CARNHILL VTB2168 - Hook-up & Phase - POLARITY - CJ ?

I just finished my second Neve 1272 pre & used the CARNHILL VTB2168's that I got from Joel (JC) from the groupbuy over a year ago. They are the input trannys.

Well, when I hook them up normal (like the 10468) the phase gets reversed :?

I know it's a simply fix but I thought these were copys of the old originals... neither Joel or anyone else has mentioned the phase on these. If you are using these you better check your phase.

I wish I could get a hold of the DATA Sheet, or even Joel. If anyone has one let me know... but I doubt it because I think they were "Custom made" & have unique part #'s.

Wow, that's interesting. You may be the first one who has used these. I don't think there is a datasheet, as such. I know CJ designed the bobbin to flip, or the windings reversed, or flipped, or whatever, to match the originals, unlike the current Carnhills, and that may swap the polarity. And maybe Carnhill forgot to reverse again out to the proper pin outs.

We should do some testing and verify this is reversed in other people's transformers.

Same thing here !
The output is phase reversed, i've triple checked the connections.

Anyone can shed a light on this ???

BTW... they sound GRRRRRRRRREAT !

Neeno, are you using both the custom inputs and outputs? Which one is reversing the polarity?

The inputs are reversing the polarity.

I have been using mine, blissfully ignorant of the polarity reversing now for many months in my 1272's.... with stellar results, BTW. Not until Kevin got ahold of me last night was I aware of the polarity issue.

After speaking with Kevin for about an hour I located and studied the winding information CJ provided for these and it appears that he marked a different pinout than that used on the original Marinair or later St.Ives which results in the polarity reversal when connected as Neve did.

I believe I know the 'proper' pinout of these inputs based on the winding docs, but I'll wait till he either confirms or corrects my conclusions before reporting back to the group.

Also, for those who like to test the sound of preamps 'live' (that is, by speaking into a live mic while simutaneously monitoring through speakers or headphones), don't do this to compare the sound of circuits with opposite polarity as the two polar positions will often sound dramatically different, not because of actual character differences in the circuit, but because of the phase relationship of the amplified signal to the sound resonating in your head from your actual voice.

Instead, record your tests and listen back to them. This is the only real way to objectively examine the character of the circuit.

More soon.

JC

Thanks for the heads up. I will have my JC1272 with groupbuy transformers ready for a session on Saturday. Just need to mount it in the chassis. :grin:

Hey, Skipwave,

If I may be so bold, may I recommend you breadboard the circuit and put it (them?) through a good testing before you bother mounting all the bits and pieces in a chassis? It seems pretty common that people have at least some minor troubleshooting to do before everything is nice and happy with their Neve build, and this usually means tearing much or all of it apart to find and fix an issue in the circuit somewhere. By proving the circuit(s) before you bolt all the pieces in a chassis you might save yourself some hassle.

Just a thought that keeps popping in my head when helping people with their Neve builds.

Not that I've ever actually followed that advice myself!

:razz:

Peace,

JC

[quote author="rascalseven"]The inputs are reversing the polarity.

I believe I know the 'proper' pinout of these inputs based on the winding docs, but I'll wait till he either confirms or corrects my conclusions before reporting back to the group.JC[/quote]

JC, so what is the proper pinout?

Well, CJ is no where to be found, so I still don't have a confirmation from him.

However....... based on the winding documents CJ supplied (and subject to CJ's further input into the matter), I am confident that the proper pinout that matches the original performance of the Marinairs is:

Primaries: connect pins 3 and 4, pin 2 hot, pin 5 cold
Secondaries: connect pins 7 and 10, pin 9 hot, pin 8 cold
Pin 6 is the chassis connection, so jumper it over to the screw in the corner of the pinboard, and then bolt the tranformer to the chassis of your device.

Unfortunately keeping pins 8 and 9 connected and simply using 10 as the + and 7 as the - isn't the same as connecting it as described above.

They sound freaking phenomenal, BTW... :grin:

I don't know why CJ altered the pinout of the secondaries. I would have thought it to be a mistake, but if so, then he made the same 'mistake' on both halves of the winding information (two separate documents), which doesn't seem likely. I can't locate him at the moment.

Does anyone know where CJ is? He's not answering emails, and his phone number (the one I have, anyway) is no longer in service.

Has he gone the way of Winston? I sure hope not.

JC

[quote author="Neeno"]The output is phase reversed, i've triple checked the connections.[/quote]
Polarity people, polarity :wink:

Thanks, JC.

I've had no replies to my emails to CJ for some weeks.

It is the kayaking season now and he may be very busy in the Sierra white water kayaking. I don't think he's on the run for any DIY issues like Winston was! Maybe DUI... but that's another matter. :grin:

I just remembered, CJ is doing internet VOIP phone only now, that's why his old phone line is out.

CJ posted here a couple of days ago. Relax.

A P

[quote author="clintrubber"][quote author="Neeno"]The output is phase reversed, i've triple checked the connections.[/quote]
Polarity people, polarity :wink:[/quote]
Being rigorous about the terminology, I'd have to agree. :wink:

Checking this out.
Been on vacation for a couple of weeks, took it at the spur of the sales slump, thats the way it works in small biz.

I was worried about something like this, especially when I sw the numbers climb on the order. But if it's just a lead flip, and the sound/hum is OK, ...

Still...I took apart more than one of those guys, it will be interesting to see what happened.

Do the carnhills have flying leads, or pins like the stock?

I got this Magnetics Dept running at work now, and every friday off til Sept 30 :grin: :grin: :grin: :grin:

so DIY city. If it's just a matter of opening up the case and swapping leads, I will be happy to do that if needed.

Blew up my Wi Fi box trying to squeeze out 10 more milliwatts, so no surfing at home.

Joel, the 2 xfmr's are boxed, email that Fed Ex acct # if you need overnite.

cj'

:green:

CJ, Please get a hold of JC on this... I think he was trying to call you but your # didn't work. I have his # if you need it - PM.

It's very important we get to the bottom of this & thank you. :thumb:
Glad your back.

BTW, I got the 610 schematic so you can dump my PMs about it.

Is there an inverting stage ahead of the trans?
If Neve had one in there that is not being used by you guys...

probably wrong, but just want to eliminate that as a possible cause.


As long as the turns and the core are right, the sound will be the same, so no unwinding or rebuilding necessary, just a lead swap.

To my knowledge there is NO invert before the trans.

OK, a lead swap... but which ones (exactly which pins) - Primary or secondary.

I think that everyone will want to know how the Original tranny should be wired.

Could you recheck your data & schematics you drew up that were sent to Carnhill?

Thanks again CJ :thumb:

Hey, CJ! Glad you're here! :grin:

No polarity inversion before the input transformer on the Neve stuff. The inversion is definitely happening in the transformer itself.

Check out http://www.danalexanderaudio.com/neve.html and click the first "Transformer Information" to check out the pinout if you don't already have that document. I compared that doc against your numbered terminations in your T1454 winding documentation to come up with the suggestion I made earlier in this thread. Please let us know if that was right or wrong.

JC

If the primary windings are reversed shouldn't the prim pin connections also be reverse like 2 & 4 reversed with each other and 3 & 5 ?

Something is strange as I can't recall that I have had any phase problem with original T1444 / T1454

JC! Received a bax of Motorola MJE3055 for the moduls today! Finaly!

You may be right but I'd rather not speculate & instead what for a SOLID answer from CJ or Joel.