Dumb phonostage PSU question

Hi,

Can anyone advise why pretty much all phono stages have off-board PSUs? I assume that this is to enhance sound quality, without any crosstalk etc. from the PSU. Just wondering if anyone knows of a decent phono stage below £100 with a built-in PSU. I'm not a big fan of those power bricks that are normally supplied.

Thanks!

 

you mean wall warts? Its cheap because they're off the shelf generic boxes.

 

You may like to consider a Rotel RQ970BX phono stage. These items are usually only available s/h these days via places like e-bay, expect to pay somewhere in the region of £45 - £75 for a mint , boxed example , certainly don't pay any more than this. I am on my second one in just over 3 years after selling my first and instantly regretting it. I have also just modified mine with a DIY upgrade that was featured in HFW magazine from a few years ago.

There seems to be a ready market for these fine little amps and so if you buy at the (my) recommended price you should have no problem offloading it without any loss ( or at least very minimal) in the future, if you decide that the sound isn't for you.

I have also just discovered something quite startling this week concerning my Rotel.
I have been plagued for about 2.5 years now with mains noise from my Gas Central Heating boiler,( and probably bored the pants off just about everybody by telling all about it ) this problem only really occured whilst my Pre-Amp was selected to Phono (using the built in phono stage) or Aux ( using several other budget Phono stages). I have just discovered during the last two days that the Rotel RQ970BX has completely eradicated this noise altogether ! I can switch my central heating on and off and no noise gets through ( Loud clicks. pops and Grrrrr's as the relays, solenoids or motors-whatever kick into life) as soon as i take the RQ970BX out of the Phono source chain the noise returns. I am not completely sure now whether the un-modified RQ970BX suffered from these mains problems , or whether doing the HFW modifications has done something, what i do know without any shadow of doubt is that a little £60 s/h phono amp has completely removed a major source of irritation and misery for me that a dedicated Hi-Fi Mains spur, an Active electronic mains filter network and several other little mains type tweaks couldn't !

BTW the Rotel is a Normal sized Hi-Fi unit ie 430mm wide x about 65mm high although it is only about Half sized front to back.

Here are some links if you are bored ( )
http://forum.hifichoice.co.uk/viewtopic.php?t=15763
http://www.worldaudiodesign.com/forum/showthread.php?t=18228
http://imageevent.com/sidandcoke/rotelrq970bxmod

HTH

 

Hi.

Phono stages have to deal with very small signals. At 50Hz the level from a MM cartridge is about 1/10000 the output from a CDP. They are therefore very suseptible to picking up stray fields from transformers.

Transformers can be produced with much reduced external fieilds by winding with a very low flux density within the core, but this requires a larger core and many more turns which drastically increases costs. On a sub £100 phonostage it is often thought better to use a cheaper transformer removed the unit case and use the money saved for better quality components in the signal path.

Even with a £1400 phonostage I found it beneficial to design an external PSU to increase the signal to noise ratio.

Chris

 

Anex - yup, I meant wall-warts.

Sid & Coke - I've been eyeing up one of those Rotels for a while. They look superb. My problem is getting hold of one, but I will keep an eye out for one. A new job starting soon means a bit more spare cash (plus I managed to get a few days leave that I have no time to take whilst in the current job) payed for in dosh, so as soon as I can find a Rotel, I'll be buying.