Bean LA2A optical limiter

mybud

mybud

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I breadboarded this last September, according to my notes, but couldn't get it to work at the time. I built it from @bean's original 2016 schematic.

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Futzed about with it yesterday and found it functional but squealing to beat the band. At least the level pot seemed to work but obviously unuseable as it stood. Last night I double-checked the components and found a 6k8 sneakily masquerading as a 68k MFR.

Corrected this and resumed double-checking this morning to find an off-by-one error which effectively disconnected one end of the vactrol (NSL-32 in this case) from opamp 1 (LF353 as called for). Fixed that. Finally, the output stage revealed that I'd inadvertently connected the 1uF output cap to the bias voltage. Backtracking with an audio probe revealed this particular problem. Replaced the output cap and voilà, it works.

IMG_4423.jpeg

My only standard of comparison is UA's plugin and it sounds more or less comparable. The analogue version I built adds a nice sheen to the sound and the limiting is evident (gain reduces as the pot's advanced, which one might expect). It has plenty of makeup gain available and does nice things to both guitar and bass.

Haven't decided whether or not to make a standalone or combo version (with some neutral-ish preamp, perhaps) or exactly the best spot for it in my signal chain, hence not housed yet. But I'm glad to have put last year's failed attempt to rest and to have a functional and very nice-sounding limiter at hand.

Thanks for reading as ever and wish you every success with your projects.
 
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Here's the finished article gutshot of the abovementioned.

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Since it's based on the Teletronix levelling amplifier, it's called the leveller, as you see. That's also a veiled reference to the poem 'Death the leveller' (James Shirley 1596-1666), one of my favourites from undergraduate English studies.

Perhaps I'm reading too much into it, but here's the first stanza anyway:

'The glories of our blood and state
Are shadows, not substantial things;
There is no armour against Fate;
Death lays his icy hand on kings:
Sceptre and Crown
Must tumble down,
And in the dust be equal made
With the poor crookèd scythe and spade.'

Appropriate for our times? You be the judge.
 
bluedmc777 said:
I wish there was a pcb available for this.
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I had a look at the site and it seems like Brian no longer carries that model. If you’re not averse to starting on breadboard and then either moving to a permanent version or Veroboard, it’s doable by all means. That’s the route I went, as you see, and if I can do it, I figure anyone else can.
 
bluedmc777 said:
I wish there was a pcb available for this.
Click to expand...
Haven't seen any PCBs yet.
I've only ever seen self-etch stuff for it, from the Bean himself, and from Bajaman. Also IVIark's Alex's vero layout...

The Demeter Compulator is very similar, available by way of PedalPCB's Constrictor PCB in the store, but alas it is not similar enough to build the Holy Roller on the Constrictor PCB.


mybud, I may have to follow suit and build this on a permanent-breadboard PCB — diggin' your "Leveller" build.
 
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Thanks, Feral. Honestly don’t know why the previous build was such a struggle: operator error, evidently. Perhaps my troubleshooting has improved (not very likely), perhaps I got lucky (more likely). But I’ve been doing a lot of +-12V breadboards of late, which are more complex beasts to fix so maybe this has improved the troubleshooting. Nah, forget it, I got lucky 🍀
 
Feral Feline said:
Haven't seen any PCBs yet.
I've only ever seen self-etch stuff for it, from the Bean himself, and from Bajaman. Also IVIark's vero layout...

The Demeter Compulator is very similar, available by way of PedalPCB's Constrictor PCB in the store, but alas it is not similar enough to build the Holy Roller on the Constrictor PCB.


mybud, I may have to follow suit and build this on a permanent-breadboard PCB — diggin' your "Leveller" build.
Click to expand...
Aaah I didn’t know this was Bajamans LA2A style comp. I’ve thought about posting that in the project wish list thread. That one has been on my radar for the longest. Hey if we are lucky @vigilante398 will release one of his compressor designs to the masses some day. Not that I wish him any bad fortunes!

@Feral Feline Have you had a chance to check out the Hagerman 12AU7 compressor? https://www.hagamps.com/collections/pedals/products/12au7-compressor-tube-pedal

Or the deadendfx Stretta based off the Ciognanni Sexy Comp 76? https://www.deadendfx.com/product/stretta

Unfortunately I just don’t have the time to learn how to breadboard. It’s hard enough juggling work, kids, guitar time AND just building using pcbs into the schedule.
 
bluedmc777 said:
Aaah I didn’t know this was Bajamans LA2A style comp. I’ve thought about posting that in the project wish list thread. That one has been on my radar for the longest. Hey if we are lucky @vigilante398 will release one of his compressor designs to the masses some day. Not that I wish him any bad fortunes!

@Feral Feline Have you had a chance to check out the Hagerman 12AU7 compressor? https://www.hagamps.com/collections/pedals/products/12au7-compressor-tube-pedal

Or the deadendfx Stretta based off the Ciognanni Sexy Comp 76? https://www.deadendfx.com/product/stretta

Unfortunately I just don’t have the time to learn how to breadboard. It’s hard enough HOARDING TUBES.
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There, I fixed it for you...
 
bean said:
I think I designed one to fit in my Standard Series of 1590B projects. I'll check. There's a bunch of those I still haven't released.

Update: yeah I have one. It's the revised design from Bajaman that includes a tone control but all the same circuitry is still there.
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ald8jn.jpg

I miss football
 
bean said:
I think I designed one to fit in my Standard Series of 1590B projects. I'll check. There's a bunch of those I still haven't released.

Update: yeah I have one. It's the revised design from Bajaman that includes a tone control but all the same circuitry is still there.
Click to expand...

NNNNNOWWWWW you tell me... I just wrapped up a perf layout for the Holy Roller — I coulda/shoulda waited for a V8*!




*V8 = MBP Holy Roller PCB, with TONE!
 
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