Question about minimum input voltage using Voltage Regulator L7809?

[Rob Strand]

For the 33n + 10k network going from the output (pin 5) back to feedback point pin 1, it might be worth increasing the cap to 1uF perhaps even better 10uF.

The idea behind that circuit is to decrease the gain but with 33n it acts like a bass boost, possibly boosting the humm.    A cap larger value might help reduce the hum.

[Jasonmatthew911]

Yea, thanks I replaced with a 10uf and it got rid of a tiny bit more of the background hum...Actually, my 9V supply through the 7809 is super clean, no background noise at all, and the 18V just adds a tiny bit of on hum in the background, it's usable as it is now, and at 18V the 7809 doesn't really get very hot at all, maybe because I'm using an LM386N-4, not sure...Anyhow, to answer your other question, when volume is down all the way there's no noise at all...But if I remove that 5K resistor to GND at the input I get noise and crackling sounds when turning the Volume Pot, so I had to add it, with a 1K it's the cleanest and almost makes the 18V super clean like the 9V, but it just attenuates too much...I have it with a 2.2K now, I think I can compromise with the small amount of background hum at 18V with that resistor being 2.2K...Or do you recommend trying something else to get rid of that crackling sound on the Volume pot and extra noise if I don't use that input resistor to GND?...What about other value caps at the input and output of the 7809, would that do anything to maybe help reduce noise somewhere else?...

BTW, I've been testing this with a mini 555 synth I made...How would you compare the signal strength of a of a 555 square oscillators Vs a TL072 as a Pre-Amp?

[Jasonmatthew911]

For the 33n + 10k network going from the output (pin 5) back to feedback point pin 1, it might be worth increasing the cap to 1uF perhaps even better 10uF.

The idea behind that circuit is to decrease the gain but with 33n it acts like a bass boost, possibly boosting the humm.    A cap larger value might help reduce the hum.

Also, you mentioned about the 100K Pot not being enough for guitar...On one of my inputs I'm going to go into a Klon buffer which goes into a another TL072 as a Pre-amp...Would you recommend using a 500K Audio Pot for the Guitar Pre-Amp instead of a 100K Pot?

[Rob Strand]

Actually, my 9V supply through the 7809 is super clean, no background noise at all, and the 18V just adds a tiny bit of on hum in the background,

The hum can come from the power supply or the wiring.  If you are sure the PSU is clean then it's probably coming from the wiring.    Possibly from the wires between the LM386 and the pot and also the wires from the pot to the input jack.  Shield cable helps.

Anyhow, to answer your other question, when volume is down all the way there's no noise at all...

So that confirms it's probably not from the power rails but from the wiring.

and at 18V the 7809 doesn't really get very hot at all, maybe because I'm using an LM386N-4, not sure...

With any reasonable sized resistors in series with the headphone amp outputs the output current is quite low, so the DC supply current is low, and the power dissipation is low.

But if I remove that 5K resistor to GND at the input I get noise and crackling sounds when turning the Volume Pot, so I had to add it, with a 1K it's the cleanest and almost makes the 18V super clean like the 9V, but it just attenuates too much...I have it with a 2.2K now, I think I can compromise with the small amount of background hum at 18V with that resistor being 2.2K...Or do you recommend trying something else to get rid of that crackling sound on the Volume pot and extra noise if I don't use that input resistor to GND?...

Ah yes.   The LM386 has DC current flowing out of the input pins.   That causes a DC voltage (VDC = I * R) to form on the input.  As you adjust the pot the resistance varies and that causes the DC voltage to vary creating a crackle.    By using a low shunt resistor to ground (your 2k2 to 10k) it makes the DC voltage small because R is small and that makes the variation with the pots less because 2k2 (to 10k) is much lower than the 100k pot resistance.    A common problem.   The way that is solved is to put a cap between the pot wiper and the  LM386 input pin.    What that does is makes the DC value constant.     (Unless you get noise problems you can probably remove the 2k2 (to 10k) and even then you probably won't need more than 10k.     With the 2k2 (to 10k) removed you will need a cap around 1uF.  With 2k2 you will need 10uF.

