Zany Laney mania - good link

[puretube]

free information sucks...

:?:

[gez]

Please notice the use of two PR1 IC's labeled IC2 and IC4 respectively, where one CD4069 would have sufficed for the job since a total of 4 inverters are used.  Power dissipation perhaps? (remember both IC's are operated in the linear region, i.e. more dissipation, instead of the usual cut-off operation)

Yeah, interesting.  I don't think power dissipation is the reason though.  I run this type of circuit from a 5V regulator and current consumption reduces dramatically at this voltage (check the data sheets, it's also mentioned in Art of Electronics).  Even with all 6 inverters blazing total current draw isn't that much.

Possibly, with one chip, there was some bleed through between channels if two instruments were plugged in (this is how I used this amp, alongside another guitarist), hence the separate chips?  

Wouldn't surprise me, I had this problem when I tried to use one half of a chip as an envelope follower (deliberately set up to distort) and the other half as a filter.

Also, one of the biasing pots (on the upper channel) is connected to +15V, where the lower channel biasing pot is connected to +5V.   Components on both channels are identical, and so are biasing voltages--3.35V.  Perhaps this was a drawing error or another attempt to make cloning harder, like naming the CD4069 as PR1 Laney instead

Could be a mistake, or could simply be for layout reasons...

And last, but not least, notice there are no high-frequency reduction capacitors across the inverters (usually in the 47-100pF range).  Moreover, the first inverter stage has a 2x47k resistor + 4n7 capacitor network that effectively increases high frequency content instead! Quite the opposite to the Double D or the Red Llama circuits...

Output resistance increases at lower supply voltages and interacts more noticeably with the gate capacitance of the next stage (forms an RC lowpass, in effect).  However, with a 5V supply treble cut isn't that much (though it's more noticeable if supply voltage is taken lower than this)!  I think the reason there aren't any hi-frequency reduction caps is to compensate for the filter network which follows - as Ton noted, it's set up to be supplied from a low impedance source (which inverters aren't!) so there's probably some high-end sucking going on in there.

[puretube]

... lot of experimentations, to get there...

[stm]

This is reverse engineering at its best  

[gez]

Wouldn't take much to do a stompbox with the preamp section.  The tone network would be a nice little addition to a CMOS fuzz.  Just feed the 'Master B' output to an op-amp buffer via a cap (use a dual, other half used for the input buffer).  

Running the whole shebang from a 9V supply wouldn't be detrimental to the tone as the inverters are run off 5V.  Could even use a 5V fixed regulator (low power one for battery friendly use) instead of the zener (might be quieter doing this).

[gez]

Also, one of the biasing pots (on the upper channel) is connected to +15V, where the lower channel biasing pot is connected to +5V.   Components on both channels are identical, and so are biasing voltages--3.35V.  Perhaps this was a drawing error or another attempt to make cloning harder, like naming the CD4069 as PR1 Laney instead

Could be a mistake, or could simply be for layout reasons...

Having had another look at the schematic, that must be a mistake for channel A.  With the resistor values given the gate would be pulled up higher than the Vdd pin if that chain were connected to 15V and that stage wouldn't bias up properly.

[StephenGiles]

Mark, the current guitarist in Steeleye Span, Ken Nichol uses a small Laney amp, he also used it previously in the Albion Band for several years. It always gave a good sound to my ears - I've no idea which model though. If Steeleye come your way on the North American leg of their current world tour, try to see them, Maddy Prior is in good voice again.
Stephen