[hagtech]

I made me an octal CHIME.  Just for the heck of it.  Similar to the octal CORNET2, I used a 6SL7 and a 6SN7.  It's a pain rewiring the sockets onto wires, but it really doesn't take that long.  Gain is a bit low, so output voltage is about 1/2 the normal CHIME.

First, get a pair of the P-ST8-808 or P-ST8-209M sockets from AES.  These fit the holes perfectly.  You just have to drill some 9/64 (0.141) holes to fit #6 mounting screws.  Other than that, just make the following resistor substitutions:

R424x, R425x = 1.8k 1W
R429x = 100k 1W or 2W
R428x, R431x = 680
R423 = 1.8 ohm 5W

Code: [Select]

Sok PCB
1   2
2   1
3   3
4   7
5   6
6   8
7   5
8   9
Schematic at www.hagtech.com/pdf/chimeoctal.pdf

jh

[Scott F.]

Very cool 

So how do you like the sound compared to the 12AX/AU combination? Did you try any NOS tubes?

[hagtech]

I don't have any good octal tubes to play with.  My old RCA 6SL7 is microphonic as hell.  And it doesn't help having sockets mounted to chassis (instead of the damped circuit board).  My 6188 had the center plastic break off so I don't know which is pin 1.  All I know is that the circuit works, the voltages come out right, and there is enough gain if you use a linestage. 

The only reason to build the octal version IMHO is if you already have some great NOS octals in hand.  Otherwise I would aim to put my money in the noval version.

jh

[tubesurf]

Hi Jim,

Is is reasonable to drill the PCB and use short stand offs to mount an octal socket for this mod to the Chime (or Cornet 2)?   I mean - mount the socket to the PCB rather than the chassis as you did.

Thanks

[hagtech]

Yes, you can drill holes just about anywhere on the board.  Just pay attention that you don't wipe out any traces.  Or worse, use a metal standoff/nut that shorts a few together.

The circuit boards machine very nicely.  You can drill, mill, and file.  I put in maybe a dozen holes on the CHIME board in the GOLD unit.  I've cut the battery wings off a BUGLE (great for those spacially limited).  Milled out some ground plane for clearance on the OBOE, etc.

jh