few questions

[Weston]

Hey, I am new here and new to tubes, and I have a couple questions. I read the boozhound hifi article, and would like to build a single ended amp. I dont want to spend too much money on my first amp, so I went digging and found an old tube car radio and an old tube tv. Iv'e been researching the tubes i found, and the following seem like they might be of interrest.

7Y4 rectifier>>>cant seem find a spec sheet for
7c5 >>> which is apparantly the same as a 6v6
7b6 >>>which appears to be the driver for the 7c5 in the car radio
6AS5
6au6
6au8
6U8
the car radio also has an output transformer

Anyway, i was looking for a design that might incorporate as much of what i already have as possible. I was thinking i would like to use the 7c5 as for the output. will any of the others work as a driver?

[wakibaki]

It seems 7b6=DH81, is a double-diode triode of which you could probably use all or part, if you could find a datasheet, which I couldn't.

I think that given the effort involved in designing and building an amp, it might be better to go with new tubes or NOS which are well documented and for which spares are available. There are many excellent tubes available at very reasonable prices and you will avoid the disappointment of a project which does not work because of an untested valve.

You may find this less expensive overall in the long run.

w

[Eli Duttman]

A good 7Y4 data sheet is here. The Locktal based 7Y4 is similar electrically to the 7 pin mini based 6X4 and Octal based 6X5.

Learn to use TDSL, to obtain info. about tubes.

The Locktal based 7C5 is most definitely a member of the 6V6 family. However, the 7C5's screen grid is somewhat fragile. Think of it as the electrical equivalent of the 6AQ5.

I'm guessing you are planning on a guitar amp, as 2 channels are needed for HIFI service. Unless it's damaged, reuse the radio's speaker along with the O/P trafo. The 6AU6 pentode would allow you to build a Fender "Champ" style project using the tubes already in your possession. Leo Fender used a 6SJ7 and a 6V6 in the original "Champ".

[Eli Duttman]

It seems 7b6=DH81, is a double-diode triode of which you could probably use all or part, if you could find a datasheet, which I couldn't.

A French Sylvania 7B6 data sheet is here. The type appears to be reasonably close, electrically, to the 7 pin mini 6AV6.

[mashaffer]

In English

mike

[Weston]

Thanks! you guys are awesome. I like the fender champ idea. when you say the 7c5 screen is fragile, does that mean it will sound bad, or just fry? Im guessing that it wont be as simple as just swapping the 6au6 for the 6sj7. It would help to know what the power supplied dc voltage is in the fender diagram. also i dont have the original speaker, so im wondering if there is a way to determine what ohm speaker the opt is supposed to run.

Thanks for the help.

[Eli Duttman]

Originally posted by Weston
Thanks! you guys are awesome. I like the fender champ idea. when you say the 7c5 screen is fragile, does that mean it will sound bad, or just fry? Im guessing that it wont be as simple as just swapping the 6au6 for the 6sj7. It would help to know what the power supplied dc voltage is in the fender diagram. also i dont have the original speaker, so im wondering if there is a way to determine what ohm speaker the opt is supposed to run.

Thanks for the help.

Dude,

Use TDSL to check out the electrical parameters of various tube types.

The screen grid in 7C5s is not rated for as high a voltage as the screen grid in 6V6s. "Frying", not sonics, is the concern.

The operating point a 6AU6 works at will be different than a 6SJ7 works at. Compare the plate characteristic graphs to each other.

The common impedance for radio speakers is/was 3.2 Ohms. You should be OK with a 4 Ohm speaker.

A pictorial diagram of the original "Champ", showing voltages, is here.

BTW, under no circumstances should you copy Fender's circuitry on the AC mains side of the power trafo. Install a proper 3 wire power cord and ensure the safety ground wire is WELL secured to the chassis.

[wakibaki]

A good rule of thumb is that any component you can't find a reference to by part number on google is obscure.

w