Carnhill VTT2326 Transformer

[TJS]

Hi,

I'm looking for a cheaper alternative transformer to a Carnhill VTT2326 for a 1073.

I've attached the datasheet, and it looks like it puts out 2 secondary voltages: 24.5v @ 0.5A and 38.5v @ 0.023A.

I have two questions: how much would a power transformer affect the sound? I guessing minimal?

And also, does anyone know of any cheaper alternatives that can be used in it's place?

Thanks!

 

[My3gger]

If specified properly like Carnhil 2326, mains transformer don't change the sound of this circuit. Try local toroid winders because they might be cheaper than Carnhill.

 

[TJS]

If specified properly like Carnhil 2326, mains transformer don't change the sound of this circuit. Try local toroid winders because they might be cheaper than Carnhill.

Thanks, that was what I was thinking - do you have any suggestions on alternatives - I'm struggling to find ones that put out two secondary voltages

 

[ruffrecords]

You will notice that the 38V winding is rated only at 23mA. This is for the phantom supply. The total power required from this winding is less than 1 watt. A quick search at Farnell reveals you can buy one of these for about £6 (I have chosen one with 2 x 24V secondaries which will be fine for most phantom power designs). Then all you need to dine is a 24V transformer rated for more than 0.5A. You can get a 15VA 2 x 12V toroid from RS for £17.50, So the total is £23.50. How does that compare to the Carnhill price?

Edit: I just discovered the Carnhill cost over £60!

Cheers

Ian

 

[TJS]

You will notice that the 38V winding is rated only at 23mA. This is for the phantom supply. The total power required from this winding is less than 1 watt. A quick search at Farnell reveals you can buy one of these for about £6 (I have chosen one with 2 x 24V secondaries which will be fine for most phantom power designs). Then all you need to dine is a 24V transformer rated for more than 0.5A. You can get a 15VA 2 x 12V toroid from RS for £17.50, So the total is £23.50. How does that compare to the Carnhill price?

Edit: I just discovered the Carnhill cost over £60!

Cheers

Ian

Thanks Ian, the Carnhill one is so expensive!

Ahh ok, so with your method you're suggesting using two different toroidal transformers; one to handle the phantom power with 2 x 24V secondaries, and a second toroidal transformer to power the amp with 2 x 12V secondaries?

 

[ruffrecords]

Thanks Ian, the Carnhill one is so expensive!

Ahh ok, so with your method you're suggesting using two different toroidal transformers; one to handle the phantom power with 2 x 24V secondaries, and a second toroidal transformer to power the amp with 2 x 12V secondaries?

Basically yes although the one for a the phantom power is not a toroid - I don't think toroids come that small.

Cheers

Ian

 

[Emmathom]

Basically yes although the one for a the phantom power is not a toroid - I don't think toroids come that small.

Cheers

Ian

Good advice Ian
He Can even get two "pcb Tr" : one 2x12v@15VA + one 2x24v@8VA(?)
They are small so easy to install for ex. in a 1U enclosure... My two cents
Best Regards

 

[Dan Kennedy]

Or use a 2 x 22 to generate the main rail voltage, and a voltage doubler to provide the phantom. I've done it approximately 10,000 times.

 

[Emmathom]

Or use a 2 x 22 to generate the main rail voltage, and a voltage doubler to provide the phantom. I've done it approximately 10,000 times.

Yes of course but I thought @TJS wanted 2 Tr...
Looking at the datasheet the Tr delivers 1x38,5vAC for phantom + 1x24vAC for circuit : I would get a 2x24v@18VA and do as @Dan Kennedy suggested

 

[My3gger]

Don't we need separate tap for phantom supply? If we used the same tap for Ucc and phantom, wouldn't that create grounding problem because phantom would be grounded at two places?

 

[Emmathom]

Don't we need separate tap for phantom supply? If we used the same tap for Ucc and phantom, wouldn't that create grounding problem because phantom would be grounded at two places?

Phantom supply must be grounded at one place only, to the audio input ground. No grounding is necessary at XLR connector.
The R to ground (to discharge the mic and the filtering capacitor) and the filtering capacitor must be connected to the audio input ground (which is normally connected to ground star).
If I'm not mistaken...

 

[TJS]

Thanks all!

Good advice Ian
He Can even get two "pcb Tr" : one 2x12v@15VA + one 2x24v@8VA(?)
They are small so easy to install for ex. in a 1U enclosure... My two cents
Best Regards

Do you have any links to PCB Tr's? In terms of the centre taps of using two transformers, would you link these together and to ground?

