BeePre Input Transformer Modification

fullheadofnothing · 10478

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Offline fullheadofnothing

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on: July 28, 2014, 10:34:48 AM
Well, a while ago PB and I did a photoshoot for the input transformers to give a balanced input to the BeePre. The plan always was to get it up on the website, rather than as a pdf manual. A few things came up here and there (like a full replacement of the website), and now it's finally up. It's in the blog section of the website, or here is the link.

http://bottlehead.com/bee-pre-input-transformer-modification/

Joshua Harris

I Write the Manuals That Make The Whole World Sing
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Offline Demsy

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Reply #1 on: August 31, 2014, 03:10:39 AM
Hi Josh,

It says 404 Page Not Found. Is it removed?



Offline fullheadofnothing

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Reply #2 on: September 01, 2014, 07:42:05 AM
It got lost in the recent website shuffle. I've put it back now.

Joshua Harris

I Write the Manuals That Make The Whole World Sing
Kit Packer Emeritus


Offline Demsy

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Reply #3 on: September 04, 2014, 01:48:10 PM
Thanks Josh!



Offline bombay317

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Reply #4 on: December 15, 2017, 04:08:14 AM
I am going to be following your instructions. 

I contacted Cinemag, and they have 4 week lead times on the transformers (if anyone was interested to know that).  I opted for the double shielded ones. 

Mouser ships immediately, but they always do that.  Another option would be Digikey or Jameco, but all of that stuff is usually in stock by the 1,000s.

Niagara 7000
Benchmark DAC3L (XBOX1 and TV)
CA Performance w/ Satisfy Turntable
Talismann V2 CA Cartridge
Tavish Designs Adagio Vacuum Tube Phono
BHSE Amp
Stax SR-009
BeePre 300B w/ BeeQuiet and Cinemag Transformers
Kaiju 300B w/ DC Filament
Jäger Speakers
Transparent and Benchmark Cables


Offline bombay317

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Reply #5 on: February 12, 2018, 06:04:39 AM
When I went through this I noticed a difference between the BeePre mod and the BeePre XLR procedure.

https://bottlehead.com/bee-pre-input-transformer-modification/ in this there is no step to tie Pin 1 of the XLR input to the chassis ground. 

There is a step covered in the BeePre manual at the first step of "Output Wiring" that ties Pin 1 of the XLR input to the chassis ground.

Should this be done for this input?

Niagara 7000
Benchmark DAC3L (XBOX1 and TV)
CA Performance w/ Satisfy Turntable
Talismann V2 CA Cartridge
Tavish Designs Adagio Vacuum Tube Phono
BHSE Amp
Stax SR-009
BeePre 300B w/ BeeQuiet and Cinemag Transformers
Kaiju 300B w/ DC Filament
Jäger Speakers
Transparent and Benchmark Cables


Offline Paul Birkeland

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Reply #6 on: February 12, 2018, 06:39:47 AM
It's not unreasonable to put a switch into the BeePre to make this connection.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline bombay317

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Reply #7 on: February 12, 2018, 10:10:27 AM
Paul,

I am not sure I follow your comment.  Are you saying you should put a switch in between Pin 1 and the XLR shield?  I'm trying to understand what you mean.

In the data sheet http://cinemag.biz/line_input/PDF/CMLI-15-15B.pdf for the CMLI-15/15B2 under the "TYPICAL APPLICATION" section, there is a switch installed from Pin 1 to ground, but it is also in parallel to a R and C.  Not sure if that is what you meant?

I really just followed the "BeePre Input Transformer Modification" by Joshua Harris.  These XLR inputs take the place of R3 and L3 and do use the green and brown pairs that go to the input switch.

Niagara 7000
Benchmark DAC3L (XBOX1 and TV)
CA Performance w/ Satisfy Turntable
Talismann V2 CA Cartridge
Tavish Designs Adagio Vacuum Tube Phono
BHSE Amp
Stax SR-009
BeePre 300B w/ BeeQuiet and Cinemag Transformers
Kaiju 300B w/ DC Filament
Jäger Speakers
Transparent and Benchmark Cables


Offline Paul Birkeland

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Reply #8 on: February 12, 2018, 11:25:05 AM
Sure, you can follow Cinemag's documentation.  One position gives a hard ground to the load end of the shield, while the other position looks to provide a convenient path to ground for high frequency noise.

The BeePre we used for those photos is mine, and I haven't noticed any noise on the balanced input, but I use my BeePre in a pretty quiet environment with short cables.

-PB

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline grufti

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Reply #9 on: July 27, 2019, 10:05:42 PM
The link to the page describing the input transformer modification is dead again. I would like to take a look at it. Is it still possible to revive that page one more time?




Offline Brissie

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Offline denteom

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Reply #12 on: January 19, 2024, 01:38:17 AM
Hi PB:
Do you have a photo of the xlr inputs and transformers topside?  The Cinemag transformer does not look aesthetically pleasing.  But I know the material they use is of good quality mu-metal I think.  I watched Steve Guttenberg youtube channel wherein he was featuring Devon Turnbull.  He held up a Cinemag transformer, showing it had octet like feet, so he can put it in and pull it out easily.  Not sure if that was his modification or you could order that directly from Cinemag.  You should watch it.  It's pretty cool.
Dennis



Offline Paul Birkeland

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Reply #13 on: January 19, 2024, 06:02:10 AM
There are no provisions on the BeePre for an octal based input transformer.  I'm not even sure there's room.

I've attached the only photo of Cinemag input transformers I have, which is a local friend of mine who I convinced to build his BeePre into a metal case.  I had to space them off the chassis a bit since they were hitting mounting screws for the input selector board, so that's why they look a little odd and have a squishy washer under them. 

I cannot imagine how something like this would or wouldn't be aesthetically pleasing.  These are metal cans that live in the back of the chassis where all the cabling is coming in/out.  They are mostly invisible and you really want a well shielded can over anything else. The threaded bushing mount is a good way to ensure that the shielding of the can is well bonded to the chassis.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline denteom

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Reply #14 on: January 19, 2024, 06:53:40 AM
Thanks, for the photo. It looks nice with the metal casing. Might look different in a Beepre 2 default casing.  But the default casing would be much easier to fix and troubleshoot especially for beginners like me.  Using the default casing would have the metal cans sticking on the top.  Really enjoying the Beepre2.  Looking at the photo, I'm starting to have an upgrade itch, but that is for another time.  For now just exploring music.