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Thread: Home HiFi conversion question

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    Default Home HiFi conversion question

    Hi all,

    Here goes, maybe someone here is also a HiFi person...

    I have an older home Pioneer Stereo Receiver which I have set up to run 5.1 surround sound and is connected to everything (TV box, Apple TV, DVD, Playstation, HDMI TV, Radio, etc.) and is running to 5 surround speakers via normal speaker wire. Everything is run by a programmable remote and I am really satisfied with the setup after much hard work. I recently invested in a pair of higher end Active speakers (KvK) that I was intending to replace the front (left/right) speakers with only to learn afterwards that converting a powered speaker wire to RCA connection to attach to an already powered/active speaker is a big no-no and can result in damaging both the speakers and receiver.

    I originally bought the speakers to connect to a Bluetooth receiver to be able to run wireless from my iPhone/computer/etc. but would also like to utilize them where the majority of my listening comes from (TV, Stereo, PS4, etc.).

    So my question is, is there a way to take the 100W output of the receivers speaker wire and strip this to a regular "non-powered" RCA contact and somehow keep the sound quality okay? I have seen some things for car stereos to enable this but it doesn't seem like something to use for a home system. I found this Russound ADP-1.2 Speaker-level to Line-level Adapter at Crutchfield but don't feel secure enough to try it without some insight first. In HiFi terms I think I am looking for a "speaker level converter to line level output for receivers that lack line out capabilities".

    Anyone? Thanks in advance for any directions or advice!
     

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    Default Re: Home HiFi conversion question

    First question: Does your AVR have "pre-outs"? because that would solve everything. Not sure? Post a pic of the back of the unit.
     

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    Default Re: Home HiFi conversion question

    Tape output?

    Tee Aitch

    Give a man a fish and feed him for a day. Teach a man to fish and feed him for a lifetime. Teach a man to cycle and he will realize fishing is stupid and boring. -- Desmond Tutu

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    Default Re: Home HiFi conversion question

    Tape out shouldn't have volume control though. If it is a mid level or better AVR that handles 5.1 (not a "Stereo Receiver" as mentioned) there is a good chance that it has Pre-outs.
     

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    Default Re: Home HiFi conversion question

    Quote Originally Posted by ZeroG View Post

    So my question is, is there a way to take the 100W output of the receivers speaker wire and strip this to a regular "non-powered" RCA contact and somehow keep the sound quality okay?
    Two 390 kohm resistors, one for each channel, in series with the positive speaker output. This assumes the thing it is feeding has 100k input impedance and a zero dB level of 700 mV.

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    Default Re: Home HiFi conversion question

    @Mark Kelly
    I don't know numbers but will those resistors work for all signal levels or just the 100W which is probably not what he is actually outputting?
     

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    Default Re: Home HiFi conversion question

    Quote Originally Posted by rec head View Post
    @Mark Kelly
    I don't know numbers but will those resistors work for all signal levels or just the 100W which is probably not what he is actually outputting?
    My answer above is incomplete, don't know why.

    There is a second 10k resistor in the voltage divider network, this is between the 390k resistor and the neutral line.

    If the amp is rated 100 WPC into 8 ohms it has an output swing of 28.3V at full scale*. The resistor network reduces this to 9.1 / 399** of that value, which is 650 mV. That's not exactly 700 mV but it allows for some non zero output impedance of the amp and I've stuck to E12 values for resistors as these are easier to find (the values are separated by approximately the twelth root of ten, hence E12).

    700 mV is the old standard, if the OP posts the full spec of the dvices in use I can give better advice.

    The alternative is to just suck it and see: If it's not getting to full volume, reduce the 390k resistor to 330k. If you go into clipping too early, increase the 390k resistor to 470k.

    * The OP stated it was an old home theatre receiver so I am assuming the output impedance is fairly low.

    **The 10k resistor is in parallel with the input, assumed to be 100k, so the net resistance in the bottom of the divider is 9.09 k = (100 + 10) / (100 * 10)

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    Default Re: Home HiFi conversion question

    Thanks all for chiming in and sorry for not including the model of the radio/amp in my original post. It's a older model Pioneer VSX-323 with the only line out for the sub-woofer (which is connected). I know it's nothing to brag about, but since I have it already connected to everything just the way I want it, to upgrade the radio/amp to a more robust model seems unnecessary at this time if I can just resolve how to incorporate the KvK Rokit 5 G3 Active speaker set.
    vsx-323.jpg
    vsx-323_back.jpg
    Attached Images Attached Images
     

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    Default Re: Home HiFi conversion question

    And the active speakers? I don't know KvK.

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    Default Re: Home HiFi conversion question

    Quote Originally Posted by Mark Kelly View Post
    And the active speakers? I don't know KvK.
    Sorry, my mistake not KvK but KrK if that helps: KRK SYSTEMS - ROKIT 5 G4 Professional Bi-amp Studio Monitors Speaker
     

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    Default Re: Home HiFi conversion question

    I thought as much but didn't want to presume.

