Bottlehead Forum

Bottlehead Kits => Eros Phono => Topic started by: kip.duff on December 25, 2019, 04:24:14 PM

Title: E80F OK substitute for EF86?
Post by: kip.duff on December 25, 2019, 04:24:14 PM

I bought some nice German E80F Valvo NOS tubes for Eros 2 first stage.  Based on some info in these treads, I believed they were compatible with E86F.  But I did my voltage tests- got 1.7V at OkC and OkD with kit supplied tubes- within your recommended spec of 2.0V.  With the Valvo tubes, I got 2.3V amd 2.5V.  Is this a risk running these?  Not an acceptable substitute?

Thanks, Kip..... 

Title: Re: E80F OK substitute for EF86?
Post by: Paul Birkeland on December 25, 2019, 06:48:48 PM

I personally wouldn't use them.  They use a bit more heater current, which isn't ideal for the 6.3V regulator.  They will also have less gain and likely a little more noise than an EF86.  The linearity of the EF86 with ~100V on the screen looks quite a bit better with 1.5V of bias than the EF80 with ~100V on the screen and 2.5V of bias.

Still, the Eros 2 will function as a phono preamp using them.

Title: Re: E80F OK substitute for EF86?
Post by: kip.duff on December 25, 2019, 07:38:35 PM

Ya- didn't seem right.  Glad I asked

Thanks for response- Kip.....

Title: Re: E80F OK substitute for EF86?
Post by: kip.duff on December 26, 2019, 04:03:13 PM

I don't know why I wound up with these Valvo E80Fs.  EF86s are affordable.  All kinds of EFT, Telefunken, Valvo NOS or "test-NOS" offers on eBay.  NOS matched pair of Bugle Boys or Mullard (Holland) under $100 pair on the high end.