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    two amps - one set of speakers

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    Tom

    Posts : 166
    Join date : 2011-04-04

    two amps - one set of speakers

    Post by Tom on Mon Sep 14, 2015 10:47 am

    OK, dumb question of the day:

    I currently have a VTA preamp and a homebuilt chipamp for my system,
    and I've almost saved enough for my ST-120.
    I'd like to continue using the chipamp for the radio (on all the time) and reserve the ST-120 for music.
    And I'd like to use the same set of speakers - they have posts to bi-amp.
    Any problems with running both amps to the speakers (leave the jumpers in) but only using one amp at a time.
    Easy enough to separate the inputs at the preamp,
    I'm just not sure about applying power to the amp that off, "backwards" through the speaker outs, so to speak.

    any help appreciated -

    Thanks!

    peterh

    Posts : 679
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: two amps - one set of speakers

    Post by peterh on Mon Sep 14, 2015 11:00 am

    No, i think that connecting 2 amp outputs AND the speaker will cause wrong loading on the
    active amp. And if both are "powered on" it will surly be to high loading.

    My advice :
    Sell the chipamp and but some spare tubes for the money.

    sKiZo

    Posts : 1310
    Join date : 2013-04-01
    Location : Michigan USA

    Re: two amps - one set of speakers

    Post by sKiZo on Mon Sep 14, 2015 11:24 am

    You need one of these ...



    I've got one to switch between my ST120 and the McIntosh MC2205.

    Word of Warning: Tube amps do NOT like to be hot switched and need a load at all times. Not so much with solid state, but even those can be particular. In any case, it's ALWAYS recommended to switch amps with the system powered down.

    Niles also makes switches that provide the required loading for hot switching, but they are expensive, as you're basically creating an entire driver network without the drivers, as well as impedence matching. This one switches two amps, and should set you back around $80 if you shop around.

    PS ... works either way. You can also use it for switching two speaker sets on one amp.

    corndog71

    Posts : 451
    Join date : 2013-03-19
    Location : It can get windy here

    Re: two amps - one set of speakers

    Post by corndog71 on Mon Sep 14, 2015 4:24 pm

    Rather than dealing with all this switching business, why not just drive a different pair of speakers for the radio. Are you still listening to music or is it for talk radio / traffic reports?
    Is there a particular reason you need the radio on all of the time? Just curious.

    Som1else

    Posts : 1
    Join date : 2015-08-05

    Re: two amps - one set of speakers

    Post by Som1else on Mon Sep 14, 2015 4:31 pm

    I had the same issue since my other receiver didn't have a preamp out. I picked one of these up and it works really well and is well built. Supposedly it doesn't degrade the signal in any way.


    http://www.adventuresinhifiaudio.com/13/06/2010/the-beresford-tc-7220-what-exactly-is-an-audio-crossover-network/


    sKiZo

    Posts : 1310
    Join date : 2013-04-01
    Location : Michigan USA

    Re: two amps - one set of speakers

    Post by sKiZo on Mon Sep 14, 2015 6:48 pm

    I drive my ST120 off a tape loop on this monster anyway.



    I also run the entire house off the A/B capabilities, and can switch five sets of speakers on and off as needed in stereo pairs, or three remote stereo pairs and one quad room.

    Granted, not what the OP is talking about, but extremely versatile, and proof you really don't need a pre-out to make it happen. I don't get tone/volume from the Sansui on the VT120, but don't need it - that's all handled by the volume pots on the tuber, and both hardware and software EQ/PEQ in the loop.

    I even kept that in mind with the custom case ... instead of hooking the amp into the loop with a Y cable (required to pass any post processing back to the receiver) I just added another set of internally bridged jacks on the back.



    Call it an "innie" instead of an "outie" ...

    That said, I still like the Niles switch for driving the main speakers from either the ST120 or the Sansui itself. I prefer the sound of the ST120 (of course!) but I do get more power from the QRX-9001 and it runs a lot cooler  in the dog days of August.

    Tom

    Posts : 166
    Join date : 2011-04-04

    Re: two amps - one set of speakers

    Post by Tom on Tue Sep 15, 2015 11:12 am

    I'm getting the impression that this is a no, kinda like I thought.

