LAKLAND LH-3 ONBOARD BSS PREAMP

Pickups, wiring schemes, switch techniques and onboard active electronics for guitars

LAKLAND LH-3 ONBOARD BSS PREAMP

Postby chicago_mike » 09 Mar 2012, 05:56

OFFER #2

LAKLAND LH-3 BASS PREAMP
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Re: LAKLAND LH-3 ONBOARD BSS PREAMP

Postby chicago_mike » 09 Mar 2012, 05:57

More
005.jpg
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Re: LAKLAND LH-3 ONBOARD BSS PREAMP

Postby chicago_mike » 09 Mar 2012, 05:59

:popcorn:
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Re: LAKLAND LH-3 ONBOARD BSS PREAMP

Postby chicago_mike » 09 Mar 2012, 06:07

These are the last photos I did.

I still have this pcb as its one of the best sounding eq/preamps for bass. Active OR passive pickups.

I also have the wiring as a pdf. Very clear and well laid out.

All we need is a schematic, so thats up for grabs. If I had better skills, I would have done this.

Everything except the values of the caps are pretty clear. Pots are 50KB.

40Hz bass
6Khz Treble
Selectable Mids 200-1100 hz with the DIP switch all positions select a different freq.

The trim pot...this provide TONS of clean gain. This makes this preamp so much louder than Bartolini and Aguilar and others. It has serious volume output.


I WILL BE ADDING THE OLD KEN SMITH ELECTRONICS SOON. NOT THE MODERN STUFF, BUT THE OLD EQ FROM THE 80'S THAT HAS THE BUILT IN MUTRON AND OUTBOARD POWER SUPPLY.
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Re: LAKLAND LH-3 ONBOARD BSS PREAMP

Postby george giblet » 15 Oct 2017, 08:05

I've been cleaning up a few things. Here's my trace. It's been on my "to do" list for a while.

Keep in mind the cap values are not known. I've added some values as examples but do not assume they are in anyway the real values.

It is possible to measure some cap values with any disassembly. C4, C4A, C4B, C4C could be measured by setting the dip switched to all off and just measuring the caps in circuit. (Measure on the PCB not the part and don't push too hard!).

Capacitor C11 (Treble Wiper) could be measured by desoldering the treble wiper wire then measure the part in situ. (Don't pull it from the PCB it is too easy to damage the PCB)

C5 Bass and C10 Mids can only be measured by removing them from the ckt - unless you have access to an LCR bridge which can measure in circuit. It is possible to back engineer C10 from the C4 etc. values and the frequencies. Another way to work out C5 is to use an oscillator and measure the gain (=input/output) at a few frequencies with mid & treble centered and the bass at full, centered, and minimum.

The circuit has a stack of inductors and small caps. Keep you mojo in your duds, they don't serve any audio function. They will be small values like <1uH and < 33pF. They are there to stop pips and stuff from mobile phones getting into the audio. If you want build one you can remove these. Maybe replace L1 with a 1k resistor.
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Re: LAKLAND LH-3 ONBOARD BSS PREAMP

Postby george giblet » 17 Oct 2017, 08:58

V1.0 to V1.1 update.

I might be able to add a bit more info.

In ChicagoMike's post on he states,

40Hz bass
6Khz Treble

however, he doesn't give a +/- dB spec.

I don't know where those specs originate from, but, if we assume ,
1) Bass/treble spec +/-15dB (a reasonable assumption)
2) Set the mid frequency to the default 600Hz
3) Use the C10=33n, C4A=27n version of my mid cap options for 600Hz

when we choose,
- Bass cap C2 = 68n, and
- Treble cap C11 = 8n2

Then surprisingly we get ChicagoMike's specs!

Bass: +15dB at 43Hz
Treble : +15dB at 6kHz

With C11 = 8n2 the mid-caps need a little tweak
to get the correct frequency centres,

275Hz: C4 = 120n (19.8dB @ 276Hz)
600Hz: C4A = 27n (12.9dB @ 583Hz)
900Hz: C4B = 12n (8.7dB @ 893Hz)
1100Hz: C4C = 8n2 (6.9dB @ 1.1kHz)


Maybe solved?
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