Retired:Symmetrical FET
« on: May 16, 2014, 04:07:03 AM »
PCB for an 1178/stereo 1176 circuit, designed with the help of the great people on this forum.

Left for archiving.


Schematic -  (errata - 30K should be 30R1)

BOM In addition to the list, I have been using NOS NPD5566 dual JFETs.

Board Layout






Hope you enjoy!

Gustav

« Last Edit: August 07, 2015, 09:12:15 AM by Gustav »


Greg S.

Re: Symmetrical FET
« Reply #1 on: June 30, 2014, 05:12:49 PM »
Does someone have a Backside Pic showing the connection of the Com ports between the main pcb and the gr/meter board?

thx

Greg S.

Re: Symmetrical FET
« Reply #2 on: July 01, 2014, 09:58:43 AM »
I belive, i got it..

I prefer 3 IDC 8-pin connectors


Layout Com2!

https://pcbgrinder.com/download/Symmetrical-Fet/Symmetrical-Fet-board.pdf

There is a single pin at the Main-Board's right side upper line which should be wired to the GR-Board's right side down line

This is the key!

 ::)


Re: Symmetrical FET
« Reply #3 on: July 01, 2014, 02:41:20 PM »
Greg, if you check the board drawing, they are "lined up", but I had this connecting in mind, which should make it obvious.

- Will be adding some more documentation to this project, when I get the correct size pots :)

Gustav

Greg S.

Re: Symmetrical FET
« Reply #4 on: July 01, 2014, 03:10:29 PM »
Hi G!

Check both rightsided Pins!

Re: Symmetrical FET
« Reply #5 on: July 01, 2014, 03:18:16 PM »
Hi G!

Check both rightsided Pins!

Sure, but it could be a trap!

Its still easier to just "think like the connector" I posted. Not much wizardry to it, really.  :)

Gustav

Greg S.

Re: Symmetrical FET
« Reply #6 on: July 01, 2014, 03:39:50 PM »
...
Always Funny... Sunny   ;D ;D


Greg S.

Re: Symmetrical FET
« Reply #7 on: July 02, 2014, 02:02:49 AM »
I got the last missing parts today, so I can complete the 1178.. We will see G.


Suggestions for the next Revision:
   
   2 Meter light circuits at the PSU
   Com1-3 Pin inscription

Would be great G!

In the End it's DIY and I simply love building those boxes

Re: Symmetrical FET
« Reply #8 on: July 02, 2014, 07:58:47 AM »
...
Always Funny... Sunny   ;D ;D

Its hard to foresee what people do to ones design - This was designed for the angled connector to avoid wiring completely :)

Gustav

Greg S.

Re: Symmetrical FET
« Reply #9 on: July 02, 2014, 10:28:24 AM »
Almost there,,

Some features are still not done.. (holes at the front) ..

But as far as the Com-Port-Problem/Discussion isn't solved, I wont start it up!

But it's already quite good looking..

 ;)


Re: Symmetrical FET
« Reply #10 on: July 02, 2014, 12:20:51 PM »
as far as the Com-Port-Problem/Discussion isn't solved, I wont start it up!


Sorry, I thought you already worked it out from the picture I posted.

Heres a different angle showing how the connector hooks up from the main board to the control board. Since you're not using the intended connector, just lay out how your chosen connectors/wires would follow the same path...

Gustav

Greg S.

Re: Symmetrical FET
« Reply #11 on: July 03, 2014, 03:56:59 AM »
It's working.
my Com's were right!  8)

My NPD5566 seem to work too..
(Have to calibrate. 'em)

I will match some BF245a's just for fun and try 'em too..
Which Fet's did you tried?

No Hum, thats fine.

Is there a reason, why you changed the Input Pot to 1K (original get's 10K)
I got a 22k lin at the Attack, 25k are hard to find

Changing the ratios didn't have so much effect..

I got a bit white noise at the outs,.
The noise is always there, it's not effected by some pots!
HMMM, thinking about that!
Will rewire by using shielded Cables

Next up:
The both Elcos at the outs are free to choose from 2200uF-4700uF
The G-1176 got 470uF, might you comment on that G?

Re: Symmetrical FET
« Reply #12 on: July 03, 2014, 06:36:16 AM »
It's working.
my Com's were right!  8)

My NPD5566 seem to work too..
(Have to calibrate. 'em)

The pictures you sent me by mail were fakes, but I will be checking some of those too

I will match some BF245a's just for fun and try 'em too..
Which Fet's did you tried?


Only original NPD5566 so far. I have a stack of different types, I Will be doing experiments with before offering a kit.

No Hum, thats fine.

Is there a reason, why you changed the Input Pot to 1K (original get's 10K)
I got a 22k lin at the Attack, 25k are hard to find

The original is 1K, so I can't comment on a reason to change it from 10K.

