Gain switch for 9k mic pre?????

[flaheu]

Hi,

Your idea looks cool, maybe a a little sketch ?
An other idea would be to make an output pad that would attenuate the signal by 2.5 dB, so for each switch position you have an "intermediate" gain setting.
It's also a lot cheaper than a 24 pos switch.
My 2 cent.

 

[flintan]

[quote author="drpat"]I came up with a few different versions of a switch for this. I ended up settling on a 12pos rotary augmented with a DPDT switch (pad) to kick in some extra resistance to each stage. I don't have the drawings handy, but I think the max resistance on each stage was around 2K5 without the additional switch kicked in, and around 5K with the switch on. The resistors on the rotary were calculated to simulate a revLOG taper, and I built in the 27R and 39R resistances into the calculation so that I wouldn't have to mount any external resistors.

This sounded better (to me at least) than sticking a mic pad before the input.[/quote]

A pad in front would be rather for protecting the input devices from too loud signals than to make narrower steps of gain.

What resistance did you use for the extra DPDT resistors? To me it seem hard to find a good size since the 6dB gain steps in the "beginning" are something 10R and in the "end" about 1K. Or am i missing something here?

A 2-3dB pad on the output could be a good compromise with a 12 step switch.

Still wondering if anyone tried PRRs' suggestion of different gain settings in the two stages?

 

[Knarleybass]

I have some non shorting switches that I wanted to use for gain, but now I am reading that non shorting aren't suitable as gain switches, why is this?

 

[mata_haze]

Hi,
I also have a couple of 24 positions ELMAs which I would like to use for the gain stage.
how do you calculate the resistors for the gain stage?

many thanks.

Mattia.

 

[mata_haze]

Hello,
I am still trying to understand how to calculate the various resistor values on a 24 way switch scenario.
is there any equation I could use?

any help will be much appreciated.

BEst,
Mattia

 

[mata_haze]

I have tried to do an average of the resistors values given by PRR..
can anyone tell me if I am well off (IE this is not the way to do it) or if could work...
before I start soldering 48 resistor on a very expensive switch and THEN realize it does not work..

Black values are PRR originals ,RED and BLUE are averages I have calculated.




any help will be much appreciated.

Mattia.

 

[mata_haze]

BUMP!!!!
anyone?

 

[3nity]

why dont you use the log step calculator?

Cheers.

 

[mata_haze]

[quote author="3nity"]why dont you use the log step calculator? [/quote]

thank you for the suggestion, where can i get it?

 

[3nity]

http://www.quadesl.com/attenuator.html

 

[flintan]

Doesn't work either in Firefox or Safari.. And also i don't see a reverse log option? What's that "3 Tier"?

 

[Harpo]

maybe something like this excel file can help.

--------
edit: tidyup

 

[flintan]

:shock: Awesome, thanks a lot! :thumb:

Lots of :guinness: :guinness: :guinness: for you..

 

[mata_haze]

YES!
that's awesome!

thank you guys!

 

[uncle]

My only source is farnell, and there is only one 2 pole, 12 position rotary switch to choose, and it's way too expensive. ~50GBP! :shock: So I'm forced to use two 1 pole, 12 position rotary switches, or even better 1 switch and 1 pot for fine gain.

I suppose values are different in this case than those PRR gave us.. What resistors should I use?

 

[Sredna]

Uncle:

If you want to save money, Colin at Audio Maintenance got dual gang 2,2k rev log pots for £ 2,58 each.

www.audiomaintenance.com

If you want switches try Elmas, they're about 35 Euros a piece.
Check with forum member Radiance.

Good luck,

Anders

 

[Whoops]

Hi ,
can you please tell me if this switch will work? is it the one you are talking about?

http://www.banzaieffects.com/Rotary-Switch-2-level-2x1x12-pr-20274.html


Also about the 2,2K rev log, what would be the differences of using a 2,2K instead of a 2,5K pot?

thanks a lot for you help

 

[mitsos]

not sure about the switch. Make sure it's shorting (make-before-break).  Probably have to ask them I guess.

Difference between the two pots is minimal. With 2K5 your minimum gain is lower then with 2K2. But it's not important, since your gain is ever set that low anyway.

 

[JayDee]

i agree with mitsos. i use a 2k5 in my ssl since the 2k2 was hard to find. it works great, but i also can recommand a gain switch...

 

[Whoops]

not sure about the switch. Make sure it's shorting (make-before-break).  Probably have to ask them I guess.

Difference between the two pots is minimal. With 2K5 your minimum gain is lower then with 2K2. But it's not important, since your gain is ever set that low anyway.

Thanks,
I will use the 2,2k since it's cheap and easy to get from audiomaintenence.
the only 2,5 k rev log I found was 40€ ----- Crazy
An if it doesn't really make a difference having 2,2 or 2,5 why would someone stress about it.

i agree with mitsos. i use a 2k5 in my ssl since the 2k2 was hard to find. it works great, but i also can recommand a gain switch...

probably you wanted to say the 2,5 was hard to find, and that you used 2,2 ?????




The switch would be cool because, I'm sure that it would sound better with 1% resistors instead of a carbon pot.
Anyway would that difference in sound be noticeable at all?