Help with mixer direct outs and EQ bypass

[Vyvyan]

I'm trying to implement an EQ bypass and direct outs on this Yamaha pm-200 (first photo), using the output amps from a Yamaha pm-400 (second photo). I also plan on installing input transformers, with switching jacks between the xfrmr and amp for a DI/line input.

I have some sowter 1:6 mic transformers originally used with a 220k pot on the secondary, but I'm thinking that is probably too much of a stepup for these pres. I also have some Chinese carnhill knock offs from alctron neve clones I could use and some carnhill vtb1148 for the outputs or should I just stick with the tamura 600:600 on the outs?

The photos have my idea basically laid out. The direct out will be on a switch.

I'm not quite sure how to calculate the gain of these amps, or how much gain is even needed from the output amp to reach proper +4 line level. using Rf/Rin doesn't seem to give me off results, but I'm still a noob and trying to learn the workings of different discrete topologies

so any info on the workings of these gainblocks or how i should modify the feedback network for proper gain would be greatly appreciated.

 

[Vyvyan]

Here are the full schematics of both mixers

 

[Vyvyan]

BUMP!

I'll be experimenting with this project tonight! I'm sure I'll find my way thru it via trial and error, but any info/recommendations would be very appreciated!
Thanks

 

[ruffrecords]

You direct outs look like they should work but I don't think the EQ can be bypassed simply by shorting its input to its output. You will certainly need to change the left side connection to be after the 4.7uF capacitor to avoid passing dc thought the switch which will cause thumps/clicks when operated. If you change the switch to s SPDT type you should be able to avoid this.

Cheers

Ian

 

[Vyvyan]

You direct outs look like they should work but I don't think the EQ can be bypassed simply by shorting its input to its output. You will certainly need to change the left side connection to be after the 4.7uF capacitor to avoid passing dc thought the switch which will cause thumps/clicks when operated. If you change the switch to s SPDT type you should be able to avoid this.

Cheers

Ian

Thanks that's what I was afraid of. Let me make sure I got this right: cut the trace after the 4.7u cap and send that to the switch, send the "in" side back to the 560r resistor into the EQ, send the "out" side to the 560r resistor into the base of TR4. Does that sound right?

 

[ruffrecords]

You need to disconnect the left hand side of the 0.1uF cap and connect it to the wiper of a SPDT switch. Connect one pole of the switch to where the 0.1uF was originally connected - this will be the EQ in position. Connect the other pole of the switch to the right hand side of the 4.7uF cap - this will be the EQ out position. In other words you are switching the input to the 0..1uF cap between the output of the EQ and the input of the EQ.

Cheers

Ian

 

[Vyvyan]

You need to disconnect the left hand side of the 0.1uF cap and connect it to the wiper of a SPDT switch. Connect one pole of the switch to where the 0.1uF was originally connected - this will be the EQ in position. Connect the other pole of the switch to the right hand side of the 4.7uF cap - this will be the EQ out position. In other words you are switching the input to the 0..1uF cap between the output of the EQ and the input of the EQ.

Cheers

Ian

Darn, I was hoping to keep the reverb send right after the 4u7 coupling cap, probably too much trouble tho

 

[ruffrecords]

Darn, I was hoping to keep the reverb send right after the 4u7 coupling cap, probably too much trouble tho

The modification I suggested does not affect the reverb send.

Cheers

Ian

 

[Vyvyan]

The modification I suggested does not affect the reverb send.

Cheers

Ian

Yes, thank you, just reread it lol