APE EQ PCB (See video sample)

[ForthMonkey]

Now i'm making pcb for voltage follower.But...Where is the GND? Circuit working in spice without GND pin.There are only +/-V-In-Out pins.

But this design has GND.

http://www.diyrecordingequipment.com/projects/classicapi-discrete-voltage-follower/

I don't understand.Can you help?

Thanks.

 

[JoshuaUnitt]

Can you post the schem for the voltage follower you've been working on?

 

[ForthMonkey]

It's working in spice.But there is no GND pin.Original API 550 schema has no GND pin,tonly four pin.In,Out,-V,+V.But in real life circuit has 5 pin with GND.I can't understand that where is the GND?

 

[dmnieto]

It's working in spice.But there is no GND pin.Original API 550 schema has no GND pin,tonly four pin.In,Out,-V,+V.But in real life circuit has 5 pin with GND.I can't understand that where is the GND?

Nowhere, it is just for shielding, take a look at any commercial operation amplifier or follower. Does it ever have a GND pin? No.

There is no need for a GND pad as the circuit is floating, with the gain defined as the difference between the inputs multiplied by the gain, with the "neutral" point  given by the internal biasing as some arbitrary point between V+ and V-. That is the reason for offset compensation or DC coupling in a lot of opamps.

For your circuit it is similar R8 defines the Q bias of the common-collector buffer and R14/R15 the biasing of Q2 for the output stage

 

[ForthMonkey]

And yes! Finally i fitted 6xAPIsh Eq for 19" 3U.

 

[joaquins]

There are some api eagle libraries here where there are the boards to use, the problem with this is usually the front panel sizing.
using pot with it isn't a problem, but I think API uses other part of the switch I think to do automatic Q changing, which you would be missing doing so.

Nice project and nice clean out of the messy original schematics, thanks for those, maybe I use them. waiting to see what happens...

JS

 

[ForthMonkey]

Circuit improved.

 

[rafafredd]

Maybe it's just me???, but I don't see no circuits in your posts...

 

[ForthMonkey]

Maybe it's just me???, but I don't see no circuits in your posts...

Did you look first post? Actually these circuits are only idea.Still working on it.

 

[rafafredd]

Yes, In the first post, there is nothing there... What did you changed from the original?

 

[jordan s]

I'm very interested in this but it doesn't appear to be fully documented in the first post.

 

[ForthMonkey]

There is problem about high mid.Still working on it.And trying to build it "cheapest". ;D

 

[ForthMonkey]

Forget all old versions.New one is here.

 

[Spencerleehorton]

You gonna leave us hanging?

 

[ForthMonkey]

You gonna leave us hanging?

What do you mean? Sorry about my English.Sometimes i miss meanings.

 

[Krcwell]

You gonna leave us hanging?

Check the first post of the thread.

 

[ForthMonkey]

You gonna leave us hanging?

Check the first post of the thread.

If you mean part values,i'll add.This circuit is working.It's done.Just i'm calculating center freqs.

 

[ForthMonkey]

BIG UPDATE!

 

[ForthMonkey]

UPDATE!

Waiting for PCBs for three units.One for prototype the others to sell.Then i will get PCBs for five units,too.

There will be five PCBs.As i said,four for freq boards and one main boards.

For one unit PCBs will be $50.

 

[Spencerleehorton]

Hi,

Slight confused with this, could this not have the resistors soldered onto the pots?
this would help to bring down the size of the whole thing.
Are you planning on using a dual concentric? if so which one?
be great to hear some audio samples when you have prototyped.

could something like this be used?

http://www.surplussales.com/Switches/SWSealed-2.html

Rotary Switch
8P3T

Enlarge Image
(SWR) H-229814
CTS rotary switch. 3 wafer, dual concentric shaft. Top 2 wafers on 1/4" shaft 4P3T each. Bottom wafer on 1/8" shaft 6P2T. 2 amp, sealed. 1-1/8" x 1-1/8" square. Requires 3/8" mounting hole, 1-3/4" behind panel. 1/4"D & 1/8"D shaft. 3/8"D x 3/8"L bushing.

regards

Spence.