Balanced Audio inputs for HB
I am considering building a HT Badger, but the pre-amp I'm considering using has balanced XLR line outputs (Marantz AV8802).
Would the input stage as currently designed work with balanced audio input if pin 1 of the XLR input is grounded to the chassis star ground, with XLR 2 and XLR 3 pins applied across R1?
One note about Ostripper's schematic - it looks like R1 is shorted out of the circuit. There is no clear Input+ / Input- on the schematic, only an implied one across R1. I would consider the 'input' on the wire only as a net name.
I am considering building a HT Badger, but the pre-amp I'm considering using has balanced XLR line outputs (Marantz AV8802).
Would the input stage as currently designed work with balanced audio input if pin 1 of the XLR input is grounded to the chassis star ground, with XLR 2 and XLR 3 pins applied across R1?
One note about Ostripper's schematic - it looks like R1 is shorted out of the circuit. There is no clear Input+ / Input- on the schematic, only an implied one across R1. I would consider the 'input' on the wire only as a net name.
Pin 1 of the XLR goes to Chassis.
Pin 2 of the XLR goes to +IN of the amp.
Pin 3 of the XLR cannot go to Signal Ground of the amp.
Check how your balanced Source works.
Some will automatically change the Source to suit the loading conditions.
Others will require you to change. You may have to load Pin3 with a resistor to signal ground, or you may be allowed to simply ground Pin3.
Pin 2 of the XLR goes to +IN of the amp.
Pin 3 of the XLR cannot go to Signal Ground of the amp.
Check how your balanced Source works.
Some will automatically change the Source to suit the loading conditions.
Others will require you to change. You may have to load Pin3 with a resistor to signal ground, or you may be allowed to simply ground Pin3.
You can adopt a bal to unbal adaptor at the input of the unbalanced amplifier.
Cordell shows a very simple circuit to do this. It's in his book and is discussed in one of his interviews on this Forum, before the book was published.
Cordell shows a very simple circuit to do this. It's in his book and is discussed in one of his interviews on this Forum, before the book was published.
How balanced should the output stage be. Q18 and 17 at 38-40mv. Q16 at 22mv. already changed Q16 because it was hogging. Offset at <1mv, bias at 60mv TP1 to TP2. Been powered up 5 hours and stable.
balanced means balanced impedance connection.
The impedances are balanced.
The Receiver measures and processes the voltage DIFFERENCE between the signals on Pins 2 & 3.
The impedances are balanced.
The Receiver measures and processes the voltage DIFFERENCE between the signals on Pins 2 & 3.
That could just be an emitter resistor that is out of tolerance. If it bothers you, you could try replacing that resistor.
OK I know it isn't the resistor though because that xsistr was replaced because it was running very high and after change it is now the lowest. i'm wondering if that kind of imbalance(current) in output stage will cause problems down the road
I'm interested in knowing how hot some of you have been biasing the outputs. I mistakenly biased mine mjl21193/4 at 180-200 ma each (82mv TP1-TP2). It ran stable for hours that way in a 90 deg shop. I was playing music through it to a EPOS esl 3 and it was sounding very good. I put the other board/channel in and had it biased to 40mv(TP1-2) it was not as sweet sounding and noticebly different. Can those outputs handle that kind of bias as long as the heatsink is adaquate?
Very interesting Freecrowder. I was contemplating doubling mine to 80mV TP1-TP2 just because I barely got a rise out of my heat sinks (7 degrees) when set to 40mV and yes, I am using the same MJL21193/4 outputs...
Fun to think it could sound noticably better 🙂))
Fun to think it could sound noticably better 🙂))
Great someone I can directly compare too. Did you use matched outputs? Meaning the 193 were all matched and also the 194? Did you up the bias on the VAS stage? Have you measured output? Mine is putting out 230watt single channel into 5.5ohm.
Happy so far.
Happy so far.
bjt's biased hard are known to have lower distortions, but then their life is also short, perhaps forced air cooling or water cooling can help keep things cool can help...try biasing them at 125mA and see how it sounds...