    Why is the radio on all the time? Mrs. Tom likes to listen to the radio - but does not like to mess with "my" stereo.

    "NOTHING IS LABELED! How do I know what I'm turning?!?"

    This is actually a very good point. And stuff keeps changing too. Razz

    So I bypassed the linestage for the tuner in, just goes to an attenuator for volume now, then to the chipamp. Simple and easy.

    Thanks Skizo and Som1else for those switch systems. I have a couple old SS integrateds I can cannibalize for parts. Maybe I'll scavenge the speaker A & B switch from one and install on the existing preamp to switch the amps. Just a few more ins and outs, right?

    Smile

    sKiZo

    Posts : 1310
    Join date : 2013-04-01
    Location : Michigan USA

    Re: two amps - one set of speakers

    Post by sKiZo on Tue Sep 15, 2015 2:39 pm

    Your SO would have a blast with my system ...



    Hell ... I gotta leave crib sheets so I can find my way back once I start to twiddling the knobs, and I've had 30 years to get used to it.
    .

    GreggW

    Posts : 56
    Join date : 2015-07-15

    Re: two amps - one set of speakers

    Post by GreggW on Tue Sep 15, 2015 3:38 pm

    That Sansui receiver needs a few more buttons, knobs, and switches. Glad to see the curtains weren't scorched from the 5AR4 explosion in your bazillion watt tube amp.

    bluemeanies

    Posts : 129
    Join date : 2015-02-09
    Age : 66
    Location : Folsom Pa.

    Re: two amps - one set of speakers

    Post by bluemeanies on Tue Sep 15, 2015 6:40 pm

    Tom wrote:OK, dumb question of the day:

    I currently have a VTA preamp and a homebuilt chipamp for my system,
    and I've almost saved enough for my ST-120.
    I'd like to continue using the chipamp for the radio (on all the time) and reserve the ST-120 for music.
    And I'd like to use the same set of speakers - they have posts to bi-amp.
    Any problems with running both amps to the speakers (leave the jumpers in) but only using one amp at a time.
    Easy enough to separate the inputs at the preamp,
    I'm just not sure about applying power to the amp that off, "backwards" through the speaker outs, so to speak.

    any help appreciated -


    I have the same situation and had switch boxes made that can handle two mono-blocks and my 7 channel amplifier connected to one pair of B&W804S speakers.
    Works perfect! Price less than $100.00


    Thanks!

    corndog71

    Posts : 451
    Join date : 2013-03-19
    Location : It can get windy here

    Re: two amps - one set of speakers

    Post by corndog71 on Tue Sep 15, 2015 8:20 pm

    Labels? We don't need no stinking labels!


    Tom

    Posts : 166
    Join date : 2011-04-04

    Re: two amps - one set of speakers

    Post by Tom on Wed Sep 16, 2015 9:27 am

    Laughing at the Labels! Smile

    The "simplified" system.  Note that the bottom, where the CDs are stacked, is reserved for the ST-120.

    Gotta decide on bamboo or rosewood for faceplates and do either one or the other.  Looks ridiculous as is.  Oh well.


    peterh

    Posts : 679
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: two amps - one set of speakers

    Post by peterh on Wed Sep 16, 2015 9:51 am

    Tom wrote:Laughing at the Labels! Smile

    The "simplified" system.  Note that the bottom, where the CDs are stacked, is reserved for the ST-120.

    Gotta decide on bamboo or rosewood for faceplates and do either one or the other.  Looks ridiculous as is.  Oh well.


    I wouldn't locate the vta-120 at the bottom. Heat rises upwards you know ..

    Tom

    Posts : 166
    Join date : 2011-04-04

    Re: two amps - one set of speakers

    Post by Tom on Wed Sep 16, 2015 11:19 am

    "Do you know the muffin fan?
    The muffin fan? The muffin fan!"
    (we need a "singing" smiley thing haha Razz )

    The upper three slots are ventilated with a low speed fan tied to the switched power on the chipamp.

    I'll do the same for the lower slot when the ST-120 come in, there's a solid partition between the upper slots and the lower one.

    I think this must have been an old TV cabinet. I got it at a junk store for $40.

