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Golden age Pre-73 & Comp-54 Carnhil Mod How to
Old 4th October 2011
  #1
Gear Head
Golden age Pre-73 & Comp-54 Carnhil Mod How to

After trawling the forums I found there was no clear information on how to Mod either Golden Age's Pre-73 or Comp-54. They're very simple mods to perform and i figured the information should be freely available to everyone

Therefore I have compiled this easy to follow Walkthrough for you all.

If you're at all unsure about completing these mods there are plenty of guys offering to do them for money in the forums.



Output Transformer (both Pre-73MKII & Comp-54):


Tools: Carnhill VTB1148 (Narrow Board Version), soldering iron, 2mm and 0.8mm solder, needlenose pliers, wire stripper, screwdriver.
(roughly 30 mins)

Unscrew the Original Transformer using needlenose pliers to hold the bolts.

Cut the four wires as close to the stock transformer as possible
Golden age Pre-73 & Comp-54 Carnhil Mod How to-img_0732.jpg

Strip, twist and apply solder to the ends of the wires you just cut.

As in the image below. Use the 2mm solder to link pins 7&6 and 2&4 then solder the blue and white wires accordingly.

Golden age Pre-73 & Comp-54 Carnhil Mod How to-img_0723.jpg
**If you own the MKI you need to add a zobel network with a 0.01 IF capacitor & a 1.5k resistor in series between pins 5&8. I have no experience with this so please don't ask **

Screw the Transformer back in place and you're done.

Pre-73 Mic Input Transformer mod:

Tools: Carnhill VTB9045, soldering Iron, solder sucker, 0.8mm solder, screwdriver, wire stripper, heatshrink, heat gun/ hair dryer, 10 7cm lengths of thin wire
(roughly 1.5 hours)

Golden age Pre-73 & Comp-54 Carnhil Mod How to-img_0862.jpg

Make a note of where all the cables are plugged into the PCB. It’s a good idea to write on the white tips to identify where they need to be plugged in again.


Remove the output transformer to give you space and then take out the large PCB by removing all cables and the 4 screws holding it in place.

Flip it over. Circled in red are the stock transformer pins you need to unsolder. On the topside of the PCB this is labeled ‘MIC’
Golden age Pre-73 & Comp-54 Carnhil Mod How to-img_0864.jpg

Heat the solder on each pin holding the stock transformer in place, then use the solder sucker to suck off all the solder.
Golden age Pre-73 & Comp-54 Carnhil Mod How to-img_0746.jpg

Push the pins to one side with the soldering iron to check if they're loose, otherwise keep sucking.
Golden age Pre-73 & Comp-54 Carnhil Mod How to-img_0747.jpg


Unscrew the transformer (circled red) and gently pull it free.


This is how the pins of the VTB9045 need to be connected. The numbers I’ve written on the PCB in white refer to the pins on the transformer.
Golden age Pre-73 & Comp-54 Carnhil Mod How to-img_0868.jpg
6+11 are the grounding pins and only need to be connected to one point on the PCB.


Strip, twist & tinn both ends of the wires with solder. Tinn the transformer pins, then solder wire to the end of each pin and place heatshrink over the ends.

Golden age Pre-73 & Comp-54 Carnhil Mod How to-img_0869.jpg
Then gently use a heatgun/hairdryer to shrink the heatshrink.
Golden age Pre-73 & Comp-54 Carnhil Mod How to-img_0870.jpg



Then we need to solder the wires to the PCB in the order described above. One by one push the wires all the way through, bend them to one side and solder them in place. (as shown left) Then cut off the excess.
Golden age Pre-73 & Comp-54 Carnhil Mod How to-img_0872.jpg

Finally it should look something like this:
Golden age Pre-73 & Comp-54 Carnhil Mod How to-img_0873.jpg
Now we need to make a template to screw the new transformer to the chasis of the Pre-73. Draw round the backside of the transformer making holes where the screws are.

Golden age Pre-73 & Comp-54 Carnhil Mod How to-img_0880.jpg
Place this on the chasis. Align it above the wires you soldered to the PCB as high as possible to leave space for the other components. Mark the screw holes with a marker then start drilling.
Golden age Pre-73 & Comp-54 Carnhil Mod How to-img_0876.jpg

Put the PCB back in, screw the transformer in place, then reconnect all the cables and put the output transformer back in. The result should look something like this:
Golden age Pre-73 & Comp-54 Carnhil Mod How to-img_0878.jpg




Comp-54 Input Transformers:


Golden age Pre-73 & Comp-54 Carnhil Mod How to-img_0718.jpg

Tools: Carnhill VTB9045M & VTB9046M (order direct from Golden Age) soldering Iron, solder sucker, 0.8mm solder, screwdriver.
(rougly 1.5 hours)


Make a note of where al the cables are plugged in, then take out the large PCB by removing all cables and the 4 screws holding it in place.


