gary o

Re: 1108 DIY project and PCB layout
« Reply #20 on: January 25, 2010, 07:53:12 AM »
Iv experimented with this circuit with my rev A I used a Sowter 9045  1:7 mic transformer with good results.


dmp

Re: 1108 DIY project and PCB layout
« Reply #21 on: February 02, 2010, 06:51:06 PM »
I'm not sure I understand the front end of this? I guess the R/C of 30k and 20 pf is matched to the input transformer. Why the 97.6k after that, and why so precise? The URIE manual linked to earlier only has a 1M across the input transformer, no R/C.
The next 82k is used to form a voltage divider with the LDR, yes?

dmp

Re: 1108 DIY project and PCB layout
« Reply #22 on: February 02, 2010, 07:08:01 PM »
I was going to try a UTC O-8 as the input, by the way

[silent:arts]

Re: 1108 DIY project and PCB layout
« Reply #23 on: February 03, 2010, 04:10:00 AM »
received this little artwork of PCB yesterday, thanks :)

dmp

Re: 1108 DIY project and PCB layout
« Reply #24 on: February 03, 2010, 11:30:44 AM »
ok, I'm first to answer my own question!
This thread has a great discussion and testing description:
http://www.groupdiy.com/index.php?topic=32441.0
The R/C on the secondary of the transformer forms a high frequency filter to damp high frequency ringing. The resistor across the secondary damps ringing in all frequencies. Not sure what a single capacitor across the secondary does.
I'm going to start with values from a ADM preamp using a O-8 and play around with it.

shawthing

Re: 1108 DIY project and PCB layout
« Reply #25 on: February 05, 2010, 04:50:22 PM »
 :) Thanks mnats, 1108 boards arrived today safe and sound, beautiful pieces of work! I'm gearing up to start on my first 1176 build with one of your boards, but I think I might use this as a preliminary project first, and while I gather materials. I repair a lot of stuff and I've built some little projects here and there, but these will be my first pieces of pro kit... very excited, can hardly wait, though actually I find scouring the net for just the right parts is a great piece of the fun too!
Best wishes, Chas

Re: 1108 DIY project and PCB layout
« Reply #26 on: February 15, 2010, 10:31:55 AM »
I have just missed the first run of these. Is Mako making any more? If so when? How do I pre order?What a cool mic amp!

YES  :o :D ;) :o

Re: 1108 DIY project and PCB layout
« Reply #27 on: February 23, 2010, 03:19:46 PM »
Team,

how do they sound? Anyone finished one yet? What trannie on the input did you use? How do you wire the input volume control? We need some build reports or Mako may not make any more!!! ::)

A wiring diagram would be so helpful along with any build tips

Michael

mnats

Re: 1108 DIY project and PCB layout
« Reply #28 on: February 23, 2010, 03:22:52 PM »
From my White Market thread:
Yeah,

where are the progress reports ?  :D ;D

I'd love to see to pictures and reviews and methods.

A wiring diagram would rock cos stupid here  ::) can't see where the volume pot would go. Does the input side work as with the 1176 Rev A model. Does that mean we need one of those uber expensive T PAD pots connected to the input trannie? And.....no negative rail?

XOX

The schematic is linked from the first post. The 1108 is a fixed gain amplifier (well, switchable between two gains by S1 in my schematic). There is a pad at the input created by the switchable resistor R2 and the light dependent resistor. It would probably be useful to put a T attenuator at the output to tame the signal going to your recording chain.

What is also missing from the schematic for modern purposes is phantom power but it is easy enough to tack on to the front at the microphone transformer input.

Re: 1108 DIY project and PCB layout
« Reply #29 on: March 02, 2010, 10:28:30 PM »
Looks like cinemag's CMQEE-3440A might be a good bet for input, too.  Did you find the jensen input you used to be a sufficient step-up?  I have some, but I'd be removing them from a quasi-functional unit to test; if its not a good permanent solution, would rather leave them alone.  I've used the 3440A in a different preamp driving one of fred forssell's DOAs and they sounded fantastic in that unit.  $, though.


ilfungo

Re: 1108 DIY project and PCB layout
« Reply #30 on: March 07, 2010, 12:34:58 PM »
hello
I would like PCBs 2 1108 ...
available?
Thanks!

