I'm working on my ECC88 gainclone and there is one thing I wonder about (can't test it right now) and that is the warm up time for a ECC88? How long does it take for the tube to stabilize regarding the working point?
I'm designing a mute circuit for the LM3886. I plan to use a CMOS4541, any better non-exotic reproducable suggestions? I want the delay to be fairly reproduceble and stable over time and temperature with short reset time.
I plan also to have a slow start for the heating. What is a suitable time? 5 seconds?
(This is my very first tube project..... be gentle with me )
I'm designing a mute circuit for the LM3886. I plan to use a CMOS4541, any better non-exotic reproducable suggestions? I want the delay to be fairly reproduceble and stable over time and temperature with short reset time.
I plan also to have a slow start for the heating. What is a suitable time? 5 seconds?
(This is my very first tube project..... be gentle with me )
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there is sort of diode transfer function (for AC) between heater and cathode .
when you elevate heater above (or bellow ) cathode (which is usually at near gnd potential) you're approaching horizontal part of mentioned diode transfer characteristic .
in that area any possible fluctuation in heating voltage cannot be "rectified"/transfered to cathode
place resistive voltage divider between Ub and gnd , flowing ~1mA ; put good cap across lower resistor , route potential from divider junction to heater PSU .
when you elevate heater above (or bellow ) cathode (which is usually at near gnd potential) you're approaching horizontal part of mentioned diode transfer characteristic .
in that area any possible fluctuation in heating voltage cannot be "rectified"/transfered to cathode
place resistive voltage divider between Ub and gnd , flowing ~1mA ; put good cap across lower resistor , route potential from divider junction to heater PSU .
Mr. Wright, do you use this technique also? I have never seen it before.
well , let's say just that you didn't look for it
examples are numerous on net , but explanation is still pretty much buried in old books ( and probably in AW Preamp CookBook)
Pers,
Yes, the heaters have to be circa +30V higher than the actual cathode voltage - which means in something like a SRPP stage then the same tube can't be used for both the lower and upper halves of the circuit, because the two cathodes are so far apart in voltage level, and hence two heater supplies are required - both with their own "heater lift" circuits.
You don't see it in my circuits because I don't show any full circuit with powersupplies etc - except for the PP-1C which does show this "heater lift" - for the output tubes as well as the driver tubes.
Regards, Allen (vacuum State)
Yes, the heaters have to be circa +30V higher than the actual cathode voltage - which means in something like a SRPP stage then the same tube can't be used for both the lower and upper halves of the circuit, because the two cathodes are so far apart in voltage level, and hence two heater supplies are required - both with their own "heater lift" circuits.
You don't see it in my circuits because I don't show any full circuit with powersupplies etc - except for the PP-1C which does show this "heater lift" - for the output tubes as well as the driver tubes.
Regards, Allen (vacuum State)
I never said it lowered distortion - I said IT SOUNDED BETTER.
You must be newer to this subject than I thought if you don't know the difference.
The Lux clone sounded OK but had no magic like the original - after I added the "heater lift" the magic arrived. If you can correlate "magic" to distortion, I'm listening...
Regards, Allen (Vacuum State)
You must be newer to this subject than I thought if you don't know the difference.
The Lux clone sounded OK but had no magic like the original - after I added the "heater lift" the magic arrived. If you can correlate "magic" to distortion, I'm listening...
Regards, Allen (Vacuum State)
well - Anzai preamp from Elektor is , certainly , legend amongst younger tube fans ;
not mentioning usuall overcomplicated additional circuitry ( who sane will use handfull of chips to steer few relais ?) , that project was flawed from severl reasons - not thinking about fact that you can't use two triodes in same envelope for cascode , was just first of these reasons .
