Messages

Just put a voltage follower/buffer in front. Output is fine as is.

TFZ, thanks, i kept digging after i posted, found the PQ1549 as a project here http://www.gyraf.dk/gy_pd/calreq/calrec.htm, they added a balanced input (and output) so i figured it a vf/buffer would do it, its just... sometimes "it cant be that simple" kicks in = lack of knowlegde. Ive gotten to a point where i obviously cant keep on paint by numbers.
Thanks.

Hello, however overkill it might seem to some, im considering building a Calrec pq1549 in pedal format.
I can read the schematic, draw the pcb, build it etc. but im lacking in the theory/actual circuit knowlegde department, can/will someone direct/help me figure out how to tailor a correct/functional impedance input/output for guitar. Thanks, i hope.

Rockhorst thanks. Actually my wallet says go buy a GR and a parallel mixer, my creativity/energy is torn between practice/instrument time over learning basic circuit stuff. Ill proceed.

...sparkling Rhino? Hi guys, instead of just routing a Green Rhino thru a regular clean blend unit etc. - would it make sense in anyway to combine in with the "clean" section of Sparkle drive? I understand a little circuit wise, but not enough yet so before i start breadboarding i wanted to ask and perhaps/hopefully get some pointers towards how to get it done in a proper way. See attached, thanks in advance.

Thanks everyone! Ive recognise most everything in basic pedals on schematics etc. but decided its time to learn what it is they actually do.

Thanks both of you.
Jon, ill check out that book, also the sengpiel link will turn out very usefull. By langauge barrier (dane here), english is fine, i merely mean that asking online about very specific subjects is quite different from how one could go about it if some grumpy old radio or amp tech lived just down the road, i drop by with cake and ask him, draw on napkins, smell coffee and listen to vinyl on his tube amplifier...

Yes, now i see, a highpass filter, input cap and resistor, 47n and 470k, cut off (ca. 7hz) way below our low E at ca. 80hz, that makes me think i could use 100k and still be fine but one thing is filtering, another is the impedance, a pulldown R before the coupling cap also effects the impedance to some degree etc. and then add the output impedance, suddenly the often significantly lower values in the 2nd part of dual IC´s makes a little sense, well, i know exactly what to read up on now, im glad i asked.
Thanks again.

Oh you answered while i was typing, i get it but how do i know what DC voltage is needed, hahahahah i think that is what i should have asked in a single line, thanks again.

To answer the original op amp question in a different way: 
The input cap blocks whatever DC voltage the signal is riding on, but the op amp inputs need to have some sort of path available through which they can draw a DC bias current (else some of the transistors can't work their magic).  This DC current path for the non-inverting input is provided by that resistor going to Vb. 

(In hindsight, I actually like Jon's answer a bit better...)

EBK thanks! Yes, i understand (i think i do) but not fully, how do i figure out the resistor value for the DC path between input and Vb and... is this value constant for a dual supply except for +/- that path/resistor goes to ground?
Im sorry if i keep repeating myself, i really would like to understand it.

Jon, thanks a lot for a very fullfilling answer, actually i already know most what you mention (or know the relative subjects and where to dig in), i see likely its just a matter of more hands on experience/breadboarding, i think sometimes if its simple i cant believe its so simple, doubt strikes me and i freeze.

Just so you know what got me here, on one breadboard is a optical comp (single supply), on another a variable active sallen key highpass powered a dual supply, now, tweaking components to change frequenzy response, clipping or gain is one thing but i came to a halt when i decided to perhaps combine theese.
If there is even a tiny audible difference running the comp or xx circuit on dual sup or vice versa im fine as i care more about my ears than cost, but if theres no perceivable difference saving space on a board is nice too.

For reference to get an idea with  the power supply i compared PC´s timmy with GCFX Catch 22, 470K to Vb/510K to ground etc.
Dividing the voltage to get 4.5V, virtual ground -  check, but either way what how do i interpret the resistor between Vb (or ground for +/-) and input signal, what does it do?
English is not my native langauge so im trying hard to make sense with this question, thanks again.

Hi, after 2 years of self taught learning to read schems, draw pcb´s, draw graphics/drill temps, mod, etch boards and enclosures and build the actual pedals etc. etc i realised i both have to and need to learn the math to progress. I know theres plenty electronics info online but i hope someone can point me towards some effect/pedal orientated reading learning.
Fx. single vs dual supply - signal to non inverting IC input, i understand the input bias on single sup is often halfway (4.5 from a divider) between Vc and ground, but then between Vb/4.5V  and signal to input theres is further a resistor (470K - 1M on alot of pedals) -
so input pulldown, coupling cap and then fx 470K from Vb to +input.
Id love to try out whether to run things single or dual supply and be able to breadboard whatever i feel like, how do i get my head around this stuff.
I hope my questions makes sense, in advance thanks a lot.

Hi guys, new member and first time poster. Im considering building this little box for practice. Attached file should explain the idea neatly, cab sim permanently into mix ch1, ch2 mono in (for my metronome headphone out), ch3+4 combined with a dual gang pot for stereo signal like ipad or phone and then mixer out into the headphone amp.  Though id best ask for advice before i go all yihaa, is it doable or are there any obvious no no´s. Thanks in advance.