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daveshel

vtshopdog

Kentley

Bob Latino

Dogstar

9 posters

Bi-amping with two VTA amps.

Dogstar: Posts : 361
Join date : 2014-06-23

Post n°1

Bi-amping with two VTA amps.

by Dogstar Sun Jul 10, 2016 10:55 am

In hindsight I probably should have chosen two M-125's as part of my system for driving speakers but back when I purchased my VTA ST-120 I wasn't considering that as an option.

I already had a pair of speakers that sounded very good I drove with a solid state amp and when I first got my VTA ST-120 found that, though they sounded good, they just weren't efficient enough to be driven adequately.

Since then I have acquired 2 more pairs of speakers that are much more efficient than the first pair I've owned. And both sound very good when driven by the VTA ST-120. One pair is bi-amp ready. The other is not.

Bi-amping intrigues me. If I were to bi-amp my bi-amp ready speakers would there be noticeable difference in sound quality?

And if I were to follow through and acquire a second tube amp would a VTA ST-70 to drive the the high frequency drivers and a VTA ST-120 for the low frequency drivers be good or would two VTA ST-120's be the best way to go?

I understand have two monoblocks driving the left and right channels is way different than using two stereo amps.

Bob Latino: Admin; Posts : 3274
Join date : 2008-11-26
Location : Massachusetts

Post n°2

Re: Bi-amping with two VTA amps.

by Bob Latino Sun Jul 10, 2016 1:05 pm

Dogstar wrote:In hindsight I probably should have chosen two M-125's as part of my system for driving speakers but back when I purchased my VTA ST-120 I wasn't considering that as an option.

I already had a pair of speakers that sounded very good I drove with a solid state amp and when I first got my VTA ST-120 found that, though they sounded good, they just weren't efficient enough to be driven adequately.

Since then I have acquired 2 more pairs of speakers that are much more efficient than the first pair I've owned. And both sound very good when driven by the VTA ST-120. One pair is bi-amp ready. The other is not.

Bi-amping intrigues me. If I were to bi-amp my bi-amp ready speakers would there be noticeable difference in sound quality?

And if I were to follow through and acquire a second tube amp would a VTA ST-70 to drive the the high frequency drivers and a VTA ST-120 for the low frequency drivers be good or would two VTA ST-120's be the best way to go?

I understand have two monoblocks driving the left and right channels is way different than using two stereo amps.

In your situation already having one VTA ST-120, you are better off using TWO ST-120's rather than using one ST-120 and one ST-70. The only exception would be if you have some of external active crossover which would allow you equalize the levels between the two amps. The ST-120 has almost double the power of the ST-70 and the levels would probably not match well using just the speaker's internal crossover.

Below is a forum link to an older post showing two VTA ST-120's driving a pair of Magnepan MG 3.6R's in my downstairs system. This photo was taken before the development of the VTA M-125 monoblocks. This system now uses a pair of M-125 monoblocks in place of the two ST-120's.

Two ST-120's driving magnepan MG 3.6R speakers

Bob

Kentley: Posts : 496
Join date : 2015-03-06
Age : 72
Location : Worcester, MA

Post n°3

Re: Bi-amping with two VTA amps.

by Kentley Sun Jul 10, 2016 4:35 pm

Bi-amping is something that requires a lot of preparation and research. Do you understand your speakers well enough to know if a vertical bi-amp (one stereo amp per side) or a horizontal bi-amp (one stereo amp for lows and another for highs) would yield best results?
The ultimate set-up IMHO would be an active X-over before the power amps so that you are not wasting energy. Don't forget this new product from tubes4hi-fi : http://www.tubes4hifi.com/XO.htm. This would not only allow you to use an ST-70 for the highs, but also give you flexibility of crossover points and levels. Lots of work - a big commitment. May or may not yield tangible results.
If I were you, I'd seek guidance on every forum and from every source regarding your specific speakers and your power requirements (which will be dependent on your musical taste and your listening environment). Good luck and keep us informed.