Or use a 2 x 22 to generate the main rail voltage, and a voltage doubler to provide the phantom. I've done it approximately 10,000 times.

This is nice idea. Do you have an example circuit to get the 24V to 48V for phantom power?

 

[My3gger]

See Jensen

Phantom supply must be grounded at one place only, to the audio input ground. No grounding is necessary at XLR connector.
The R to ground (to discharge the mic and the filtering capacitor) and the filtering capacitor must be connected to the audio input ground (which is normally connected to ground star).
If I'm not mistaken...

We got to evergreen discussion about grounding I think phantom ground/minus goes to input XLR pin 1, on the psu side phantom isn't grounded like Ucc/HT, heaters or whatever else is grounded right at the psu output to chasis ground, then to IEC ground connection. See how Jensen AS016 shows it, after looking at Gyraf G9 for 10.000th time i still don't understand why grounds were not drawn the way Jensen or Cinemag do it.

 

[Emmathom]

See Jensen

We got to evergreen discussion about grounding I think phantom ground/minus goes to input XLR pin 1, on the psu side phantom isn't grounded like Ucc/HT, heaters or whatever else is grounded right at the psu output to chasis ground, then to IEC ground connection. See how Jensen AS016 shows it, after looking at Gyraf G9 for 10.000th time i still don't understand why grounds were not drawn the way Jensen or Cinemag do it.

@My3gger
I use to ground 48v minus to star ground (which goes to "earth" thru - at least - 10Ω + 100nF in //)
To me, 48v ground doesn't need to be connected to XLR1... but as you said, evergreen discussion

 

[Emmathom]

Thanks all!


Do you have any links to PCB Tr's? In terms of the centre taps of using two transformers, would you link these together and to ground?

I don't know if TME ships to UK (I do think so) but here is a ref of a pcb Tr 2x24v@2x0,375A :
https://www.tme.eu/fr/details/myrra-45054/transformateurs-pour-pcb/myrra/45054/
but it's easy to find almost anywhere...

 

[My3gger]

@My3gger
I use to ground 48v minus to star ground (which goes to "earth" thru - at least - 10Ω + 100nF in //)
To me, 48v ground doesn't need to be connected to XLR1... but as you said, evergreen discussion

You will probably need phantom referenced to pin 1, i can't see how would mic get powered without it. Ruffrecords (Ian from Customtubeconsoles) described phantom wiring in details on this forum or his website.
Here is another source showing what i'm writing about, if you look closely phantom minus pole is grounded at the input xlr pin 1, phantom supply isn't connected to the psu star ground/IEC ground: https://www.prosoundweb.com/a-primer-on-phantom-power-for-condenser-microphones/2/

 

[Emmathom]

You will probably need phantom referenced to pin 1, i can't see how would mic get powered without it.

Of course ! but pin 1 is Indeed connected to ground "somewhere" , isn't it ?

Ruffrecords (Ian from Customtubeconsoles) described phantom wiring in details on this forum or his website.
Here is another source showing what i'm writing about, if you look closely phantom minus pole is grounded at the input xlr pin 1, phantom supply isn't connected to the psu star ground/IEC ground: https://www.prosoundweb.com/a-primer-on-phantom-power-for-condenser-microphones/2/

Well to be "real effective minus" to its "+" all minus must be, here or there, connected together... so does pin1 ?
I admit that "ground" is a vast subject...
Or... you mean that 48v plus & minus can (must ?) be isolated from everything else ?

One more thing : oftenly, the XLR socket is connected to pin1, or in the mic itself or by the XLR câble : so if you ground the socket by mecanical connexion to enclosure, you connect pin1 to main ground (PSU's) so...

 

[My3gger]

Of course ! but pin 1 is Indeed connected to ground "somewhere" , isn't it ?

Well to be "real effective minus" to its "+" all minus must be, here or there, connected together... so does pin1

Sure, input XLR pin 1 with phantom - pole is grounded to chasis with short cable.

 

[Emmathom]

Sure, input XLR pin 1 with phantom - pole is grounded to chasis with short cable.

So I would prefer to reference the phantom - to main ground star > especially to avoir ground loop ! But I maybe wrong...

 

[Emmathom]

@My3gger this discussion is interesting. It's good to oppose points of view because this ground subject is so vast so each info is great to collect.
Peace & respect