Tracing and modifying a Langtronics Bone Collector

[duck_arse]

it shouldn't crakle. if it was misbiased/less than optimal biased, it might clip half the signal. any chance you've wronged one of the 10M resistors? please post your voltages - supply, drain and source. the gate voltage will be weighed down by the meter against the high-value resistors, so is less meaningful. photos of build?

a resistance of 5k is a resistance of 5k. doesn't matter if it's a 10W wire wound resistor or a W taper pot, it will still work as 5k of resistance. a B taper will be seem to be at max gain for half its rotation when used as in the sho, whereas the C taper feels best to most.

[edit :] I'm think I've confused my tapers - the B would come on sudden at full rotation used in a sho, like an A taper used where a B was best suited.

and - you can fake a C taper if you can live without the lowest gain settings. for a C5k, you could sub a B1k with a 3k9 from CCW to ground, and the bypass cap to the wiper and ground.

[anotherjim]

I think a reversed/bad electro cap in the signal path can crackle like that. There is only the one -  10uF output - in that circuit.
I don't believe value substitutions could cause it.
Live sewage might 

[moid]

Thanks chaps, after a lot of testing it seems the little circuit only crackles weirdly when attached to my very crappy test amplifier, but doesn't do anything weird when attached to my bass amp or my PC... so I should've tested it elsewhere before asking, sorry for wasting your time. The circuit doesn't create a clean boost like I thought - from looking at the waveform recordings I've made it's clearly very asymmetrical so that adds distortion when I play chords / anything too loud. I then ran 18v into it instead of 9v and the volume got louder (good) and also slightly less distorted (also good), but still too distorted for a clean boost. I then tried a Mr Black Tiger Boost at 18v and it does indeed get louder and stays clean, so I'll be going with that circuit I think. I may try swapping the JRC4558 out for an OPA2134, I'd read on the gearslutz forum (I think) that this opamp should be cleaner and possibly louder, which is what I'm aiming for. It happily has the same pinout as the 4558 so I'll socket them and do some testing once the parts arrive.

Thanks for your advice - I'm going to get the correct parts for the SHO and even though I'm not going to use it for this purpose, my son was playing with it and fed an old Shin Ei FY2 I built when I first started making pedals into the SHO and loved the immense blast of sound the SHO got from it and said "Daddy I need these two pedals in one box with two switches, how fast can you make one?"... no pressure of course

Luckily the rain wasn't as heavy as forecast - some thunder and lightning but nothing torrential... so far my DIY water routing skills seem to be working. And I saved £400 on not calling out Dynorod to dredge the sewer (there are tree roots growing in it; I hacked them out, pretty smelly job but £400 is £400... and I needed to buy new glasses this month so that's where the money's going!). My advice to anyone who wants to buy a house with an extension built over a sewer is don't buy the bloody house... the sewer needs rebuilding (it's old and busted up) but to do so would require the water company to knock down half my house to get at it... the extension was put up at some point in the early 1980s with no planning permission (understandable; it wouldn't have got permission if they'd asked for it) and was fine at the time, but now the pipes underground are 60 years old they need fixing and there's a limit to what anyone can do without digging them up.

[PRR]

OT:

> new glasses this month so that's where the money's going!

zennioptical.com - two pair single-vision, shipped, for $19 -- I'm seriously happy. Frames (metal aviators) are good, http://static.zennioptical.com/images/product/41/90/419014_lg.jpg , strength (focus and astigmatism) is correct, no hassle, delivery just over a week. I do not know if off-shore prescription glasses are legal in your country.

The single-vision may sell at a loss. Bifocals cost very significantly more. I thought I would go that way, but instead use pound-shop (Dollar Tree) readers for close-in.

EDIT-- digging, I find I can get with-a-line bifocals for $24 (+$5/order shipping). This is low-index which is fine for my mild prescription. They still push high-index, tints, etc, so I can spend $58 even before they offer coatings, clip-ons, engraving... I can touch $80. Which is still 1/5th what a lesser package would cost downtown. And I am suspecting that all eyeglasses come from the few asian shops. The business is highly consolidated.

[moid]

Thanks very much PRR, that site is indeed seriously cheap! Sadly they don't cater for the special prisms I have to have in one lens to reduce double vision and to cut down on the colourful halos I see around bright objects (one of my eyes is really @#$%ed, but slightly trippy - if I ever get bored, I close the good eye and stare at bright things and watch them become psychedelic!) and although my glasses are very expensive, I'd still like to get them from the local store who I've known for years (they aren't a chain) and who have helped me immensely in the past with spotting problems and getting me referred to the right consultants for help. We just lost the only decent guitar shop for miles (closed down because people buy their guitars online now, a real shame, the two guys who ran it had been doing so for about 30 years and were amazing) and I definitely believe in supporting local businesses if I can versus corporate mass chains. I do appreciate you taking the time to help me though, thanks very much. I can see this being a good price to people with more 'normal' vision issues. I hadn't heard that some countries have a ban on off shore prescription glasses; I don't think the UK has, but then again I've never asked! That's pretty harsh.

[PRR]

OK, yes, prism is uncommon, not a standard product, not easy to know when the lens-grinder gets it wrong. I can certainly see getting that need handled locally.

I was somewhat nearsighted, then lost accommodation, so was on mild bifocals to see far and near. Cataracts spoiled that so now my eyes are brownie-cameras- fixed focus at a distance, and not exactly. I can drive without glasses (first time in my life), but part-Diopter corrections make distance better. And the same on a +1.5D base is excellent for the PC.