diy passive preamp

[PaulBarnett]

just a thought - diy passive preamp:

http://theartofsound.net/forum/showthread.php?27073-tc7240-convirted-to-a-passive-pream

[337alant]

If I was building one agian now I would use a http://www.goldpt.com/compare.html goldpoint mini V stepped attenuator say 10 - 20k
For switching I would use an 6way Elma switch, if you want to save cost on the attenuator use an alps blue pot.
Its important to keep the leads in and out as short as possible with low impedance which reduces roll off.
I used a passive pre for a few years and was very happy with it they are very transparent but ultimately the do roll off the frequency extrems at both ends compared to a line stage, still very good for what you can build one for though :) it was justs an Elma 6 way switch and 2 x 10K Sfernice P11 pots in a plastic box, it wasent pretty but it was effective and I still use it in my workshop system.

http://i259.photobucket.com/albums/hh290/337alant/variouscannon221.jpg (http://s259.photobucket.com/user/337alant/media/variouscannon221.jpg.html)
http://i259.photobucket.com/albums/hh290/337alant/variouscannon222.jpg (http://s259.photobucket.com/user/337alant/media/variouscannon222.jpg.html)

I replaced this with a Audio research LS3 but then I got the urge to build something again I made a PFM B4 and that seen of the LS3 and is still what I use now as it has the transparency of the Passive with a better overall FR and just that little bit of kick that the passive lacked

http://farm8.staticflickr.com/7046/6969569379_1a6d2441c8_z.jpg (http://www.flickr.com/photos/69508926@N05/6969569379/)
B4 Pre (http://www.flickr.com/photos/69508926@N05/6969569379/) by 337alant (http://www.flickr.com/people/69508926@N05/), on Flickr


Alan

[Graeme]

I use a passive pre, i built a stepped attenuator around an old 29 position painton switch, shunted, with metal films.
Easy to build, but took a while to work out what resistor values i wanted.
I also built a relay switching pcb, added some led's, mute switch, tape out and sorted.

Sounds great.
I also built a cathode follower to give more drive without gain but although first impressions are favourable, after a while it gets tiring and sounds better without it.

I dislike carbon pots, they dont sound good (used to use a shunted alps blue).

Light dependant resistor attenuators sound good but matching the LDR's is a pain. Got fed up with mine blowing up for no reason though hence now using the stepped attenuator.

[Cotlake]

I also built a cathode follower to give more drive without gain but although first impressions are favourable, after a while it gets tiring and sounds better without it.

That is a surprise to me. I would expect the opposite. I presume you built the cathode follower Pre-amp conversion on the WAD forum FAQ. My experience is that it has offered more life and sparkle to the sound with extended frequency exposure over the passive option. I absolutely love it in my system. It is total synergy for me.

[Graeme]

Yes, was a clone of the CF mod to preII.
To be fair, i didnt use posh components.

Whats your main source greg? Mine is Vinyl with modded clone phonoIII. The last stage of this is CF anyway.

I get what your saying about the sound, but after going back and forth a bit it sounded like the buffer forced the presentation of some aspects of the sound which gave an initial good impression but it sort of put everything in the same light at the same level. It souded a bit forced and like everything was coming at you at once.
Without the buffer things seperated out a bit, forcefull sounds had force, gentle sounds didnt.
The effect seemed to swamp a little detail too.

Make sense?

I'd imagine this kind of thing is very system dependant though.

[Cotlake]

Whats your main source greg? Mine is Vinyl with modded clone phonoIII. The last stage of this is CF anyway.

I'd imagine this kind of thing is very system dependant though.

I use vinyl, CD and also run the TV and DVDP through the system occasionally. I have modded WAD Phono II. I acknowledge the last stage in the phono is CF. Having established that the CF conversion worked for me, I went on and built it hard wired with boutique components. It works fine with the Phono II. Your experience is certainly different to mine but it is probably simply personal preference and as you say, could be system dependent.