PiTone Systems AD797 Mic preamp

[ungifted]

Hi, we've got another mic pre design based on AD797 by Vadim Volodin from PiTone Systems ( http://pitonelab.ru/software/?p=en )

Features:
- Gain 6db-60db
- Hi pass filter 85Hz
- Pad -20db
- 48v with led
- Signal level indication -20dBU (green) +20dBU (red)
- Output buffer for long lines (LM4562)
- Integrator (AD706)
- Various interstage capacitor sizes (axial, radial, 4u7 or 2u2+2u2 combination)

Schematics attached. More docs in the future.
Some PCBs with options (IC bundle, etc)  will be available at my web store. I hope we'll make full kit in some time.

PS: BTW this guy is making exellent studio monitors.

___________________________________________________________________
Update: Project docs http://diy-tubes.com/image/data/manuals/pitone797-en.pdf

 

[ungifted]

PCBs are in stock!
Some notes about project while documents are published
Zeners (12v) - BZX55C12, 1N5242, 1N4742A
RFI capacitors - С3, С5 can be 100p-470p. I used 220p.
If you have large axial interstage capacitors (C14, C15), you can use 47u/63v as C24 in phantom circuit to save some board space and fit large capacitors.
R10 - pick up according your led specs. Usually 650R-1k5.

All ICs, C10k and high quality JFX axial capacitors for the project are also available.

 

[fragletrollet]

Hey!

Read about the AD797 kit on your site, how would you characterize the "color" of this pre, in general and compared to this incarnation of an AD797 preamp design? I have a couple of 312`s but am in the market for 2-4 channels of "open/pure/uncolored gain" for use as makeup gain for some analog delays etc feeding my passive DI`s (Lundahls/Cinemag/Pikatron`s). Any recommendations and observations?  8)

 

[ungifted]

Hi, the author of this pre describes it as neutral - "low noise and distortion over the entire range of its gain. In a complex spectrum of the signal, it leaves the main character of the original musical instrument or tone of voice unchanged".
At the same time many people say that AD797 is "musical". There are many good ICs with superior params but not all of them are good for audio. Nearly everyone likes NE5532
Sure, it's all a dispute about tastes.

 

[hazel]

Hey!

Read about the AD797 kit on your site, how would you characterize the "color" of this pre, in general and compared to this incarnation of an AD797 preamp design? I have a couple of 312`s but am in the market for 2-4 channels of "open/pure/uncolored gain" for use as makeup gain for some analog delays etc feeding my passive DI`s (Lundahls/Cinemag/Pikatron`s). Any recommendations and observations?  8)

Hi Fragletrollet,

I've built 8 x AD797 preamps from ungifted's and i'm more than happy with them. I mostly record jazz, classical, chamber and opera stuff and they are very clean, not harsh but transparent and fast transient friendly.

the author of this pre describes it as neutral - "low noise and distortion over the entire range of its gain. It leaves the main character of the original musical instrument or tone of voice unchanged".
Sure, it's all a dispute about tastes.

I'd like to know if there are audible differences between AD797 and Crook preamp

 

[fragletrollet]

Hey!

Read about the AD797 kit on your site, how would you characterize the "color" of this pre, in general and compared to this incarnation of an AD797 preamp design? I have a couple of 312`s but am in the market for 2-4 channels of "open/pure/uncolored gain" for use as makeup gain for some analog delays etc feeding my passive DI`s (Lundahls/Cinemag/Pikatron`s). Any recommendations and observations?  8)

Hi Fragletrollet,

I've built 8 x AD797 preamps from ungifted's and i'm more than happy with them. I mostly record jazz, classical, chamber and opera stuff and they are very clean, not harsh but transparent and fast transient friendly.

the author of this pre describes it as neutral - "low noise and distortion over the entire range of its gain. It leaves the main character of the original musical instrument or tone of voice unchanged".
Sure, it's all a dispute about tastes.

I'd like to know if there are audible differences between AD797 and Crook preamp

Cool! I`d like to know the difference with the crook version aswell.

 

[ungifted]

I really cannot say if there is any audible difference. At least we have LM4562 at output stage and integrator.
Our first AD797 pre is "purist" one, no protection, no additional stages, no addons. It's for home, studio usage, short lines, good working environment.
Crook is more "adapted to real life".

 

[ungifted]

Updated docs. Soldering instructions, schematics, image for home etching, dimentions etc.
http://diy-tubes.com/image/data/manuals/pitone797-en.pdf

 

[fragletrollet]

Is there any way to incorporate this into a 500-series system?

 

[ungifted]

I'm not sure. It's 140mm depth. Suitable for vertical placement in 2U, but not intended for 5XX

 

[fragletrollet]

Yep, and I guess that it would be kinda wasteful using a "whole" 500-slot for such a cheap preamp?  8)

How would this stack up to something like this:

http://www.soundonsound.com/sos/jul13/articles/dacs-clarity-micamp-500.htm

(if just comparing the amps, not thinking about filters and phantom power etc)

 

[ungifted]

Yep, and I guess that it would be kinda wasteful using a "whole" 500-slot for such a cheap preamp?  8)

I can make it a bit more expensive for you.  ;D
We will think about 500 version. If you like expensive things. ))

 

[ungifted]

All indication is tested and works as it must.

 

[ungifted]

If someone interested - limited quantity of DIY Kits available.  Don't miss if you're looking for a good neutral mic preamp.

Some pics from the author. THD:

Noise level:

 

[fishdrop]

Hey i have two questions.

if i put them vertically into a 2U case. How many of them can fit in one case?

what's the input impedance?
What kind of power supply is needed to power 8 pieces?


thanks in advance

 

[ungifted]

if i put them vertically into a 2U case. How many of them can fit in one case?

If you have enough place to place PSU near the rear panel (deep enough case) I think you can fit about 8-10 channels. Dimentions of PCB: 70x140mm. Height of mounted potentiometer is about 22mm.

Load impedance - min/max 150R/600R.

30-50VA trafo like this one or similar should be enough for 8 channels. (AD797x2 - 10.5mAx2, AD706 - 1.4mA, LM4562 - 10mA, TL072 - 2.5mAx2, LEDs - about 1-3mAx2, phantom power - 14-30mA, total about 75mA (rough calculation) for one channel).
Any project of mic preamp PSU like this or any you like, which gives +15v, -15v and phantom.