[Squalish]

This is based on Sijosae's layout, from staring at Subsonic's board. I plan eventually, when I get enough cash, do do a balanced bridge gilmore based off this. Are there any obvious mistakes?

 

[Arzela]

I think the bases of the 2SK109 and 389's
need to be connected in both channels (you just have one of the pairs connected).

Lowest pin in the three pin column
of the 109 needs to tie to the lowest pin
in the three pin column of the 389.
Input also ties into this node.

Also, I think you need pin 7 of
the left channel OPA227 tied to V+.

 

[Squalish]

Thanks Arzela. I fixed the bottom pins of the FETs and the input, pin 7 of OPA227 is intended to be hooked up via jumper(in order to turn BB on and off, or possibly use it as a 2channel section, or does that make sense?) using the hole ot the right of the cap.

fixed pic uploaded

 

[Arzela]

Quote:

pin 7 of OPA227 is intended to be hooked up via jumper(in order to turn BB on and off, or possibly use it as a 2channel section

Oh...Could you explain this in more detail?
I can't quite see what it is you plan to do. Don't the 227's need power always?

I'm working on a switchable Gilmore myself. Here's my plan.


So, I'll have a standard Gilmore amp
with the layout excately as yours.
Except that pin 7 of the 227's are connected
and pin 3 is not. I'll refer
to this as the "positive" board.

Another board, the "negative" board, will accomodate the
negative output.
For each channel on the positive board,
from the appropriate pins on the fets,
I'll lead two wires A and B to the negative board.
These lead to the transistor banks.
I'll also lead a wire C from
the + input of the 227 (pin 3) of the positive board to the negative board.

For each channel,
a switch will put the three wires into one
of 2 configurations:

1) (normal) A and B are broken, and C goes directly to ground.

2) (bridged) A and B are unbroken and C ties to the extra cap needed for bridged mode.

I suppose power for the negative board also
needs to be switched...

Sorry if this seems confused....


And this all seems unnecessary too...
Why not have the amp in bridged mode always?
One can then use the two + outputs
for normal headphones (would the
two - outputs work?), or use both the
+ and - outputs for dual mono. A 4 pole
double throw switch would accomodate
this setup....

I've also toyed with the idea of converting
the + and - outputs into a single ended output using this circuit
http://sound.westhost.com/project51.htm
(for use with normally wired cans, of course);
but I'm afraid sound quality
might then be compromised.

Any comments would be
appreciated.

 

[Subsonic]

You only need one pair of 109's and 389's per bridged channel. So pretty much you can erase the FET's, LED's, opamp and a bunch of resistors from the the o+ channel.

You need tie the two FETs at pin6 like you did on the other channel.

Here's one of my early pic of my BB version:

 

[Squalish]

I was basically copying Subsonic's board hole-for-hole

This should probably be just the power supplies, since I have 3 of his boards already, but that doesn't saturate the 150 inches of the 4PCB.com 33each terms. Thanks to the extension of their free PCB offer, if I work on this for a while, and think its ready for prime time, I might just use the $150 credit and get a bit more than three.

Subsonic: I plan to make it switchable from balanced to not(why? I don't know, partly to see the diff balanced makes, partly for novelty. <newbiequestion>Can I use it with non-balanced phones when in balanced mode?</newbiequestion>) and perhaps even make it possible to do a 4 channel HT preamp setup. I will use the same hookups as you describe on the BB diagram on your site, but hooked up to a 2 position, many pole rotary switch.

Sidenote: What modifications are necessary to run a gilmore as a preamp?