[Niteshade]

 

[doug s.]

c'mon blair - don't tell me you have penis enwy, too?   

doug s.

[mfsoa]

Hi Mike,

Glad to hear you are a smitten kitten w/ the glowing orbs!

I was wondering, if your speakers are biwire-able are you going to try the NuForces on the bottom?

-Mike

[Niteshade]

No no no... 

Weren't you talking about this?

[mcullinan]

I was thinking of it. Will I gain anything? Instead of running my second outputs to the sub run them to the lower connections? How does the power match in the same speaker?
M

[toobluvr]

I was thinking of it. Will I gain anything? Instead of running my second outputs to the sub run them to the lower connections? How does the power match in the same speaker?
M

If your speakers are biwire, just try it and see.  It is completely 100% safe.  I guarantee it.

Power output on both amps does not need to be the same, but amp gain s/b very similar or one part of the speaker will be louder than t'other and things will sound unbalanced and disconnected.  The solution is to have a volume pot on one of the amps to balance things out.

I am passively biamping at the moment (two different amps) with only my line stage master volume control, and I like the results very much --  better than any of my amps run full range.

Most folks say active is really the only way to go with biamping, and that passive is not worth the trouble and expense over single amping, but I am getting different results. 

As always, YMMV.

[mfsoa]

Yeah, what Toob said.

Just try it and see.

If the Mahis have taps for different impedances, these can be exploited to adjust the output level a bit (At least it does on my VAC amp - the 8, 4 and 2 ohm taps give less and less output, respectively). Got that tip from a helpful AC member, forget who but thanks anyway!

When I biamp w/ the VAC on mid/tweets and the Cherry on bass, not only do you get the advantage of the grip of ClassD on the bass, but because the tubes on top will be loafing along with not having to do bass duties, the quality of the mid/tweet reproduction takes a big step up, IMO and in my system. Are Merlins 2-ways, though? I find the VAC/DAC biamp to work well on my Vons because the crossover from bass cabinet to mid/tweet cabinet is about 200 hz. I don't think it'd work so well on a 2-way, where the crossover may be 2K to 3K hz, since the tubes would only be doing the tweeter and the SS would still do the bulk of the musical signal - you'd lose the tube magic through the midrange.

I don't know what you'd do for your sub, though.

Have fun,

-Mike

[toobluvr]

....., but because the tubes on top will be loafing along with not having to do bass duties, the quality of the mid/tweet reproduction takes a big step up, IMO and in my system. Are Merlins 2-ways, though? I find the VAC/DAC biamp to work well on my Vons because the crossover from bass cabinet to mid/tweet cabinet is about 200 hz. I don't think it'd work so well on a 2-way, where the crossover may be 2K to 3K hz, since the tubes would only be doing the tweeter and the SS would still do the bulk of the musical signal - you'd lose the tube magic through the midrange.

-Mike

Correct on both points, Mike!   

I forgot to mention that tubes breeze on top cause they are doing so little work.   A circuit builder friend of mine told me I could probably get away with as little as 10 to 20 wpc on top, despite the fact that I need about 100 wpc when running my Sunnys full range/ single amp.  Most of the amp current is needed to control the big 10 inch woofers that are so capable of prodigious heft and impact.

Also correct about being mindful of crossover point.   If it is high, it is doable with SS on bottom, but one must be more selective about choosing the bottom amp for refinement and not just grunt...like you could do with a low crossover situation. 

But in Mcullinan's case I assume he has been using SS full range to this point, so he will simply be adding greater refinement (maybe?) to the top part of his speaker by putting tubes there.  The bottom part will stay the same, or maybe get better.  Overall, the sound might get more confused d/t different voicings around the crossover point.

I am currently using a pair of borrowed Soliloquy 6.2.  It is a simple 2-way so I'm guessing crossover at around 3kHz.   I am using a Class A SS amp on bottom, tubes on top and find the overall sound to be very fluid, coherent and refined.   I probably just got lucky, but I lose nothing in the midrange, despite having SS so high in the range.  Voices are very natural and weighty and rich with inflection, nueance and presence.   Scary real sometimes.

And pertinent to Mike's point about the tube amp just cruising cause it has so little work to do,  I did notice how much more refined and sophisticated the treble got moving from single tube amp to biamping with same tube amp.

The other thing that has improved with the passive biamp is timing and pace.  The music just moves along nicely with great naturalness and smooth flow.   I also notice more drama and grace to the musical message.   Tension builds and releases better....like live music does.

