transformer for balance the signal?
- Thread starter ilfungo
- Start date
Help Support GroupDIY Audio Forum:
Nice M6 lams and a lot of 0.30mm wire!
if you could drive it nice, they will work like a charm, recommended really low Z outputs, but maybe you could add some choke inductors in parallel with the output resistors to archive that and still not have trouble with cacpacitive loads, with this you could estimate the price at less than 10 Eur/unit depending your suppliers, if you get 49%Ni they may be better with not so low Z outputs but little more expensive. Output transformers aren't really hard to get it right as inputs are, so with a hand rig to wind them in multifilar in a week winding hard at afternoon you may have all of them working.
You won't get cheaper than that, you may find easier than that dough.
JS
if you could drive it nice, they will work like a charm, recommended really low Z outputs, but maybe you could add some choke inductors in parallel with the output resistors to archive that and still not have trouble with cacpacitive loads, with this you could estimate the price at less than 10 Eur/unit depending your suppliers, if you get 49%Ni they may be better with not so low Z outputs but little more expensive. Output transformers aren't really hard to get it right as inputs are, so with a hand rig to wind them in multifilar in a week winding hard at afternoon you may have all of them working.
You won't get cheaper than that, you may find easier than that dough.
JS
ruffrecords
Well-known member
The cheapest you are likley to get with half decent quality is Edcor. I would not normally recommend them but, as long as you drive them from a fairly low impedance they will work fine.
Cheers
Ian
Cheers
Ian
RuudNL
Well-known member
ruffrecords said:
I noticed that the drive impedance is often ignored.
Driving from a higher impedance will increase distortion.
Sometimes people try to make an output short circuit proof by adding a series resistor to the primary winding, thus increasing the drive impedance.
It this is necessary, it would be better to add that resistor to the secundary winding.
I always try to drive an output transformer from a (almost) zero ohms impedance.
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Samuel Groner
Well-known member
You don't need a transformer to balance an output, a resistor is basically enough. See page 3, top left of this document: www.jensen-transformers.com/an/an003.pdf
Samuel
Samuel
ruffrecords
Well-known member
Samuel Groner said:
To be absolutely honest. I am not at all happy about that article. Trouble is, the name Jensen carries a lot of weight so it is easy for people to assume what they say is right. However, this is not the place to debate that. Sam raises an important point. You say you want a balanced output but you don't say why. It would be better to say waht you are trying to achieve then we could tell you whether a balanced output is necessary or not.
Cheers
Ian
ruffrecords
Well-known member
RuudNL said:
You have to be carful with that if there is a series capacitor involved. The capacitor and the primary inductance of the transformer form a resonant circuit which will have a peak at some (hopefully) sub-sonic frequency. The amplitude and sharpness of that peak depends on the Q of the resonant circuit which in turn depends on the series resistance of the circuit. The series resistance usually has two components; the transformer primary dc resistance and the source impedance of the driving amplifier.
Cheers
Ian
ruffrecords
Well-known member
OK,so what you want to do is create a balanced output from point 24 on the schematic. This looks like a fairly powerful output stage but how pawerful depends on the transistors Q39 and Q40. Do you know their part numbers?
Assumimg they are good enough then you would probably be OK with a 600:600 transformer like the Carnhill VTB2281. Basically you would connect it across R72.
Cheers
Ian
Assumimg they are good enough then you would probably be OK with a 600:600 transformer like the Carnhill VTB2281. Basically you would connect it across R72.
Cheers
Ian
Samuel Groner said:
I knew about it but he asked for a transformer...
He could balance the signal for better CMRR but won't isolate the output if it's necessary. How far is the desk to the converter? Are you having trouble with unbalanced or you just want balanced because is ''pro"?
JS
ruffrecords
Well-known member
ilfungo said:
I checked out the data sheet for the 2N2905 and it looks like a typical low power type. I expect it would have no trouble in a class B stage in driving a 600 ohm load. So, it looks like the 600:600 Carnhill should be OK.
Cheers
Ian
Cheap xfmr will get you cheap performance.ilfungo said:Hi
I'm searching a good and cheapaudio transformer for balance the direct out of my mixer...
Suggestions?
Thanks!!!
cheap because I need 32 of them...
Do as Sam suggests. One resistor and one cap.
ruffrecords
Well-known member
ilfungo said:
I am not sure. There is no information in the Carnhill design guide about this. So far I have not found it necessary to use one and the frequency response measurements I have made, both loaded and unloaded, indicate it is not necessary.
Cheers
Ian
I recall those from the '60s The 2n2905 is the t0-5 higher power dissipation version of the 2n2907 (GP PNP), and the 2n2219 is the similar higher power version of the 2n2222 (NPN).ruffrecords said:
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adding good transformers, can be expensive to deliver very high performance audio.
The Apogee shows differential inputs (separate + and - audio signal inputs). You should be able to maintain good signal integrity by connecting to the Apogee differentially. Connect to the Apogee + and - input leads, through similar value resistors. Connect the - input to a clean local 0V for each send. Use 2 conductor shielded so the local 0V is treated the same as the hot signal.
Looking at the schematic you posted I do not see any build-out resistor. I would be inclined to add something like 300 ohms in series with the audio hot (feeding Apogee + input) and another 300 ohms in series with local audio 0V on that strip (feeding apogee - input).
Note: you might want to experiment where you grab the local audio 0V for best results. Note: if you add transformer outputs you will also need to select where to attach the transformer primary low for best results.
JR
ruffrecords said:
Transformers designed for matched loads will usually give a smiley faced EQ when driven from a much lower source Z. Most modern transformers, particularly 1:1 outputs, will not do this, and in fact tend to require a much lower source Z.
