There has been alot of theory of Fully Balanced and Unbalanced amplifiers. To my surprise many go with Unbalanced amplifiers but very few True Fully Balanced amplifiers are visible. The amplifiers which are true balanced right from the input to the output rather than an opamp converting balanced input to input to the unbalanced amplifier. If anyone has built the fully balanced amplifiers I would like to know fromyour perspective what are the advantages and disadvantages?
As far as I know Fully Balanced amplifiers they
1. Run on lower voltage mostly close to half of the unbalanced amplifier voltage rails.
2. More SOA but at the same time more current being delivered I think if bipolar there will be a beta droop making the effect falling on the previous stages or have double the OPS transistors to compensate the droop.
3. Reduced noise floor compared to Unbalanced
4. Double the output impedance resulting half the damping factor.
Looking at krell`s input on Fully balanced amplifier there is one thing they speak about is cone centering? I didnt understand the point here from a review from Soundstage about krell FPB 300c
Its stated as
>>
On top of these proprietary technologies, Krell also employs several fundamental construction philosophies that have served well over the years. For one thing, the amplifier is fully complementary (balanced). This doubles the amount of circuitry involved, but, of course, Krell maintains that symmetrical circuit paths independently running the positive and negative amplification signals not only reject noise and insure integrity, but also lock the speaker into a push-pull relationship. In other words, balanced operation guarantees speaker control.
>>
In the following link
SoundStage! Equipment Review - Krell FPB-300c Stereo Amplifier (12/2001)
I didnt understand what is that Fully balanced amplifier is soo unique in locking the speaker into a push pull relationship. Balanced operation guarantees speaker control?
How does that happen? Even in Un balanced you have that 0 reference right? or lack of zero voltage reference in the Output makes it to rest at 0 stage? I dont think so even when we have few milli volts of DC offset it makes it more or less in almost center of the cone reference resting place when signal is not provided.
What are the other advantages of using Fully Balanced amplifiers?
As far as I know Fully Balanced amplifiers they
1. Run on lower voltage mostly close to half of the unbalanced amplifier voltage rails.
2. More SOA but at the same time more current being delivered I think if bipolar there will be a beta droop making the effect falling on the previous stages or have double the OPS transistors to compensate the droop.
3. Reduced noise floor compared to Unbalanced
4. Double the output impedance resulting half the damping factor.
Looking at krell`s input on Fully balanced amplifier there is one thing they speak about is cone centering? I didnt understand the point here from a review from Soundstage about krell FPB 300c
Its stated as
>>
On top of these proprietary technologies, Krell also employs several fundamental construction philosophies that have served well over the years. For one thing, the amplifier is fully complementary (balanced). This doubles the amount of circuitry involved, but, of course, Krell maintains that symmetrical circuit paths independently running the positive and negative amplification signals not only reject noise and insure integrity, but also lock the speaker into a push-pull relationship. In other words, balanced operation guarantees speaker control.
>>
In the following link
SoundStage! Equipment Review - Krell FPB-300c Stereo Amplifier (12/2001)
I didnt understand what is that Fully balanced amplifier is soo unique in locking the speaker into a push pull relationship. Balanced operation guarantees speaker control?
How does that happen? Even in Un balanced you have that 0 reference right? or lack of zero voltage reference in the Output makes it to rest at 0 stage? I dont think so even when we have few milli volts of DC offset it makes it more or less in almost center of the cone reference resting place when signal is not provided.
What are the other advantages of using Fully Balanced amplifiers?
Neurochrome Modulus-686: 240W(8Ω); 360W(4Ω) @ 0.00025% THD+N is one you can build (well solder in the through hole parts). There is a long thread on this in the vendors bazaar where you can read.
I'm on the fence over if it is worth the increased heat and reduced peak current capability. Certainly handy if (like me) you happen to have some big but lowish voltage transformers hanging around.
Push pull on speakes? Kirchoff might want to have words. Current flow goes both ways in any amplifier. The voice coil doesn't care which terminal is source and which is sink.