ClassAB has an "optimum bias" current.
The output when lower than twice the "optimum bias" current is always in ClassA. It is very clean because there is NO crossover distortion.
The output when higher than twice "optimum bias" current has the least crossover distortion for that ClassAB amplifier.
If the output stage is biased to less than optimum then the output at all levels has more crossover distortion. At typical domestic listening levels the crossover distortion will be gross, because at ½W to 2W the % crossover distortion content is VERY HIGH !
If the output stage is biased to more than optimum, then the output at low levels stays in ClassA. The output at higher levels will have more crossover distortion than "optimum bias". Listening at normal domestic levels may result in most of the output being ClassA.
Only the transient peaks may stray into higher distortion ClassAB.
This could be quite pleasant to listen to. Especially with higher efficiency speakers and in quiet surrounds.
The next stage above that last (higher than optimum bias) is full ClassA, but the heatsinking requirement usually results in much lower maximum output. This too can sound very good and yet again this works very well with higher efficiency speakers.
The decision on whether to bias to "optimum", or higher than optimum, depends very much on the your own listening habits and your typical output currents delivered to the speakers.
The output when lower than twice the "optimum bias" current is always in ClassA. It is very clean because there is NO crossover distortion.
The output when higher than twice "optimum bias" current has the least crossover distortion for that ClassAB amplifier.
If the output stage is biased to less than optimum then the output at all levels has more crossover distortion. At typical domestic listening levels the crossover distortion will be gross, because at ½W to 2W the % crossover distortion content is VERY HIGH !
If the output stage is biased to more than optimum, then the output at low levels stays in ClassA. The output at higher levels will have more crossover distortion than "optimum bias". Listening at normal domestic levels may result in most of the output being ClassA.
Only the transient peaks may stray into higher distortion ClassAB.
This could be quite pleasant to listen to. Especially with higher efficiency speakers and in quiet surrounds.
The next stage above that last (higher than optimum bias) is full ClassA, but the heatsinking requirement usually results in much lower maximum output. This too can sound very good and yet again this works very well with higher efficiency speakers.
The decision on whether to bias to "optimum", or higher than optimum, depends very much on the your own listening habits and your typical output currents delivered to the speakers.
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This statement is misleading.
It omits the limited conditions for which it holds true.
In general the limiting conditions are not met and the opposite is the case.
BJTs biased hard are known to have higher crossover distortions, than an optimally biased ClassAB, when the output current exceeds twice the bias current.
AndrewT, in the case of the honeybadger, what is the optimum bias?, give us a number we can work on...
my experience tell me this is not true....i have had amps that had heatsinks very painfully hot to touch and yet sounding so good...
maybe your experience is different, no?
my experience tell me this is not true....i have had amps that had heatsinks very painfully hot to touch and yet sounding so good...
maybe your experience is different, no?
Freecrowder, I "diode matched" my 193s and 194 outputs. I have not altered the VAS.
I have not actually run the bias up...yet. I have huge heat sinks. I am waiting to hear from others any cautions I should hear before I risk loosing my Honey Badger; it is a pretty sweet amp!
I have not actually run the bias up...yet. I have huge heat sinks. I am waiting to hear from others any cautions I should hear before I risk loosing my Honey Badger; it is a pretty sweet amp!
if you read up and follow Ostrippers' build recomendations you should have no problem,
i did and my badger worked the first time, you can too...😉
i did and my badger worked the first time, you can too...😉
Ok after testing boards seperately for a couple of days just now testing with both running. Problem, one board has higher gain than the other probably 6-8 dB. Hopefully just a resistor misplaced. I did not match any transistors could that be the problem. Offsets look good and biases ok.
I built to spec, no issues at all 🙂.
I'm just wondering if more bias, keeping it in class A longer, will make it even better ?
I'm just wondering if more bias, keeping it in class A longer, will make it even better ?
Well the amp I have been listening to for many years now is a Class A design. I think it sounds very good. So the longer it is in A as long as the heatsinking is up to the task I think it would sound better.