Changing to a 50K Valab attenuator

[Loquah]

A good friend has offered to sell me a 50K Valab stepped attenuator which I have heard good things about. My only concern is that I currently struggle to get past 25% on the existing (stock) 100K pot. Am I correct in thinking that a 50K attenuator will lead to higher base volume (and therefore even less usable range) or am I getting it wrong?

[murray]

You may not notice much difference.  All pots go from 0% to 100%, the different overall resistance may just change the loading of the preceding stage slightly.  You can adjust the operating range of a pot by adding resistors between the "bottom" of the pot and ground, or between the "top" of the pot and the input.  In this second case it will give you more usable range in your situation.  I have done this to a 10k pot on my sold state headphone amplifier.  The 10k has 33k (I think) resistors between the input and the pot.  This makes the pot "appear" to be a 43k pot which is only at 1/4 volume (-12dB) when the pot is actually at maximum position.

[Grainger49]

In a word, No!  Regardless of the attenuator value it will still work like the stock pot. 

But you are in luck, you chose a lower value, just put a 50k Ohm resistor in series with the lead from the inputs' hot lead to the attenuator.  This will give you more usable range on the attenuator.

I would suggest you buy several pairs of resistors and use clip leads to attach them.  When you find the ones that are right for you solder them in.

Try a pair of 50k, 100k & 200k Ohm resistors.

[Loquah]

Thanks both. I was worried that adding resistors might alter the sound. Is this the case?

I can buy the same attenuator in 250K guise. Would this be a better option?

[Grainger49]

The resistor will add some flavor, a little bit.  So find the value you want and buy a designer resistor.  They are under $10 each.

[coca]

Does anybody know where a Vlab step attenuator can be purchased/

Bernie.

[Grainger49]

Bernie,

They sell on ebay.  Look here:  http://i244.photobucket.com/albums/gg7/Grainger49/Smiles/ROLF.gif

The attenuators are shown on that page.

[mcandmar]

Thanks both. I was worried that adding resistors might alter the sound. Is this the case?

I can buy the same attenuator in 250K guise. Would this be a better option?

Hi Loquah,

I highly recommend you buy this version http://www.ebay.com/itm/Assembled-Dale-23-Step-Attenuator-Volume-Control-100k-/270311271326?pt=US_Amplifier_Parts_Components&hash=item3eefceab9e as it uses Dale resistors which i always found to be the most transparent. If i am not mistaken the BH guys used them in the mainline attenuator.  It doesn't have the nice PCB's that the Valab version has but the better resistors are more important IMO.

As for using 50k or 250k, best to ask the BH guys.  PB did confirm that 75k was absolutely fine on the S.E.X. amp.

[w0lfd0g]

Why not buy a BH Submissive 

[Loquah]

Thanks both. I was worried that adding resistors might alter the sound. Is this the case?

I can buy the same attenuator in 250K guise. Would this be a better option?

Hi Loquah,

I highly recommend you buy this version http://www.ebay.com/itm/Assembled-Dale-23-Step-Attenuator-Volume-Control-100k-/270311271326?pt=US_Amplifier_Parts_Components&hash=item3eefceab9e as it uses Dale resistors which i always found to be the most transparent. If i am not mistaken the BH guys used them in the mainline attenuator.  It doesn't have the nice PCB's that the Valab version has but the better resistors are more important IMO.

As for using 50k or 250k, best to ask the BH guys.  PB did confirm that 75k was absolutely fine on the S.E.X. amp.

Thanks for the link mcandmar. That is a perfect fit - 100K and as you say, the same resistors as used in the Mainline. Thank you!!

[mcandmar]

I've used them in a few amps, bargain for the money as it would cost as much for me to buy the resistors on their own from Mouser.  I've actually just upgraded my S.E.X. amp to a Goldpoint ladder attenuator, details in my main thread here http://bottlehead.com/smf/index.php?topic=5316.msg58412#msg58412