Eros2 C4S Circuit board voltage measurements plus alpha

[mdlewis978]

Hi,

Just completed assembly of my Eros2 phone preamp which was an unexpected Christmas gift.

Very nicely done kit!

When conducting the final voltage tests on the C4S board terminals, everything was spot on with

IA = IB = 216.5 V
OA = OB = 162.4 V
OC = OD = 97.4 V
OkA = OkB = 98.5 V

However, OkC = 1.36 V and OkD = 0.98 V.
I thought that this might be related to the EF86 placement so I swapped them and got OkC = 0.603 V and OkD = 1.42 V.

Is something miswired or is this just related to tube variability?

Manual was fabulous; however I did find two errors (I think):

Page 11: 47K Ohm 2W resistors should read (yellow, violet, orange, gold) [they read red, violet...]
Page 69: same parts are misidentified

Best regards,

Michael

 

[Paul Birkeland]

Those voltages depend on both the EF86 and the 6922.  You may also notice that they completely change after 50-100 hours of operation.

-PB

 

[mdlewis978]

Thanks, Paul.

Got it, no worries then I guess.
Just listened to Stonny Stitt and the Top Brass thru the Eros2->Crack OTL and it sounds great!

Michael