Neve 1290 preamp - output pad , 4 step attenuator

Hello everyone,

I have one question. How can I do a stepped output pad (attenuator) for the Neve 1290 preamp?

I know it can be done by putting a 5K (or 10K) linear conductive plastic potentiometer behind the second section i.e. BA283NV and before the output section i.e. BA283AM.

I have some 4 position (3 deck) switches that I want to use for that. I would like to have these values of attenuation:

0 switchs position (fullclockwise) …………….….. 0db
1st switchs position……………………………….........-6dB
2nd switchs position ………………………………......-12db
3rd switchs position (counterclocwise)……....-20db

Would be there funktional a basic 600 ohm L pad for attenuating unbalanced signal?
Is good idea to use rotary switch instead of a conductive plastic pot?

Any help would be much apriciated!

Best

Milan

You can get reasonably close to these values by using a 4K7 resistor between the first and second positions, a 2K4 between the second and third positions, a 1k$ between the thrid and fourt positions ans a 1K from the fourth position to 0V.

Cheers

Ian

I'm doing a 1073 right now and I added a relay to switch the secondary of the OT from series to parallel but in doing so it also switches in a 150 ohm load. The idea is to be able to overdrive things and provoke the character of the gapped OT but without blasting downstream gear that can't handle it.

I haven't tried it yet though.

ruffrecords said:

You can get reasonably close to these values by using a 4K7 resistor between the first and second positions, a 2K4 between the second and third positions, a 1k$ between the thrid and fourt positions ans a 1K from the fourth position to 0V.

Cheers

Ian

Click to expand...

Thank you Ian

You think like this?

Update 1: Changed resistor order
Update 2: Changed 1K to 1K3
Update 3: Changed 1K to 910R and 1K3 to 1K4

Vac11 said:

!


Thank you Ian

You think like this?

Click to expand...

I am afraid you got it back to front. The -20dB position is by the 1K resistor to 0V.

Cheers

Ian

I am afraid you got it back to front. The -20dB position is by the 1K resistor to 0V.

Cheers

Ian

Click to expand...

Thank you, I updated the scheme. Hope is correct now.

M.

Vac11 said:

Thank you, I updated the scheme. Hope is correct now.

M.

Click to expand...

That is better. The 1K between the -12 and -20 switch positions should be 1K3.

Cheers

Ian

Thank you very much Ian. I updated scheme, so other members can use it...

M.

Vac11 said:

Thank you very much Ian. I updated scheme, so other members can use it...

M.

Click to expand...

That is exactly as I designed it in my head. Looking at it now the -20dB is a bit inaccurate. If you change the 1K to 910 ohms and the 1K3 to 1K4 it should be more accurate.

Cheers

Ian

> the 1K3 to 1K4 it should be more accurate.

That's what I thought you said the first time.

> a 1k$ between the thrid and fourt

Clearly fumble-fingered. "$" is shift-4 on my keyboard. Probably yours also.

PRR said:

> the 1K3 to 1K4 it should be more accurate.

That's what I thought you said the first time.

Click to expand...

I did but I forgot to make the bottom R=900 ohms. The I realsised the 6dB position was wrong because the lower arm was 4K8 so for some reason I took the extra 100 ohms off the 1K4 instead of off the 1K. The  I realised the 20dB position was wrong and took 100 off the 1K and added it back to the 1K3 to make it 1K4.

Just shows that perhaps at my age I should not still be trying to do these in my head.

Cheers

Ian

Cheers

Ian