Flip it over. Circled in red are the pins you need to unsolder.
Golden age Pre-73 & Comp-54 Carnhil Mod How to-img_0722.jpg



Heat the solder on each pin holding the stock transformers in place, then use the solder sucker to suck off all the solder.
Golden age Pre-73 & Comp-54 Carnhil Mod How to-img_0746.jpg


Push the pins to one side with the soldering iron to check if they're loose, otherwise keep sucking.
Golden age Pre-73 & Comp-54 Carnhil Mod How to-img_0747.jpg



Unscrew the transformers (circled above) and gently pull them free.

Place the VTB9045M in position T3 with the sticker facing the front of the Comp-54 and the VTB9046M in position T2 with the sticker facing the back of the Comp-54
Golden age Pre-73 & Comp-54 Carnhil Mod How to-img_0752.jpg


Make sure they're as close to the PCB as possible (or you'll have trouble getting the lid on afterwards) and solder each pin.
Golden age Pre-73 & Comp-54 Carnhil Mod How to-img_0753.jpg



Screw the board back in, replace the cables, move CZ8 to jack CZ8* & you're done.
Golden age Pre-73 & Comp-54 Carnhil Mod How to-img_0756.jpg


Enjoy your Nevey goodness ;-)


Good Luck
Tom
Old 4th October 2011
  #2
Lives for gear
 
Matti's Avatar
Thanks! This will help many!

Matti
Old 4th October 2011
  #3
Gear Maniac
 



(aplause) Thanks a lot, also to many helpful
Old 5th October 2011
  #4
Gear Maniac
 

We do also stock the VTB9045M and VTB9046M but there was never really a demand so they do not appear in our on-line store yet..... I'll get it sorted out.

Colin
Audio Maintenance Limited
Old 5th October 2011
  #5
Gear Head
Hey Colin

Good to hear.

As far as you know, is there a difference, other than, size between the M and normal versions?
Old 5th October 2011
  #6
Gear Maniac
 

They are internally the same thing (core, windings, EMI screen etc etc)... the difference is only the case. ..... On the MuMetal version, one of the pins is also attached to the case.... on the original style the case is only connected to ground via the screws....

Colin
Audio Maintenance Limited
Old 18th November 2011
  #7
Here for the gear
 

Great tutorial,thanks for sharing !

Just wondering,do you wire the line Xformer same as the mic Xformer ?
It seems logical,but can you confirm ?
Old 26th November 2011
  #8
Gear Head
Im not sure about the Line xformer Bassinyourface. I'd suggest looking at the original Neve schematic and comparing it to the GAP schematic
Old 27th November 2011
  #9
Here for the gear
 

Thanks,I didn't have access to the 1073 shematics

Nobody seems to bother modding the line transformer.
Old 30th November 2011
  #10
Here for the gear
 
eagleman's Avatar
 

Hi for me with just some tiny solderingexperience… I’ve done some guitarpedals is this guide gold worth. I know near to nothing about how different components inside are working together and their individual function but I can solder

If there were a similar guide how to change the stock capacitors with Tantalum capacitors what to change and their values then this guide would be complete! (I don’t even know how a capacitor looks like!)

Thumbs up!
Old 30th November 2011
  #11
Here for the gear
 
eagleman's Avatar
 

---
Old 8th July 2013
  #12
I have a question about modding a comp 54. Why are there two input transformers. Are both in the audio path or should both be changed?
Old 19th July 2013
  #13
Gear Head
Both are in the signal path. One boosts the signal from the other so both need to be changed
Old 22nd January 2014
  #14
Gear Head
***UPDATE***
The guide shows the wrong mounting of the input transformers. Both need to be flipped 180 degrees so that the VTB9045M in position T3 has the sticker facing the back of the Comp-54 and the VTB9046M in position T2 has the sticker facing the front of the Comp-54.
Sorry for any confusion.

So in the end it will look like this:
Old 2nd February 2014
  #15
Here for the gear
Gap 573

Is this mod applicable for the 573 Lunchbox Version too?
Old 2nd February 2014
  #16
Lives for gear
 
skillz335's Avatar
wow thanks for this.
Old 3rd February 2014
  #17
Quote:
Originally Posted by Trashjive View Post
Is this mod applicable for the 573 Lunchbox Version too?
I remember reading somewhere tht the Carnhill's are too big for the 500 series version.
Old 3rd February 2014
  #18
Here for the gear
Thx for that!
Old 18th February 2014
  #19
Gear Head
Yep as far as i know there are no mods for the 573. It's just too damned cramped in there
Old 15th May 2014
  #20
Here for the gear
 

anyone ever tried a vtb9046 as a replacement of the line input xformer on the pre73? if so any thoughts about the results?

thx
m
Old 16th September 2014
  #21
Here for the gear
 

Unhappy

Hello everyone!
I'm trying to make the "upgrade carnhill" in my comp-54, and I find conflicting information!
I'm a mess and do not know what to do ...

On the one hand, in the instructions they attached me who sold me the upgrade, it is stated that:
-The label 9045 (T3), should face the front of the compressor.
-The label 9046 (T2), facing toward the back of the compressor.

On the web Hispasonic indicate exactly the same, as you can see in the first pic:
CARNHILL MOD COMP-54

But here, in gearslutz, you write that it have to do it backwards ... And I know this Hispasonic compressor worked properly, because they did a complete review with it and I also know a bit of the author.

