gar918BC build thread

[gar381]

NOTICE OF PART CHANGE 10/5/23

Had to happen sometime... The pnp BC560C has been out of production
for some time now and my current supply of NOS Fairchild BC560Cs
that I have been using for last 3 years is running very low. I will be using
the remainder of my supply for only for the matched pnp input pairs for the
garOA10 and gar918.

I knew this day was coming so I have auditioned many possibilities.
From now on I will only be using..

BC557C mouser # 637-BC557C in the following positions...

gar2520 Q6, Q9.
gar1731 Q3, Q4
garAM10 Q1,Q5,Q6,Q7
garOA10 Q2, Q3, Q5, Q7, Q9
gar918 Q3, Q4

Note that these are all on tape and will just drop in place to the silk
just like the original BC560C

Gary


The Build PDF manual is good but here a few notes that might make the kit
A little less confusing.....

1) The little bag with the Millmax pins also contains Q1 and Q2 which are BC560C Matched Pair.
NOTE: This matched pair of transistors are different transistors than my other gar kits (2520, 1731)
and are not interchangeable.
2) The small bag of 3 transistors labeled Q5,Q6,Q7 are BC550C
3) The tape strip with 2 transistors are Q3,Q4 BC560C
See Page 6 of the manual for location
4) The little bag of caps..
The tan ones are CD1, CD2.
The blue ones.. see page 4 of the assembly manual
for value and location.
5) Please meter the resistors to determine value. See page 7 of the
manual for value and location.
6) There are 12 diodes in this build. Make sure the band on the diodes(cathode)
goes in the circles on the silkscreen. Note.. All diode pads on the PCB are
square. No other pads on the pcb are square. See page 5 of the manual.
7) After assembly PLEASE double check for unwanted solder bridges
on the Bottom of the PCB. See page 9 of the manual and make
SHURE THAT on the top of the PCB that no component lead wires
are touching each other.
8) When inserting your new DOA into the millmax sockets of
a module, Please insert straight down and not at an angle.
DO NOT push down on the component parts but use the edges
of the DOAs PCB. Remove DOAs the same way. Pull straight up
from the edges of the PCB and not at an angle.
9) Never insert a DOA or a module with the power on.

10) HAVE FUN !!

A pdf download of the manual can be found here:

Classic Audio Products, Inc.


GARY

 

[gar381]

Reserve 

 

[3nity]

Looks like Im the only one building this...
Anyways...i was finishing the first one when solderings the mill max pins i heard some craking noises ...not sure if it was some components burning...i did follow the build guide and last step is to solder those mill max pins.. anyone?

Havent tested yet though.

 

[gar381]

Yes... Last

I have built lots of these guys.  Love them for Balanced receivers and summing.

GARY

 

[3nity]

Thanks Gary.
Yes i know pins are last.
But when i was solderings i heard some craking noises..is that normal.

 

[living sounds]

Hi Gary,

would it be detrimental to build the op amp with BD139-16 / BD 140-16 instead of MJE172 / MJE182? I've still got lot's of the former and sourcing the latter would be a little difficult.

Thanks!

 

[3nity]

they dont seem to be compatibles!

 

[living sounds]

they dont seem to be compatibles!

Well, they're pin compatible, there's a  918 schematic that uses those (and otherwise exactly the same components in the relevant part of the circuit ) and these are very common in 2520 pinout based op amp output stages.  I've read people have switched out BDs for MJEs in 2520 op amps, too.

http://www.pcb-audio.com/pcb-audio_com/schema-j918.png

Am I missing something?

 

[gar381]

I never tried them but they should work. 
They may sound slightly different but give them a try.
There is always the good old Hakko 808 if you don't
like them.

GARY

 

[living sounds]

Thanks Gary, I'll try it. Will do a comparison as well, maybe the MJE transistors are part of the special sauce of superior sounding op amps.  8) I'll report back.

 

[TillM]

I don't know why this fantastic DOA is so underpresented.
I build four of them and used it in my two Hairball Lola.
I really like the color.
Gary thank you so much for another piece of art.

 

[gar381]

Your welcome TillM. 

GARY

 

[JW]

Built four of these. They're great. A fine replacement for my yammy line amps too because they can run +/-24 by changing (3 27K resistors? Can't remember now. Info is around)

But yeah, real nice in summing position. Clear but not harsh.

 

[gar381]

Hi JW

For +/- 24v operation...

The exact value to replace the 3  27ks depends on who you talk to.
Both 43k and 47k  are both mentioned  in the all the forums that I have
perused.  I have tried both values and either will work.  I don't believe that is all that
critical.

I am using these  for Balanced receivers and summing applications at 24v
with great results.

GARY