Orange 86 Build Thread New
« on: May 20, 2009, 07:05:09 PM »


PSU for P48, Relays and balanced or elevated AC Filaments

Build Docs Folder:
https://www.dropbox.com/sh/g6n57y9ju6hwknz/AABrx_uyGpweCHkqwwMQi6Xja?dl=0

New BOM as of 1.8.2019
https://www.dropbox.com/s/ggegayarww0spk2/Orange%2086%20Preamp%20BOM.2019a.xlsx?dl=0

Better Gain Switch Files:
https://www.dropbox.com/s/vqzx9pvux8wq3x8/Gain%20sw%2030k.jpg?dl=0
https://www.dropbox.com/s/pnannsc1o3cmw5l/ORANGE%2086%2030K%20GAIN%20SW.xlsx?dl=0

Note: This should be used in conjunction with No Negative feedback Compensation caps.  The modification is this post:
https://groupdiy.com/index.php?topic=33657.msg891913#msg891913


Record Engineering Development Department Type 47 inspired dual tube preamp used on well known 1960’s British recording sessions to replace the Siemens V series amps.  Featuring a pentode front end and second stage military parallel triode configuration.  (EF86/EF806/6267 and 6DJ8/6922/E88cc respectively). Stable, quiet, compact and efficient 290-300 VDC power on preamp PCB; linkable for stereo units. Very clean signal path with 2 high quality coupling capacitors and extra bypass cap options.  Film bypass caps on cathodes.  Practical NFB 12 position gain switch using an ubiquitous Grayhill PCB mount switch with 2 polystyrene caps for HF compensation.  Film bypass caps on high voltage decoupling caps.  4 Auxiliary PCB’S make P48, dual PAD, DI, and GAIN wiring a breeze. 2 relays take care of automatic MIC/DI switching and Output polarity switching duties.  Some engineers have really been enjoying the subtle ‘SQUISH’ compression option.  Filament options for AC or DC and stage 2 tube variations like a 12V 12bh7.  Tweeker’s Delight!

Power PCB sets P48 and relay power, balances Filament AC, and provides and easy route to ON/OFF indicator lamp. Optional circuit to elevate Filament ground reference. P48 doubler or trippler. Unregulated Relay/Auxiliary 12 or 24 volts.


Squish Notes
The Squish is just to experiment with Compression.  I forgot to mention in the build docs, but it is very important.  Make sure you Jumper the Squish Pads together if you do not want it.  I would start without it to make sure the preamp works,then play with it to see if it's something you like.  Maybe add a pot with a switch so it can be shorted when the squish is not in use.

Insert a 500K pot wired as a variable resistor. Or use a 500K pot with a switch so that you can turn squish off and have the path go to ground to disengage it.
Pot with switch:
https://www.tubesandmore.com/products/potentiometer-alpha-audio-spst-switch
or bourns: PTR902-2020K-A504 and just use one side

Notes on LED indicator for P48
If your LED hole is above your P48 switch it will be necessary to extend the LED's leads with some 24-26 AWG solid wire.  I used some CAT-5 network cable with solid wire for one LED.  Just make sure to trim LED leads or the wired bends may be on the solder joint which is never good.  24 AWG is better since it is stiffer.   Strip 2 solid 24-26 AWG wire.  Cut 1/2" off of LED leads.   Solder solid wire to LED leads.  Apply heatshrink to Positive(long lead) of LED.  Bend leads appropriately.  Solder to P48 PCB - Positive pad is on top and Negative pad is below.  Adjust LED to proper height and apply dab glue to keep in place.





Orange 86 Constant Impedance Gain Switch

This way of varying Negative Feedback to alter the first stage pentode gain is similar to the Siemens V76 topology, just implemented differently to suit the REDD.47 circuit.  We were testing some recording at 98K sampling rates and the high were sounding harsh compared to our differential tube preamp. We then tried various methods of varying gain and found this method gave best THD and frequency response through the Audio Precision.  Many have found they like the full gain settings better in the REDD preamps which confirms our findings.  Since with lower gain settings the impedance would be a resistive load of 10K at +40 dB and 6.4K at +34 dB, and the high frequency would extend out to 40-60 KHz (Read up on Bode plots and feedback theory, which explains this in more detail).

This Constant Impedance gain switch along with 2 capacitors solves the inconsistencies of the old gain switch.  The first cap at the pentode input and R3 rolls off highs so any high frequency problems are corrected at the input, rather than in the feedback circuit. The other cap across R8 compensates for high frequency loss at high gain settings. The original switch tries to fix high frequency problems after the fact and is partly what lead us to a new gain switch in the first place.


1.  Omit C-FB-1 & C-FB-2

2.  C-M1 - Put a 330pf  ceramic COG/NPO cap from V1 grid(Pin 9) and use 1K on R3 grid stopper
-Silver Mica is fine here too and may be preferred by some. You can use a range down 220pF and
increase R3 to 5k7 to 10k if that’s what you have.

