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Bi Amping with tube amplifier


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13 replies to this topic

#1 of 14 OFFLINE   Jef_DC

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Posted May 17 2003 - 03:13 AM

I'm considering to use my tube amp to bi-amp the center speaker. As I sometimes read that it is a bad idea to power up a tube amplifier without speakers ... (why exactly ? The primary of the transformers present a resistance I would think) ... I consequently wonder whether it is possible to use it for bi-amping because one channel will not be able to dump the lower frequencies into the speaker and the same for the higher frequencies in the other channel. Best regards ... Jef

#2 of 14 OFFLINE   Brett DiMichele

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Posted May 17 2003 - 06:13 AM

I am in no means an expert here (not even a dumbass in fact) But what I gather is that without an output load on the output tubes they can run rampant and fry..This is if you send them a signal.. Powering them up with no signal and no speakers, I am unsure if that will kill them also..
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#3 of 14 OFFLINE   Jef_DC

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Posted May 17 2003 - 06:39 AM

Hi Brett, meanwhile I learned that some tube amplifiers can go into oscillation (and self destruct) when powered without a suitable load (4 - 8 ohm) attached - even without input signal. Question remains : will they oscillate when only a tweeter or a woofer is attached. I guess not, but confirmation by 'those in the know' would be nice. Thanks for your reply. Jef

#4 of 14 OFFLINE   Michael R Price

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Posted May 17 2003 - 09:56 AM

Jeff, They won't oscillate with only one driver connected, unless something is really wrong. Don't worry about it... lots of other people biamp with tubes successfully. Start out using both your active crossover and the passive one in your speakers, to make sure you don't damage a driver or something with the wrong frequencies. Then you can remove the speaker level crossover, which should make a pretty big difference in sound. Your speakers won't have the same tone as they did before unless you carefully tweak the crossover, though.

#5 of 14 OFFLINE   Mark Leitch

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Posted May 17 2003 - 01:19 PM

I have biamped (tubes on top, solid state down below) and there is nothing to worry about... other than cost and the dangers of rethinking the speaker designer on the crossover ;-) M.

#6 of 14 OFFLINE   Greg Monfort

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Posted May 17 2003 - 02:27 PM

>As I sometimes read that it is a bad idea to power up a tube amplifier without speakers ... (why exactly ? The primary of the transformers present a resistance I would think) ==== When the tube conducts, and it's conducting even with no load, it stores energy in the OPT in the form of an electromagnetic field. In fact, quite a bit of energy is stored while the amp is idling, so no load = no damping of the tranny, which means that the back EMF could create thousands of volts at the plate of the tube, damaging the tube and the insulation of the tranny. GM
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#7 of 14 OFFLINE   Jef_DC

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Posted May 18 2003 - 04:16 AM

Thanks for all the replies. Meanwhile I have bi-amped the Center speaker and the sound changed more than I anticipated - in the positive sense. A lot more detail - maybe even a bit on the bright side now. But I still have multiple options to fine tune the timbre - which was not optimal so far - by playing with the 4 & 8 ohm tabs of the amplifier. Looks and sounds very good. Thanks ... Jef

#8 of 14 OFFLINE   Judy Y

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Posted May 19 2003 - 04:24 AM

Question, how do you use a tube amp and a solid state OR ANY two different amps to bi-amp? Don't you have to, some way, match the levels being sent to the speakers? Is there a unit one can buy to do this? (I would really like to use a small tube amp on my tweeters but am very happy with the sound I am getting on my woofers and mid range with solid state amplification).

#9 of 14 OFFLINE   Brett DiMichele

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Posted May 19 2003 - 06:45 AM

Judy, I run a pair of tube monoblocks on my towers which are bi amped. I run the Tubes to the Tweeter/Mid (HF) section of the internal crossover and I run a big solid state plate amp with it's own gain control to the Subwoofer (LF) side of the crossover. I can match levels this way. Most any S.S "Power amp" will have gain control over the channels so matching isn't an issue really.
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#10 of 14 OFFLINE   Judy Y

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Posted May 19 2003 - 07:17 AM

A plate amp?? Wow, I hadn't even considered that....... I use a plate amp for my SVS.... it sounds great for the sub.. Hmmm, and I wouldn't need two BIG plate amps. I could get a couple of small ones for next to nothing, add a tube amp for the front two channels and VOILA, instant home theater and music nirvana? (Do I exagerate?) How many watts are your tube mono blocks? How many watts would you recommend? Thanks for the info!!!! Judy

#11 of 14 OFFLINE   Brett DiMichele

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Posted May 19 2003 - 07:50 AM

Judy, I wouldn't use a plate amp for anything but a sub woofer and that is my useage. The low side of my crossovers connect to a pair of 10" subs and that is what the 500 watt plate amp feeds. If you had a Bi Ampable set of mains that used say a pair of 6.5's or something on the low side I would say to use better amplification (a good 2 channel amp with gain control) My tube amps put out 20 Watts Class A per channel
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#12 of 14 OFFLINE   Brett DiMichele

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Posted May 19 2003 - 07:52 AM

Judy, I forgot to address your question about what amount of power to use. With tube amps power rarely comes affordably. Most of the "cheaper" tube amps are very low wattage SET's that only develop 3-9 watts per channel. I wouldn't even consider using something like this with anything less than a 100+Db Sensitive speaker. A good 20 watts per channel mated with a reasonably efficient speaker (say 89 to 93 Db Sensitive) should get you more than adequate listening levels. You should be able to easily exceede 100Db.
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#13 of 14 OFFLINE   Judy Y

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Posted May 19 2003 - 07:57 AM

One more stupid question........ "gain" control = "level" control? I was actually just looking at some 2 channel amps and none say "gain" but almost all have "level" control. I was also thinking 30 watts or so- and looking at a Jolida integrated. (My speakers are rated at 89db) Thanks again for your replies!

#14 of 14 OFFLINE   Brett DiMichele

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Posted May 19 2003 - 08:01 AM

Yep "Level" is gain.. The Jolida sounds like a good choice.. Also check out the offerings from Antique Sound Labs (Divergent Technologies) and there are even some very nice kits if you was so inclined to build your own.. There is a nice kit called the Ella I am not sure who makes it (Michael Price knows if I am not mistaken.)
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