Also, you mentioned about the 100K Pot not being enough for guitar...On one of my inputs I'm going to go into a Klon buffer which goes into a another TL072 as a Pre-amp...Would you recommend using a 500K Audio Pot for the Guitar Pre-Amp instead of a 100K Pot?

Normally you would need to add your own input buffer to the circuit and the volume control would be between the output of the added buffer and the input of the LM386.   Pretty much what you are doing now but the buffer is moved inside the headphone amp box.

BTW, I've been testing this with a mini 555 synth I made...How would you compare the signal strength of a of a 555 square oscillators Vs a TL072 as a Pre-Amp?

You mean the signal level?   The output of an NE555 is enormous compared to a guitar output level.   You would need to attenuate the NE555 output somewhat to equalize the levels.

[Jasonmatthew911]

The wiring may be the small hum issue, cuz I'm also not using shielded cables for the input and output right now, I will for the final design though...Also, you mentioned about adding a Cap from the Pot wiper to the input of 386 in order to get rid of the 2.2K-10K resistor that's attenuating at the input, but isn't my 10uf Capacitor already doing that?...

So, this is what I had planned for the guitar/Bass input...First into a Klon style buffer (TL072) going into another TL072 as a Pre-Amp, and a 100K Volume Pot is coming out of the TL072 PreAmp output, for some signal boost above unity gain I hope, this input will also have a CabSim circuit with 3PDT to turn on and off...Then my other input is just going through a TL072 as a PreAmp for a Synth or other line instruments with a 100K pot on the output of TL072 PreAmp, and both inputs mix into the same unbalanced PreAmp output, headphone amp and XLR DI Jensen transformer...So, are you saying that I should move my Volume Pot to the output of the buffer instead of the output of the TL072 Pre-Amp?...I actually did that in the past, and the Volume only worked as an attenuator if I put it after the Buffer and right before the PreAmp, I would have to max out Volume in order to get unity gain, so I figured I should have the Volume at the output of the PreAmp this time, cuz the Buffer doesn't boost the signal...Let me know your thoughts?...Thanks for all your help/advice.

[Rob Strand]

The wiring may be the small hum issue, cuz I'm also not using shielded cables for the input and output right now, I will for the final design though...

Probably asking for noise.

Also, you mentioned about adding a Cap from the Pot wiper to the input of 386 in order to get rid of the 2.2K-10K resistor that's attenuating at the input, but isn't my 10uf Capacitor already doing that?...

My apologies, you do have that cap.   I'm so used to not seeing the cap on LM386 circuit I've filtered it out.   That's very weird then.   
If I got crackle  I'd start thinking something was wrong, like the caps is leaking or around the wrong way or the circuit is oscillating.

The normal way you do attenuation is some like this (not necessarily with a 1k pot or a 100n cap),


You trim the input resistor (the 100K in this case) to set the attenuation.

In this circuit, the impedance at the input is increased due to the added 100k  input resistor but the impedance around the LM386 is kept low.   

The input impedance is relatively constant over adjustment range of the pot.  With the 2k2/10k shunt resistor the input impedances drops of 100k when the pot is set to a low volume and 2k2 when the pot is set to full.

So, this is what I had planned for the guitar/Bass input...First into a Klon style buffer (TL072) going into another TL072 as a Pre-Amp, and a 100K Volume Pot is coming out of the TL072 PreAmp output, for some signal boost above unity gain I hope, this input will also have a CabSim circuit with 3PDT to turn on and off...Then my other input is just going through a TL072 as a PreAmp for a Synth or other line instruments with a 100K pot on the output of TL072 PreAmp, and both inputs mix into the same unbalanced PreAmp output, headphone amp and XLR DI Jensen transformer...

That's fine.

So, are you saying that I should move my Volume Pot to the output of the buffer instead of the output of the TL072 Pre-Amp?...I actually did that in the past, and the Volume only worked as an attenuator if I put it after the Buffer and right before the PreAmp, I would have to max out Volume in order to get unity gain, so I figured I should have the Volume at the output of the PreAmp this time, cuz the Buffer doesn't boost the signal...Let me know your thoughts?...Thanks for all your help/advice.
Modify message

The right location depends whole picture.

