No more leds..i try a lot of led types including infrared leds and to be onest it felt to me that they somehow distort things.I spend some hours experimenting with them and scope testing and i personaly come to the conclusion that the 1n4148 diodes are more suitable for this.I don't know about using one diode how it works against the led because i needed 2 or four in series ,but in series they are much better for me than leds i don't know why
The original schematic had an ecc83 with 100k anode and 1k2 in the cathode at 150v .it also had a 1mohm potentiometer on input.I change the ecc83 with the ecc82 and by the look of the datasheet chart ,i chose the 220k with the 3k9 for less distortion and for to be impedance close to what the schematic needed��*♂️
I tried to ask something else, i.e. what kind of load is after this ECC82 ?
What are you feeding with it ?
What are you feeding with it ?
After this ecc82 is a baxandall crossover and after that is the ecc83 driver for the el84..is a single ended amp
1. What is the maximum signal voltage to the grid of the ECC82?
2. What is the maximum output signal voltage you need from the plate of the ECC82?
3. With only 150V to power a plate load, RL, and the plate voltage, you may have limited swing, and even more importantly, high distortion.
The distortion tends to be higher at low plate current.
To get more current, RL has to be a lower resistance; or the bias voltage has to be lower and that limits the maximum signal at the grid.
Distortion tends to be higher with low resistance RL.
The stage gain tends to be lower with a low plate load, RL.
Those factors 'fight' each other, when you only have 150V B+ (and so the plate voltage has to be even lower)
A CCS in the plate circuit, may help with the above factors.
4. The optimum cathode voltage for a Class A1 stage, is always more voltage than the maximum signal voltage that will be applied to the control grid, g1
2. What is the maximum output signal voltage you need from the plate of the ECC82?
3. With only 150V to power a plate load, RL, and the plate voltage, you may have limited swing, and even more importantly, high distortion.
The distortion tends to be higher at low plate current.
To get more current, RL has to be a lower resistance; or the bias voltage has to be lower and that limits the maximum signal at the grid.
Distortion tends to be higher with low resistance RL.
The stage gain tends to be lower with a low plate load, RL.
Those factors 'fight' each other, when you only have 150V B+ (and so the plate voltage has to be even lower)
A CCS in the plate circuit, may help with the above factors.
4. The optimum cathode voltage for a Class A1 stage, is always more voltage than the maximum signal voltage that will be applied to the control grid, g1
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Do you have a schematic of this crossover ? Obviously it is a frequency dependent load and possibly quite low impedance.
150 V supply voltage is the most limiting factor to make a good driver for the crossover.
A higher Gm tube such as ECC88 or 6N6P is better that 12AU7 at such low supply voltage.
I also was stumbling over that crossover thing. This would mean a HP and a LP filter at least, hence two amplifiers that follow. But he only metiones one?!?
Or is it a Baxandall tone control with adjustible bass and treble response?
Best regards!
Or is it a Baxandall tone control with adjustible bass and treble response?
Best regards!
It is a baxandall crossover with 3 channels .I solved the problem .47k anode with 4 x 1n4148 in series for cathode did the job soo good ...thanks a lot everyone!!!
LED’s will try to equalize the current in a circuit. When looking at the spectrum I see a lower THD. Just try this for yourself and I would like to see measurements / comparisons by others. Both LED’s, diodes and resistors are cheap, so it’s worth trying.
It works for me and my ears (using a 6SN7) 🙂
Regards, Gerrit
It works for me and my ears (using a 6SN7) 🙂
Regards, Gerrit
In my preamp, it has B+ option configuration for 100, 150, 200, 250, and 300, does it affect the sound base on the voltage? I like to get the best out of ECC82 but confuse about the B+ option.
In my circuit at this moment at 150v my ecc82 works outstanding with 100k on anode and 4 x 1n4148.I have tryed earlyer with 47k and it is good ,but to my ears 100 is like the middle choise .It realy depends on what you have after the tube like guys sayd earlyer in this topic.So at 150v with 100k anode and 4 x 1n4148 in series ,you get exactly 2.3 v in cathode and it sounds great to my ears..cheers
Leds happen to have around 2V drop (just by sheer chance), which is a common bias voltage for popular signal triodes so might be a Godsend to some, they do "regulate" voltage drop across them , sort of, and same way as plain diodes do (hey, they *are* diodes after all) , so they became somewhat popular.
They do not regulate current at all, if somebody needs that.
They do not regulate current at all, if somebody needs that.
ECC82 has higher bias for normal operation , lower anode resistor ... maybe 2 or 3 leds depending on color .
The autor seems to like it runing at Ia < 1mA , low voltage , his choice 😉
The autor seems to like it runing at Ia < 1mA , low voltage , his choice 😉
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I still don't understand why leds and not signal diodes.Everyone is talking about leds and no one about signal diodes.I try like 10 types of leds and it is very weird because it distorts like saturation type with them.I made a simulation and also the signal is bad with them��*♂️,realy ..i was about to quit the led idea until i found some 1n4148 and i gave them a try...huge difference in every way .I finaly get a sweet clean sound ..i put them on every preamp stage
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I’ve read that LEDs have less junction noise than diodes. Plus there is the cool factor felt by some, look at my amp it lights up!
Problem is you use *words* with no defined meaning, we need numbers (voltages in principle, current, measured distortion) and images (scoped waveforms) , at least their weak Cousin: simulated waveforms.