5670 Thoughts?

[TonyTecson]

NOS 6386's are worth their weight in gold! The 6386 is a variable Mu version of the 5670. It was designed for AGC control in RF or IF amplifiers. It was used as the control element in virtually audio compressor made during the vacuum tube era. The Fairchild 660 and 670 are still being used, and the tubes are getting scarce.

yes, i have a pretty good idea of those compressors and will do them in time....😉

 

[Tubelab_com]

JJ is offering a re-issue of the 6386. No idea how good or bad it is though.

I haven't tried it because it is priced at over $100 each!

I have a fair collection of used 6386's. I started down the road of mapping out the distortion VS level and gain characteristics of the 6386 in the Fairchild push pull VGA circuit. I was looking for another way to get similar results with a $5 tube. This is on hold until I rebuild my lab.

There are a few TV tuner tubes that others are using in Fairchild knock offs, but the distortion characteristics don't match.

The 6386 puts out a fairly high amount of second harmonic distortion. This varies with applied signal level and gain control setting. Most of the 2H is cancelled in the output transformer IF the tube sections are well matched.

 

[Palustris]

I played around with several tube types in my "El Cheapo" circuit installed in a Scott 299B. I tried all the usual tubes like the 12AT7 and 6072, but found the 12AV7 my favorite until I tried the 5670. This is a very good sounding amp and the 5670 is well worth trying. I bought about a dozen of them and was easily able to find a couple with matched sections.

 

[Paul Joppa]

I use them as a driver for 300B outputs (Bottlehead Paramount amp). It's a long life, high reliability design, so the cathodes are high purity and quiet. I've found the parameters to be unusually stable. Very linear, even better than the 5965 (a previous favorite for linearity and clean cathodes). Tiny little thing, you barely notice it next to the 300B!

 

[Jaap]

Here is a 5670 driving a 832

 

[TonyTecson]

I haven't tried it because it is priced at over $100 each!

i got mine for just 250 pesos each, about U$5 each.....i told the seller the going prices after getting those tubes but he just shrugged his shoulders, he sold them all to me...😀

 

[Tubelab_com]

The unique pinout makes symmetrical PCB layouts easy too.

 

[krelac]

hi, didi enyone trien an SE amp using 5670 in the way I seen 12au7 amplifiers (bedroom power)?????

(image removed by moderators)

 

[famousmockingbird]

This looks to be powered directly off the mains

This is dangerous and against forum rules.

 

[krelac]

Probably it is... But what I wonder is if 5670 is capable of sounding nice in such a circuit? With a proper regulated power of course 🙂

 

[jean-paul]

hi, didi enyone trien an SE amp using 5670 in the way I seen 12au7 amplifiers (bedroom power)?????

Anyone building that amp must be suicidal. Please think of family members that touch the metal case when the plug is plugged in just the "wrong" way....

I reported this schematic to be removed.

 

[krelac]

Thank you for pointing out terrible, horrible, unforgivable, suicidal (and probably made to kill other family members) power supply on image I used. So so so sorry about that... That was not my image and that was not my intention to tickle with it.
My interest is in opinion about building se pow amp with one 5670 per chanel. I heave seen 12ua7 or other dual triodes in such "bedroom apms". I would like to build something of my 5670 since I heave a lot of those. I jus wonder if anybody did it? (without killing family embers or pets in house)