For some reason, the link to the specific page of the tubes4hi-fi website regarding the new crossover does not operate. It can easily be found with a Google search. Sorry.

vtshopdog: Posts : 155
Join date : 2015-07-11
Location : UT, USA

Post n°4

Re: Bi-amping with two VTA amps.

by vtshopdog Sun Jul 10, 2016 10:56 pm

My limited understanding of biamping and active speakers is that all the cool kids run DSP and usually (gasp!!) SS amps for bass drivers as typical SS watts are cheap and the higher damping factor inherent in SS amp is desirable with bass drivers.

daveshel: Posts : 169
Join date : 2011-11-06
Location : Tucson AZ USA

Post n°5

Re: Bi-amping with two VTA amps.

by daveshel Mon Jul 11, 2016 5:18 pm

I've been wanting to try a biamp system. I rebuilt an ST-35 a couple years ago, and it has the sweetest mids and highs I've ever heard, but I found I was sometimes wanted more bass. Later I got ahold of a pair of MK IIIs with upgraded caps that give me all the bass I want, but aren't quite as velvety in the upper ranges.

What I don't have are biamp ready speakers. The MK IIIs have pots so I can adjust the level if need be, but I would expect to have to use more power for the lows in horizontal setup. What I don't know is weather I'll need an electronic crossover. I imagine some speakers would work better with an active crossover, but I've had some good results in the past with passive horizontal car audio systems, so I'd like to be able to do it passive.

wildiowa: Posts : 237
Join date : 2012-03-19

Post n°6

Re: Bi-amping with two VTA amps.

by wildiowa Tue Jul 12, 2016 10:08 am

We bi-amped for years in live bands and PA applications and most setups have considerably higher watts on the low end and less on the tweeters, but agree in obtaining a front end component that allows selection of the crossover point/points and level adjustment for high and low balance. AND...always, always remember with bi-amping you have no crossover protection on the horns so anything as simple as plugging in a cable to an amp or a short or other transient is going to take out your diaphragm. We used to put a cap in the line to protect the drivers but not sure if that screws up hifi sound...it was OK for live shows and stuff. All I know is I replaced a lot of drivers because somebody pulled a cable or tripped on something and put full load through my horns. It's very cool when set up right, though.

Dogstar: Posts : 361
Join date : 2014-06-23

Post n°7

Re: Bi-amping with two VTA amps.

by Dogstar Wed Jul 13, 2016 5:50 am

Bob,

When you had the two VTA ST-120's biamped to the the Magnaplanars did you control the output to the upper and lower frequency drivers on the speakers with attenuators as you offer as an option for the amps?

As much as an active crossover would look cool on my audio rack I'm kind of reluctant to add another device that alters sound between the source and the speakers.

Just out of curiosity can a VTA preamp be built to have two outputs?

Bob Latino: Admin; Posts : 3274
Join date : 2008-11-26
Location : Massachusetts

Post n°8

Re: Bi-amping with two VTA amps.

by Bob Latino Wed Jul 13, 2016 7:46 am

Dogstar wrote:Bob,

When you had the two VTA ST-120's biamped to the the Magnaplanars did you control the output to the upper and lower frequency drivers on the speakers with attenuators as you offer as an option for the amps?

As much as an active crossover would look cool on my audio rack I'm kind of reluctant to add another device that alters sound between the source and the speakers.

Just out of curiosity can a VTA preamp be built to have two outputs?

When I biamped, no crossovers were used and there was no attenuation to either the woofer or tweeter sections of the MG 3.6R speakers. Vertical biamping was used in which one VTA ST-120 amp was used on each stereo channel.

Bob

deepee99: Posts : 2244
Join date : 2012-05-23
Location : Wallace, Idaho

Post n°9

Re: Bi-amping with two VTA amps.

by deepee99 Wed Jul 13, 2016 12:30 pm

Bob Latino wrote:

Dogstar wrote:Bob,

When you had the two VTA ST-120's biamped to the the Magnaplanars did you control the output to the upper and lower frequency drivers on the speakers with attenuators as you offer as an option for the amps?

As much as an active crossover would look cool on my audio rack I'm kind of reluctant to add another device that alters sound between the source and the speakers.