For this simple case, the idea is to have a "guitar friendly" input and headphone amp, a good set-up would be,

     Guitar -->  Buffer --> volume control ---> Headphone amp

However if you are incorporating more circuitry into the same box then that will change what is best since the guitar no longer needs to connect to the headphone part along.  There's more circuit in-between and that circuit can provide the "guitar friendly" input.

So like this ?

    Guitar -->  Buffer --> Pre 1 --> Vol 1 100k  -->  Cab sim (+ in/out switch) --  \ 
                                                                                                                                      +-->  Mixer  -->   Headphone Amp
    Kbd    -----------------> Pre 2 -->  Vol 2 100k -------------------------------------------- /


That will work.

Depending on how the Pre 1 is designed you might not need a buffer.  It depends if the preamp can be designed with a high-impedance input.     

You need to limit the preamp gain since there's no way to dial the level back if the preamp clips.

If the mixer has a low impedance output it could drive a third Master volume control if you wanted that.  Also the low impedance output means there's not need for a buffer at the input of the headphone amp.

The 100k pot Vol 1 driving the input of the cab-sim might  need care/attention.  Some cab sims need to be driven by a low impedance output.  So driving it from a 100k pot will affect the cab-sim behaviour.   Other cab-sims have guitar friendly inputs already and they will work fine being driven from the 100k pot.

[Jasonmatthew911]

The wiring may be the small hum issue, cuz I'm also not using shielded cables for the input and output right now, I will for the final design though...

Probably asking for noise.

Also, you mentioned about adding a Cap from the Pot wiper to the input of 386 in order to get rid of the 2.2K-10K resistor that's attenuating at the input, but isn't my 10uf Capacitor already doing that?...

My apologies, you do have that cap.   I'm so used to not seeing the cap on LM386 circuit I've filtered it out.   That's very weird then.   
If I got crackle  I'd start thinking something was wrong, like the caps is leaking or around the wrong way or the circuit is oscillating.

The normal way you do attenuation is some like this (not necessarily with a 1k pot or a 100n cap),


You trim the input resistor (the 100K in this case) to set the attenuation.

In this circuit, the impedance at the input is increased due to the added 100k  input resistor but the impedance around the LM386 is kept low.   

The input impedance is relatively constant over adjustment range of the pot.  With the 2k2/10k shunt resistor the input impedances drops of 100k when the pot is set to a low volume and 2k2 when the pot is set to full.

So, this is what I had planned for the guitar/Bass input...First into a Klon style buffer (TL072) going into another TL072 as a Pre-Amp, and a 100K Volume Pot is coming out of the TL072 PreAmp output, for some signal boost above unity gain I hope, this input will also have a CabSim circuit with 3PDT to turn on and off...Then my other input is just going through a TL072 as a PreAmp for a Synth or other line instruments with a 100K pot on the output of TL072 PreAmp, and both inputs mix into the same unbalanced PreAmp output, headphone amp and XLR DI Jensen transformer...

That's fine.

So, are you saying that I should move my Volume Pot to the output of the buffer instead of the output of the TL072 Pre-Amp?...I actually did that in the past, and the Volume only worked as an attenuator if I put it after the Buffer and right before the PreAmp, I would have to max out Volume in order to get unity gain, so I figured I should have the Volume at the output of the PreAmp this time, cuz the Buffer doesn't boost the signal...Let me know your thoughts?...Thanks for all your help/advice.
Modify message

The right location depends whole picture.

For this simple case, the idea is to have a "guitar friendly" input and headphone amp, a good set-up would be,

     Guitar -->  Buffer --> volume control ---> Headphone amp

However if you are incorporating more circuitry into the same box then that will change what is best since the guitar no longer needs to connect to the headphone part along.  There's more circuit in-between and that circuit can provide the "guitar friendly" input.

So like this ?

    Guitar -->  Buffer --> Pre 1 --> Vol 1 100k  -->  Cab sim (+ in/out switch) --  \ 
                                                                                                                                      +-->  Mixer  -->   Headphone Amp
    Kbd    -----------------> Pre 2 -->  Vol 2 100k -------------------------------------------- /


That will work.

