Hi Keiron. just buy a 20db barrel pad. many places in the US sell them for $5. Good luck. CR

Hi Chris
I have an original Altec 436c in which the output level is too high. The desk fader has to be pulled 20db lower with it patched in.
I don’t want to drill holes to mod it and saw that you had photo of a stand alone attenuator unit. Is the output simply plugged into it or is invasive surgery required? Do you sell or make these or do you know where I might get hold of one.
Many thanks in advance

Hi Clive,

It’s been a couple of months… any update on the details for the bridged H attenuator for the Altec 436C? Couldn’t find it on your website.

Cheers,
Chris

Yes… I certainly am! See previous comment for details of the pad…

Hi… Clive here. I’ll get it together and publish the values for the bridged H attenuator for this and other devices. You strap the output for 600 ohms and put this on it. It fits just inside the chassis to the right of the meter. It uses 3 wafers from the RS switch kit.
Look on my website in about 2 or 3 months (probably about August 2016) for the details.
TTFN

It is due to the action of the pad, but not the pad itself.
Putting in the pad allows more cranking of the input level control, since it’s now possible to due so without sending the device following the 436c into flames.
Interestingly it seems the harder the unit compresses, the bigger the bass boost gets. Up to about 3bD at 40hz, and more at lower frequencies. At least on my stock 436c. This is OK, I’m happy with the character of the compressor the way it is, I’m not looking to improve it. Well, maybe the DC on heater mod will get put in next. But it’s used for it’s character, I’m not interested in “fixing” the imperfections. Thanks for putting the info on the webpage, it helped get me motivated to do the mod. I used the values from the Sta-level schematic you link to, which are different than the ones right in your post. I used a 158 Ohm resistor in place of the 200 ohm and 1K pot, the 270’s on the input and 158’s on the output. This produced a loss of 18 dB and presented an impedance of approx. 600 ohms to the compressor output transformer. This is more or less unity gain with the input control at 4, and threshold at +10. With over +20 dBu input to the compressor the output is less than +10. I forget exactly the numbers, but it’s unlikely to cause a problem downstream, which was the complaint up to this point. Maybe this went too far, I’ll find out. Maybe one day I will get a variable pad made, but this will do for now.

I am gonna run a frequency sweep through the lil stand-alone version of the pad (https://www.preservationsound.com/wp-content/uploads/2011/05/Variable_h_pad_2.jpg) and see if I encounter the same thing.

TBC…