Two 2-ch set-up in one room

organ

Well, last night I was feeling bad for the NAD amp and decided to try setting up a second system in the same room without disturbing the LSi. I sit right against the back wall and have the RT800i beside the couch. What I did was hook up the NAD to the ASL with a Y-adaptor and hooked up the RT800i to the NAD. So now when I want to listen to the 800i, I take one of the chairs and place it right in front of the TV.
My question now is...Should I place the amp closer to the 800i's and use a longer interconnect or leave the amp where it is now and keep using the loooong run of speaker cables? The 800i's were used as surrounds when I still had my receiver.

Maurice

Tour2ma

Me... I'd choose the longer speaker runs and keep the IC's short.

Reasons:
Cost.
Signal strength.

madmax

I tend to keep the speaker wires as short as possible even if it means longer interconnects. Since the signal through the interconnects are delivered to a high impedance load they have very little loss and mess with the signal quality less than speaker cables where resistance is more of an issue.
madmax

Tour2ma

Well max, between the two of us, we have pretty well covered the options... Maybe we can explore this a bit more to the benefit (or confusion or amusement) of all.

Seriously, your polar opposite opinion has made me stop and think. So what did that get me? I think whereas you are coming from an emphasis on transmission signal loss, I was focussing on unwanted additions to the signal, i.e., acquired noise.

On your resistance position, I'm seeing that in either case the resistance of the "wire" is much, much smaller than the impedance of the load, less than 0.0001 ohm vs. loads of 4 and 40,000 ohms respectively for speakers vs amps. So, yes, you are correct in that wire resistance is "more" negligible in the case of the IC's by a factor of 10,000, bit in either case the wire's resistance can mathematically be argued to be negligible.

Where I am coming from is that in the case of a 4 ohm speaker, a 1 watt signal produces a voltage potential of 4 V and a current of 0.25 amps (250 mA or 250,000 uA). If we assume a nominal 100 W amp with a "typical" input sensitivity of 1.5 V at rated output, then the corresponding input signal for the 1 W output would be 0.015 V. At the 40 kOhm input impedance this corresponds to an input signal of 0.000000375 amps (0.375 uA). Obviously the IC's 100,000 times lower signal strength is more susceptible to interference.

So on one hand we have a 10,000 times edge against loss of detail, and on the other a 100,000 times edge in significance of noise gained. In the final analysis it may come down to the effectivnesss of the IC's shielding vs. how much detail we can hear.

Please feel free to check my calc's, assumptions and approach here. I am really looking for a dialogue and an education...

TroyD

I'm really interested in this.....I've always been told keep the IC's as short as possible...

BDT

madmax

What I see you doing is multiplying by the amplification factor times the noise of the interconnect which at first sounds reasonable. The downside to your comparison is that the shorter run has the same amplification factor. To even out your statement you would have to take the noise in the longer interconnect and subtract the noise in the shorter one to know what the difference is. From my understanding most of the noise/distortion in an interconnect is present because of dissimular materials being mated at the connector/jack assembly. If this is true then length won't matter too much unless you have some particular noise emissions close by such as higher energy RF. (I don't remember exactly where I learned this but I experienced it myself at work). In any case it could be negligable or not in the 0 to 4 volt range. To move on to the speaker cable, it is my understanding that losses in transmission of the higher power signal causes more audible distortion and increases steadily by the amount of power being transmitted. I think if you look towards the higher end crowd you will find mono-blocks sitting next to the speakers with long interconnects. There are of course other things to consider such as "why would someone bi-wire if they are only one foot of wire away from the speaker and how does a bi-wired speaker of X length compare with a shorter run of Y length.

...disclaimer...
This is just my take on the whole fiasco of mating components. A lot is still to be learned and all ideas subject to change immediatly without notice.

madmax

tryrrthg

those crazy audiophiles over at Audio Asylum were talking about this topic...

LINK

Tour2ma

Disclaimer noted... lol.

Actually I think you may be crediting me with a deeper analysis than I performed. All I was trying to do was get a feel for the relative current involved in the transmission of the music signal for the IC vs. speaker run options. Just strikes me that the lower strength signal has greater protential to be "compromised" by RF. In retrospect, I guess it was a relative S/N exercise minus any specifics about the noise source's strength.

