Toroids are plenty.
Ringkern-Transformator SE-RKT offen - hifituning24.de
Some say that they couple more dirt into the circuit though.
Ringkern-Transformator SE-RKT offen - hifituning24.de
Some say that they couple more dirt into the circuit though.
Can it be possible to avoid the zeners as Vref ? Maybe using a resistor over a ccs ?
That way the whole thing could be tuned by carefully choosing the resistor bypass cap 🙂
And I sometimes have noise issues with zeners (even 27v ones) and I guess 24v ones are the same. Super low noise zeners exist but.....
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My circuits always use toroid’s, and I always use a mu-metal box to separate the transformer from the rest of the box. I do like the dynamic behavior of the toroid although this is not the most important for small signal circuits.
Balanced RIAA preamp | Flickr - Photo Sharing!
The inter-winding capacitance is higher certainly. However, good filtering on the mains side and a solid inter winding screen go a long way to making the differences quite minimal.
R-cores are a great buzz word for the high end audio industry.
EI are a good compromise if using 2 boxes anyway. R-Core are better than the rest in all respects in my experience.
A string of LED's is also possible. Use a selected resistor (trimmer) for R7. The more LED's the better; I would say a minimum of five.
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Now were talking power-supply,,, the total consumption at 24V is app 100 mA each rail, so in total app 5W each channel
If the circuit consumes 100mA then I need to recalculate the power supply for a current source of 150mA. Can you tell me what the maximum consumption of one mono channel will be (I guess we go for full dual mono).
That is one mono-channel... 105 mA is drawn from each voltage source...
So we need 10 green lED's, a zener is app 20uV noise and an LED can be as low as 3-4uV, question is.. does that sum up or does is stay low due to the random spectra of the noise..??
So we need 10 green lED's, a zener is app 20uV noise and an LED can be as low as 3-4uV, question is.. does that sum up or does is stay low due to the random spectra of the noise..??
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I can see I remember a bit Wrong on the values for noise, Here there is a nice piece of work regarding noise in LED and Zeners, Made by Swedish DIY-Audio forum member Christer (Majstang, Krebs og surstrømming)
Non linearly though, because uncorrelated. You got to sum their squares and then sqrt that number.
Given that the zener's may be a bit inconsistent, you may still like to select LED's for the reference. Using a string of 12 Yellow LED's would (Vrms added) generate about 1.3uV down to 1uV (being very optimistic) of noise (according to the list). I would say, we make place for the string of LED's and the builder can always stuff an zener diode in their place.
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Frans, you are very pragmatic and i like that. Yes, we should make place for some Leds.
I personally have no problem with toroids either. I agree that the transformer should be in another compartment or in a separate box. This is the only way to avoid hum in a low lever circuit like that. Your preamp looks great inside. I like the copper pipes.
MiiB, that is what i was expecting. Gain goes up and so does distortion. -96dB is of cause excellent and the distortion distribution looks great. The only think i would like to see is when you go back from 50 Ohm degeneration to 20 Ohm and adjust the RIAA again for a gain of 61dB. If we get out the same distortion then the 20 Ohm degeneration would give somewhat less noise. I think after that experiment, we fix the parameters.
I personally have no problem with toroids either. I agree that the transformer should be in another compartment or in a separate box. This is the only way to avoid hum in a low lever circuit like that. Your preamp looks great inside. I like the copper pipes.
MiiB, that is what i was expecting. Gain goes up and so does distortion. -96dB is of cause excellent and the distortion distribution looks great. The only think i would like to see is when you go back from 50 Ohm degeneration to 20 Ohm and adjust the RIAA again for a gain of 61dB. If we get out the same distortion then the 20 Ohm degeneration would give somewhat less noise. I think after that experiment, we fix the parameters.
Thanks 🙂 and yes I think so 🙂
Here a version with the filter, snubber resistors and LED's. The current has now been set to 150mA ( 105mA for the amplifier, 45mA to warm the planet).
