LND150 pre on input jack

[maxkracht]

Here's an untested board, will report back when I get it from the fab. https://oshpark.com/shared_projects/HPcRfbH0
It's a pretty generic LND150 circuit but it fits on an input jack and a trim pot is accessible through the jack, similar to a commercial version from Granger. I'm pretty confidant it will work ok, but let me know if you see anything stupid. I think my clearances are ok, but it is a bit smooshed. Just trying to keep the footprint as small as possible.

Some info and schematic for a generic lnd150 pre here: http://www.hawestv.com/amp_projects/amp ... _200v1.htm
more detailed info here: http://www.hawestv.com/amp_projects/des ... weaks1.htm

[Guy77]

Here's an untested board, will report back when I get it from the fab. https://oshpark.com/shared_projects/HPcRfbH0
It's a pretty generic LND150 circuit but it fits on an input jack and a trim pot is accessible through the jack, similar to a commercial version from Granger. I'm pretty confidant it will work ok, but let me know if you see anything stupid. I think my clearances are ok, but it is a bit smooshed. Just trying to keep the footprint as small as possible.

Some info and schematic for a generic lnd150 pre here: http://www.hawestv.com/amp_projects/amp ... _200v1.htm
more detailed info here: http://www.hawestv.com/amp_projects/des ... weaks1.htm

This looks great!!
Excited to see this coming together and very excited to hear back on the test results!

Thank you !
Guy

[Roe]

how many db gain boost does it offer? 36 like an ecc83?

[maxkracht]

This looks great!!
Excited to see this coming together and very excited to hear back on the test results!

Thanks for the kind words, and thanks for your help!

how many db gain boost does it offer? 36 like an ecc83?

I don't know exact figures, but I believe the LND150 can have slightly more gain than an ecc83, depending on the setup.

[john65b]

Any thought for a Thru hole (non SMD) version? Interested / following.

I slapped together a similar pcb, but no pot - instead of 330 source resistor, I put in a 1.6k ohm resistor, and so far gain is manageable. B+ at 240v.

A bit noisy....

[maxkracht]

Any thought for a Thru hole (non SMD) version?

Happy to do a quick swap for TH parts on this board and make a second version, but I don't really see the benefit. Even if you have a chunky iron and a shaky hand, 1206 isn't much harder than TH resistors and diodes.

I slapped together a similar pcb, but no pot - instead of 330 source resistor, I put in a 1.6k ohm resistor, and so far gain is manageable. B+ at 240v.

A bit noisy....

I haven't messed with this circuit enough to give pointers about noise problems, but I'm guessing the more common issues would be hum from a bad grounding scheme, insufficient decoupling, or crosstalk from everything being so close together.

[maxkracht]

Here's a through hole version. Don't think I could get everything to lay flat without a redesign and/or making the board bigger, but should still work.
https://oshpark.com/shared_projects/GPk8IIbW

[Guy77]

Here's a through hole version. Don't think I could get everything to lay flat without a redesign and/or making the board bigger, but should still work.
https://oshpark.com/shared_projects/GPk8IIbW

This looks great!
Thank you.

Cheers
Guy

[maxkracht]

Got the boards in and they are working properly. The jack and trim pot holes are a bit too small, will edit the packages and post an updated design. Otherwise, i'm pretty happy with it. Little bit of hiss, but that's expected, didn't notice any added hum. Might add some extra shielding on the top of the board for good measure, but doesn't seem to be needed.

[maxkracht]

Through hole: https://oshpark.com/shared_projects/JvQecioH
SMD: https://oshpark.com/shared_projects/tEsCK0wL

Just moved a couple traces and added a top ground plane for extra shielding. Holes for the pot and jack should be corrected. SMD version now has a through hole drain resistor because there's room and it's easier to find th resistors with better voltage ratings. I also rounded the corners of the board for style points.

I ordered the new smd version to test, I'm not going to try the TH version myself. They are probably fine, but probably wise to check my work if you want to order one.

Pot should be 10mm side adjust like: PT10LH01-105A2020-S, top adjust should be fine as well if your not into the through the jack thing but the square ones wont fit on top of the board.
input cap has a 7.5mm spacing, should be rated for your B+ voltage
output cap has a 10mm spacing
There is just enough room for a small (8mm dia) electrolytic to hang off the extra pads for decoupling, probably not necessary in most circumstances

[Guy77]

Through hole: https://oshpark.com/shared_projects/JvQecioH
SMD: https://oshpark.com/shared_projects/tEsCK0wL

Just moved a couple traces and added a top ground plane for extra shielding. Holes for the pot and jack should be corrected. SMD version now has a through hole drain resistor because there's room and it's easier to find th resistors with better voltage ratings. I also rounded the corners of the board for style points.

I ordered the new smd version to test, I'm not going to try the TH version myself. They are probably fine, but probably wise to check my work if you want to order one.

Pot should be 10mm side adjust like: PT10LH01-105A2020-S, top adjust should be fine as well if your not into the through the jack thing but the square ones wont fit on top of the board.
input cap has a 7.5mm spacing, should be rated for your B+ voltage
output cap has a 10mm spacing
There is just enough room for a small (8mm dia) electrolytic to hang off the extra pads for decoupling, probably not necessary in most circumstances

This looks great Max!
Can you tell us which Surface mount LND150 to buy, I see a bunch with the same first numbers SOT-23 in Mouser
If you have a parts list for the surface mount components that would be great too!

Thanks again
Guy

[Guy77]

double post, apologies

[maxkracht]

Can you tell us which Surface mount LND150 to buy

I'm using LND150K1-G, but any sot-23 or to-92 should be fine. The angled D on the silk screen is for to-92 orientation. I did test one of those to make sure I got it right. TO-92 does have a better power dissipation, but these shouldn't be getting hot. Add a bit of solder in the to-92 pads if using a sot-23 to act as a bit of a heatsync.

[maxkracht]

Didn't see the bit asking for a parts list. I consider this a generic gain stage, so use whatever values you think are best, but here's what i'm using. OSH park sells boards in multiples of 3, so best to order enough for 3. It's $4.60 for 3 boards and parts are about $6 per board if you're going with my selections and not ordering in quantity. Some of the smd stuff makes sense to order more for the price break, and odds are you will drop one on the floor and never see it again.

these are mouser part numbers

LND150:

SMD 689-LND150K1-G

TH LND150N3-G-P013



1206 resistors:

660-SG73P2BTTD105J

660-SG73P2BTTD4702F

660-SG73P2BTTD3300F



through hole resistor: (PR01 series is 1w in a 1/4w package, that's what I would use if I were building the all through hole version, regular 1/4 w resistors are probably fine)

594-PR01000101003JA5



Zener 2x:

78-BZT52C12-E3-18



Trim:

531-PT10H-1M-S
(1M is for a new build replacing a tube, use something smaller if you are adding to an existing amp)



Jack:

550-12202 metal cap

550-10201 plastic cap



film caps:

667-ECW-FD2J104KB (input cap, optional local decoupling cap)

667-ECQ-E6103KF output cap



Mlcc bypass cap:
187-CL31B475KBHNFNE