here is one for the rare tube heads...6GY8, 6EZ8

aletheian · 27th September 2006, 07:59 AM

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?

EC8010 · 27th September 2006, 02:02 PM

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?

aletheian · 27th September 2006, 06:13 PM

Quote:

Originally posted by EC8010
The 6GY8 clearly expects two of the triodes to be used as a cascode

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...

SY · 27th September 2006, 07:18 PM

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.

Geek · 27th September 2006, 09:55 PM

They make great OD tubes in da shtompbox

(try a 6AC10)

aletheian · 28th September 2006, 04:21 AM

Quote:

Originally posted by SY
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.

Ah yes... I see it now. Thanx again.

aletheian · 28th September 2006, 04:22 AM

Quote:

Originally posted by Geek
They make great OD tubes in da shtompbox

(try a 6AC10)

Not a bad idea... ... ...

...

I have some of those around.

Geek · 28th September 2006, 05:06 AM

Quote:

Originally posted by aletheian

Not a bad idea... ... ...

...

I have some of those around.

Here's one I made that works great with guitar and bass:
http://geek.scorpiorising.ca/contrib/Geek/GuitarPre.png

searon386 · 25th July 2011, 12:27 AM

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.

mashaffer · 25th July 2011, 01:09 AM

Hmmm... 6GY8... cascode... Is there a potential spud phono preamp there?

27th September 2006, 07:59 AM	#1
aletheian diyAudio Member Join Date: Apr 2004 Location: Philly	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? __________________ Heghlu'meH QaQ jajvam!

27th September 2006, 02:02 PM	#2
EC8010 diyAudio Moderator Emeritus Join Date: Jan 2003 Location: Near London. UK	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? __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

27th September 2006, 07:18 PM	#4
SY diyAudio Moderator Join Date: Oct 2002 Location: Chicagoland Blog Entries: 1	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. __________________ If there's a sucker born every minute, where do the rest of them come from?

25th July 2011, 01:09 AM	#10
mashaffer diyAudio Member Join Date: Jun 2004 Location: Indiana	Hmmm... 6GY8... cascode... Is there a potential spud phono preamp there? __________________ If We The People refuse to hear the truth we will be ruled by liars.

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27th September 2006, 09:55 PM	#5
Geek diyAudio Member Join Date: Sep 2004	They make great OD tubes in da shtompbox (try a 6AC10)

25th July 2011, 12:27 AM	#9
searon386 diyAudio Member Join Date: Jul 2011 Location: Houston, TX	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.

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