Just out of curiosity can a VTA preamp be built to have two outputs?

When I biamped, no crossovers were used and there was no attenuation to either the woofer or tweeter sections of the MG 3.6R speakers. Vertical biamping was used in which one VTA ST-120 amp was used on each stereo channel.

Bob

Wow, Bob, two ST-120s strapped even to Maggies must've got your neighbours' attention.
Yes, to answer Dogstar's question, you can put an extra pair of outputs on most any pre-amp, including VTA/Tubes4Hifi's. Ideally, you'd want another pair of coupling capacitors as well. They can be the same or of different values (so long as they match the amps' requirements) than your primary outputs, allowing you to experiment with which caps sound best. The added advantage is you can use a "Y" connector if you can't decide which output sounds better.

Tube Nube: Posts : 707
Join date : 2008-12-06
Age : 61
Location : Calgary, AB

Post n°10

Re: Bi-amping with two VTA amps.

by Tube Nube Sat Jul 16, 2016 10:29 pm

With this horizontal bi amping, or tri amping, as it's being referred to, your cross kver will have to take account of a couple more parameters than so far mentioned.

In addition to the cross over frequency and relative volume level (to the low vs high freq.s), you also ned to consider the slope of the fall off (i.e., rate of attenuation per octave) and you probably also need to consider if phase shift is an issue.

While a cross over component does put something else in the signal path, consider what youre getting in the bargain... The work load is divided up between several amps each specializing in a limited and less taxing bandwidth of frequency range.

It can really sound wonderful.

deepee99: Posts : 2244
Join date : 2012-05-23
Location : Wallace, Idaho

Post n°11

Re: Bi-amping with two VTA amps.

by deepee99 Sun Jul 17, 2016 11:09 am

Tube Nube wrote:With this horizontal bi amping, or tri amping, as it's being referred to, your cross kver will have to take account of a couple more parameters than so far mentioned.

In addition to the cross over frequency and relative volume level (to the low vs high freq.s), you also ned to consider the slope of the fall off (i.e., rate of attenuation per octave) and you probably also need to consider if phase shift is an issue.

While a cross over component does put something else in the signal path, consider what youre getting in the bargain... The work load is divided up between several amps each specializing in a limited and less taxing bandwidth of frequency range.

It can really sound wonderful.

Noob, sounds a bit like rocket science although I think frequency-specific demands on the amps is a good idea. My worry is that all those crossovers would add a lot of extra stuff in the signal path and I'm kind of a minimalist in that department.
Tyler Acoustics and Vandersteen have both made me a believer in a s/s powered subwoofer, which can be rolled in at any frequency from about 200 on down. Really takes the heavy lifting off the tubes. I am going to try a pair of Tyler's H-1s, which due to their efficiency don't require extra power to the subs, unlike the Decades, which use a Class D amp for that rumbling bottom end and he says can be run quite well on an ST-120-type amp.
They take a few months to build so I'll get back to you in September with a book report.

Tube Nube: Posts : 707
Join date : 2008-12-06
Age : 61
Location : Calgary, AB

Post n°12

Re: Bi-amping with two VTA amps.

by Tube Nube Sun Jul 17, 2016 11:35 am

I look forward to hearing your report, Dave.

I agree with you about cross overs, so would be concerned if the speakers internal xo is being replaced with a poorer quality external xo to allow for bi amping. Keep in mind, though, that multi amping isn't adding any new cross overs. It's substituting external, usually activ cross overs to do the same work as the internal cross overs were doing inside the speakers.

deepee99: Posts : 2244
Join date : 2012-05-23
Location : Wallace, Idaho

Post n°13

Re: Bi-amping with two VTA amps.

by deepee99 Sun Jul 17, 2016 12:04 pm

Tube Nube wrote:I look forward to hearing your report, Dave.

I agree with you about cross overs, so would be concerned if the speakers internal xo is being replaced with a poorer quality external xo to allow for bi amping.

