Setup Advice for Old School Amp and New Speakers

Hi All,

Here are my components for a simple iPhone-based setup I'm trying to build using some freebie parts:

Soundstream DA-1 200W x 2 @ 8ohm amplifier

2 pairs of 8 ohm Speakercraft MT6 One Speakers rated for 100Watts RMS

Niles Audio SVL-2 Speaker Selector with Volume Control (Rated for 100Watt per channel @ 8 ohm)


My goal here is to use an iPhone (in universal dock) as a source and drive my 2 pairs of speakers (in ceiling) using this amp and speaker volume control unit. The amp is old but good and overrated for the Niles speaker selector/volume control unit (or at least I think so). I was hoping that by not turning the amp volume up past 50% or so, I'd be able to use this speaker volume control unit and its impedance correction to power my speakers safely. I am probably making a bunch of newbie errors here, but I tried my best to research a bit before posting. Any thoughts/advice on how to make this work without blowing up the speakers, amp or speaker selector?
Edited by factoryfast - 9/12/12 at 7:57am

So I think I should at least use a preamp to level the line output from my iOS device to the amp. However, I have no idea what the line input sensitivity is on my amp and I also realize there is no volume control on the amp whatsoever. I'm pretty nervous to hookup directly to the amp as I described in my first post. Still, nobody has any thoughts?

Here is the manual on the amp - perhaps it will help.

Wow, thank you Arny!

I have a question about the signal level of my iOS device however. I read this article and I plan to use the line out from a Apple Universal Dock. Now I'm not sure if the article is talking about Vpp or Vrms but does this mean that a 2 volt line out level from the dock will work well with the 1 volt input sensitivity of my amp? I'm thinking that it is too much but I'm obviously new here. I think the SM Pro Audio Nano Patch product may be the perfect solution. Thanks for the help!

My theory is this:

2 Vrms x 39.8 = 79.6 Vrms. P = 79.6^2 / 8 = 792 W

vs

1 Vrms x 39.8 = 39.8 Vrms. P = 39.8^2 / 8 = 198 W


So, if I attenuate my line input to the amp by 1 volt, I'll be within spec for the amp. Whereas a doubling of line input voltage makes a big difference if volume control is accidentally turned up by an unknowing user right?

Last thing: I'm estimating then that I need to set the Nano Patch unit to -6db in order to level my apple dock audio output (2 volt) to my amp's input sensitivity (1 volt), correct?

Reference Article

Any reason why you would use this crimped-on braided and wrapped piece of wire to terminate into a volume control? I planned on just using plain 14 AWG speaker wire to make the connections to the screw terminals. I'm finishing up what someone else started and this patch cable was left behind...

So I connect the amp to my volume control (SVL-2 by Niles). I only have one speaker connected to the speaker selector/volume control, but neither of the speaker pair selectors are enabled. I'm of the opinion that this means the speakers are not connected to the amp until I select at least one pair of speakers.

I plug in the amp and turn it on for the first time to see if it powers up. A brief wooshing sound can be heard/felt through the unit for about one second before smoke puffs out of where the Channel 1 Overload LED is mounted. I immediately shut off the amp - it had been powered on for about 3 seconds total. Did I do something wrong here or was this amp (circa 1990) of dubious operating condition simply letting out the last bit of its magic smoke? The unit has several screws missing from the top cover plate suggesting the unit had been opened up (carelessly) in the past. The current owner had never powered it on himself and he had bought it at a foreclosure auction. I'm certain I observed all proper polarity and after checking the fuses, they seem to be intact for both channels...

Any suggestions? I'm considering buying an Onkyo M-282 and trying again but prefer to avoid another puffage episode.
Edited by factoryfast - 9/12/12 at 10:39am