I'm on the fence over if it is worth the increased heat and reduced peak current capability. Certainly handy if (like me) you happen to have some big but lowish voltage transformers hanging around.
Push pull on speakes? Kirchoff might want to have words. Current flow goes both ways in any amplifier. The voice coil doesn't care which terminal is source and which is sink.
A properly built balanced amplifier should have 20dB less even harmonics than the equivalent balanced one,
due to cancellation between positive and negative phase.
A balanced signal with good CMRR should also be less susceptible to noise pickup in cables between equipment.
The other arguments are secondary, IMHO.
Patrick
due to cancellation between positive and negative phase.
A balanced signal with good CMRR should also be less susceptible to noise pickup in cables between equipment.
The other arguments are secondary, IMHO.
Patrick
Oh my gosh .... only uneven harmonics left .... it shure must sound like crap *looolll*
jauu
Calvin
jauu
Calvin
Yes, many, myself including, prefer an amplifier that has e.g. -110dB H2 and -100dB H3, to one with -85dB H2 and -100 H3.
Apparently those customers for Curl, Pass, Hansen also. 😉
But of course not those who like -60dB H2, to cover up all the other distortions and sweeten the sound.
Patrick
Apparently those customers for Curl, Pass, Hansen also. 😉
But of course not those who like -60dB H2, to cover up all the other distortions and sweeten the sound.
Patrick
A bold statement indeed, it does keep the center of the voice coil at 0. Is this a benefit? As for changing the V/I relationships, I'm not so sure.
So whats your choice Pat? Fully Balanced or Unbalanced? I think you have built some full balanced pass F5? since you have heard both what are your listening impressions on both if you can elaborate that will be really helpful.
XEN stands for class A fuly differential push-pull.
Except for kitchen radios, everything else is fully differential.
The only exception is our DAO headphone amplifier.
Even this has (can accept) differential inputs.
Patrick
Except for kitchen radios, everything else is fully differential.
The only exception is our DAO headphone amplifier.
Even this has (can accept) differential inputs.
Patrick
but can you please describe the sound difference what you have observed in Fully balanced and unbalanced that will really help.
Fully balanced is not two BTL connedted amps.
You can see both versions in the F5 Turbo article.
http://www.firstwatt.com/pdf/art_f5_turbo.pdf
No, I don't have a habbit of describing sounds.
I only know what I like, personally.
Maybe you should ask Nelson.
Patrick
You can see both versions in the F5 Turbo article.
http://www.firstwatt.com/pdf/art_f5_turbo.pdf
No, I don't have a habbit of describing sounds.
I only know what I like, personally.
Maybe you should ask Nelson.
Patrick
I have no technical references to cite, and sound differences between the two are probably best left to the ear of the beholder....
but, one is clearly (technically) better than the other, and when a hobby like this often morphs towards the extreme of anything, it really just becomes a question of what do you want? Reassurance that it's worth $$? That it's the best? That it will physically affect you better? That is your decision and question. Personally, I started my foray with balanced sources and look for every opportunity to implement that further (within my ability), everything else represents a compromise of sorts.
but, one is clearly (technically) better than the other, and when a hobby like this often morphs towards the extreme of anything, it really just becomes a question of what do you want? Reassurance that it's worth $$? That it's the best? That it will physically affect you better? That is your decision and question. Personally, I started my foray with balanced sources and look for every opportunity to implement that further (within my ability), everything else represents a compromise of sorts.
I have been in audio since 1980 and have never found a need for balanced inputs or outputs.
Any amps I have designed have always been noise free and if not have been fixed to be noise free.
Poor design is more the reason for noise.
Good decoupling of the front end of an amp is vital for hum free operation.
Any amps I have designed have always been noise free and if not have been fixed to be noise free.
Poor design is more the reason for noise.
Good decoupling of the front end of an amp is vital for hum free operation.
Yes, it also makes it simpler to connect up a multitude of gear without running into hum problems
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