Need help with guitar buffer circuit...

You folks who know electronics, please advise me! I am wanting to design some buffer circuitry for a homebrew fancy guitar selector gadget. I know that op-amps will give me more flexibility in circuit design over JFETs, but some people have observed that op-amp buffers sound "colder and more sterile".

Do you have any opinions? Would a JFET circuit really preserve the guitar's tone better? If there is a difference that could be noticed, I think I'd be willing to do the more involved JFET design, though I'll need to know how to boost the gain (I'll want to boost the signal be a few db), which of course op-amps can do more easily.

Also, seems to me a JFET circuit might consume less power than using op-amps -- Agree? Disagree?

I know this is a rather ethereal question, but if any of you know about this, please advise.

/Mark

ps for those wondering, I am designing a DIY guitar selector switch to the following requirements:

- 3 guitars selected and routed into one amp or effects pedal (e.g. a deluxe ABC switch)
- Option of selecting guitars in OR or AND mode (e.g. exclusive or combined)
- anti-pop solid state switching, audio path will not directly use the mechanical footswitches
- built-in buffering for all 3 guitar inputs with gain controls (3 volume knobs, one per guitar), very hi input impedance for guitars, low impedence output to drive pedal or amp
- the amount of buffer gain is not yet decided, somewhere between 3 and 12 db
- LEDs, one per guitar
- Powered by either 9v battery or ext power, so power consumption is an issue

jeghers said:

You folks who know electronics, please advise me! I am wanting to design some buffer circuitry for a homebrew fancy guitar selector gadget. I know that op-amps will give me more flexibility in circuit design over JFETs, but some people have observed that op-amp buffers sound "colder and more sterile".

Click to expand...

They sound accurately like the guitar!

Do you have any opinions? Would a JFET circuit really preserve the guitar's tone better?

Click to expand...

No, opamps do that better - crude JFET circuits (like valves) affect the guitars sound, but some people prefer this altered sound.

If there is a difference that could be noticed, I think I'd be willing to do the more involved JFET design, though I'll need to know how to boost the gain (I'll want to boost the signal be a few db), which of course op-amps can do more easily.

Also, seems to me a JFET circuit might consume less power than using op-amps -- Agree? Disagree?

Click to expand...

Depends on the design.

I know this is a rather ethereal question, but if any of you know about this, please advise.

/Mark

ps for those wondering, I am designing a DIY guitar selector switch to the following requirements:

- 3 guitars selected and routed into one amp or effects pedal (e.g. a deluxe ABC switch)
- Option of selecting guitars in OR or AND mode (e.g. exclusive or combined)
- anti-pop solid state switching, audio path will not directly use the mechanical footswitches
- built-in buffering for all 3 guitar inputs with gain controls (3 volume knobs, one per guitar), very hi input impedance for guitars, low impedence output to drive pedal or amp
- the amount of buffer gain is not yet decided, somewhere between 3 and 12 db
- LEDs, one per guitar
- Powered by either 9v battery or ext power, so power consumption is an issue

Click to expand...

I suspect either will make very little difference - you could always use a single JFET as an input buffer, then opamps to provide the gain.

You might have a look at this for some ideas?

**broken link removed**

My goal is that I do not want to color the guitar sound. I am designing a switching device (to select multiple guitars) that includes gain control (with the ability to boost a few db). Later devices will color the sound, so I want this device to ONLY select which guitar without changing the tone. The point of the buffering is A) to present a high input impedance to the guitars so their passive pickup/tone circuits are not loaded down and colored in any way and B) low output impedance to drive the amp/pedal that it feeds into really well.

As you don't want to colour the sound then use opamps, the TL0xx (072, 082 etc.) series are a good choice.

People want their electric geetars to sound as distorted as is possible. Extremely colored. FUZZ! That's why they use an amplifier made with vacuum tubes.

I think i answered this thread a few hours ago on another website.

audioguru said:

People want their electric geetars to sound as distorted as is possible. Extremely colored. FUZZ! That's why they use an amplifier made with vacuum tubes.

I think i answered this thread a few hours ago on another website.

Click to expand...

True to an extent. However, A) as I said, I am distorting with other components (amp/pedal) at a later point in the chain, and B) there are times when we *do* want a pristine clean sound.

So since altering the sound is not the purpose of the selector, I really want it to be tonal-neutral, if you know what I mean.

Nigel Goodwin said:

As you don't want to colour the sound then use opamps, the TL0xx (072, 082 etc.) series are a good choice.

Click to expand...

What is the difference between the TL072 and TL082? I imagine the 82 is better, but in what way?

The TL07x is a TL08x selected for low noise. The TL07x is better.

This one works great:

Discrete FET Guitar Preamp

Hi Analog,
That is the same guitar preamp circuit that I posted on the other website. This thread is now on at least 3 websites.

audioguru said:

Hi Analog,
That is the same guitar preamp circuit that I posted on the other website. This thread is now on at least 3 websites.

Click to expand...

Great, I guess we think alike!