    Smile

    sKiZo

    Posts : 1310
    Join date : 2013-04-01
    Location : Michigan USA

    Re: two amps - one set of speakers

    Post by sKiZo on Wed Sep 16, 2015 12:39 pm

    I'd still consider relocating the ST-120 to the top shelf, and maybe put the turntable on a slider on one of the lower sections.

    We're talking a LOT of heat here ...



    If nothing else, it'll keep the room quieter ... get rid of those muffins, man, the muffins man!!!

    Tom

    Posts : 166
    Join date : 2011-04-04

    Re: two amps - one set of speakers

    Post by Tom on Wed Sep 16, 2015 1:52 pm

    Wow!
    That's enough heat to cook some muffins man, some muffi... oh enough. Very Happy

    No love for my muffin fans?
    There's some good electronics salvage around here owing to KSC and Cape Canaveral nearby
    so I got a couple big (8"?) 24v fans for almost nothing.
    Running at 12v you can't hear them at all but I don't know how many cfm they're moving.

    I checked the spec for similar fans at mouser and they're about 500-600 cfm.
    Maybe half the cfm for half voltage, maybe less - who knows.
    Using 250 cfm, and my lower cabinet space at around 5 ft^3,
    that an air exchange a little more than every second or so.

    Can't be much worse than radiant cooling?
    Maybe I try to borrow Skizo's ray gun to find out.
    When I finally get my 120. Razz


    sKiZo

    Posts : 1310
    Join date : 2013-04-01
    Location : Michigan USA

    Re: two amps - one set of speakers

    Post by sKiZo on Wed Sep 16, 2015 2:12 pm

    I suppose another option (assUming I can't talk you out of the muffins, man) ...



    The laptop cooler used to sit right on top of my HTPC and pulled air through the vented top. Adjustable speed, moved quite a bit of air, and very quiet. You'd need a 5V power source, as they're mostly powered off a USB port. I expect you could drill a few holes an attach it to the underside of the shelf with standoffs ... IF you had enough room and could still provide good clearance. There's always the possibility of it melting if you turned on the amp and forgot to turn off the fan ... clown

    No longer a problem - the original build could cook eggs with six fans running full time. I've since upgraded to an ITX board and 60 watt APU. Only the chip cooler and power supply fans run now, and those just barely tick over ...


    Tom

    Posts : 166
    Join date : 2011-04-04

    Re: two amps - one set of speakers

    Post by Tom on Wed Sep 16, 2015 3:01 pm

    +1 Like!

    peterh

    Posts : 679
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: two amps - one set of speakers

    Post by peterh on Wed Sep 16, 2015 4:16 pm

    The most quiet fan is no fan.
    That's why i place my poweramp on top of all shelfs, close to the ceiling. It used to be a D-75A but these days it's a VTA-70.
    Locating a tubeamp below vinyl records is no luck, a friend did this. Also a tube amp in a location that anyone might by accident place something above is a no-good thing. Children, spouse or even You might do this(i have !).

    sKiZo

    Posts : 1310
    Join date : 2013-04-01
    Location : Michigan USA

    Re: two amps - one set of speakers

    Post by sKiZo on Wed Sep 16, 2015 6:59 pm

    Yup ... I ventilated the shelves over the receiver and Big Mac, and the tube gear goes up top where it can "see the sky".

    Couldn't abide fans, not even muffins, man ... which is why I upgraded the HTPC. The original build was too loud even with speed controllers. Can't hear the new one at all.

    When I'm really into listening, I even switch off the aquarium and furnace, as well as stop a big mechanical clock that's in the next room. I like it quiet enough that I can hear a mouse fart ...

    PS ... I don't know the muffin man, but I've stayed at the same Holiday Inn Express!

    Tom

    Posts : 166
    Join date : 2011-04-04

    Re: two amps - one set of speakers

    Post by Tom on Thu Sep 17, 2015 8:02 am

    laughing at the turning all the stuff off, even the clock (?!?)

    we have a tiny "recording studio" set up in one of the girls bedrooms (all off to college)
    and you can often hear the AC kick in half way through whatever on the playbacks
    seems to always happen in the middle of a soft passage Razz

    FLORIDA. I AM NOT TURNING THE AC OFF. Mad

    Very Happy


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