Neil McBride and a 27ohm resistor

[slapup]

Following the advice on the McBride website

But it turns out that when you do make the effort of mounting the regs inside the preamp box, right next to the circuit, and whip out that 27 ohm resistor (so allowing a true low impedance power rail) then I find the preamp performance (particularly timing) suddenly blossoms. And this is why you should stick the reg circuits INSIDE the preamp box. If you decide to keep the regs in the psu box, then leave the 27 ohm resistor in.

i have moved the regs from inside my SNAPS to inside my 32.5. Being a total gimp however, can someone explain to me where the 27ohm resistor is? Do i need to replace it with a wire link?

 

[pm1961]

A quick answer without diagrams is to follow the power rail to the individual sections and the 27R is the first component you'll come across.

A quick check with a multimeter will confirm this..... you don't have to take it out to check it. I should be able to tell you the colours but I can't!

With the separate cards on the 32, I guess they should be easy to find, like on the phono cards.

I only have 42/62 preamps so my internal shots wouldn't be much use to you.

Cheers,

Paul

P.S. Do a search on this subject because opinion is divided as to whether to remove the 27R and it's cap or not.

 

[RichardH]

Red, purple, black, gold according to my Maplins resistor calculator-o-matic.

On the 321 cards, it's above the two 47uF electrolytics - top right of board. There's a pic of it here

 

[ced]

generally, only remove the 27R if you have a reg for each and every board in the preamp (ie 8 for a 32.5 with phono boards, even 9 if you have one to feed the relay and led) as it reduces intermodulation between the boards.
If you only have the 2 regs from the snaps, it is probably better to leave 27Rs in. If you go to the picture on the avondale site http://www.users.zetnet.co.uk/avondale/ , about half way down, the resistor in question on the gain board is in the top right hand corner.
With a reg for each board intermodulation is negligable so my experience is that taking the 27Rs out, putting in a veropin and attaching the reg output direct to the power rail, does as Neil Mcbride says, really make an improvement- much livelier, dynamic and more 'present' sound. However it is technically more complex and Andy Weekes has given a good explanation of what it does on this thread http://63.99.108.232/forum/showthread.php?s=&threadid=1937
try it and see.
cheers
Ced

 

[slapup]

Thanks guys. I only use CD and so the only thing I have in my 32.5 is a pair of 321 boards and the relay circuit so will give it a try. Speaking of the relay circuit, any advice on whether or not it can be removed? I've tried it with a wire link in place of it but it seems to introduce audible distortion.