FET "Grinder"

[tata]

hello gents,

noob builder here, id need a little help.

populated the FET Grinder PCBs, PSU seems to be OK - but got stuck at the Ratio Switch. am i right that i need to "stop it down" - it has 12 positions by default. if yes, where i should put the stop ring? (very basic question, i know..) i guess 4/8/12/20 means 4 positions..?

the 2x BF245 arent from the same company (they look different at least) in my kit - does this make a difference? im not really into having a super accurate meter, but id like to have some. (Plasma VU would be so cool..)

i was trying to fix the 220nF on the silkscreen, but damn. i fixed its neighbour's label. :/  my proper 22nF label fix looks much worse than the wrong one.. noob, i know.

thanks for the help, and thank you Gustav for this awesome kit! im planning to buy more and hopefully your stereo version too

 

[Gustav]

hello gents,

noob builder here, id need a little help.

populated the FET Grinder PCBs, PSU seems to be OK - but got stuck at the Ratio Switch. am i right that i need to "stop it down" - it has 12 positions by default. if yes, where i should put the stop ring? (very basic question, i know..) i guess 4/8/12/20 means 4 positions..?

Yep, 4 positions (and it deserves mention that its common to put the programming pin in 4, turn the switch 3 steps and get confused by the lack of a 4th step)

the 2x BF245 arent from the same company (they look different at least) in my kit - does this make a difference? im not really into having a super accurate meter, but id like to have some. (Plasma VU would be so cool..)

For audio tracking accuracy, you will need matched FETs, but for metering, you are good to go - some would disagree, stick in it, see what you think.

thanks for the help, and thank you Gustav for this awesome kit! im planning to buy more and hopefully your stereo version too

Thank you so much!

The 1178 prototype is done and tested, but it will be a week or so before I have boards and documentation ready.

The final revision of this circuit while you wait.

https://pcbgrinder.com/index.php?route=product/product&path=59_69&product_id=149

Gustav

 

[rock soderstrom]

+1 for the 1178!  8)

 

[tata]

The final revision of this circuit while you wait.

https://pcbgrinder.com/index.php?route=product/product&path=59_69&product_id=149

Gustav

cool, looks very nice imo - what are the benefits of this new version over the rev3 sound wise?

id like to know the basic dimensions / hole positions of the front panel - can you pls check this quick drawing for accuracy?

thanks!

 

[Gustav]

The final revision of this circuit while you wait.

https://pcbgrinder.com/index.php?route=product/product&path=59_69&product_id=149

Gustav

cool, looks very nice imo - what are the benefits of this new version over the rev3 sound wise?

There are none - just a better layout of the circuit, and a better board to work with..

id like to know the basic dimensions / hole positions of the front panel - can you pls check this quick drawing for accuracy?

thanks!

If you load this into front panel designer, you can lift the relative distances you need off of it.

http://pcbgrinder.com/download/FET_GRINDER/FET_frontpanel.fpd

Gustav

 

[tata]

thanks for the frontpanel layout Gustav!

now i can see the accurate drilling coordinates, can compare with my measurements. is there any reason why the GR and Meter switches arent on the same Y axis? there is 1.12mm difference (i measued 0.9) - this could be compensated on the Meter PCB / switch position i guess, there is enough room.

sure the switches can be mounted on the frontpanel instead of the PCB if one wants them perfectly aligned (i think i  do), but then i wonder if the Lorlin would really stay inplace without these "stabilizers".  i think the best (for me) would be to DIY a new panel for this block?

the "Ratio" is labeled as "Release" in the .fpd  - sorry for nitpicking.

i was preparing for weeks of troubleshooting, but my 1st build seems to be alive and kicking now!
just a blind Q Bias and no meters, no case/racking/proper GND for now - but it works!

just one little thing : Dirt pot adds lots of buzz when going up - i hope this will go away as soon as i put it in a case?

 

[Gustav]

thanks for the frontpanel layout Gustav!

now i can see the accurate drilling coordinates, can compare with my measurements. is there any reason why the GR and Meter switches arent on the same Y axis? there is 1.12mm difference (i measued 0.9) - this could be compensated on the Meter PCB / switch position i guess, there is enough room.

sure the switches can be mounted on the frontpanel instead of the PCB if one wants them perfectly aligned (i think i  do), but then i wonder if the Lorlin would really stay inplace without these "stabilizers".  i think the best (for me) would be to DIY a new panel for this block?

the "Ratio" is labeled as "Release" in the .fpd  - sorry for nitpicking.

i was preparing for weeks of troubleshooting, but my 1st build seems to be alive and kicking now!
just a blind Q Bias and no meters, no case/racking/proper GND for now - but it works!

just one little thing : Dirt pot adds lots of buzz when going up - i hope this will go away as soon as i put it in a case?

I didnt have buzz, but the dirt pot is only good for a small subtlety on very transient materials (snare drums with hard attack etc). I ditched it on the latest, because 99% of the time, it turned out it will just sound bad.

Gustav

 

[tata]

now that ive got a working build and done some research on this forum.. can i please have some information about doing a 2:1 ratio mod ( http://groupdiy.com/index.php?topic=47168.msg592958#msg592958  - would this work? no reply in this thread so far..)

and where could i find info on doing a true bypass (need relays and maybe extra PSU rails?) and HP SC modes (simple 12dB/oct filters inserted to..?)

and if you got some detailed info on calibrating this particular FET Grinder, id love to follow it. honestly im too noob yet to use the mnats, etc calibration videos..  (i have an old MCI VU meter for testing - not sure its the perfect choice)

thanks!