Depending on how the Pre 1 is designed you might not need a buffer.  It depends if the preamp can be designed with a high-impedance input.     

You need to limit the preamp gain since there's no way to dial the level back if the preamp clips.

If the mixer has a low impedance output it could drive a third Master volume control if you wanted that.  Also the low impedance output means there's not need for a buffer at the input of the headphone amp.

The 100k pot Vol 1 driving the input of the cab-sim might  need care/attention.  Some cab sims need to be driven by a low impedance output.  So driving it from a 100k pot will affect the cab-sim behaviour.   Other cab-sims have guitar friendly inputs already and they will work fine being driven from the 100k pot.

Ok, now that we're at it...I'm attaching my PreAmp circuit without the Power rail so you can let me know what you think (I haven't breadboarded this just yet cuz I have to order some TL072's, I can't find the ones I thought I had, I have made this Pre-Amp before, but now I made a few changes, and this PreAmp also has a lot more headroom at 18V...Let me know your thoughts on it, and that 100K resistor going from pin3 to pin7, if you think that extra Gain is necessary or not?...Also consider a simple klon style buffer going into my PreAmp1...For the CabSim, I'm going with the Simple Cab Sim due to it's simplicity and many people saying it sounds pretty good, plus I like circuits with J201's, especially at 18V...So with that you know more a less all the small circuits I want to put together in the same small enclosure...Let me know, that way I'll get it right from the get go...Cheers!

[Rob Strand]

Ok, now that we're at it...I'm attaching my PreAmp circuit without the Power rail so you can let me know what you think (I haven't breadboarded this just yet cuz I have to order some TL072's, I can't find the ones I thought I had, I have made this Pre-Amp before, but now I made a few changes, and this PreAmp also has a lot more headroom at 18V...Let me know your thoughts on it, and that 100K resistor going from pin3 to pin7, if you think that extra Gain is necessary or not?...Also consider a simple klon style buffer going into my PreAmp1...For the CabSim, I'm going with the Simple Cab Sim due to it's simplicity and many people saying it sounds pretty good, plus I like circuits with J201's, especially at 18V...So with that you know more a less all the small circuits I want to put together in the same small enclosure...Let me know, that way I'll get it right from the get go...Cheers!

The preamp doesn't look right.   I can't see how it will work as drawn.  Also it's unlikely to have any gain. 
You might need to dig-up the old circuit you built.

The inverting preamp + the extra 100k a the input will push the input impedance down to 50k ohm.   Pretty low for a guitar friendly input, which is typically 220k to 1MEG ohm.

The Simple Cab Sim has a guitar friendly input impedance so not problem there.

The mixing at the output with 10 ohms is far too low.   Maybe 10k?
   

[Jasonmatthew911]

That's the thing, I built one similar, except I had the Volume pot at the input just going into the .1uf cap and 100K resistor into pin 2, so here I added the 1K and 100K to GND on input, is that no good?...Also, I had pin 3 connected with pin 5 with a 100K resistor and 22uf Cap to GND, then with a 100K going to +V, I'm not even sure what that does...Lastly, at the output of pin 7 I just had the 2.2uf and 1M to GND because I was only sending to one output, I always figure for splitting the same signal that I have to add some BiPolar caps at least...My first build worked, but had no extra Gain, I had to use it with the Pot turned all the way up to get unity gain, since Pot was on the input it was just attenuating...Also, I added those 1uf/10 ohm resistors at the output because I thought they help to avoid mixed signals from feeding back into each other since I'm splitting the signals to 2 different places...Or would you say those aren't necessary?...Overall, why do you say it wouldn't work or wouldn't have any gain, what would you change right away?...So, maybe those 10 ohms are fine for a speaker/Phones out, but not to the output jack nor DI Transformer input?...You say those 10 ohms should be changed to 10K or just taken out completely?...

Can u help me make it right, so I can start with something better on the breadboard once I get my parts which I just ordered last night, so I can start breadboarding the rest of the circuits...Consider just the Klon Buffer going into the PreAmp for the guitar input...Maybe help me make the PreAmp appropriate for receiving the simple Klon Buffer, and so that the PreAmp gives me a little extra gain, so I can add a few decibels beyond unity...Also, would u do the 2nd PreAmp for synths differently, or can they be similar since the PreAmp1 is going through a Buffer first?...Thanks a lot for all your input, I really appreciate it.