Also I have a question regarding the transformer output (tOUT): Output terminals are #5 and #8, that I am clear. But ... where are they connected?
I think the pin#8 of the transformer goes to pin#3 of CZ14 connector and pin#5 of the transformer is connected to the pin#2 of CZ14.
I'm right?
I do not know whether it is or backwards.

My language isn't english, sorry. I hope I explained well...
Thank you for your attention!
Old 21st March 2015
  #22
Question

Quote:
Originally Posted by skizotom View Post
***UPDATE***
The guide shows the wrong mounting of the input transformers. Both need to be flipped 180 degrees so that the VTB9045M in position T3 has the sticker facing the back of the Comp-54 and the VTB9046M in position T2 has the sticker facing the front of the Comp-54.
Sorry for any confusion.

So in the end it will look like this:
Hi! Are you sure of that? Look at post #21 , it's a bit confusing. Thx to confirm!
Old 21st March 2015
  #23
Gear Head
hey guys
Regarding the transformers.I sent my comp-54 back to Golden Age as there was a distortion issue with it.While fixing that Bo noticed that I had my transformers backwards and changed them for me.It worked both ways, but flipped is apparently the right way.ill take a photo of the inside of mine later to make it clearer
Old 25th March 2015
  #24
Here for the gear
 

I appreciate this thread as I too was looking for specific info on modding the Gap Pre 73.

I received a used one and unfortunately there were and still are some issues. Firstly the included transformer was missing some plates so I replaced it with the Carnhill according to the instructions(was going to do this regardless) here and I was also hoping that it would fix the second issue with the Pre, it sounds as if all of the frequencies below 300 hz is missing!! I managed to find a local shop that can do repairs and will send it to them, but i would like to know if anyone has a clue as to what the problem could be that is causing these dead frequencies.

a little more background also...when i received the unit it did not have a power supply, despite that not being said on the EBAY ad, so the seller refunded me some money to go towards a new power supply. fine.

I ordered a replacement PSU from B&H, they sell the original PSU that comes with the unit, so upon arriving, i plugged it into the PRE and heard the missing frequencies for the first time, arghh, while in my disappointed state i begin to hear a buzzing sound that was coming from the power supply, loud buzzing, so I realized the PSU was bad and sent it back to get another, once this arrived, I tried again with fingers crossed, but it was no go, the dead freq issue was still heard, needless to say i contacted the seller and he offered to return and refund me for the preamp or keep it and refund me back more than half what i paid for it to have it repaired. I decided to keep it and get it repaired.

so here is where i am at and still baffled as to what is wrong.

The repair guy did mention that an incorrect power supply may have been used on it which got me to thinking if the seller who said the unit was tested, did not have the original power supply to go with the unit what did he test it with?

Anyway any suggestions on what the issue may be could help me to at least have some piece of mind and maybe a heads up for the repair tech.

thanks
Old 28th March 2015
  #25
Gear Head
Quote:
Originally Posted by skizotom View Post
hey guys
Regarding the transformers.I sent my comp-54 back to Golden Age as there was a distortion issue with it.While fixing that Bo noticed that I had my transformers backwards and changed them for me.It worked both ways, but flipped is apparently the right way.ill take a photo of the inside of mine later to make it clearer
So i took the lid off and the 9045M in position T3 should be facing the back of the until
while the 9046M in position T2 should be facing the front

Hope that clears it up
Attached Thumbnails
Golden age Pre-73 & Comp-54 Carnhil Mod How to-dsc02079.jpg   Golden age Pre-73 & Comp-54 Carnhil Mod How to-dsc02080.jpg  
Old 28th March 2015
  #26
Lives for gear
 
DirkP's Avatar
 

There will be new versions of the GAP Pre73 and the Compressor with "plus" in the name, pre-equipped with Carnhils. Just saw this on their webpage.
I have a Pre73DLX and the EQ81 and although I use mostly a Warm Audio strip, I still like the Gaps a lot.
Old 8th December 2015
  #27
Does anyone have any information on how to do the IMOD Carnhill Input transformer mod to the Chameleon Labs 581?
Old 12th December 2015
  #28
Here for the gear
 

I'm looking for info regarding converting the trs output jack into an insert jack to be used with the eq's. GAP's website mentions the mod but is not very specific in the steps involved. Anyone here have any experience doing this mod?
Old 4th February 2016
  #29
Gear Maniac
 
kilroyrock's Avatar
i just got my carnhill transformers in, and I gotta say, this output tranny is HEAVY. Is the chinese one this heavy too and I didn't realize it? I'll be taking it out soon so i'll know then!
Old 5th February 2016
  #30
Quote:
Originally Posted by kilroyrock View Post
i just got my carnhill transformers in, and I gotta say, this output tranny is HEAVY. Is the chinese one this heavy too and I didn't realize it? I'll be taking it out soon so i'll know then!
The VTB9045 is pretty heavy as well, and definitely added weight to my 581 \m/
The Carnhills are definitely heavier than the stock chinese transformers, very much so.
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