Question:
If you look at the attached schematic from BBA3 frontend. If I short "-IN" to ground for non balanced behavior, you'll expect to have shut down the negative half of the amplifier and have no output signal on the "-OUT".
But when measuring with AC-voltmeter I discovered there is still music output on "-OUT" ???
Is it because of R5? The two 100 Ohm resistors who normally go to ground but are now connected together forming a 200 Ohm resistor? Is it modulating the negative side from the positive side?
Can someone explain how this works?
If you look at the attached schematic from BBA3 frontend. If I short "-IN" to ground for non balanced behavior, you'll expect to have shut down the negative half of the amplifier and have no output signal on the "-OUT".
But when measuring with AC-voltmeter I discovered there is still music output on "-OUT" ???
Is it because of R5? The two 100 Ohm resistors who normally go to ground but are now connected together forming a 200 Ohm resistor? Is it modulating the negative side from the positive side?
Can someone explain how this works?
Attachments
Hi Walter,
Here is an additional ltspice simulation I did using the DIYA VFET balanced frontend with IRF9240/IRF240 common drain outputs (like in the M2).
It does not have the VFETs in the simulation, but it shows pretty well (I think) what's going on.
Indeed the channel you tried to shut off with grounding the IN- is still half fed by the R332/R322 resistors as a feedback signal to the jfets. If you additionally ground the middle of the R332/R332 resistors your minus channel is at 0 volt output.
In the 2 attachments you see the "half" amp left and the full differential amp on the right. One picture is the front end Jfet and mosfet outputs, the other has the in/output signals.
in/output pic: green=IN+, blue=IN-, red=IN+-, cyan=OUT+, purple=OUT-, gray=OUT+-
jfet/fe: green=jfet+, blue=jfet-, red=middle off R332/332, cyan=fe_out+, purple=fe_out-
Had this simulation on hand for trying to understand my diya balanced vfet2 build.
Here is an additional ltspice simulation I did using the DIYA VFET balanced frontend with IRF9240/IRF240 common drain outputs (like in the M2).
It does not have the VFETs in the simulation, but it shows pretty well (I think) what's going on.
Indeed the channel you tried to shut off with grounding the IN- is still half fed by the R332/R322 resistors as a feedback signal to the jfets. If you additionally ground the middle of the R332/R332 resistors your minus channel is at 0 volt output.
In the 2 attachments you see the "half" amp left and the full differential amp on the right. One picture is the front end Jfet and mosfet outputs, the other has the in/output signals.
in/output pic: green=IN+, blue=IN-, red=IN+-, cyan=OUT+, purple=OUT-, gray=OUT+-
jfet/fe: green=jfet+, blue=jfet-, red=middle off R332/332, cyan=fe_out+, purple=fe_out-
Had this simulation on hand for trying to understand my diya balanced vfet2 build.
Attachments
Haven't really got the time for working on the front panel. I did had an offer from a member to put my design of the front panel in AutoCAD, so I can order at a professional firm.
Schaeffer doesn't do front panels thicker than 10 mm, same with Modushop.
I made the design for the top plate which is going to look nice
But I have to experiment with blue LED's and Perspex before ordering...
There's this online tool https://www.onshape.com
It's for free if the designs are open to public. It's very capable and simple to use.
Martin
Sent from my HTC 10 using Tapatalk
It's for free if the designs are open to public. It's very capable and simple to use.
Martin
Sent from my HTC 10 using Tapatalk
Only designing, so I can let it produce in a CnC shop.
Attached is what I want to be designed, 25 mm thick brushed aluminum with the front edges like in the picture, but I don't know how to describe it in the picture.
In FPE it is called front edge bevel 30 degrees or 45 degrees with a depth of certain amount of mm's.
Attached is what I want to be designed, 25 mm thick brushed aluminum with the front edges like in the picture, but I don't know how to describe it in the picture.
In FPE it is called front edge bevel 30 degrees or 45 degrees with a depth of certain amount of mm's.
Attachments
What a great forum this is, this gathering of DIY fanatics
Member Jotom750 sent me this beautiful piece of artwork.
Thanks Richard!
Another member showed me a CnC company and some examples how to order with them. Thanks also!
With this PDF I can start ordering my frontpanel, get some quotes.
Member Jotom750 sent me this beautiful piece of artwork.
Thanks Richard!
Another member showed me a CnC company and some examples how to order with them. Thanks also!
With this PDF I can start ordering my frontpanel, get some quotes.