[Jasonmatthew911]

Ok, now that we're at it...I'm attaching my PreAmp circuit without the Power rail so you can let me know what you think (I haven't breadboarded this just yet cuz I have to order some TL072's, I can't find the ones I thought I had, I have made this Pre-Amp before, but now I made a few changes, and this PreAmp also has a lot more headroom at 18V...Let me know your thoughts on it, and that 100K resistor going from pin3 to pin7, if you think that extra Gain is necessary or not?...Also consider a simple klon style buffer going into my PreAmp1...For the CabSim, I'm going with the Simple Cab Sim due to it's simplicity and many people saying it sounds pretty good, plus I like circuits with J201's, especially at 18V...So with that you know more a less all the small circuits I want to put together in the same small enclosure...Let me know, that way I'll get it right from the get go...Cheers!

The preamp doesn't look right.   I can't see how it will work as drawn.  Also it's unlikely to have any gain. 
You might need to dig-up the old circuit you built.

The inverting preamp + the extra 100k a the input will push the input impedance down to 50k ohm.   Pretty low for a guitar friendly input, which is typically 220k to 1MEG ohm.

The Simple Cab Sim has a guitar friendly input impedance so not problem there.

The mixing at the output with 10 ohms is far too low.   Maybe 10k?

Hey Rob, check this schematic and let me know if it makes more sense to you, this is a little more like the first time I made it with pins 3 & 5 connecting through a few components and going to +V...I guess this is the alternative if not using a Bipolar Power supply...Except in this one I'm putting the Volume at the output of Pin 1, will this give me a few extra db beyond unity gain or maybe not?...Let me know your thoughts on this and if you'd add or take anything out?

[Jasonmatthew911]

Here's another option for the PreAmp with pins 3 & 5 connecting to +V through a few components...I think I read that wired like this you can get 2x Gain up to +6 db, can I, or would it require slightly different values?...What do you think about controlling the Volume connected like this schematic between pin 6 & 7?...Let me know what you think of these last 2 schematics I posted when you get a chance, thanks...

[Rob Strand]

Here's another option for the PreAmp with pins 3 & 5 connecting to +V through a few components...I think I read that wired like this you can get 2x Gain up to +6 db, can I, or would it require slightly different values?.

Both your circuits will work but the input impedance on both of them is very and it will load the pickup.  The inverting first stage doesn't help.

Having all the gain at the first stage means it will clip.   OK for a distortion pedal but not for a clean signal.

I'd probably do a non-inverting stage with a small amount of gain, say 2 or 3, then if I wanted more gain I'd put a but more gain in the second stage.    The small amount of gain in the first stage means it won't clip, since you can't dial back the level to the first stage.   Once it hits the volume control you can decrease the level to set the *overall* gain and also prevent clipping on the second stage.

[Jasonmatthew911]

Here's another option for the PreAmp with pins 3 & 5 connecting to +V through a few components...I think I read that wired like this you can get 2x Gain up to +6 db, can I, or would it require slightly different values?.

Both your circuits will work but the input impedance on both of them is very and it will load the pickup.  The inverting first stage doesn't help.

Having all the gain at the first stage means it will clip.   OK for a distortion pedal but not for a clean signal.

I'd probably do a non-inverting stage with a small amount of gain, say 2 or 3, then if I wanted more gain I'd put a but more gain in the second stage.    The small amount of gain in the first stage means it won't clip, since you can't dial back the level to the first stage.   Once it hits the volume control you can decrease the level to set the *overall* gain and also prevent clipping on the second stage.

So basically, you say I should use the non-inverting inputs instead of the inverting?...I thought the inverting inputs gave less noise for some reason, at least that's what I think I've heard...Also, can you explain exactly how to set the lower 2 or 3 Gain in the first stage, and what I need to use to set slightly more for the 2nd stage?...Thanks again.