I've experienced "hum" due to speaker wire runs paralleling AC wiring and due to similar TT to phono stage connection issues, an even lower signal strength. The former could be masked by increased music volume, whereas the latter... well, not.

Agree about the potential of connections overriding the length of IC or wire runs in any noise concerns. And I have also noted that most "high-end" set-ups do tend to at least split the difference in the postioning of the pre-amp and mono-block components. Generally I have attributed this to "displaying" the amps rather than signal integrity. At least I know I'd be that vain about a pair of major mono-blocks...

EDIT: Thanks for the link... AA sems to have at least as good a handle on the topic as we do...
Were some interesting notes on components ability to "drive" a signal, not that it appplies here...

madmax

Wire and interconnect topics in this forum tend to degrade quickly into name calling and an inability to consider oposing opinions. I like the oportunity to investigate other opinions without this happening.

So, as long as everyone agrees with me there will be no problems...

They brought up some good points about the source components ability to drive a long cable length so as not to let the characteristics of the cable take over. Never thought of that one.

madmax

HBombToo

I'm in the longer speaker run camp here fellas...

In any system noise cascades or is additive from each active circuit; therefore, all stages prior to the final gain stage should be protected from additional noise components.

For demonstration and ease of disscussion assume that 1.4V ~ 0dB.
Imagine if you will a noise spike of only .0875V across an interconnect between the preamp/amp stage. This noise is -12dB down from reference. Now apply a final gain stage of 24dB from our amplifier we have a noise gain of +12db which is actually 22.4V across our speaker. That very same .0875V noise spike, if not introduced within the active stage via the interconnect but is across the speaker itself, sees no gain from the amp and is really 36dB down istead of the 12dB from above.

I hope this makes sense and if not knock the hell out of me.

HBomb

madmax

I have another issue to point out. There is a difference between noise and distortion. Also, if you have a noise being induced to the interconnect it will be amplified. To induce a noise into a cable wavelength becomes important. If the length of the cable is 1/4 wavelength of the present RF noise then it will pick up the noise much better. It is very likely that if you pick up a lot of RF noise at one length you could lengthen (or shorten) the cable and eliminate the problems. So how about that, a longer cable may be better!
madmax

HBombToo

Originally posted by madmax
It is very likely that if you pick up a lot of RF noise at one length you could lengthen (or shorten) the cable and eliminate the problems. So how about that, a longer cable may be better!
madmax

Hmmmmmm...... I guess at a your 1/4 wave theory your safe to about 11,700 feet???? If I read this correct :rolleyes:

HBomb:D

Tour2ma

Originally posted by HBombToo
Hmmmmmm...... I guess at a your 1/4 wave theory your safe to about 11,700 feet???? If I read this correct :rolleyes:

HBomb:D

So we all need to move to Denver?

VR3

I have a great comparison for this!

We have outdoor speakers, with a 50 foot run to each speaker. We have pushed 200 watts in the Atrium 55 to get nothing but 95db (yes measured) -- (Yes, also on the amp, with the wattage meter). That should speak for itself.

HBombToo

Originally posted by Tour2ma
So we all need to move to Denver?

I wonder how Sids atriums would fair in Denver @20k ft?

boy is this thread degening fast:D

HBpmb

RuSsMaN

Oh shut up Sid, leave this thread alone - will you? There's actually some decent info here.

organ

Holy ****. You guys really know your stuff. Thanks for the info. I'm going to look around and see if I can find some cheap 12ga cables. The 3 year old 14ga I have now are starting to oxydize. Once I get everything in the basement cleaned up I'll try some long interconnects.
First I'll have to find something to place between the wall and speakers. The 800i's are a few inches away from the wall. It wasn't a problem when I was listening at low levels though. It just felt pretty weird that I was facing an empty couch while listening:).

OK, I have another question. Do you think this amp is going to have any problems driving the 800i's? They're mono blocks and only cost $100 a piece.

http://www.divertech.com/aslwaveav8.htm

Maurice

Tour2ma

Originally posted by RuSsMaN
Oh shut up organ, leave this thread alone - will you? There's actually some decent info here.

Sorry, had to borrow this from Russ... then I looked and it's your thread so you can do wnat you want, I guess...

RuSsMaN

Ha friggin Ha Ha....

