Bi Amping with tube amplifier (1 Viewer)

[Jef_DC]

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

 

[Brett DiMichele]

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..

 

[Jef_DC]

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

 

[Michael R Price]

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.

 

[Mark Leitch]

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.

 

[Greg Monfort]

>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

 

[Jef_DC]

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

 

[Judy Y]

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).

 

[Brett DiMichele]

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.

 

[Judy Y]

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

 

[Brett DiMichele]

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

 

[Brett DiMichele]

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.

 

[Judy Y]

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!

 

[Brett DiMichele]

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.)