MS, Pultec, 1/2-BA283 boards support thread!

[craigmorris74]

Jandoste,

I'm not totally sure what you're asking, but based on what you've posted, I think I may see the problem.  I might be wrong, because I'm not using the stepped attenuator board, but I don't think you need to twist the two resistors across pin 1 like you have it.  You should only have a 690R resistor across the two pads for R1.  690R plus the resistance of all the other resistors on the switch plus the 56R resistor at R9 (the one NOT associated with the switch) gives you a total resistance of 1K6.  So  R10 only needs a 19R resistor across it, etc.

Craig

 

[jandoste]

Jandoste,

I'm not totally sure what you're asking, but based on what you've posted, I think I may see the problem.  I might be wrong, because I'm not using the stepped attenuator board, but I don't think you need to twist the two resistors across pin 1 like you have it.  You should only have a 690R resistor across the two pads for R1.  690R plus the resistance of all the other resistors on the switch plus the 56R resistor at R9 (the one NOT associated with the switch) gives you a total resistance of 1K6.  So  R10 only needs a 19R resistor across it, etc.

Craig

Thanks Craig.

 

[jandoste]

and finally the carnhill vtb9046 has to be wired in normal to remain unity gain... so that must be all my questions answered...
Kasper Nyhus

Hey Kasper,
how you wired the VTB 9046? I tied the pins 8-9 is it right?
Igor is busy and bumping everywhere but any feedback from him
Thanks,

 

[reanimatorstudio]

Am I right about this: MS board will work for Igor's 2254C

 

[gandhalf3]

My Nevetec Unit works great, apart from that :

I have a 6dB drop on the R/S channel when the unit is bypassed. a Relay is wrong on the MS board ? or something else ?

Is it normal to have a huge boost when we unbypass the unit ? (10dB of boost ?)

 

[wave]

Can the M/S bypass boards work with a Cinemag 15K:15K bridging transformer and a Cinemag 600Ω:600Ω output tansformer?

 

[MatthisD]

Both transformers should have equal dual secondaries to allow for m/s functioning.

 

[gandhalf3]

My Nevetec Unit works great, apart from that :

I have a 6dB drop on the R/S channel when the unit is bypassed. a Relay is wrong on the MS board ? or something else ?

Is it normal to have a huge boost when we unbypass the unit ? (10dB of boost ?)

An idea : my problem could come from a wrong value on the make up switch ? if i get down the level from 10db. there ill be no more boost. Sorry for this truism.

But i have no idea about the 6db drop on the R/S channel when the unit is bypassed...

 

[wave]

Both transformers should have equal dual secondaries to allow for m/s functioning.

Thanks MatthisD.

So for my own clarity, if I used a 10K:10K bridging transformer with equal dual secondaries like a Sowter 8920
http://www.sowter.co.uk/specs/8920.htm

and something like a Carnhill 2281
or a Sowter 4652
http://www.sowter.co.uk/specs/4652.htm

I should be cool?

Dave

 

[MatthisD]

Yes but it being a 1:1+1 means the load placed on it will need to be 40k impedance or higher to reflect 10k to the input. The suggested transformer for the m/s pultec is 1+1:2+2 mic input used backwards to act as a 4:1+1 (4.8k:300R+300R) but the transformer used will depend on what load you will be putting on it. 2:1+1 with a 10k load to provide a 10k input. Its the same story for output, it will depend on the output impedance. Presuming there will be no DC running through the windings, the Carnhill 2281, Cinemag or other quadfilar wired 600R:150R+150R will be suitable. Hope that helps.

 

[jandoste]

Igor?

 

[MatthisD]

Hey Kasper,
how you wired the VTB 9046? I tied the pins 8-9 is it right?
Igor is busy and bumping everywhere but any feedback from him
Thanks,

8-9 would put the secondaries in series but this transformer is a stepdown in normal operation already so you would not use it wired backwards in this case. See the carnhill design guide.
For 4:1+1, primaries in series join pin 3 to 4, secondaries; pin7: S1+, pin9: S1-, pin8: S2+, pin10: S2- for the left channel as marked in the M/S wiring PDF. The right channel pin8: S1+, pin10: S1-, pin7: S2+, pin9: S2-

 

[jandoste]

Hey Matthis,
Thanks man! Awesome!
Just I don't know that what to do with pin 2 and 5/6pins? do you have any idea?
thanks

Hey Kasper,
how you wired the VTB 9046? I tied the pins 8-9 is it right?
Igor is busy and bumping everywhere but any feedback from him
Thanks,

8-9 would put the secondaries in series but this transformer is a stepdown in normal operation already so you would not use it wired backwards in this case. See the carnhill design guide.
For 4:1+1, primaries in series join pin 3 to 4, secondaries; pin7: S1+, pin9: S1-, pin8: S2+, pin10: S2- for the left channel as marked in the M/S wiring PDF. The right channel pin8: S1+, pin10: S1-, pin7: S2+, pin9: S2-

 

[MatthisD]

No problem, input + goes to pin 2, input- to pin5 and pin 6 to ground.

 

[jandoste]

Wowwwww I didn't found this info on MS/Pult wiring guide from Igor or on this thread! Thanks man!
Ok, I will solder them and let you guys!
Thanks  Matthis!

No problem, input + goes to pin 2, input- to pin5 and pin 6 to ground.

 

[jandoste]

No problem, input + goes to pin 2, input- to pin5 and pin 6 to ground.

Hey Matthis,
I think that the carnhill vtb9049 wiring is not same as EA1166?
Did you use the same vtb9049 for your build?
Thanks

 

[MatthisD]

The output transformer? I had a look at both and their windings use the same pin numbers so the vtb9049 should be wired the same as the ea1166. Have you tried it?

 

[jandoste]

The output transformer? I had a look at both and their windings use the same pin numbers so the vtb9049 should be wired the same as the ea1166. Have you tried it?

Hey Matthis,
Yes, I tried it and now I hear some more sound but it's very low  [on M/S mode! I don't get any sound on L/R mode] for vtb 9046 I tied pin 3-4? when I connect them with Prim on the M/S board I lost the sound? I hope I'm not wrong?  :
and maybe I need to change make up resistors value? the first resistor is 19r on the make up board...
thanks

 

[MatthisD]

I see how confusing it is now with the coloured wires in the diagram. Pins 3 and 4 of the 9046 correspond to grey/yellow, pins 2 and 5 to violet/orange, pin 6(earth) to green.

Pin 7 and 9 to brown/red, pins 8 and 10 to white/black. As far as I can tell that is how it should be wired, is that how you have it?

 

[jandoste]

Awesome! Thanks Matthis
I got it now! my connexion was wrong  : with the VTB 9046
now I just must  to change the make up resistors value... because I lost more dB when Eq is on!Did you use same values as like me?
cheers

EDIT: Make up gain is not working... I was feeling that the swtch is changing the gain but not at all... maybe I Zobel part needs some modification...

___________

I see how confusing it is now with the coloured wires in the diagram. Pins 3 and 4 of the 9046 correspond to grey/yellow, pins 2 and 5 to violet/orange, pin 6(earth) to green.

Pin 7 and 9 to brown/red, pins 8 and 10 to white/black. As far as I can tell that is how it should be wired, is that how you have it?