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Can a single ended amp be truly balanced? - Page 3

post #31 of 54
Quote:
Originally Posted by Steve Eddy View Post


I would call that a common misunderstanding rather than a common meaning.

se

 

I'm going to start drinking very heavily to make me forget I read all this.

post #32 of 54
Quote:
Originally Posted by Chris J View Post
 

 

I'm going to start drinking very heavily to make me forget I read all this.

 

:beerchug:

 

se

post #33 of 54

say "I dont like it myself, but can see where others would". Its a very nice amp: even people who dont like it like it! Thats the mark of a winner in my book.

IvOKvh

post #34 of 54
Concluding thoughts:

If it's a Single Ended amp then it's not really Balanced, is it?

Because if it's a Single Ended amp, then it has a SE input and SE output.
Edited by Chris J - 12/4/13 at 1:51pm
post #35 of 54
Quote:
Originally Posted by DavidMahler View Post


If a single ended amp has balanced ins and outs, what does this mean.  Is it really balanced?



 



Will there be a sonic difference between the the balanced out and the single ended out if the amp if the amp is a single ended design, or is it just implemented to accept balanced connections without sonic improvement?

 



Let me guess, is this another "Is the Bryston BHA-1 really balanced?" question.

Yes the Bryston has a differential input stage, so it can accept a balanced, differential signal via a balanced line from a balanced line driver (i.e. a source with balanced outputs) and rejects noise.

The Bryston output stage has two output amplifiers PER CHANNEL, configured in a bridged arrangement, one output is Non-Inverting, the other output is Inverting so, yes, it is a balanced line driver.

Who cares what happens between input and output?
It seems to have a lot of fans, i.e. they think it sounds excellent for the money.
It can accept either SE or balanced inputs.
It can drive headphones set up for SE operation and headphones set up for "balanced" operation.
It's versatile.
post #36 of 54

Balanced Signal flow-

Analog signal is inserted into T1.  Transformer T1 separates Positive and Negative portions of the Analog signal and applies them to the base of NPN transistors Q1 and Q2. The NPNs share a grounded emitter.  The DC power supply is connected negative lead to ground, and the positive DC voltage follows two paths:  1.) Through R1 to the center tap of T1’s secondary coil, applying voltage to the base.  2.) Through the primary coil of T2 and to the collectors of Q1 and Q2.  The secondary winding of T2 is connected to the output speaker.

Theory of operation-

NPN transistors require more voltage/current at the base than the emitter to function (0.7V depletion range for Silicone / 0.3v for Germanium).  VDC is applied to the collector and base for each transmitter in order for them to function. Since the emitters are grounded, the analog signal applied to the bases of Q1 and Q2 is amplified at the collector by changing the collector current output in response to changes in the analog signal applied to the base.  Using transformers at the input and output stages give us impedance matching, and therefore a balanced input and output for the amp.

Note:

One consideration I may have taken is noise being added to the circuit from combining Analog and DC at the primary for T2. Perhaps feeding the DC back to the collectors without using T2 and adding caps to filter out the DC before the signal reaches the T2 primary winding would alleviate that.  Also, I am not sure if Q2 was meant to be a PNP instead of a NPN so that it could pull the collector current instead of pushing it along with Q1.  The push-pull relationship may better develop the output signal.

post #37 of 54

The ground in the schematic is connected to the emitter for the NPNs. This shouldn't cause any interference with the analog signal, since it does not travel through the transistors. The signal is applied to the base. The Collector changes its current response directly in correlation with the received signal. Therefore, the signal does not see ground in this scenario. The only other path to ground is isolated by the DC power supply. For those who are still a bit queasy at the thought of using the emitter ground, using a resistor and cap in parallel prior to connecting the ground will raise the voltage potential some at this point. It might help, but it doesn't seem to be necessary in this application.

post #38 of 54

900x900px-LL-abee0647_Push-Pull_Balanced_Amp.jpeg

Quote:
 The ground in the schematic is connected to the emitter for the NPNs. This shouldn't cause any interference with the analog signal, since it does not travel through the transistors. The signal is applied to the base. The Collector changes its current response directly in correlation with the received signal. Therefore, the signal does not see ground in this scenario. The only other path to ground is isolated by the DC power supply.