[Jasonmatthew911]

Also, what do I need to do at the input to set the proper impedance?...I'm really bad with impedance...Keep in mind that I was planning on going from a simple Klon style Buffer into this PreAmp...So far, I got these changes from you...Use non-inverting inputs, change gain for both stages, and change impedance at input...Let me know about how to set those Gains for less and slightly more in 2nd stage, and how to set my appropriate input impedance for a guitar/bass, I'm not exactly sure what to do...Thanks

[Jasonmatthew911]

One last Pre-Amp option (See schematic drawing), in case you think this is any better than the last 2...I still need your guidance for setting the gain in the 2 stages, as I'm not exactly sure how to set the desired Gains, also on the input impedance...What do I need at my input considering the simple klon Buffer and/or if I had no Buffer?

[Rob Strand]

One last Pre-Amp option (See schematic drawing), in case you think this is any better than the last 2...I still need your guidance for setting the gain in the 2 stages, as I'm not exactly sure how to set the desired Gains, also on the input impedance...What do I need at my input considering the simple klon Buffer and/or if I had no Buffer?

That last circuit is looking better.

The input impedance is high so very little to nothing is achieved by adding another buffer.  The input part of the circuit is in fact quite similar to the klon buffer.

The gain is set by the ratio of the 47k and the 1k;  gain = 1 + 47k / 1k.    So both of your stages have gain 48.   For the first stage a gain of 48 is too high you need to drop it down to 2 or 3.   If you use it for bass maybe 2 is better for a 9V supply.

You don't need the 100k on pin 5 of the second stage, maybe drop the value to 1k.

For the first stage you can add a 10MEG (to stop pops when you plug in) and a 1K (to stop RF) as shown in this thread,

https://www.diystompboxes.com/smfforum/index.php?topic=125355.0


The first parts of the preamp in this thread are close to yours.    The second stage + volume like yours and the second stage like the one in the thread are a matter of taste.    Small difference in practice so you can go either way.

[Jasonmatthew911]

One last Pre-Amp option (See schematic drawing), in case you think this is any better than the last 2...I still need your guidance for setting the gain in the 2 stages, as I'm not exactly sure how to set the desired Gains, also on the input impedance...What do I need at my input considering the simple klon Buffer and/or if I had no Buffer?

That last circuit is looking better.

The input impedance is high so very little to nothing is achieved by adding another buffer.  The input part of the circuit is in fact quite similar to the klon buffer.

The gain is set by the ratio of the 47k and the 1k;  gain = 1 + 47k / 1k.    So both of your stages have gain 48.   For the first stage a gain of 48 is too high you need to drop it down to 2 or 3.   If you use it for bass maybe 2 is better for a 9V supply.

You don't need the 100k on pin 5 of the second stage, maybe drop the value to 1k.

For the first stage you can add a 10MEG (to stop pops when you plug in) and a 1K (to stop RF) as shown in this thread,

https://www.diystompboxes.com/smfforum/index.php?topic=125355.0


The first parts of the preamp in this thread are close to yours.    The second stage + volume like yours and the second stage like the one in the thread are a matter of taste.    Small difference in practice so you can go either way.

Cool, very helpful thanks!...So I'll add in the 10M and 1K at input, replace that 100K going into pin 5 with a 1K or maybe take it out...For the first Gain stage I can do (2) 100K Resistors from Pin 2 to 1 and that means I'll have 1 + 100K/100K = 2....What do you thing the gain on my 2nd stage should be not to saturate, but to maybe give a clean boost of +3 or +6 db...Maybe a 100K and 10K, that would give me a Gain of 11, is that good to start, too little or too much?...I can also experiment now that I know the formula.

So doing this PreAmp, there's no need for the extra Klon Buffer, correct?...You're right they are very similar at the input now...I think with this I have a simple solid PreAmp to start breadboarding once I get my parts...

Lastly, what would you do differently for the Synth Pre-Amp, like at the input for the proper impedance with a Synth and other Line instruments?...Just let me know recommended values and placements for Synth PreAmp input and I'll be good to start breadboarding everything, thanks again...Cheers!

[Rob Strand]

For the first Gain stage I can do (2) 100K Resistors from Pin 2 to 1 and that means I'll have 1 + 100K/100K = 2....