(that's OK if you're using them for RF (ECC88 is made exactly for that , per example ) .
anyway - if you make SRPP with two triodes from same envelope , and SRPP with lower triodes from one , and upper triodes from another one tube envelope , you'll hear difference .
even if boys from elektor were clever enough to elevate heating to have same H-K difference for both triodes in one envelope ( from lower cathode in + , from upper cathode in - ) , "squeeling" ( term known in RF world) is what's pretty obvious even in LF domain .
some things aren't measurable easily ; or they are , if you know what to look .
not mentioning usuall overcomplicated additional circuitry ( who sane will use handfull of chips to steer few relais ?) , that project was flawed from severl reasons - not thinking about fact that you can't use two triodes in same envelope for cascode , was just first of these reasons .
(that's OK if you're using them for RF (ECC88 is made exactly for that , per example ) .
anyway - if you make SRPP with two triodes from same envelope , and SRPP with lower triodes from one , and upper triodes from another one tube envelope , you'll hear difference .
even if boys from elektor were clever enough to elevate heating to have same H-K difference for both triodes in one envelope ( from lower cathode in + , from upper cathode in - ) , "squeeling" ( term known in RF world) is what's pretty obvious even in LF domain .
some things aren't measurable easily ; or they are , if you know what to look .
I'm starting to believe that I should consider the lifted heater but if I'll use +- 50 volts could I let both heater be at the same potential, for instance + 30 volts?
Datasheet below says max 200 V between heater and cathode.
6N23P = E88CC = 6DJ8 = 6922 tube. Double triodes - Vacuum radio tubes, capacitors, socket for tubes, nixie, ferrites from military Russia. Datasheets tubes and help. Worldwide shipping
If the ECC88 can manage max 200 V heater-cathode, why can't I use one tube in a cathode follower with tube current source?
Datasheet below says max 200 V between heater and cathode.
6N23P = E88CC = 6DJ8 = 6922 tube. Double triodes - Vacuum radio tubes, capacitors, socket for tubes, nixie, ferrites from military Russia. Datasheets tubes and help. Worldwide shipping
If the ECC88 can manage max 200 V heater-cathode, why can't I use one tube in a cathode follower with tube current source?
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50 V is good - from my experience even better than 30V , but in your case it's wiser to make voltage divider from 50V to gnd - to have 30-35V point ;
in that manner - any residual ripple from 50V rail will be additionally filtered , and you'll have clean potential point
regarding using two triodes in one envelope for any type of cascoding - I told you already - that's good enough for RF usage , but not for LF usage .
reason is ,say, "whistling" ..... interelectrode capacitances have their own life
maybe you can't hear their influence when using one envelope for entire cascode, but it's certain that you'll hear their non-existence when you are not using one envelope for entire cascode
in that manner - any residual ripple from 50V rail will be additionally filtered , and you'll have clean potential point
regarding using two triodes in one envelope for any type of cascoding - I told you already - that's good enough for RF usage , but not for LF usage .
reason is ,say, "whistling" ..... interelectrode capacitances have their own life
maybe you can't hear their influence when using one envelope for entire cascode, but it's certain that you'll hear their non-existence when you are not using one envelope for entire cascode
Hey Per-Anders,
If you plan to use the second half of the ECC88 as a CCS it will work, but it will make a sloppy one with a Ri of 15-20kohm. Go MOSFET instead, a depletion FET like DN2540 will do with only -12V.
Normally you choose a Ia of ca 5mA for this tube but it differs. Probably you need to go lower here like 2-3mA due to the lowish B+. I´d recommend a voltage doubler to get at least 70-80V regulated B+
In a "normal" tube circuit with descent B+ one normally lifts the heaters to 70-80V to guarantee a humfree function.
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My idea was to have two tubes, one tube for each channel but also one tube for both channels and have a passive/active current source. In other words three tube positions on the pcb. The all tube solution was to be aimed at "full tube sound, high budget" and the single tube solution was the low budget solution.
Maybe it's better to have one tune for the cathode follower (both channels) and the second one for constant current source (for both channels). This configuration needs two heater supplies, according to you guys? Both heaters should be decoupled to ground?
Maybe it's better to have one tune for the cathode follower (both channels) and the second one for constant current source (for both channels). This configuration needs two heater supplies, according to you guys? Both heaters should be decoupled to ground?
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