Discussion in 'General Audio Discussion' started by z-adamson, Mar 12, 2018.
It'll be fine...
With a regular pair of RCA cords, you can try the preamp only to the separate power amp only with a pair of speakers to get an idea if you are gonna like it or not.
That's not a carved in marble requirement, just a general rule of thumb. You should be fine.
Another question, if I have an eq hooked up to the Onkyo via the tape loop, the second amp will get an eq'd signal too, right?
If values are correct as @E-Stat has stated, there should not be problems- at least not to such an extent it would become audibly objectionable.
@tarior 's suggestion of up to 10 inputs +/-(?) can be fed by a set preamplifier outputs without affecting sonic quality is just plain wrong.
I just judge by my own ears. To me, Y-jacked rigs on my particular equipment just don't sound as good. What sounds really good is when I cable things the way the manufacturers intended for them to be interfaced. I also somewhat agree with this statement:
It's been my experience that components from the same manufacturer simply are also designed to be in phase with each other, for the most part. I learned this from forty years of collecting, to me, for example, all Marantz systems and all Pioneer systems simply sound better than systems that are a mish mash of both, IMO. Your ears may differ.
It really totally depends on the specific equipment involved. His suggestion could be quite accurate depending on the specific equipment involved.
I'm sure different manufacturers hold to different standards for different reasons. While i recognize the 10:1 rule as a general guideline, there are specific manufacturers whose recommendations go well beyond that in both directions while others specify the 10:1 ratio as a minimum. For example i had a CJ PV-5 with a rated output impedance of less than 200 ohms, yet they recommend driving amplifiers with input impedance of 100k or greater.
I often refer to the Peavey white paper on impedance, it's a good primer and easy to digest. I would offer this segment quoted from there:
Here's the link to the entire white paper, note that the "next page" links are very small : https://peavey.com/support/technotes/concepts/impedance.cfm
My meaning wasn't to ascribe an exact number on unknown amplifiers that could be driven by a TX-8500, but just as an example. To know the exact number, one would have to know the output impedance of the preamp section (if you're lucky, it will be in the SM. If you're really lucky, it will be in the OM), and the input impedances of amplifiers and then do the math.
The point is (was) that the OP's Onkyo is extremely unlikely to experience any ill effects from driving an outboard power amplifier and its own internal amplifier at the same time.
Y-cords will not change sound quality one way or the other. A non-defective Y cord will not be wired backwards, and virtually every quality amplifier ever made has the same phase at the output as it does at the input.
Stop making the OP worry about silliness.
Indeed it does depend on the equipment in question. However the hypothetical situation involving the outputs of a typical receiver being able to run 10 modern outboard amplifiers without adverse affects has to be extremely unlikely.
For example, the preamplifier in my main system has three sets of output jacks is stated by the manufacturer to be used with input impedance of 5,000 ohm or greater. Connected to it I have 2 amplifiers of 100,000 ohm input each, plus another of 50,000 ohm which results is 25,000 ohm. So no problems there. I could even get away with doubling the number of amplifiers (of the same models) and still the result of 12,500 ohm is still higher. (However, I can guarantee higher volume settings necessary to obtain the same amount of output from each amplifier than when only 3 are connected).
Now, later model amplifiers from the same manufacturer are rated at only 20,000 ohm input (at unbalanced inputs), 6 of those would present only 3,333 ohm which is almost certain to result in frequency response irregularities as well as drastically higher volume settings needed which would also negatively affect S/N.
I know this because when I once tried using a tube tuner-preamp (designed to be used with 100,000 ohm or greater) with the 50,000 ohm input amplifier. It didn't sound good and I couldn't understand why since the same tuner preamp sounded fine with the other SS amplifier. I later realized the other amplifier had input impedance of 200,000 ohm thus it was designed to work with that tube tuner preamp but the other amplifier at 50,000 ohm, was not.
I have also noticed line impedances have dropped significantly over the years - and a lot of older equipment may not fare so well with much newer gear.
In any case, I would be extremely surprised if "auxiliary" preamp outs of most consumer grade Japanese receivers can come close to the 5,000 ohm specified output of higher end dedicated preamplifier equipment such as would be necessary to correctly operate a string of multiple outboard amplifiers. No manufacturer of such equipment would ever have designed it with such an expectation, thus would make no sense to incur the extra costs of doing so.
THAT said...I concur...there will probably not be a problem connecting most amplifiers to the OP's receiver (along with its own internal amplifier section) - assuming the outboard unit nothing "too far off the beaten path", as it were.
It just got too complicated. Z, just try it. Forget all the complicated reasons and just know that it won't hurt a thing.
Hook it up, enjoy it, and while you are doing so, then read up on it to find your answers.
Rather than quoting and parsing your post, I have several preamps with output impedance of 100 ohms or less. Only one of them I'd really classify as somewhat high end and that is a Proceed PRE. Output impedance is given as "Less than 20 ohms". A couple of Yamahas are rated 47 ohms output impedance.
Not meant to start anything, but low/lowish output impedance particularly from SS gear isn't too uncommon.
I think even my Grounded Grid tube preamp specs indicate output impedance is a reasonably low 200 ohms.
Those low output impedances I speculate are why some differences reported by others don't seem to present themselves in my systems. They're just more immune/less sensitive to the effects of cable capacitance, amp loading, etc.
Not certain the point but I certainly don't find any fault with that statement - as I had noted above that line impedances in modern equipment is significantly lower than it had been in the past when 10s of thousands had been the norm (usable).
Incidentally - I assume internal impedance of 20, 47 or 100 ohms would translate to 200, 470 and 1,000 usable loads going by the 10x rule.
In any case, I think we can all agree the correct answer to OP is "it depends".
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