3.  C-HF1  Put a 22p COG/NPO cap rated at 1KV across R8. 


https://www.dropbox.com/s/p3jugxio9f96e8u/IMG_2269.jpg?dl=0

It takes all of 5 minutes and is pretty easy.  The blue cap is the 22p and ones side goes into the valve PAD which has plenty of room and the other side goes into C3's bypass cap pad.

The Yellow cap is the 330p cap the top wraps around the lead of the 1K grid stopper and the bottom lead going into the ground pad for R2, which is not needed.

With the above complete here is the Constant Impedance Gain Switch Directions
-Above mod necessary for Constant Impedance Gain Switch

1.  Jumper R-FB-1

2.  Omit these Parts

C-FB-1
C-FB-2
R-17
R-5
VR-1

3. Follow schematic of Gain Switch Connections

Here is the basic Diagram without the Gain Switch PCB:

https://www.dropbox.com/s/vqzx9pvux8wq3x8/Gain%20sw%2030k.jpg?dl=0

Here is the Gain Switch Modification diagram:

https://www.dropbox.com/s/ifymtwdoqcxtnv3/Gain%20sw%2030k%20PCB%20mod.jpg?dl=0

My definitive termination configuration for Input transformer secondary is  130K for R-T
For DI-L a 2M-4M  resistor.  And omit R2. Use the appropriate R-z and C-Z depending on the transformer used.

The 130K will reflect 2K at 1KHz and 1.5KHz at higher frequencies.

Also, if you want to cut your high frequency response you can play around with the blue cap from 47p-100p for +1 dB or so from 5-10 KHz.

Fine Gain Switch   +/- 5 dB Can be added to Original Gain Switch

Using these values in place of R5 and removing VR-1 and R17 pot adjustment that alters the lower feedback divider resistor.  These values are from stringing series resistors together like on the gain switch.  It should give  a 10 dB range with 1/2 a dB between steps other than the 200R step.  The Pole of a 12P switch will go to Th V1 Gain switch point. The 43R and Position 1 will go to the negative side of C2. The 36R will hang off position 12 and go to ground.

You can wire with switch from several points:
the 2 R5 PADs
R17 - provided one side meet the feedback of the fain switch
or Just take it from the V1 connection on the gain switch and the other end directly to ground.
-a look at the scheme should clarify this

OTHER UPDATES

Recommend R5 or 120R and omit VR1 and R17 network.  IMHO a waste of $2
R-T = 130K (list of reflected Impedance on BOM sheet)
DI-L = 2M
Omit R2
R3=1K (can't hurt and may help)

Edited and added non-Kit Part options
Yellow Highlights for non-Kit Parts for better clarity

Happy DIY-ing folks!
« Last Edit: January 11, 2019, 03:20:14 PM by guavatone »


idylldon

Re: Orange 86 Build Thread
« Reply #1 on: May 20, 2009, 07:43:52 PM »
Thanks! 

Cheers,
--
Don

deuce42

Re: Orange 86 Build Thread
« Reply #2 on: May 21, 2009, 07:07:40 AM »
Awesome Charlie

Thanks!

alexc

Re: Orange 86 Build Thread
« Reply #3 on: May 21, 2009, 07:18:15 AM »
Fruitilicious!
I ping therefore I am

iomegaman

Re: Orange 86 Build Thread
« Reply #4 on: May 22, 2009, 07:34:00 PM »
Got my boards today awesome work thanks so much for your effort on this, I am looking forward to building this!!!
Since the development of the internet millions of people have died, the two may or may not be related.

Kingston

Re: Orange 86 Build Thread
« Reply #5 on: May 26, 2009, 05:45:20 AM »
obnoxious p%d's and other guitar modeling box's that so many people record with.

Are you sure you understood what this project is? This is a microphone preamp. There is absolutely no way you could replace any amp modeling box with this one.

Sure you could get a beatles "revolution" type direct to mixer distortion with this, but that's it. It's a decent DI, but nothing to replace proper amp models with this.

SUPERMAGOO

Re: Orange 86 Build Thread
« Reply #6 on: May 26, 2009, 06:13:14 AM »
nice pcb! but what are the differences with the version of winston "four seven"?

jdbakker

Re: Orange 86 Build Thread
« Reply #7 on: May 26, 2009, 08:33:33 AM »
I had a brief look at the schematics, and some things look a bit off.

- On page 1, the polarity at the 'RELAY PWR' connector doesn't match the polarity of the attached components (Q2, D10, RL1)

- On page 7, if J2 is tied to J3 (as suggested), what is the function of D12 and D14? I don't think you'll need reverse voltage protection here.

- On page 7, U2 must have a 100nF capacitor between Vin and ground to keep it from oscillating at certain loads/load steps, as R5 can be considered "an appreciable distance from power supply filter" (quote from the ON Semi LM317 datasheet; the NatSemi version has words to a similar effect).