Dave, those external xovers on the H-1s are for looks only and can be installed internally, which shaves quite a bit off the price -- and a bit of space and wiring as well. I am actually quite loathe to give up the D-12xs, having lived with them a year. They are simply superb speakers. But then this OCD thing kicks in. The woof drivers in the Decades are Daytons, no flies on them, one passive and one active in each tower. I would say they need at least six months or so to fully loosen up. Expect I'll go through the same with the Danish drivers in the H-1s and the big reason for the switch-over is the Scanspeaks are simply the finest drivers in the world, and (according to Ty) are so efficient they don't need the electronic boost on the bottom end, even for a tube amp. The failure rate of the Chinese-made Class Ds is fairly high. I was googling around on them the other day and if you believe the reviews, it's on the order of 30 percent. Most of the US retailers -- Madisound, for example -- make good on them but it's still a pain in the butt to reinstall, plus you're without music for several weeks while the shipping crosses. So I'm just going to try straight pipes through Tyler's internal xovers and my KT-88-tubed amps, see what happens.
I still like Dynaco's approach to crossovers: a single cap and a resistor. Sure does the trick in my septuagenarian A-35s. Wouldn't part with 'em for the world.

Tube Nube: Posts : 707
Join date : 2008-12-06
Age : 61
Location : Calgary, AB

Post n°14

Re: Bi-amping with two VTA amps.

by Tube Nube Sun Jul 17, 2016 3:49 pm

Heheh.

Reminds me of the cross over in the 3a MM -- a speaker that, at something like $3500, Ultra High Fidelity magazine considered to be among the best in the world at any price....

It's cross over was a single cap between midwoof and tweeter.

deepee99: Posts : 2244
Join date : 2012-05-23
Location : Wallace, Idaho

Post n°15

Re: Bi-amping with two VTA amps.

by deepee99 Sun Jul 17, 2016 5:26 pm

The resistors were only there to trim the tweeter in the Dynacos, the cap necessary to shift the frequency off the woof.

Dogstar: Posts : 361
Join date : 2014-06-23

Post n°16

Re: Bi-amping with two VTA amps.

by Dogstar Sun Jul 17, 2016 11:21 pm

Bob,

Even though vertically bi-amping your Magneplanars the way you did worked out ok I imagine that that may not always be the case for every speaker?

Bob Latino: Admin; Posts : 3274
Join date : 2008-11-26
Location : Massachusetts

Post n°17

Re: Bi-amping with two VTA amps.

by Bob Latino Mon Jul 18, 2016 8:26 am

Dogstar wrote:Bob,

Even though vertically bi-amping your Magneplanars the way you did worked out ok I imagine that that may not always be the case for every speaker?

Vertical biamping > Each amp is used on one stereo channel.
Horizontal biamping > One amp is used on the two woofer sections of your speakers and the other amp is used on the two tweeter sections.

This is just my opinion but > Vertical biamping is probably best when using two TUBE amps. By having one amp on each stereo channel, there is better signal isolation and imaging is usually better this way. Also - the bass notes at higher volume levels really tax the power supply. By vertical biamping you split the bass notes between TWO power supplies rather than have just one amp handle all the bass notes.

Horizontal biamping is usually better if you have one solid state amp and one tube amp. Using the solid state amp on the two woofer sections and the tube amp on the two tweeter sections is a common practice and usually works out well ... I say "usually" because sometimes it is difficult to get a seamless transition between the two amps because of different gain characteristics. If you go the horizontal way, sometimes you may need an outboard crossover with level controls to strike the proper balance between the two amps used.

Bob

arley: Posts : 7
Join date : 2016-03-18

Post n°18

Re: Bi-amping with two VTA amps.

by arley Wed Jul 27, 2016 3:59 pm

FWIW my setup consists of a VTA-70 and a ss NAD 2100 amp,with a dbx crossover set at about 300hz. The VTA 70 drives a pair of horns from the Horn Shoppe. The NAD amp drives a couple of homemade subs. I've been very pleased with the result. My next improvement will probably come in Dec when Santa brings me the VTA tube crossover to replace the dbx.

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Re: Bi-amping with two VTA amps.

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