RE Designs SCPA-1 discussion etc.

nathanm · « **Reply #20 on:** 3 Dec 2004, 07:08 pm »

CNC would certainly be Full Ass, but I think if I do it it'll have to be within the realm of my own DIY means. My thought was to cut the panel out of either aluminum or wood and cover it with black suede leather. It would be cool if the lettering could be embossed and filled in with white paint of some sort, but this is just a fantasy considering I don't know anything about leather embossing. I thought it would be cool to get away from the 'metal' look and have something a little more textural and organic, sort of like an old book maybe.

nathanm · « **Reply #21 on:** 3 Dec 2004, 07:37 pm »

I won't venture a formal review as of yet considering I need to get new amplifiers before this system is working as desired, but I can say without a doubt that the SCPA lives up to its lofty design principles of extremely low noise and shielding and all that good stuff. It doesn't make a peep! I noticed that the 30' or so run of cable I have going between my two systems no longer exhibits a hum. Nice.

I don't presume to know anything beyond the most simplistic of electrical principles, but my feeling is that this is the type of product you'd get if the world was devoid of marketing schmoes. This thing is just pure engineering-driven performance. This product would never survive a marketing onslaught, it wouldn't be what it is at any rate. If this thing was designed by a big corporate committee it would probably do a little more, not be as precise and nobody besides millionaires could afford to own one after all the markups. So it is a pretty unique device in that regard.

I like it because it's all knobs and no annoying onscreen menus to scroll through. It's just 1:1 function to control ratio, grab and adjust simplicity. It could be made even more hardcore if the mapping of the trimmer dials imitated the placement of speakers. But this is of course a minor detail.

Dan Banquer · « **Reply #22 on:** 3 Dec 2004, 08:25 pm »

Thanks Nathan.
I have outlined a lot of the techniques I use in the Lab forum here at AC. These techniques have all been literally "stolen" from classic low frequency instrumentation applications developed god knows how many years ago.
My thanks to Nathan for doing some excellent photography on the inside of this unit.
d.b.

lonewolfny42 · « **Reply #23 on:** 4 Dec 2004, 07:57 am »

Hello Dan,

Quote

O.K. folks; when one of my demo units comes back from Pro Audio Review I will consider a tour.

Dan Banquer · « **Reply #24 on:** 4 Dec 2004, 10:50 am »

Well, Pro Audio Review hasn't returned the demo unit yet so I'm afraid we will have to wait until then.
d.b.

monotube · « **Reply #25 on:** 5 Dec 2004, 04:40 am »

I'd like to congratulate nathanm on his acquisition of Dan's fine preamp.

Nathan's observation of the low noise and Dan's comments about his shielding and ground plane techniques inspired me to join the forum so I could share the following anecdote. I hope I'm not violating any protocols by posting this before Nathan has done his review.

I've been fortunate to audition the SCPA-1 at length. One outstanding attribute I have to talk about: it is the quietest, lowest noise, lowest hum active preamp I have ever experienced.

Many preamps start adding very audible noise or hum at some point in the upper range of the volume control. In my system, this is the only active preamp I've tried that I could turn up all the way (no music playing), maximum gain DANGER territory folks, and there was no trace of added hiss, hum or any type of noise even when standing right next to the speakers. Total silence with the volume control way above an insane level. I couldn't believe it. (for reference, most music played too loud with the volume at 12 o'clock)

When I raved about my risky little experiment to Dan, he said that a preamp should add as little noise as possible. Duh! It's an understatement to say I was impressed by this astonishing low noise performance.

Looking forward to a full review, when you can, Nathan!

cheers,
monotube

JoshK · « **Reply #26 on:** 5 Dec 2004, 06:20 pm »

Nathan,

I assume your not using it for surround, or are you? Are you using it to active multiamp behind the xo?

nathanm · « **Reply #27 on:** 5 Dec 2004, 09:05 pm »

No, I am using it for surround:
http://www.audiocircle.com/index.php?action=systems;system=416

However, I did think of a use for it in a stereo configuration (in combo with the switchbox): Three stereo sources with independent balance settings for each. Perhaps a little excessive, but it's possible that your CD player. phono preamp, cassette deck, computer soundcard or whatever else isn't putting out exactly equal levels on each channel and this would allow you to have a 'preset' for each. Actually I did find this to be the case with running my soundcard into the SCPA. The left channel was about 2 or 3db lower than the right one when I had calibrated the 5.1 channels using the Denon's pink noise as the source. It's also probable that a TT doesn't have perfectly matched levels as a CD player might.

In essence calibrating this thing with perfection and convenience would require one of the following:

1. SCPA within arm's reach while you are sitting in the sweet spot
2. SCPA at front of the room and using binoculars so you can see the SPL meter needle from 12 feet away.
3. Having a friend in the sweet spot give hand signals to you while you adjust the SCPA.
4. Use something besides a radio shack meter which allows you to see the levels while you are at the controls. Like a laptop or something.

Eventually I will want to opt for #1 as I would like to move the electronics near the chair\couch. So it is somewhat of a logistical challenge not having a remote control for this preamp, but it's clear why there isn't one and why it's probably not practical.

I also thought that using a single sine wave instead of pink noise might be a way to faciliate doing it the sneakernet way, and running back and forth to check the levels since pink noise is more random and makes the needle wiggle more.

eico1 · « **Reply #28 on:** 5 Dec 2004, 10:57 pm »

Quote from: nathanm

I also thought that using a single sine wave instead of pink noise might be a way to faciliate doing it the sneakernet way, and running back and forth to check the levels since pink noise is more random and makes the needle wiggle more....

Not only use a sine wave, but also a DVM to balance electrical differences between equipment. Then an spl meter to compensate for the room and speakers.

steve

nathanm · « **Reply #29 on:** 5 Dec 2004, 11:31 pm »

I must admit that a lot of this precision stuff, while very cool and all, only really applies to ONE single point in space. If you move the meter over to another person's perspective on the couch the levels will be off. Not by much, but... I can't help but think that for as nifty as it may be, multi-channel audio is sure a big pain in the ass!

Morton · « **Reply #30 on:** 7 Dec 2004, 03:19 pm »

javascript:emoticon(':idea:') Dan - How is the traveling wave tubed headphone amplifie for the Ipod going.javascript:emoticon(':mrgreen:')

audiophile39 · « **Reply #31 on:** 30 Dec 2005, 07:39 pm »

Hi, has anyone compared the SCPA with a Herron preamp? The latter also being highly well-regarded but with a tube design. Thanks