I have read about how passive biamping is not worth it, and usually sounds worse than single amp full range, so initially I was questioning what I was hearing.  But I listened long term and could find no real nits to pick.  I was digging it.  Then an experienced audio buddy visited (he owns gear I can only dream of) and he listened to all my possible setups ---  both single amp and biamp combos --- and he too preferred the biamp setup that I like, and also ranked all the others in the same order as me.  The single SS amp run full range was at the bottom of our list.

[mcullinan]

The speakers are Merlin VSM Mx and can be biamped. Not sure of the crossover point. Will see.
M

[toobluvr]

Almost all 2 ways are crossed over in the 2k to 3k range.  I'm sure the VSM is no different.

[JakeJ]

Here's my .02 on bi-amping based on my limited experiences.

First if passively bi-amping it is important for the two amps to match in sensitivity.  This means that no matter what each amps maximum output is they must get there at the same input voltage. Example:  Tube amp "A" puts out its max rating of 25 Watts for 1 volt of input from the preamp and SS amp "B" puts its max rating of 225 Watts for the same 1 volt of input from our bespoke preamp.  We have a match!  These amps will work well in a passive bi-amp situation.  Now, tube amp "Y" puts out its max rating of 32 Watts at 1.5 volts of input and SS amp "Z" puts out its max rating of 150 Watts at .75 Volts of input.  This won't work without an adjustable attenuator on the more sensitive amp.  Quiz: which amp is more sensitive requiring the attenuator?

The above scenario addresses horizontal bi-amping.  If one is bi-amping vertically, i.e. channel "A" of an amp is running the mid/tweeter section and channel "B" is running the bass section of one speaker (another amp is required for the other speaker) then it is typically done with a pair of matching stereo amps whether they be SS or tubed.

Now if you are actively bi-amping then the active crossover will usually have some attenuation/boost controls to help match outputs and make things much easier.  I'm sure there are other possible combinations but these scenarios are the most popular and for good reason.

Gerald, it appears you are pissing into the wind.

Have fun fellers but keep it civil.

Jake

[mfsoa]

But Gerald, what would you do if you heard Amp A that had 1000 times more distortion, a tenth the power bandwidth, much worse damping factor, lower power output and 20 db higher noise level than Amp B (Not Aunt Bea from Mayberry, Amp B) - Yet sounded vastly superior to Amp B?

Seriously, would you not rather listen to Amp A?

I would.

-Mike

[toobluvr]

Here's my .02 on bi-amping based on my limited experiences.

First if passively bi-amping it is important for the two amps to match in sensitivity.  This means that no matter what each amps maximum output is they must get there at the same input voltage. Example:  Tube amp "A" puts out its max rating of 25 Watts for 1 volt of input from the preamp and SS amp "B" puts its max rating of 225 Watts for the same 1 volt of input from our bespoke preamp.  We have a match!  These amps will work well in a passive bi-amp situation.  Now, tube amp "Y" puts out its max rating of 32 Watts at 1.5 volts of input and SS amp "Z" puts out its max rating of 150 Watts at .75 Volts of input.  This won't work without an adjustable attenuator on the more sensitive amp.  Quiz: which amp is more sensitive requiring the attenuator?


Jake

BZZZZZZZZZZZZZZZTTTTTTTT!

Logical and intuitive, oh wise one, but not true!!        

I thought exactly the same thing....that matching input sensitivities was the critical criteria to getting balanced sound when using two different amps.  Then I asked a circuit builder who surely knows more than me.  The key is  the amp's "voltage gain" which is a function of input sensitivity (and output power), but not the same thing.  This is copy / paste of our actual email conversation.

*********************************************************
Q:  In general, does the more sensitive amp need the volume control?   

A:   Not necesarily.   Choosing the amps for biamping based on its sensitivity spec... that may be tricky.  There are several variables.  What really matters is the amp's voltage gain. In theory you want the figure to be identical for the two amps.
 
Amplifier sensitivity is (typically) defined as input voltage that will drive the amp to the brinks of saturation. So 1.1V sensitive 100W amp will have much higher voltage gain than 1.1V sensitive 30W amplifier.
 
Let's assume 8 ohm load... 100W amplifier will have output voltage (Vout) of ~28V and 30W amp ~15V (I'm rounding numbers here). Pout=(Vout)^2 : Rout
 
So the voltage gain is going to be 28/1.1=25 and 15/1.1=14, respectively.
 
If the 30W tube amp is to match gain of the 100W SS amp (25x), it's sensitivity will need to be (14:25)x1.1=0.5V.
 
