My freshly finished 4P1L preamp.
An externally hosted image should be here but it was not working when we last tested it.
It sounds a little bit "cold"
Third harmonic is almost as second, maybe because of that
But everything else is great
I'm using custom output transformer on double C core and some MEC CGS wirewound resistors
Third harmonic is almost as second, maybe because of that
But everything else is great
I'm using custom output transformer on double C core and some MEC CGS wirewound resistors
You don't use separate transformers for each heater reg?
The customs OPT are impressive, where did you ordered & how much did you paid?
The customs OPT are impressive, where did you ordered & how much did you paid?
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unfortunately I have only one transformer for heater, with two independent secondaries
OPT is made by Tatic Audio, check here:
Untitled Document
OPT is made by Tatic Audio, check here:
Untitled Document
I guess are you using Rod Coleman heater regs, because Rod's don't recommend use only one transformer for two valves.
Yes I'm using Rod's regs.
It will be better to use two transformer, but I had only this one.
It works like this without problems because this is two independent secondaries.
Latter I will add one more 😉
It will be better to use two transformer, but I had only this one.
It works like this without problems because this is two independent secondaries.
Latter I will add one more 😉
I don't know. I had this one at my hand.
Maybe one day I will go with some non inductive resistor.
This preamp is not final version, just test 😉
Maybe one day I will go with some non inductive resistor.
This preamp is not final version, just test 😉
Here are some measurements 😉
THD 0,012% 😉
THD 0,012% 😉
An externally hosted image should be here but it was not working when we last tested it.
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Your potmeter is close to the power supply and can be picking up radiation. What's behind the potmeter?
That was a 64 step relay attenuator, but I replaced it with cheap epay smd attenuator
To much noise from relay attenuator.
Yesterday I tried to reverse wires on primary of OPT and got something strange.
Originally Freq response was falling on both ends with positive impulse response.
10Khz square wave looks very sharp, almost like triangle wave.
With reversed wires I got negative impulse response but with much better (wider)Freq response and very good shape of 10kHZ square wave on my scope.
How to determine what is a proper way to connect wires of primary of unknown transformer?
Originally Freq response was falling on both ends with positive impulse response.
10Khz square wave looks very sharp, almost like triangle wave.
With reversed wires I got negative impulse response but with much better (wider)Freq response and very good shape of 10kHZ square wave on my scope.
How to determine what is a proper way to connect wires of primary of unknown transformer?
Seems a capacitance issue.
You could try a small cap (100- 500pF) over the primary to limit bandwith.
I'd use other OPTs, frankly speaking 😉
You could try a small cap (100- 500pF) over the primary to limit bandwith.
I'd use other OPTs, frankly speaking 😉
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Maybe I misunderstood, post a picture of the new situation.
Generally speaking an output transformer must have high bandwith so the HF pole is far away from 20KHz. This demand is counteracted by the need for inductance which is derived from lots of windings. What your OPT might be suffering from is stray capacitance, interfering with the integrity of the signal. Triangle shaped square waves at the output is no good sign. What's the level?
The right way to connect is with the highest bandwith.
Generally speaking an output transformer must have high bandwith so the HF pole is far away from 20KHz. This demand is counteracted by the need for inductance which is derived from lots of windings. What your OPT might be suffering from is stray capacitance, interfering with the integrity of the signal. Triangle shaped square waves at the output is no good sign. What's the level?
The right way to connect is with the highest bandwith.
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