F-5 boards

The F5 schematic in the store shows P3 on the F5 board. However, I don't see P3 on the board. Is it now included or are there plans to add P3 to the board? Also there are some small changes to the F5 circuit as seen in the F5 Turbo manual. Are those changes on the boards yet?
 
Hi,

P3 is for fine tuning the input section for minimum distortion. However, it entails the use of elaborate spectrum and distortion analyzers which may not be available to the common builder (I for one don't have one).

It was included in the schematic to keep it updated with the most recent schematic from Nelson, and also in the BOM for the sake of completeness. However, if you are to use P3, it should be "hard-wired" or soldered "point to point" on our boards.

In our official F5 prototype, P3 was set aside and was not used. I believe the small changes, especially the parts values, are already included in our board and BOM.
 

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The changes in the bias ciruitry are not changed in the schematic that's in the store. I assume they are not on the board either?

P3 could have been added to the board. The builder could choose to install it or not. Adding it in as a Kludge makes the board look messy.
 
The changes in the bias ciruitry are not changed in the schematic that's in the store. I assume they are not on the board either?

P3 could have been added to the board. The builder could choose to install it or not. Adding it in as a Kludge makes the board look messy.


What changes in the bias circuitry are you referring to? Could you please elaborate on that? The two schematics were drawn differently but still have the same bias circuitry the last time I checked except for the position of the thermistors which should not be an issue at all.

Regarding P3, iirc the boards have long been here before P3 came about. However, if the equipment needed to adjust it is available to you, then it is very easy to adopt the board to accept P3 without it looking messy or as you say, a kludge.
 
What changes in the bias circuitry are you referring to? Could you please elaborate on that? The two schematics were drawn differently but still have the same bias circuitry the last time I checked except for the position of the thermistors which should not be an issue at all.

Regarding P3, iirc the boards have long been here before P3 came about. However, if the equipment needed to adjust it is available to you, then it is very easy to adopt the board to accept P3 without it looking messy or as you say, a kludge.

The thermistor is not connected to the rail but the other other side of the .47 ohm resistor. The resistors on the input are configured differently. P3 was added.

I don't think one neccessarily needs equipment to experiment with P3. The changes are audible. It would be nice to have the option anyway.

BTW, If the changes don't make a difference then why were they made?
 
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Nelson Pass told me that originally the F-5 didn't have the P3 and they ended up spending way too much time with the Audio Precision swapping out resistors to set the amp to the "sweet spot" He then made the changes- added the pot to make it much easier to set the amp to the lowest distortion, again, using the AP. He said that in his opinion you can't set it to lowest distortion by ear. Now he does say it changes the sound, so it might be fun to play with, but for now we're going to stick with not having the P3. I don't think it would look kludgy at all to add it though- get a full sized pot- the type with the short slotted shaft and mount it right next to the board. I think it would look cool, you may not agree, but it can be done.

We have way too many projects to get to, including the F-5 turbo so we have to choose our battles.
 
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The thermistor is not connected to the rail but the other other side of the .47 ohm resistor. The resistors on the input are configured differently. P3 was added.

Thank you for elaborating.

The thermistors will work either way, it will affect the bias as it is still effectively connected to the rail even via the 0.47 ohm resistor.

The input resistors are changed to lower the impedance, either configuration should work.

We have already discussed about the P3.

I don't think one neccessarily needs equipment to experiment with P3. The changes are audible. It would be nice to have the option anyway.

We respect your opinions and will surely take it under consideration.


BTW, If the changes don't make a difference then why were they made?

To show the world that the F5 design is so flexible.
 
Nelson Pass told me that originally the F-5 didn't have the P3 and they ended up spending way too much time with the Audio Precision swapping out resistors to set the amp to the "sweet spot" He then made the changes- added the pot to make it much easier to set the amp to the lowest distortion, again, using the AP. He said that in his opinion you can't set it to lowest distortion by ear. Now he does say it changes the sound, so it might be fun to play with, but for now we're going to stick with not having the P3. I don't think it would look kludgy at all to add it though- get a full sized pot- the type with the short slotted shaft and mount it right next to the board. I think it would look cool, you may not agree, but it can be done.

We hve way too many projects to get to, including the F-5 turbo so we have to choose our battles.

I'm not saying it can't be done, just that there's been a few updates to the circuit and it would be nice to have them incorporated into a new board instead of cutting traces and gluing parts on. I'm not sure a full sized pot for P3 that's off of the board wouldn't cause a hum, noise or oscillation.

Thanks for the explanation though.
 
F5 V2.0 board vs. various schematics???!!!!!

I purchased two of the V2.0 boards from the store, never dreaming that they wouldn't have provision to adapt to the latest schematic.

I understand that P3 isn't on the board, that's not an issue. The issue is being able to stuff the board from the most recent schematic on which the part numbers are different from the original, and the circuit has changes as well.

The store shows the original schematic, but does nothing to help this situation.

I want to build the most recent schematic but could sure use some help with an updated stuffing guide, otherwise I guess I should return the V2.0 boards and look for a more recent design?

Sure would appreciate some help with this; every other purchaser must face the same dilema!

Jeff