I have a H-K TA5000 and I m running an inexpensive active sub. My rig is in a small room so I use the sub because I'm running small bookshelf speakers; I just turn the sub up enough to barely hear it and fill the bottom - I dont rattle the windows with it. This sub has a line level input connection that I m using off the tape-out on the receiver. I was going to put the sub in a new location so I unplugged it. The volume and bass response of the main speakers increased dramatically with the sub unplugged. Obviously not the best way to connect a sub to this receiver. I don't ever turn the sub up passed 1/3 volume or so. There is no chance I'm trying to drive a passive sub with this amp.
Would putting a resistor in the line going from the receiver to the sub work and would it be a good way to keep the audio signal from being pulled down by the sub? If so, where would I start with resistor values. Is there a better way to go?
Would putting a resistor in the line going from the receiver to the sub work and would it be a good way to keep the audio signal from being pulled down by the sub? If so, where would I start with resistor values. Is there a better way to go?
Typical active subs have input impedances that are too low to play well with vintage valve gear, 10K Ohms or even less. A second issue is that tape outputs are upstream of the volume control, so don't track with volume changes.
One solution for both issues is to make a voltage divider that hangs off the speaker output, in parallel with the main speakers, and feeds into the sub. Resistor values are totally non-critical, Maybe something like 10K to 1K Ohms (a ratio of 10 or 20 is about right) and you can graft an RCA/phono cable right onto it. Really doesn't even need to be shielded, just a rat's nest construction works and is safe.
All good fortune,
Chris
One solution for both issues is to make a voltage divider that hangs off the speaker output, in parallel with the main speakers, and feeds into the sub. Resistor values are totally non-critical, Maybe something like 10K to 1K Ohms (a ratio of 10 or 20 is about right) and you can graft an RCA/phono cable right onto it. Really doesn't even need to be shielded, just a rat's nest construction works and is safe.
All good fortune,
Chris
Does the S/W have speaker level I/Ps? If it does, connect it in parallel with the main speakers. Don't "daisy chain". Adjust the S/W controls to fill in underneath.
Using the arrangement given above allows the "plate" amp in the S/W to pick up some of the tube main amp's sonic signature. The speaker level cross over in a S/W presents a high impedance to the main amp, below the "corner" frequency. Not "daisy chaining" causes the S/W's cross over to present a high impedance (open circuit) above the "corner" freq. too. "Audiophool" speaker wire is unnecessary for connecting the S/W to the main amp, when the parallel arrangement is used. 16 AWG OFC zip cord is plenty good enough.
Using the arrangement given above allows the "plate" amp in the S/W to pick up some of the tube main amp's sonic signature. The speaker level cross over in a S/W presents a high impedance to the main amp, below the "corner" frequency. Not "daisy chaining" causes the S/W's cross over to present a high impedance (open circuit) above the "corner" freq. too. "Audiophool" speaker wire is unnecessary for connecting the S/W to the main amp, when the parallel arrangement is used. 16 AWG OFC zip cord is plenty good enough.
Thanks for the input Chris. I will look into a making a voltage divider. I believe I made a similar device to play mp3s with my vintage radio.
Thanks Eli. To be clear, your suggestion is to construct a voltage divider and use the speaker inputs in lieu of the line inputs, correct? And I agree completely regarding daisy chaining. The s/w has speaker level in and out's; I tried it (w/o a voltage divider) and it killed the sound quality of the main speakers.
So the million dollar question is, with a voltage divider and speaker and sub in parallel what kind of impedance is my amp going to be seeing?
Thanks Eli. To be clear, your suggestion is to construct a voltage divider and use the speaker inputs in lieu of the line inputs, correct? And I agree completely regarding daisy chaining. The s/w has speaker level in and out's; I tried it (w/o a voltage divider) and it killed the sound quality of the main speakers.
So the million dollar question is, with a voltage divider and speaker and sub in parallel what kind of impedance is my amp going to be seeing?
Another possible solution might be a FET buffer. Shouldn't hurt the bass sound nor load the tube amp enough to affect its performance.
+1 on adding a Tube Friendly Buffer, either straight FET or unity gain (or whatever´s needed) FET input Op Amp, even something as simple as a TL072.
I would NOT pull signal from Speaker Out (too late, too distorted) but some earlier point at Preamp, including Pre Out to Power Amp In link.
I would NOT pull signal from Speaker Out (too late, too distorted) but some earlier point at Preamp, including Pre Out to Power Amp In link.
Thanks Mark and JMF, that sounds like a great way to go. I also like the idea of getting the signal before the amp because I really don't want any added stress on the 55 year old output transformers.
No voltage divider needed, when the speaker level parallel technique is employed. Just tweak the S/W controls to get the best result.
Your tube amp is, for all practical purposes, going to "see" only the main speakers, as its load. The crossover in the S/W presents a high impedance below the "corner" freq. and, since nothing is connected to the above "corner" freq. terminals, a high impedance is presented there too.
Remember, when impedances are connected in parallel, the lower value is dominant.
An 8 Ohm speaker and a 10,000 Ohm sub-filter, parallel, make 7.993 Ohms.
No amplifier would care. ("8 Ohm" speakers run 6 Ohms to 60 Ohms.)
What Eli is suggesting is to use the voltage divider built into your sub's speaker level inputs, but not its speaker level crossover. IOW, don't connect your speakers to the sub's "main speaker outs" (daisy-chained), rather, leave them connected directly to the main amp, in parallel with wires running down to the sub.
No simple ideal solution for mating subs exists, there are only crude compromises. The main speakers' fundamental resonance is within an octave, etc. Fortunately we don't hear very good down there, and room issues dominate(ish).
All good fortune,
Chris
No simple ideal solution for mating subs exists, there are only crude compromises. The main speakers' fundamental resonance is within an octave, etc. Fortunately we don't hear very good down there, and room issues dominate(ish).
All good fortune,
Chris
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So quick update. I have some hours listening to my setup without a s/w over the last couple of days and I'm amazed at how good the bottom end is with just the combo of this receiver paired with my little Wharfedale Diamond 9.1s (better, bolder ect. than with the sub connected as it was). I've played these speakers with a Halfer DH-100 pre-amp - Speakercraft BB275 amp combo and they needed a s/w bump for sure. I not feeling the need for a sub with the HK receiver. btw, i upgraded these 9.1s with the GR Research crossover upgrade and they are as detailed and smooth as promised.
$4000 Revel VS $350 Wharfedale | The Results Might Surprise You! - YouTube
$4000 Revel VS $350 Wharfedale | The Results Might Surprise You! - YouTube
+1
Totally agree. Why take the signal out of a tube amp, which is not always known for bass quality. Years ago at a hifi store, it was bewildering to me to see a system with Avant-Garde horn speakers using the signal from a pair of Jadis 300B SE amps for their subwoofers! The bass sounded like mud. The best and cleanest way is to take the signal via buffers with high input impedance and then do the summing to mono for a single subwoofer. Some preamps have buffers for the tape outputs and that would be ideal and easiest.