- On page 7, consider replacing D10 with a ~35V zener diode to keep U2 from getting killed by overvoltage; this typically happens at turn-on or when the +48V supply is accidentally shorted to ground.

JDB.
[maybe some/all of these have been fixed in the PCBs; I haven't checked]
« Last Edit: May 26, 2009, 08:35:28 AM by jdbakker »

nielsk

Re: Orange 86 Build Thread
« Reply #8 on: June 08, 2009, 09:28:29 AM »
Alternate audio transformer suggestions?

Re: Orange 86 Build Thread
« Reply #9 on: June 08, 2009, 05:23:33 PM »
nielsk,

You may try Edcor XSM15K/6000 for output and WSM10K/150 (reversed) for the input.  I can't guarantee anything but for $25 it's worth a shot.  


jdbaker,

The relay circuit works as is.  Yes  page one is mislabeled, I will update it soon.  If you follow the connections on the board labels, they are right.  Sorry, but as you can see the schem is a bit crowded up there in the upper right.

Thanks for your suggestions about page 7.  I remember the 35V Zener being a nuisance on the JLM power supplies I worked with a while back.  Maybe I will revise the PS with a 100nF cap before the reg. You could always sacrifice R6 if you would rather have a cap there.
« Last Edit: June 10, 2009, 12:50:19 AM by guavatone »


Biasrocks

Re: Orange 86 Build Thread
« Reply #10 on: June 10, 2009, 05:39:03 PM »
main schemo corrected and tip for P48 LED added.

I tried d/l'ing the new Build Doc's and got this message

You don't have permission to access /free/0-PCB/O86_BuildDocs.zip on this server.

Mark
http://SharktankPro.com

"I'd rather use an SPX90 than a UA plugin....." Joe Barresi

Re: Orange 86 Build Thread
« Reply #11 on: June 30, 2009, 01:26:06 AM »
Docs on top edited with additions.  I will be away from July 1-8 but I will try to check in.

kambo

Re: Orange 86 Build Thread
« Reply #12 on: August 02, 2009, 09:33:33 PM »
has anyone made any progress on this, yet ?

kam



Re: Orange 86 Build Thread
« Reply #13 on: August 06, 2009, 09:09:51 AM »
I just did a quick test of an Edcor which will give another 4 dB of gain.

I will try a zobel to see if that HF can be tamed.  The 600:15K may be better but I do not have one one hand.

Left= cinemag output  Right= Edcor 600:10K

kato

Re: Orange 86 Build Thread
« Reply #14 on: August 06, 2009, 09:50:09 AM »
A < 2db rise outside my range of hearing doesn't sound like it needs much taming, at least not for tracking purposes. I'd be willing to try the Edcor without zobel and see how it sounds.

 - come to think of it, I might get this built faster if I don't have to first save up for cinemags...

deuce42

Re: Orange 86 Build Thread
« Reply #15 on: August 06, 2009, 10:00:15 AM »
Yes am I missing something as well? It seems that the difference shouldn't matter at all.

People with more knowledge than me please tell me if I am going wrong but it seems to me that the only difference between the Edcor and Cinemag is the extremely high end of the high end? 


bernbrue

Re: Orange 86 Build Thread
« Reply #16 on: August 06, 2009, 02:35:08 PM »
Hi,
the Edcors seem to work fine. What input transformer did you use in your test setup? Three channels waiting for iron here.
regards
Bernd

kambo

Re: Orange 86 Build Thread
« Reply #17 on: August 06, 2009, 02:53:31 PM »
Yes am I missing something as well? It seems that the difference shouldn't matter at all.

People with more knowledge than me please tell me if I am going wrong but it seems to me that the only difference between the Edcor and Cinemag is the extremely high end of the high end? 


as far as i have tested some tranies ( on different projects ) , they all sound different... test specs doesnt show actual color of the tranie...

Re: Orange 86 Build Thread
« Reply #18 on: August 06, 2009, 02:59:41 PM »
Hi,
the Edcors seem to work fine. What input transformer did you use in your test setup? Three channels waiting for iron here.
regards
Bernd

Cinemag CMMI-7C for both tests

deuce42

Re: Orange 86 Build Thread
« Reply #19 on: August 06, 2009, 08:38:50 PM »
Kambo - yes I accept that the colour is something that is unique to every transformer. But as long as the Edcor can substitute its nice to know there are options.



 

Related Topics

  Subject / Started by Replies Last post
76 Replies
24056 Views
Last post November 03, 2010, 01:51:16 PM
by pH
73 Replies
30877 Views
Last post September 26, 2010, 01:51:30 PM
by SIXTYNINER
205 Replies
48637 Views
Last post April 22, 2017, 11:03:10 PM
by duantro
64 Replies
23599 Views
Last post January 09, 2017, 10:32:15 AM
by kosi