Removing Unused Preamp Connections

[Mike]

Could be!.... but I couldn't hear it.

[The Grand Wazoo]

I've just stumbled on this thread but it interests me because of the experience I had with my headphone amp - a HFN/RR Headcase.

I once noticed that the hi-fi sounded a little quieter than usual & rather shut-in. I couldn't pin down the cause, pulled the whole system to pieces, tried replacing different components, checking phase - all sorts of stuff that couldn't possibly cause this.

Finally, I twigged that it was the volume pot on my headphone amp that was causing it. If it was left at anything other than zero setting, it had this effect - whether it was plugged into the mains or not. It was connected to the preamp via the tape out sockets.

Crap quality volume pot - changed it for a Sfernice & unplugged the Headcase from the system when it was out of use.

Moral - beware little used components with volume pots.

[MartinT]

I only have three inputs into my (Pass Labs) preamp - phono XLR, CD XLR and digital. All digital inputs are switched before the DAC. I can't detect any difference by unplugging other inputs and I'm pretty sure my preamp switches signal + earth, so total disconnection anyway.

[Andre]

All you need is an handfull of RCA phono plugs , wire the signal to ground in the plug, plug em in the spare source input sockets...Don't do this for outputs tho...Remove any tape recorders from the Pre when not in use aswell.

[DSJR]

Originally Posted by Marco

If your preamp has most (or all) of its inputs used when your CDP, T/T, tuner, phono stage, etc, is plugged into it, have you ever tried disconnecting everything other than what's necessary for playing music at the time?

So if you're listening to, say, CD, disconnect the leads that are plugged into your other source inputs...

Doing so, in my experience, improves sound quality and gives a more natural, detailed, and 'focused' sound. Quite often, a lot of the stuff that's plugged into your preamp isn't used regularly so why not maximise the performance of the components that are? The improvement is subtle but in my opinion definitely worthwhile.

Marco.

Yes I have and sometimes it does improve things. Even better is to use shorting plugs on the inputs not used and properly screened/shielded interconnects on the inputs you do use.

Some input selector switches also allow breakthrough across their connections and this of course muddies the noise floor..

[Themis]

Some preamplifiers disable unused inputs (other than the selected), no ?

[Andre]

So people think

[CornishPasty]

I've built a few preamps in my time and I always switch the return as well as the signal.

Many manufacturers bring everything back to a common or star point, signal return, psu ground, etc. I've never favoured this practice. I keep the signal and return together and completely seperate from any power supply grounding.