4EH7 opinions anyone?

[bacon665]

I acquired a box with a couple hundred miniature and subminature tubes the other day for $5
ive found i have 8 of the amperex 4EH7.
i looked up the datasheet there doesnt seem to be much on the frequency response but it says its a remote cut off pentode designed for use as a wideband IF amplifier.

my plan at the moment besides finding more info is to see what people think of these if anyone has used them and maybe to build a small equalizer/preamp using this tube.

a futterman wouldnt be out of the question either but as i dont fully understand the design it might not happen anytime soon

-edit-
also if anyone would be interested in buying some of these i have a spreadsheet available

[Arnulf]

This is a different heater version of EF183, you can look up schematics under that name on Google. I don't think there is any use for it in audio, except in AGC or distortion circuits.

[bacon665]

hmmm... so i guess this things useless unless someone gets the crazy notion to build a Class D amp using tubes to amplify the PWM or use it for a buffer but that creates a couple places for distortion to come out.

[leadbelly]

Yup, useless for hifi. You can use them to make a distortion stage for a guitar amp or a vari-mu compressor, but not hifi.

[bacon665]

IVe also got 8 6fq7's they seem to be listed as general purpose.
i seen a design using these as the grid driver for some 300B's and also as a driver for an EL84.
i have a spreadsheet with about half of the tubes ive sorted from the pile.
http://bacon665.110mb.com/Untitled%201.xml right click and select save as.

theres also two compactrons 12HC7, 8AR?? looks like ll or II maybe H

[Arnulf]

Originally Posted by bacon665

IVe also got 8 6fq7's they seem to be listed as general purpose.
i seen a design using these as the grid driver for some 300B's and also as a driver for an EL84.

Looks like a variation on ECC82 theme. Using it as a driver tube (wired as cathode follower) is a no-brainer, but you mentioned you're interested in building a preamplifier. Have you decided on specific parameters (load impedance, amplification factor, input type) for your preamplifier yet ?

ECC82 is often shunned when it comes to linear amplification (because there are many other alternatives avaliable, which perform better in one way or another), but if all you wanted of your "preamplifier" was a tube buffer, I'd say go for it with this tube - you'll definitely get your $5 worth out of this thing alone

Low mu is an obvious limitation, so you'd be better off finding some other candidate if you wanted to get huge amplification factor.

[Arnulf]

I went over your list quickly and I noticed you got some 6AQ5-As there. This is essentially a 7-pin version of EL84. You could combine a pair of those with two of your 6GH8s (use pentodes as CCS for the triode sections) and get a couple of watts of single-ended goodness per channel out of them.

There is plenty of fun to be had with the stuff you purchased

[Jim McShane]

Originally Posted by Arnulf

Looks like a variation on ECC82 theme. Using it as a driver tube (wired as cathode follower) is a no-brainer, but you mentioned you're interested in building a preamplifier. Have you decided on specific parameters (load impedance, amplification factor, input type) for your preamplifier yet ?

ECC82 is often shunned when it comes to linear amplification (because there are many other alternatives avaliable, which perform better in one way or another), but if all you wanted of your "preamplifier" was a tube buffer, I'd say go for it with this tube - you'll definitely get your $5 worth out of this thing alone

Low mu is an obvious limitation, so you'd be better off finding some other candidate if you wanted to get huge amplification factor.

6FQ7s are essentially 6SN7s in a miniature bottle. They are much more linear than a 12AU7, and IMHO a much better sounding tube.

[bacon665]

so if i find another one in the box then I could build an 8 band stereo equalizer (pump them to a fet mixer) and then use another one for the preamp output?

-note
i havent pulled all the datasheets yet if I find I haven enough pentode/tetrode or maybe even a heptode (doubt it) then i could use tubes for the mixers. if im not mistake you just feed the output of the eq bands into grids and it mixes them on its own right? I've heard tale that mixing with tubes diminishes bass response (eew distortion) clear that up before I get too far into this.

[bacon665]

my main source is my pc so 3.55mm plug and rca jacks will be the input (fibre optic dac is planned later) to the person who asked earlier (got called away from the pc when i was typing that several hours ago)