would be a UTC A-12, it has split windings on the secondary for push pull.
Have not take the time to look @ 1108 in detail so cannot give you anything but a guess on the output trafo's impedance but could be around 600 ohms.

I can guarantee the frequency response of the A-10 as I used them in a 6 input 3 channel mike muxer in 64; when I was doing on location mastering for a couple of small rcord co's.

Hope this helps.
Bill W.

P.S.: the dbm figures on the transformers are for the 600 ohm impedance.

dmp

Re: [BUILD] 1108 DIY project and PCB layout
« Reply #232 on: January 04, 2021, 03:48:17 PM »
Gain control - I used 1Meg audio pot in place of the LDR for level control. This worked great. If you are controlling them further away with a fader you might want a LDR, but in a single unit it's not necessary. This gives you control from off to max. You could easily build a stepped switch instead of a continuous pot if that were preferred.
The gain control on these is a two position switch that changes the amount of negative feedback. I've always used them on high and don't the switch is even necessary. You could probably make a stepped switch to change the gain in more steps, but I don't think you can get much more gain out of them than the 'hi' setting of the design.
And I put a pad on the front ahead of the input transformer.
These sound great. I used UTC O-1 / O-2 but any 1:10 mic transformer will work


 

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