:beerchug:

post #39 of 54
Quote:
Originally Posted by ElectEnthusiast View Post

Balanced Signal flow-
Analog signal is inserted into T1.  Transformer T1 separates Positive and Negative portions of the Analog signal and applies them to the base of NPN transistors Q1 and Q2. The NPNs share a grounded emitter.  The DC power supply is connected negative lead to ground, and the positive DC voltage follows two paths:  1.) Through R1 to the center tap of T1’s secondary coil, applying voltage to the base.  2.) Through the primary coil of T2 and to the collectors of Q1 and Q2.  The secondary winding of T2 is connected to the output speaker.
Theory of operation-
NPN transistors require more voltage/current at the base than the emitter to function (0.7V depletion range for Silicone / 0.3v for Germanium).  VDC is applied to the collector and base for each transmitter in order for them to function. Since the emitters are grounded, the analog signal applied to the bases of Q1 and Q2 is amplified at the collector by changing the collector current output in response to changes in the analog signal applied to the base.  Using transformers at the input and output stages give us impedance matching, and therefore a balanced input and output for the amp.
Note:
One consideration I may have taken is noise being added to the circuit from combining Analog and DC at the primary for T2. Perhaps feeding the DC back to the collectors without using T2 and adding caps to filter out the DC before the signal reaches the T2 primary winding would alleviate that.  Also, I am not sure if Q2 was meant to be a PNP instead of a NPN so that it could pull the collector current instead of pushing it along with Q1.  The push-pull relationship may better develop the output signal.

Q1 and Q2 are a differential pair.
T1 is obviously used to convert a single ended signal into a differential signal.
R 1 is used to bias the bases of Q1 and Q2.
This is actually more of a concept schematic, an actual practical schematic would be more complex.
post #40 of 54
Quote:
 Q1 and Q2 are a differential pair.

 

I agree. It's a classic transistor based push-pull design.

 

Quote:

 T1 is obviously used to convert a single ended signal into a differential signal.

 

I disagree. The input schematic symbol is for balanced input. I agree with EE:

 

Quote:

 Transformer T1 separates Positive and Negative portions of the Analog signal and applies them to the base of NPN transistors Q1 and Q2.

Edited by robrob - 12/27/13 at 10:57am
post #41 of 54
Quote:
Originally Posted by robrob View Post
 

 

I disagree. The input schematic symbol is for balanced input. I agree with EE:

 

Perhaps it would be more accurate to say that the primary side of T1 is floating.

Therefore you could apply a Single Ended or Balanced signal to the primary side of T1.

The secondary side of T1 has a centre tap tied to signal common, therefore created a balanced output which is then used to drive the Inverting and Non-Inverting inputs of Q1 and Q2 differential pair.

 

Saying that it separates the positive and negative portions of the analog signal is confusing and misleading.

This implies that the positive half wave and the negative half wave of the sine wave would be separated by T1..

post #42 of 54
Quote:
Originally Posted by Chris J View Post

 

The secondary side of T1 has a centre tap tied to signal common, therefore created a balanced output which is then used to drive the Inverting and Non-Inverting inputs of Q1 and Q2 differential pair.

 

Saying that it separates the positive and negative portions of the analog signal is confusing and misleading.

This implies that the positive half wave and the negative half wave of the sine wave would be separated by T1..

 

Yea, that's a good point. T1 is acting as a phase splitter or inverter (audio amp guys tend to call it a splitter and guitar amp guys call it an inverter).


Edited by robrob - 12/29/13 at 3:32pm
post #43 of 54
Quote:
Originally Posted by ElectEnthusiast View Post

The signal is applied to the base. The Collector changes its current response directly in correlation with the received signal.

Referenced to... what exactly?

se
post #44 of 54
Quote:
Originally Posted by Steve Eddy View Post

Referenced to... what exactly?

se

Base to emitter voltage modulates collector current.
Read some transistor theory.
Re:
The active region.
post #45 of 54
Quote:
Originally Posted by Chris J View Post


Base to emitter voltage modulates collector current.
Read some transistor theory.

 

And what are the emitters tied to?

 

se

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