So that was easy... The problem is that we do not know power distribution below and above 800Hz. It depends from track to track, but I would WAG typically 80% below, 20% above 800Hz.... for complex (orchestral music), 90/10 for less complex pieces....
 
Knowing that you're not blasting music and need higher power to get a good grip on the woofers, I am guessing that even 20W is pretty conservative number for the tube amp... which gives you a lot of options to play with...

In practice, volume control does the job.... Which amp is more sensitive is not that relevant as long as the lower sensitivity amp has enough gain to give you adequate sound levels.

**********************************************************

Hmmmmm....easy for him to say.       Most of it is Greek to me, but I was able to figure out that for a given input to the amp (as given by the master volume control), each amp must put out the same number of watts into the speaker.  This is determined by "voltage gain", not "sensitivity". 

His example clearly shows that it is possible to have identical amp input sensitivites, yet different voltage gains.  Therefore, the amps are not a match, and the louder amp (ie: one w higher voltage gain) would need the volume pot to attenuate and balance things.

(He mentions 800Hz and power distribution because that is the Sunny crossover point.)

[toobluvr]

quiz answer:  amp "Z" is the more sensitive one, but not necessarily the one that needs the volume control.  The one with the highest voltage gain gets the volume pot.

[doug s.]

personally, w/typical speakers w/x-overs in the 1.5k-4k range, i wouldn't bother bi-amping, unless i were using identical amps.  w/a tube amp, i would want the tubes operating in the range from 300hz to wherever the x-over point is.

now, if you were using a 3-way speaker, or using a full-range driver and a woofer/sub, that were crossed over at 300hz or lower, then i would recommend a s/s amp on the bottom and tubes on top.

in m's case, i would recommend bi-wiring his merlins w/the mahi's, but use an active outboard x-over and subs, crossed over at 60-80hz, with s/s amps for the subs.  yust relieving the tube amps and speakers of seeing anything below 60-80hz is all that's needed, and it will work wonders, imo.     of course, you could go totally nuts and bi-amp using four mahi's.     even so, i'd still recommend using an active outboard x-over w/subs, and s/s below 60-80hz...

doug s.

[gerald porzio]

"But Gerald, what would you do if you heard Amp A that had 1000 times more distortion, a tenth the power bandwidth, much worse damping factor, lower power output and 20 db higher noise level than Amp B (Not Aunt Bea from Mayberry, Amp B) - Yet sounded vastly superior to Amp B?"

I'd say life on the pipe is very good for those who throw all measurements out the window proudly proclaiming that they know what they hear. Even the fish who inspire the designers would join me in choosing amp B..

[doug s.]

"But Gerald, what would you do if you heard Amp A that had 1000 times more distortion, a tenth the power bandwidth, much worse damping factor, lower power output and 20 db higher noise level than Amp B (Not Aunt Bea from Mayberry, Amp B) - Yet sounded vastly superior to Amp B?"

I'd say life on the pipe is very good for those who throw all measurements out the window proudly proclaiming that they know what they hear. Even the fish who inspire the designers would join me in choosing amp B..

you would knowingly choose an amp whose sound you didn't like as much, yust cuz it looked better on paper.  wow...     that's all i need to know, to not take into serious consideration any opinions you may have about audio.   

doug s.

[maxwalrath]

Where do you live Gerald?  Maybe some AC member with a nice tube setup would be willing to give you a listen to tube sound in a quality set up, and perhaps A/B power amps?  Even if you've heard some great tube gear, it could be an interesting comparison for everyone involved.

[mcullinan]

The Manley isnt warm or slow, its very fast, neutral, dynamic & detailed. The Parasound I have upstairs (SS) which does the first 14 watts(about that) in Class A is warmer sounding than the Manleys. They (Manleys) seem pretty accurate to me.
M

[Niteshade]

The fish sound good! C'mon- give the fish a chance.

I hear a Tuna Tuna might supersede these.

You sound so depressed.  Lighten up!

On a little more serious note: A tube or solid state amp making a song sound better then it should is not technically right. It might be enjoyable, but it isn't right. It has been my experience that amps which 'choose songs' to improve often make other ones sound worse.

"But Gerald, what would you do if you heard Amp A that had 1000 times more distortion, a tenth the power bandwidth, much worse damping factor, lower power output and 20 db higher noise level than Amp B (Not Aunt Bea from Mayberry, Amp B) - Yet sounded vastly superior to Amp B?"

I'd say life on the pipe is very good for those who throw all measurements out the window proudly proclaiming that they know what they hear. Even the fish who inspire the designers would join me in choosing amp B..