Good news and bad news on the Wave 8's. Those little monos sound great, and 8-10 w/ch is plenty for most casual listening apps. The only drawback I see with RT800's is the ported design of the speakers, and low damping factor of the amps.

Cool factor is through the roof though. How about getting four of em' and bi-amping? That, or step to the 20w model, or hell, get real crazy run a pair of 8's on the tweets, and 20's on the woofs...

Cheers,
Rooster

organ

LOL Tour:)

Russ,
I may just get the 20w model. I'll have to keep listening and play around with placement with the 800i's first. If I feel that I need a tube amp, I'll get them. I only thought about those Wave 8's because they're so dang cheap. Very cool idea about bi amping with the 8's and 20's. Thanks

Maurice

Tour2ma

Russ,
Why the damping factor concern? Bass control?

organ,
I have no idea any more on when to get concerned about a tube amp's rating. I've come to look more at their power consumption than their output...

Back on Sid's drop in...
Sid,
A little apples and oranges here. Outdoor, anechoic measurement of speaker output is not going to impress. At least not Atriums (VOT's another matter).
If you want to complete the test, compare the measured output of the amp with the input at the speaker terminals. You're not going to see that much difference.

RuSsMaN

Originally posted by Tour2ma
Russ,
Why the damping factor concern? Bass control?

Ed Zachry.

Cheers,
Rooster

madmax

Originally posted by HBombToo
Hmmmmmm...... I guess at a your 1/4 wave theory your safe to about 11,700 feet???? If I read this correct :rolleyes:

HBomb:D

Not into RF Hbomb? What type of engineering do you do?
madmax

organ

Tour,
That's very interesting. I've yet to max out the Dynaco's 35w/ch but the 8 watts on the Wave-8's does seem very little. Maybe I'll try them out and if they don't provide enough juice, I'll do what Russman suggested by bi-amping with the 20's on the woofers.

Maurice

Tour2ma

Dynaco ST70:
35 wpc continuous
80 wpc peak
Power Consumption 190 W

I actually believe the 80 wpc peak is conservative.

madmax

Originally posted by Tour2ma
Dynaco ST70:
35 wpc continuous
80 wpc peak
Power Consumption 190 W

I actually believe the 80 wpc peak is conservative.

So does anyone know why the Dynaco ST70 is rated at 35 wpc while some other amps using the same four EL-34's are rated at 50 wpc? The only real difference I see is that the Dynaco uses a rectifier tube whereas the other ones I've seen use diodes. (who came up with the idea of using cheap sand diodes in tube amps anyway?)
madmax

organ

maxmax,
The ST-70 is a push-pull amp and it was designed to drive the EL-34's to 65% of it's power.

Maurice

gidrah

I've heard that the 35 watt rating is actually a little high and that it's closer to 25/ch.

HBombToo

Originally posted by madmax
Not into RF Hbomb? What type of engineering do you do?
madmax

I have been an wireless RF Engineer since the early 90's and a radar guy before that; however, that does not say I'm an audio expert. I have learned a bunch right here and have a long way to go.

I have not hooked my computer up in my new place yet so no evening surfing for me yet. Sorry for the late re-entry.

Back to the long interconnets though. The other consideration that has not been discussed is if we put the Dac and amps at the speaker and keep the transport at some remote location. Depending on the lenth of the 75 Ohm connection will determine your losses (which are very high for pcm) and as the line increases you will suffer from additional jitter. I would be very concerned about this and would say that the quality of the shielding will be the governing force of accurate digital to analog conversion. Even balanced xlr have line limitations and are a consideration for laying out a professional recording or broadcast stations. I believe AES3or5 actually calls these specification out as a guidline but the document is not very laymen oriented.

HBomb

gidrah

Good call HBomb. That's one of the main reasons I bought a DAC.

My $.02:
How far are we talking? I've always been taught that the shorter the speaker cables the better. Same for ICs, but not to the same degree. I've also read that if you have long IC runs, use 75 ohm (ie video, digital or some sub)

Either way, if your runs are less than 30ft or so you should be fine.

Psst: I'm thinking of trying twisted strands of magnet wire on the VOTTs. Don't tell anyone though.

madmax

Originally posted by HBombToo
I have been an wireless RF Engineer since the early 90's and a radar guy before thatHBomb

I thought I had heard that somewhere. So where did you come up with 11,700 feet?

So where do I get one of these DAC's for my turntable

madmax