Rolleum

Re: 1108 DIY project and PCB layout
« Reply #31 on: March 09, 2010, 06:58:50 PM »
Hello Mnats,


beeing still busy with the 1176 Rev.D , I am planning already some DIY Preamps with FETs.  I would like to build the hamptone with your layout, but I was wondering why you made phantom power only 24Volts? Is it possible to change some resistor values to rise the phantom power on "correct" 48 Volts? A schematic of your hamptone layout would be very useful.
By the way, your PSU Boars would fit really good in this project.

Greets from Berlin

Rolleum

Re: 1108 DIY project and PCB layout
« Reply #32 on: March 10, 2010, 02:05:59 PM »
Are you talking about the 1108 boards?  The 24V is what is required for the circuit only, the psu is not inherent to the pcb, you need to supply it separately, at which point you would select a power supply that provides both the +24V that the circuit needs, as well as +48V to be pumped into your condensers.  
« Last Edit: March 11, 2010, 12:56:46 AM by bdubya »

Rolleum

Re: 1108 DIY project and PCB layout
« Reply #33 on: March 12, 2010, 10:32:18 AM »
Sorry, my post was a bit  confusing.Before starting the 1108 project, I want to build the hamptone preamp, which mnats got on his page. By the way, the power supply boards from mnats are perfect for building different DIY projects. In mnats hamptone layout, he got the phantom power set on 24 Volts, and I would like to use 48V to avoid a loss of sound.
As I am not a electronical profi, I' ll wait to the next revision of the 1108, when the phantom power supply and the poti question is solved.
So, please mnats, would be great to have an idea of amounting the phantom power in the hamptone preamp, or the schematic of your design.
Greets from Germany
Rolleum

dmp

Re: 1108 DIY project and PCB layout
« Reply #34 on: April 06, 2010, 06:36:18 PM »
I finally got this wired up and tried today.
Added a 8.2k resistor in parallel with R20 (found this in 1108_manual-schematic.pdf, linked to on pg 1). Improves behavior. Tames gain and makes the L position work without squealing.

SIXTYNINER

Re: 1108 DIY project and PCB layout
« Reply #35 on: April 07, 2010, 04:00:12 AM »
jump
>>" 1 Picture say what billions words cannot "<< - >>"SMD Kill the DIY STAR"<<
Why in the  forum  if no share

mnats

Re: 1108 DIY project and PCB layout
« Reply #36 on: April 07, 2010, 04:56:43 AM »
Added a 8.2k resistor in parallel with R20 (found this in 1108_manual-schematic.pdf, linked to on pg 1). Improves behavior. Tames gain and makes the L position work without squealing.

Thanks for your report.

The option to add the resistor between points "E" and "5" was added to the design earlier this year on the 23rd of January. Production boards will include this feature.

myker

Re: 1108 DIY project and PCB layout
« Reply #37 on: April 17, 2010, 05:22:37 PM »
are the 1108 boards to be available again soon? and does anyone have a BOM made up? im not sure about which LDR to use..
thanks,
mike

mnats

Re: 1108 DIY project and PCB layout
« Reply #38 on: April 17, 2010, 09:06:35 PM »
are the 1108 boards to be available again soon?

Maybe not soon, but I will do a production run in the future. Meanwhile the self-etch files are still available on my site.
 
and does anyone have a BOM made up?

That is also part of the PDF on my site.
 
im not sure about which LDR to use..

I used a Vactrol VTL5C9 but there are probably a lot of different ones you could use there. Each one will require playing around with the LED drive circuit to get the range you require.

Re: 1108 DIY project and PCB layout
« Reply #39 on: May 01, 2010, 08:25:05 PM »
HI there,

what is the point of the LDR? What does it do? If I were to leave it out what would eb the effect? How can I leave it out?

Thanks team

Michael

ps how does it sound you lucky folk who bought the first run of boards? Come on ;D


 

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