6AQ7 - why so cheap???

[engels]

This audio triode sells for quite cheap and at some point I've bought a couple. I wonder is there's something wrong with it and if someone tried it.

6AQ7GT

[Tom Bavis]

Supply and demand - I don't know of a single radio that used it, though there must have been SOME demand... it won't plug in in place of any of the more common tubes, so it's only useful for DIY. I COULD rewire a socket to use them instead of 6SQ7 - but WHY, when I have plenty of those as well? 6S8 is another one with little demand (though I have a Zenith radio that uses one).

[18thell]

I think those tubes were used in TV or radios. Today, I have seen many kinds of radio, TV, and equipment tubes are sold on market, they sold them by lots, cheap, very cheap, you can't think of the price, hundred of pieces only sold for 20 bucks. numbers like 6be6, 6ba6, 6aw8, 6an8, 6u8, 6c4, 6fq7, 6bl8, 6dq6, 807, 813, 866a---- many, many, I don't know the usage of these numbers, otherwise I will buy them all!!!.

I have checked from tube data, none of them are for audio! could anyone tell me the use of these numbers. Thanks

[Miles Prower]

Originally posted by 18thell
numbers like 6be6, 6ba6, 6aw8, 6an8, 6u8, 6c4, 6fq7, 6bl8, 6dq6, 807, 813, 866a---- many, many, I don't know the usage of these numbers, otherwise I will buy them all!!!.

I have checked from tube data, none of them are for audio! could anyone tell me the use of these numbers. Thanks

I don't know them all, however, I can tell you about these:

6C4: Half a 12AU7 -- RF amp/driver/oscillator/buffer. May make a decent cathodyne or cathode follower. 7 pin mini format

6FQ7: Electronically very similar to a 6SN7 or a 6CG7. This one is an excellent audio VT. Use for small signal amplification, or as a power triode for headphone amps. 9 pin mini format. Used this one to make grid drivers (cathode followers).

6DQ6: Horizontal deflection VT -- May very well make an excellent audio final. George (Tubelab) has used these for guitar amps.

807: Just about the best audio BPP. Class AB1 THD= 1.8% (before NFB!) Class AB2 THD= 3.0% before NFB. I used this one and it does sound great, but needs a bit of help from local NFB: feedback 10% of Vp from plate to grid driver (O. Schade (807 type developer) recommendation). Like a 6L6, but can take much higher plate voltage due to plate cap connection.

813: RF final -- Used to make lots of audio amps, either running as a pentode or trioded.

866A: High voltage Hg vapour diode. Use a couple to power up that 813 amp. Lots of extra glowey bottle coolness points.

About those 6AQ7s, it looks like the triode is half of a 6SL7 -- one of the better small signal triodes out there.

[engels]

Originally posted by Miles Prower
About those 6AQ7s, it looks like the triode is half of a 6SL7 -- one of the better small signal triodes out there.

Unfortunately, it's not like 6SL7 - the general ratings look close but curves and suggested values for RC amp are pretty different.

[planet10]

Originally posted by Miles Prower
813: RF final -- Used to make lots of audio amps, either running as a pentode or trioded.

Some of the big Altec theatre amps (ie 260A) used the 813 to good effect.

dave