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Mixed Bi-Amplified Transistor and Valve system

89.168.89.168

Posted on March 30, 2015 at 07:41:01
FlyGuy
Audiophile

Posts: 85
Location: London
Joined: April 13, 2000



I am a very happy owner of a Musical Fidelity Nuvista Power 300, Chord Electronics Blu/QDB76, Sonus Faber Electa Amator II, Tannoy ST100 Super Tweeter HiFi system all wired with Townshend Audio DCT cables and interconnects.

I just added a Musica Fidelity X-AS100 power amplifier so I have Bi-Amplified my Electa Amator II's, the NuVista on the bass and X-AS100 on the treble.

I have noticed a surprising increase in bass definition, however on some tracks I am getting a more forward high frequency balance, the highs sounding less defined and more present. I have read that valves and transistors a not a good match because of response, damping factor and gain matching.

Would a valve based power amplifier for the treble smooth out the forward balance, which valve amplifiers would you recommend to match the NuVista?

Regards
David

Make It Funky Now!

 

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My experience: You need two identical amps. nt, posted on March 30, 2015 at 08:40:35
oldmkvi
Audiophile

Posts: 10574
Joined: April 12, 2002
/

 

RE: Mixed Bi-Amplified Transistor and Valve system, posted on March 30, 2015 at 08:50:33
airtime
Audiophile

Posts: 11287
Location: Arizona
Joined: February 4, 2003
Just from my experiences, you are just going to make live very difficult by mixing things up that much.

Basically if you have to do this much twisting with your system then it's time to re-evaluate the ENTIRE system. Weaknesses, strengths, what you like, what you don't like. Your problem could be more a cable issue. Or a speaker issue. Try a more simple approach before you tread down a very complicated and expensive road.

Just been there dude!
charles

 

RE: Mixed Bi-Amplified Transistor and Valve system, posted on March 30, 2015 at 08:59:45
Hornlover
Manufacturer

Posts: 2529
Joined: March 8, 2002
I have used mixed amps for bi-amping many times with great success. However, you will get best results using SS for the bass, and tubes for the mids/highs. That way, you take advantages of the best qualities each topology possesses.

 

RE: Mixed Bi-Amplified Transistor and Valve system, posted on March 30, 2015 at 09:50:13
AbeCollins
Audiophile

Posts: 46200
Location: USA
Joined: June 22, 2001
Contributor
  Since:
February 2, 2002
I've had decent but not outstanding results bi-amping and that was with very similarly spec'd amps. The extra equipment, cables, matching levels, and tweaking cross-overs wasn't worth the hassle for me.

In the end I found it much easier to use a single larger amp of higher quality which produced noticeably better results.

In your setup the mismatched amps have wildly different specs for power and input sensitivity so you're starting off with an even bigger disadvantage to work through.

Just my 2-cents worth of course.

P.S. - I have similar feelings about subwoofers. They can help but they're a royal pain to 'get right' in a particular room to integrate seamlessly with the other gear. Bigger amp & bigger speaker is my preferred route vs a subwoofer.




 

RE: Mixed Bi-Amplified Transistor and Valve system, posted on March 30, 2015 at 09:56:16
Victor Khomenko
Manufacturer

Posts: 55296
Joined: April 5, 2000
***In your setup the amps have wildly different specs for power and input sensitivity

People often get confused - you don't need the same input sensitivity, you need the same GAIN. Different power ratings are OK as long as the gain is the same.


 

RE: Mixed Bi-Amplified Transistor and Valve system, posted on March 30, 2015 at 11:17:34
AbeCollins
Audiophile

Posts: 46200
Location: USA
Joined: June 22, 2001
Contributor
  Since:
February 2, 2002
Ah OK, I double checked the input sensitivity vs power output into 8 Ohms on each of his two amps. They do in fact calculate out to approximately the same GAIN of 30dB. 1/3dB difference actually. Not much.

Amp #1:
100-Watts into 8 Ohms =
3.536 Amperes and 28.28 Volts
900mV drive for full output
= 29.95dB GAIN

Amp #2:
300-Watts into 8 Ohms =
6.124 Amperes and 48.99 Volts
1500mV drive for full output
= 30.28dB GAIN



 

RE: Mixed Bi-Amplified Transistor and Valve system, posted on March 30, 2015 at 21:03:28
neolith
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Posts: 4841
Location: Virginia
Joined: February 21, 2002
Contributor
  Since:
December 2, 2004
Sorry to bust your bubble but there is a lot more to biamping than just adding another amp to the mix. First and foremost, you need to have amps with identical gain or a means of equalizing the gains. Next, just picking two different amps because they are available may be disappointing. While you can use tubes on top and SS on bottom, getting everything to integrate can be difficult. It is much easier to use identical amps or at least two amps from the same manufacturer and series.
Finally speaker level biamping is not really all that beneficial. Instead of having a crossover where the treble not being used by the bass is "crossed over" to the tweeter, speaker level biamping is just two parallel filters and what's not used by the woofer goes to ground and visa versa for the tweeter. You really want to do the crossover at the line-level (before the amps) either passive or active. This usually means by-passing the speaker crossovers completely and may require surgery to accomplish. Ideally you will want to design the LLXO to simulate the OEM design. It's not rocket science but does take some knowledge about electronic filters and crossovers.



"Our head is round in order to allow our thoughts to change direction." Francis Picabia

 

the same gain? gee, what a surprise, I think I was taught that a few decades ago., posted on March 31, 2015 at 02:54:50
Timbo in Oz
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Posts: 23221
Location: Canberra - in the ACT - SE Australia
Joined: January 30, 2002
Thanks Victor, for putting Abe straight.


Warmest

Tim Bailey

Skeptical Measurer & Audio Scrounger


 

If I had $1000 for every time..., posted on March 31, 2015 at 06:05:50
Victor Khomenko
Manufacturer

Posts: 55296
Joined: April 5, 2000
...people asked about input sensitivity, I would be able to buy a decent suit.

Last time was yesterday.

This forum is not just for Abe.


 

Gain question, posted on March 31, 2015 at 06:17:56
airtime
Audiophile

Posts: 11287
Location: Arizona
Joined: February 4, 2003
If you have two different amps with different gains would volume changes become a problem as well???

 

That's cuz you're so damned smart and know everything, posted on March 31, 2015 at 10:08:33
AbeCollins
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Posts: 46200
Location: USA
Joined: June 22, 2001
Contributor
  Since:
February 2, 2002
Good on you Timbo!

 

RE: Gain question, posted on March 31, 2015 at 10:09:38
AbeCollins
Audiophile

Posts: 46200
Location: USA
Joined: June 22, 2001
Contributor
  Since:
February 2, 2002
I believe the volume changes will be proportional.

 

Tube amps make gain matching a challenge, posted on March 31, 2015 at 10:22:48
Victor Khomenko
Manufacturer

Posts: 55296
Joined: April 5, 2000
First of all - their gain depends on the load resistance, much more so than that of solid state amps.

Second - many of them have several sets of output taps, each one with its own gain.

Bottom line - ideally you would have some means of adjusting the amp with the highest gain.


 

RE: Mixed Bi-Amplified Transistor and Valve system, posted on April 1, 2015 at 10:09:51
pictureguy
Audiophile

Posts: 22597
Location: SoCal
Joined: October 19, 2008
What are the crossover frequencies?

IF you'd like the amps to redline at about the same level, the power split between amps and the crossover frequency should be factored in as well.

The 50:50 power point is ABOUT 350hz for 'normal' music.
Too much is never enough

 

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