Neumann PV76 modification

[thekid777]

Hi! I'm thinking about doing a mod to a pV76 in order to bypass the low cut.
Would you have any ideas about how I could do it?
Attached is the schematic
Many thanks!

 

[PRR]

Do you mean the high-cut??

Jumper the chokes, lift one end of C8.

 

[Whoops]

Are you referring on how to bypass the Low Cut Filter?
it's  the switch that has 3 positions , 40hz, 80hz and 120hz, even if you switch it to 40hz you are always cutting.
Well if it's that switch you want to bypass it seems you just got a free high end lift mod from PRR!

 

[thekid777]

Hi guys! many thanks
I'm referring to the low cut which I would like to bypass at times.
There's 3 positions: 40Hz, 80Hz, 120Hz.
I feel 40hz cut is still doing too much.
Attached you will see the inside of the preamp.

 

[thekid777]

Neumann did a version of the PV76 later with the added Bypass position
but they changed completely the Low cut circuit, the rest remaining the same.

It is named the PV76N, schematic attached!

 

[gyraf]

Thanks! Never ever seen a PV76N before...

(Do you by chance have the other half of that schematic? Would be nice to see dates, revision numbers etc..)

Jakob E.

 

[thekid777]

Hi Jakob,
Just updated the schematic to the full one!
Do you think the pv would be even more enjoyable without low cut at times?
What is your experience with them?

 

[Whoops]

Neumann did a version of the PV76 later with the added Bypass position
but they changed completely the Low cut circuit, the rest remaining the same.

It is named the PV76N, schematic attached!

Hi, the way Neumann did it in the updated schematic seems better than in the old schematic.
If you take out the High Cut circuit PRR suggested you'll see there's not many differences.

What I would do is remove the chokes and the High Cut part, and then copy exactly the newer schematic and apply that to your circuit. It really not hard. You need a new switch though 3 pole 4 positions instead of 3 pole 3 positions, I guess it's a shorting switch but you might have to confirm that by measuring the stock 3x3 switch.

 

[gyraf]

Imo, Neumann did know  exactly what they were doing- don't change filtering in this unit unless you don't like it's basic sound (in which case, sell the unit and get something else)

Jakob E.

 

[Whoops]

Imo, Neumann did know  exactly what they were doing- don't change filtering in this unit unless you don't like it's basic sound (in which case, sell the unit and get something else)

Jakob E.

Jakob, if the schematic was updated it's because there was a reason for it.
I agree with you I'm also sure Neumann did know exactly what they were doing when they did the first filter and when they updated it for the second one.
If you compare the 2 schematics there's not a big difference, and by updating his circuit thekid777 will have exactly what he wants, an option to bypass the low cut.

 

[Michael Tibes]

Did you recap the unit? If not, it might be the reason for the lack of lowend.

Michael