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Discussion Starter · #1 ·
I was wondering if using something like an Aphex 124A or an Aphex 228 would be beneficial for going from a Pioneer 54TX to some Pro Amps. Basically, I am trying to improve the signal to the amps.


The PIO line level out is 335mV/2.2kOhm impedance (unbalanced of course)


The Amps Inputs are 1.15V(+3.34dbu) /20K ohms impedance (BALANCED)


I guess one of those units will convert unbalanced to balanced and allow for an increase in the pre-amp voltage, which would in turn allow the amp to work more effeciently...as I understand it, but I'm not 100% on that (hence the thread).


I was hoping to improve the noise floor and create some headroom.


I'm not looking for " Buy a new amp " or " Get another receiver "


Both sound great as it is, but there's always room for some improvement. I've tried attaching this to the "New Amp..." thread, but not everyone reads that thing, especially in it's entirety.


Anyone using something similar to interface "Consumer" to "Pro" components?
 

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I used a DI4000 with my proamps for a while. As someone already indicated in the new amp thread in my experience the sound was better but the noise floor was raised a fair bit as well.


Hope this helps.


Sincerely,

-dollarman
 

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The line level outputs may be 335mV, but I don't believe that is the same as the pre-out levels. You would be using the pre-outs, right?


Have you tried this arrangement, or just doing due diligence?


I'd bet those pre-outs will have enough juice without the black box...


As to the unbalanced to balanced, I believe the RCA center pin goes to XLR pin 2, the RCA "shell" goes to XLR pins 1 and 3 which get jumpered together. Perhaps not the perfect setup, but I think it works for most people...
 

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It seems that some manufacturers are not publishing preout voltage in the owner manuals.

he PIO line level out is 335mV/2.2kOhm impedance (unbalanced of course)


When I first saw this spec, I thought "if this is preout voltage, the design engineer needs to be banned from electronic design as those specs are horrible for preouts".


A good home audio spec is 1v - 2v with ~200 ohms or less output impedance.
 

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Discussion Starter · #7 ·
So I'm right, the Line level out is the pre out...and that does suck, because it's only a 3rd of a volt.
 

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No, I don't believe that you are correct. The line out level is not the same as the pre out level.


Don't spend your money on the black box until you've first tried it without - you will not be out anything to try it other than $20 for some cheap RCA cables to hack up and some XLR plugs from RatShack to cobble together the connections I previously described. Then, you will find it works just fine and not really be out anything at all...


If you don't believe me, call Pio tech and ask them. Hopefully, you will eventually get someone that knows more than what is written in the manual because the pre-out level specification is missing.
 

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manual because the pre-out level specification is missing.


I noticed that by looking at other products too, from other manufacturers. What are they trying to hide? :heh:
 

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There are record outs and there are preamp outs (preouts). Both are "line level".


The 54TX manual states the sensitivity and input impedence for the line level inputs and the level and output impedence for the line level outputs. 335mV/2.2kOhm.


The problem I see is that in my V1400 manual, Yamaha states different specs for the record out and preamp out "line level outputs". Record out is 200mV/1.2kOhm; preamp out is the expected 1V/500Ohm. The line level inputs have the same volt rating as the record out, not as the preamp out.


Pioneer would be nuts to put the preamp outs at a 1/3 the industry expectation for mass market consumer electronics output level. So it's likely whoever wrote the manual is not a techie and certainly not thorough. You're likely looking at just the record out specs in the 54TX manual.


Of course, this should be quite simple to test. Connect a CD player via analog connection, play a test CD with a 1kHz sine wave at digital zero (make sure no speakers are connected), crank the volume knob to max, read a voltmeter on one of the preamp out jacks and on one of the record out jacks. If they are the same, .... (I assume the Pioneer is like most and only analog inputs are present on the analog outputs).
 

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Discussion Starter · #11 ·
I called their Tech Support, and they told me that the line level was the pre out, but that the signal was attenuated. When I asked why all other specs were listed at their max, why would they list the pre-out at an attenuated value, he could not give me an answer.
 

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Discussion Starter · #12 ·
It's funny too, because the manual says something along the line of "there's more than enough power to run any speaker set-up, so external amplification should not be necessary..."
 

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That's the trouble with most tech support these days. They don't really know the product - only what is written in the manual or what is in their call center database.


Again I say, just cobble up the cables and give it a go. There are too many people doing just what you propose that are not needing any kind of device between the receiver and pro amp.


Hey, if you want to spend the money and put another device in the chain, it's your $$, but I honestly think you'll be fine without it.
 

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Discussion Starter · #14 ·
I bought 2 of the Apex 124A's off Ebay, for just over $100, so it's worth the test anyway.


I hooked them up today, and there was a vast increase in Headroom. Before the 124A, the gains were at 3/4 for a 75dbA reference...now they're at the 10 O'clock. Noise floor is about the same, no real decrease, and definitely no increase. I have some more testing to do, so I'll check back in when I've done a better audio analysis.
 

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Discussion Starter · #15 ·
Listened to some music, and it does sound better, especially at lower volumes, much more detailed. At higher volumes, it also sounds better, less strained. It did wonders for my IB. With the BFD installed, I found that I would choke the LFE out, in order to prevent the BFD from clipping, while keeping the amp gains in check for adequate headroom to prevent any transients from possibly damaging the woofers. Now, I can set the amp gains for substantially higher output at a level that is lower than before, while keeping the LFE in check with the BFD. A huge improvement in my book, and worth the ebay price I paid for both units. All in with XLR to XLR cables, it cost me less than $150. To me, worth the price, since I didn't want to go through the hassle of selling my receiver and buying a new one, or selling my amps, in favor of something more HT freindly. Plus it adds another component, which always looks good.


As for Pioneer's Tech Support, they can't tell you anything that's not in the manual. I called again, got a different person, and got virtually the same response as the first and second time I called. I like their receivers, they have good processing, nice power, decent connectivity, but their lack of detailed specifications, and ridiculous tech support, will make me think a little harder the next time I buy a new receiver. Of course, I know a lot more now than I did when I bought this one, so that should help as well.


In any case - I'll also try "Cobbling up" some RCA to XLR cables, but I really don't think there will be any difference from using RCA to TS cables...unbalanced is unbalanced whether it's one type of connector or another, isn't it?
 
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