    Basically, you are screwed. The KRK's are prosumer gear so they use the pro level standard which is a balanced line input. You could derive a balanced signal from your existing amp but it requires more work than it's worth.

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    Default Re: Home HiFi conversion question

    Like Mark said, you need to pick either the AVR or the speakers. I had a feeling that is how it was going to go. Depending on the video features you need of the AVR getting a different one with the pre/outs should be pretty easy to swap out. Depends on how much you like those KRK speakers.

    Or just go with your original plan and use the speakers with the BT receiver.

    Either situation will probably require going from an unbalanced output to balanced. This isn't the same problem you have now. It would mean more chance of noise in the signal. In the basement I have an old AVR with pre-outs running to a set of powered speakers. Works fine for what I need. You just need adapter cables.
     

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    Default Re: Home HiFi conversion question

    I thought up a left field solution.

    Get yourself a couple of line matching (PA) transformers with multiple output taps. I can get a suitable one here*, 100V line, 40 watt match to 8, 6, 4, 2 ohm.

    Connect the amplifier output to the 100V line input, bridge the output 8ohm tap to 2 ohm tap and 2 ohm tap to Common with large wirewound 3.3 ohm resistors rated at 10 watts or so (Dale for preference). Ground the 2 ohm tap and take the balanced line for the KRKs from the 8 ohm and Common.

    PA Txs are too small to make decent bass, but you use a subwoofer so that shouldn't matter.

    * But you aren't going to want to pay shipping. I had a brief look on Digikey and didn't see anything suitable. If you want to go this way I'll find something that suits stateside, Antique Audio are good for things like this.

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    Default Re: Home HiFi conversion question

    Quote Originally Posted by Mark Kelly View Post
    I thought up a left field solution.
    * But you aren't going to want to pay shipping. I had a brief look on Digikey and didn't see anything suitable. If you want to go this way I'll find something that suits stateside, Antique Audio are good for things like this.
    Left field solutions are more than welcome!

    I really like the KRK speakers, and feel it is a shame to waste the quality when watching movies, listening to CD's, etc. and just use my older/not as good non-active speakers (so that's why I wanted to see if there was a way to incorporate them in my setup). So the converter I original posted, won't work? It seems like it should as it accepts line in on one side and RCA output on the other, but again, I am a dummy when it comes to this so that's why I am asking.

    Russound ADP-1.2 Speaker-level to Line-level Adapter at Crutchfield
     

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    Default Re: Home HiFi conversion question

    It's basically the pad I first outlined with different resistor values*. It does not provide the second inverted signal that balanced connections require.

    Consumer audio mostly single uses ended signal wiring: one voltage between a "signal" wire and a "ground" wire. The RCA standard connector is commonly used.

    Pro audio mostly uses balanced signal wiring: two equal but opposite voltages between each of two signal wires and a ground wire, the signal is taken from the difference between the two signal wires. The XLR standard connector is commonly used.

    This begs the question: what's feeding the active speakers now?


    * My resistor values were predicated on a 100k input impedance which is a common consumer standard but doesn't apply in this case.

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    Default Re: Home HiFi conversion question

    My suggestion is that you give up. Powered speakers are not compatible with an amplified output.

    Or take Tee Aitch's suggestion in the second post and use the connections from the tape output. Run it through a $50 Schitt SYS volume control using a second pair of RCA jacks and you're done.
    GO!

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    Default Re: Home HiFi conversion question

    Suck.... thanks everyone! I was hoping for some kind of converter to get the most usage for these active speakers, but now understand that this isn't a likely solution. I unfortunately don't have another pre-out (tape) option, however do have a single pre-out for the subwoofer (which is already used to the subwoofer). Don't think it goes to split this to all three aktiv speakers (subwoofer plus left/right KrK speaker) and get good sound since I presume it is just the deeper bass signal.

    Skärmavbild 2020-01-10 kl. 15.59.30.jpg


    Quote Originally Posted by Mark Kelly View Post
    This begs the question: what's feeding the active speakers now?
    Mark, what's feeding the active speakers now is a RCA cable connected to the Logitech Bluetooth receiver.
    bluebox2-gallery.png
     

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    Default Re: Home HiFi conversion question

    Well if you are already OK with running a single ended input to the KRKs you can use a resistive pad. I finally found the input sensitivity of the KRKs is -10 dBV, that translates to about 350 mV in ordinary terms. To get that from the receiver you'd need to use a resistor ratio around 80 : 1, so say 39k / 470R. The Russound unit has a ratio around 10: 1 (3k9 / 430R) but since the KRKs have a software pad function you can use that to set the level.

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    Default Re: Home HiFi conversion question

    Awesome! Thank you and I’ll give the Russound a go then ��
     

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