That will work.   To keep noise down it's normally a good idea to keep the resistors below say 10k.   At worst you would make the smaller resistor 10k or less, at best make the largest resistor 10k or less,    Very rough guide.

What do you thing the gain on my 2nd stage should be not to saturate, but to maybe give a clean boost of +3 or +6 db...Maybe a 100K and 10K, that would give me a Gain of 11, is that good to start, too little or too much?...I can also experiment now that I know the formula.

It won't saturate because you can dial the gain back  with volume pot.   Too much gain make can promote noise problems and it's hard to adjust depending whether you use linear or log pot tapers.    A gain of 5  to 10 OK.     The inverting stage has a slight advantage for higher gains in that it can lower noise.   

So doing this PreAmp, there's no need for the extra Klon Buffer, correct?...You're right they are very similar at the input now...I think with this I have a simple solid PreAmp to start breadboarding once I get my parts...

Correct, there's no point really.

Lastly, what would you do differently for the Synth Pre-Amp, like at the input for the proper impedance with a Synth and other Line instruments?...Just let me know recommended values and placements for Synth PreAmp input and I'll be good to start breadboarding everything, thanks again...Cheers!

I don't think a synth preamp would need as much gain.  I would just use a "guitar friendly" input impedance.   There's no real advantage to deliberately making it a lower impedance.

[Jasonmatthew911]

For the first Gain stage I can do (2) 100K Resistors from Pin 2 to 1 and that means I'll have 1 + 100K/100K = 2....

That will work.   To keep noise down it's normally a good idea to keep the resistors below say 10k.   At worst you would make the smaller resistor 10k or less, at best make the largest resistor 10k or less,    Very rough guide.

What do you thing the gain on my 2nd stage should be not to saturate, but to maybe give a clean boost of +3 or +6 db...Maybe a 100K and 10K, that would give me a Gain of 11, is that good to start, too little or too much?...I can also experiment now that I know the formula.

It won't saturate because you can dial the gain back  with volume pot.   Too much gain make can promote noise problems and it's hard to adjust depending whether you use linear or log pot tapers.    A gain of 5  to 10 OK.     The inverting stage has a slight advantage for higher gains in that it can lower noise.   

So doing this PreAmp, there's no need for the extra Klon Buffer, correct?...You're right they are very similar at the input now...I think with this I have a simple solid PreAmp to start breadboarding once I get my parts...

Correct, there's not point really.

Lastly, what would you do differently for the Synth Pre-Amp, like at the input for the proper impedance with a Synth and other Line instruments?...Just let me know recommended values and placements for Synth PreAmp input and I'll be good to start breadboarding everything, thanks again...Cheers!

I don't think a synth preamp would need as much gain.  I would just use a "guitar friendly" input impedance.   There's no real advantage to deliberately making it a lower impedance.

Thanks!...So, for the 2nd stage, do you think it's a better idea for the Volume wiper to go into the inverting input (Pin 6 instead of Pin 5) in order to have lower noise with higher gains, and then I just switch the 2 Gain resistors/Cap going from pin 5 to pin 7 instead?

[Rob Strand]

Thanks!...So, for the 2nd stage, do you think it's a better idea for the Volume wiper to go into the inverting input (Pin 6 instead of Pin 5) in order to have lower noise with higher gains, and then I just switch the 2 Gain resistors/Cap going from pin 5 to pin 7 instead?

It's not less noise *at* higher gains.  It's less noise if the circuit has the capability to be set for higher gain but the gain is actually set to a low level.  Confusing  I know.   In the non-inverting case the second stage has to be set for the maximum gain and you adjust the signal going into it to be lower to get lower gains.    The high gain of the non-inverting second stage will boost it's own noise by that gain factor.  In the case of the second stage being inverting the volume control adjusts the gain itself so it's not boosting its own noise as much.

When the second stage has low gain the it's the non-inverting stage which often ends up with lower noise.

It's one of those devil in the details things.   So it's a matter of picking the right circuit for job.

For the non-inverting case you can also reduce a bit of noise using a 10k volume pot instead of the 100k pot.