 

[jicama]

Hello I´m confuse about some components of FET grinder
1.the Poly caps, has to be 22nf or 220nf??
2. BF245A can be replaced for 2N5458??

Thanks for your help

 

[tata]

gents,

would this work as extra 2:1 and HP SC mod for the FET Grinder, please?

thank you

 

[jicama]

gents,

would this work as extra 2:1 and HP SC mod for the FET Grinder, please?

thank you

Don't know about that mod, sorry

Tata did you use 22nf poly caps or 220nf??

Cheers

 

[tata]

Don't know about that mod, sorry

Tata did you use 22nf poly caps or 220nf??

Cheers

220 and 22. all printed on the PCB - except one mistake. but thats covered in the .pdf. (the cap. at the right side of the attack pot. is 22nF, not 220nF.

 

[tata]

i was trying to remove the hum/buzz when i realized my build works like a good quality radio recevier (88.4MHz?) if i touch T1. i guess this is not good - or is it normal?

sadly i couldnt fix the hum/buzz but ive found thousands of variations in its level (input gain doesnt have effect on it, but dirt, and especially output have.) touching other transistors sometimes helps reducing the noise a bit.

i did my best to wire the unit as written in the docs - but the buzz is still there.

anyone can give me some hints on fixing this?

thanks a lot.

 

[Harpo]

would this work as extra 2:1 and HP SC mod for the FET Grinder, please?

For the HPF, leave out R100 and only short out the 10nF cap for no HPF. The resistive part of this R/C is already in the following attenuator string R78...R201. Without your 56K in parallel to the 283K attenuator, the 10nF cap value will set this HPF for 56Hz (4n7 for 120Hz, 3n3 for 170Hz, ...).
There are other spots (FI decreasing C13,...) to archive this HPF function. For DIY chose whatever plan matches yours best.
The DPST slam switch is missing its other half to short out R81...R82.
The 150R R66 from Gustavs schematic will be 68R then (R65 and R66 would better be positioned in the ratio section, not in GR control amp section).

 

[tata]

thx Harpo,

i will check these - but i need to fix the hum/buzz first.. i have the potentiometers and the 2 switches wired to the PCBs with 6-7 cm long cables (not shielded), because i wanted a slightly different layout. is this a very bad idea?

intresting experience : if dirt pot is at max the buzz increases by a lot. (10-14dB-ish). now if i gently push the 22nF capacitor a bit from the top the buzz reduces. but if i have the dirt pot at min and i push the same capacitor the buzz increases. (4-6dB-ish)

i also experienced that if i crank up Dirt to the max a vocal sounds much, much cleaner. i love that sound - except the buzz/hum..  Dirt at minimum gives an oversaturated, not really useable output. i checked the Dirt potentiometer wiring - its definitely wired as it should be right in the PCB.



i only have an RME Fireface 800 and a cheap old DMM (no real RMS metering) as "test equipments". is there hope for me?

 

[salomonander]

does this unit have the all buttons in mode as well?

 

[tata]

afaik not by default - but you can add it.
check the previous posts, you can find some info on how to. (called "SLAM" on the schemo i linked and read Harpo's correction too)

 

[Gustav]

i also experienced that if i crank up Dirt to the max a vocal sounds much, much cleaner. i love that sound - except the buzz/hum..  Dirt at minimum gives an oversaturated, not really useable output. i checked the Dirt potentiometer wiring - its definitely wired as it should be right in the PCB.

Not enough info to fix the buzz problem, but..

thanks for the frontpanel layout Gustav!

now i can see the accurate drilling coordinates, can compare with my measurements. is there any reason why the GR and Meter switches arent on the same Y axis? there is 1.12mm difference (i measued 0.9) - this could be compensated on the Meter PCB / switch position i guess, there is enough room.

sure the switches can be mounted on the frontpanel instead of the PCB if one wants them perfectly aligned (i think i  do), but then i wonder if the Lorlin would really stay inplace without these "stabilizers".  i think the best (for me) would be to DIY a new panel for this block?

the "Ratio" is labeled as "Release" in the .fpd  - sorry for nitpicking.

i was preparing for weeks of troubleshooting, but my 1st build seems to be alive and kicking now!
just a blind Q Bias and no meters, no case/racking/proper GND for now - but it works!

just one little thing : Dirt pot adds lots of buzz when going up - i hope this will go away as soon as i put it in a case?

I didnt have buzz, but the dirt pot is only good for a small subtlety on very transient materials (snare drums with hard attack etc). I ditched it on the latest, because 99% of the time, it turned out it will just sound bad.

Gustav

 

[tata]

is this the position where the Q-Bias calibration should start from, the position that places the wiper closest to GND / "fully off"?

if yes, then my build works "upside down" i guess.

the FETs (BF245) are placed as shown on the silkscreen - but if i had 2n5457 they should be placed in the opposite direction, right?

 

[tata]

oops..

"Please note that there is an error in the video. At 1:54 the video says to turn the trimmer so the wiper is closest to ground. In fact, you want to turn the trimmer so that the wiper is in the opposite position or furthest from ground. "

(referring to mnats' "Step One: "Q" Bias Adjustment v2" video on YouTube)

so my build is not "upside down" it seems.  (need to investigate "Dirt" tho)