22K/25K - Different series land on different values (Alpha pots land on 25K, OMEG on 22K), but I consider those identical.

Changing the ratios didn't have so much effect..

Maybe the transistor you used isn't a good choice, or maybe your lack of calibration plays a part. Worked perfectly here.

I got a bit white noise at the outs,.
The noise is always there, it's not effected by some pots!
HMMM, thinking about that!
Will rewire by using shielded Cables

Since you're using alternative wiring, you may experience alternative results from my prototypes. Measurements were fine here.

Next up:
The both Elcos at the outs are free to choose from 2200uF-4700uF
The G-1176 got 470uF, might you comment on that G?

Its what I had laying around/tested it with, so the note stayed on the silk screen. You could probably ask the same for a few other values in the build. You may not even need it, and if you run transformerless, bigger can't hurt in case your signal should see some ginormeous impedance..

Gustav
« Last Edit: July 03, 2014, 08:12:07 AM by Gustav »

gyraf

Re: Symmetrical FET
« Reply #13 on: July 03, 2014, 09:58:22 AM »

Changing the ratios didn't have so much effect..

Maybe the transistor you used isn't a good choice, or maybe your lack of calibration plays a part. Worked perfectly here.

Remember that this circuit lowers the threshold when you select lower ratio - trying to keep average GR the same. This means that you can't expect levels to change significantly with ratio - measure real ratio by comparing input level increase (initially over-threshold) of say 10dB to output increase dB.

Jakob E.
..note to self: don't let Harman run your company..

Greg S.

Re: Symmetrical FET
« Reply #14 on: July 19, 2014, 05:01:41 AM »

Changing the ratios didn't have so much effect..

Maybe the transistor you used isn't a good choice, or maybe your lack of calibration plays a part. Worked perfectly here.

Remember that this circuit lowers the threshold when you select lower ratio - trying to keep average GR the same. This means that you can't expect levels to change significantly with ratio - measure real ratio by comparing input level increase (initially over-threshold) of say 10dB to output increase dB.

Jakob E.

Dear Jakob,,

I finally found yesterday a really good pair of BF245a's, Mason's Site was very helpfull.. thx Mason..

The effect of compression is not as good a pair of Gustav's 1176ers.(Rev V/K, sold out meanwhile)

Do you have any suggestions for other Fet's?
BF245B? 2N5457?

Or what did you used?




Re: Symmetrical FET
« Reply #15 on: July 19, 2014, 12:27:15 PM »

Changing the ratios didn't have so much effect..

Maybe the transistor you used isn't a good choice, or maybe your lack of calibration plays a part. Worked perfectly here.

Remember that this circuit lowers the threshold when you select lower ratio - trying to keep average GR the same. This means that you can't expect levels to change significantly with ratio - measure real ratio by comparing input level increase (initially over-threshold) of say 10dB to output increase dB.

Jakob E.

Dear Jakob,,

I finally found yesterday a really good pair of BF245a's, Mason's Site was very helpfull.. thx Mason..

The effect of compression is not as good a pair of Gustav's 1176ers.(Rev V/K, sold out meanwhile)

Do you have any suggestions for other Fet's?
BF245B? 2N5457?

Or what did you used?

Jakob didn't build this unit, so he would have no way of answering this.

As mentioned, I only built it with the original NPD5566 thus far, but I will be trying out some different FETs, after I get an order of pots in.

Did the fake you tried out not work?

Gustav

(And a side note, Phat Phet=my final 1176 board revision, so not sold out but updated)

Greg S.

Re: Symmetrical FET
« Reply #16 on: July 20, 2014, 08:02:13 AM »
I meant your early 1176er that are close to Mnats layout G.
I don't have any others 76ers PCB's..

This is what I got for my three NPD5566 B0923 from eBay - 5bugs each..
They seem to work, Both Channels are pretty close-up, but the all div to each other..





Greg S.

Re: Symmetrical FET
« Reply #17 on: July 20, 2014, 08:04:17 AM »
as jpg

Greg S.

Re: Symmetrical FET
« Reply #18 on: July 20, 2014, 11:01:18 AM »
working now!!!  NPD5566 is doing what it should.

by the way, 3 different Ratios, right?

I will hard-wire anything,
hope, my tiny white noise is affected by the molex I used..
but in the end, it's all right..

THX for all that were part of this Project.

It's been a great Pleasure and a Privileg for me!


Special THX to Gustav..

=)
« Last Edit: July 20, 2014, 11:35:04 AM by Greg S. »

Greg S.

Re: Symmetrical FET
« Reply #19 on: August 13, 2014, 06:50:46 PM »
I reworked the Frontpanel and the Wirings, no more Molex and I added a MU-Shield for the Transformer!

Noise got less..  :)

But there is still some at one channel, but I will get this!