here is one for the rare tube heads...6gy8, 6ez8
I came across them in a search for compactrons... They are both 9-pin triple triodes, but the 6gy8 pin 4 shares a connection among the heater, anode of one triode element and the cathode of another, while pin 4 on the 6ez8 shares a connection among two cathodes and the heater?!
I assume these are for some RF tuner usage, but how one go about using something like that?
I came across them in a search for compactrons... They are both 9-pin triple triodes, but the 6gy8 pin 4 shares a connection among the heater, anode of one triode element and the cathode of another, while pin 4 on the 6ez8 shares a connection among two cathodes and the heater?!
I assume these are for some RF tuner usage, but how one go about using something like that?
The 6GY8 clearly expects two of the triodes to be used as a cascode, and probably the other triode as the local oscillator. Perhaps the 6EZ8 expects to use a cathode coupled amplifier plus local oscillator?
EC8010 said:
How is that? I see how tying the grid/heater connection together would work for the top element of a cascode since it would bias the grid as well as elevate the DC reference for the heaters, but I can't visualize why the cathode of another section would be tied there...
IIRC, the 6EZ8 was marketed for ultra-cheap radio use. The idea was to combine mixer, oscillator, and if amp all in one package.
Regarding the cascode, the cathode of the upper tube would be tied to the plate of the lower. The heater would be referenced to that point, not to the grid.
Regarding the cascode, the cathode of the upper tube would be tied to the plate of the lower. The heater would be referenced to that point, not to the grid.
aletheian said:
Here's one I made that works great with guitar and bass:
http://geek.scorpiorising.ca/contrib/Geek/GuitarPre.png
I'm not extremely well versed in the radio tube department. my knowledge is mostly about guitar amplifiers. I have a Fender Champ 5F1 that I build myself, and I accidentally stumbled upon a box of 6EZ8s. when I looked them up I thought it would be great to turn my Champ's preamp from a 2 gain stage amp to a 3 gain stage amp. Only problem is I have no idea how the bias is supposed to work on the two sections where the cathode is connected to the heater. I've only used dual triodes before, and I usually use cathode bias resistors between 820 and 3.3K ohms depending on if I want preamp distortion or not. Could someone please shed some light on how to replace my 12AX7 with an 6EZ8? I mean, I gave it a try, but bad things happened. I hooked the triodes together like in a normal guitar amplifier preamp circuit, and gave section 3 a bias resistor of 1.5K ohms. this is the last triode in the preamp and the cathode is connected to a negative feedback loop from the OT. I know the triodes work, as I can hear them working. the only problem is there is a nasty *** hum i assume is coming from the heater supply that just gets louder and louder and louder. I'm sure this is just a case of I didn't know how to wire this tube up properly, but I would like someone to tell me exactly what's going wrong here. Much appreciated.
Now that I think about it, the 5F1 heater tap from the transformer is wired in that weird Fender way (one side of the heater tap coil grounded with the other running to half of the heater pins) could this be my problem? (is a center tapped; or simply just an ungrounded, heater supply necessary for the 6EZ8?)
Which resistor value is for distortion and which is for clean? Also at what HT voltage and what anode resistor?
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