On board Preamp

[Atk]

What do you think about this on board preamp?

http://www.till.com/articles/GuitarPreamp

can be indispensable?

Please tell me your impression...

Bye

[Thomas P.]

What do you think about this on board preamp?

http://www.till.com/articles/GuitarPreamp

can be indispensable?

Please tell me your impression...

Bye

Nice! I use a simillar one, but I have trimmers for level and drain voltage!

[petemoore]

I like Jfet boosters and built this one too !!! Good one.

[erio fraga]

I had installed one in my guitar ( single-coils ) some years ago and was really pleasant with the gain output increase without significative distortion; a clear and cristaline sound ! I used a BF245A  and a trim-pot in the drain to bias the FET, as usual. I use a push-pull switched in the guitar volume pot to by-pass or not the preamp.
As mentionated in the link you have indicated, play a little with the resistor and cap values adapting the preamp according to your pick-ups and taste.


Erio

[Mark Hammer]

Erio's posting is excellent advice.  I've had onboard preamps on my guitars since about 1980.  Occasionally I like them.  Occasionally I hate them.  What makes the difference is how optimally they are suited to the instrument and what you want to plug the instrument into.  If a person has low output pickups like Danelectro lipstick pickups, you will be impressed with how much more volume is obtainable from your amp (you may even decide you will never need more power than you currently have!), and how much better some types of effects like compressors, noise gates, and envelope controlled filters behave.  Of course, if you have high-powered pickups already, inserting a gain of more than 1 may result in having a hard time getting a clean sound or getting your compressor to compress lightly.

Don Till's single Fet design, or some of the ones Tim Escobedo has posted on his circuit snippets page, will work just fine.  You probably don't want to set the gain much higher than 3-5 in any case.  I think I have about a gain of 4 on mine, and with a slightly more efficient speaker in my puny little 4-1/2 watt Princeton you would be very surprised at how much volume and grind can be gotten from a small rig.

One of the advantages of the single-FET preamps is that they can be built into phone plug housings. (I used to build them into small dental cement headcaps on rats), and phantom-powered.   This provides an advantage in that you can use PS voltages other than 9v, and it also means you don't have to get into your guitar to replace a battery.  If you have a Strat, you will DEEPLY appreciate not having to remove the entire pickguard.  True, the preamp may perform differently if it is placed between pickups and volume control than if it simply follows the guitar's usual internal electronics.  Placing it in the phone plug assembly that goes into the guitar, however, will provide all the benefits of sending a clean low-impedance signal through that first 12 feet of cable to your first effect or your amp.  If you want a preview of what it can sound like, plug your guitar directly into your amp using the shortest patch cord you have, then plug your guitar in with the longest patch cable you have.  Whatever the difference is that you hear, will be close to what the preamp helps you to hang onto.

[nero1985]

i built it a couple of months ago with the help of PAUL fro www.DIYGUITARIST.com,,,,, it rocks, it eliminates the little noise u get when u arent touching the strings (it makes ground itself) and has enough gain to work with anything!!!!!!!!!!!!!

[Gilles C]

I still use the FET preamp cable I built a few years ago, and I even began to work on another version of it to send a balanced signal to a preamp.

A bit like this one:

http://www.uwm.edu/People/msw/ActivePlug/

Or this one:

http://www.uwm.edu/People/msw/ActivePlug/BootStrap.html

It really helps.

Gilles

[dolhop]

Great post Mark.  I too built the preamp....and in some instances it is great to have.  However, note that it does tamper with your tone....it is not a flat response.  I added a switch in my guitar to flip it in and out of the signal path.  In this case, it works great as a quick boost for a solo rather than playing with the volume knob.  What I did notice is that the preamp gives a significant teble boost.  If you intend to always use the preamp then you can build your tone around it.  My issue is that I have one guitar with the preamp and one without.  So, my tone settings differ radically for the two guitars.  Now I've found that I don't use the preamp too much so that I can stick with pretty much the same amp setting for both guitars.

Nevertheless, a great project and a great addition to my arsenal.  I built it into my guitar on perfboard - the preamp measures about 1cm x 2cm.  I wrapped it in electrical tape with wires coming out of it.

[DDD]

dolhop,
actually on-board preamp gon't give any treble boost except of intended. Preamp just reduces treble loss.
Think of onboard preamp gain as of part of your total gain chain. In any case you dial the needed gain independently of physical location of gain stages.
So why not to place one stage on board? Plus you'll have a lot of considerable advantages.

[dolhop]

Wow, members from Kazakhstan, very impressive, glad to see the site gaining some serious international exposure.  

I see what you're getting at - a natural loss of highs without the preamp and the preamp just reinstates the full signal.  Possible.  I haven't mathematically analyzed the frequency response of the circuit.  In fact I haven't done much math since I left EE school eight years ago....it definitely would have come in handy!

[Paul Marossy]

I built it, as nero said. I like it quite a lot.  

[Ben N]

Paul,
What kind of guitar do you use it in, is it onboard or off, and do use it always on or as a boost?

Ben

[TheBigMan]

I used to use the Tillman preamp in an AB box.  It was my signal chain input and maintained the signal integrity through TB loops and buffered pedals.  I now have a high input impedence pedal at the start of the chain and don't use it any more, but it's a great circuit, especially for strats.  There's vero layouts for the standard version and booster version in my gallery.

[Paul Marossy]

Paul,
What kind of guitar do you use it in, is it onboard or off, and do use it always on or as a boost?

Ben

I have it in both of my Ibanez guitars and my "frankenstrat". In my Ibanez guitars, they are always on. In my frankenstrat, it's bypassable, so it can (and does) act like a booster. 

[Ben N]

thanks.  I wonder if you can wire one of the single FET types (Tillman, Alembic) like the AMZ Mosfet boost, i.e., where it is easily switchable from buffer to boost mode.  i think that and a pull-pot may be the ticket for a Squier Strat that I am ready to pull a disappointing eq circuit out of.

Ben

[aron]

You should be able to easily do that Ben. Hmmm.... if you do it right, you can make your push/push knob be a lead/rhythm pot.

[Paul Marossy]

You should be able to easily do that Ben. Hmmm.... if you do it right, you can make your push/push knob be a lead/rhythm pot.

The only problem with using that Tilman circuit on a Strat is where do you put the battery?! 

[aron]

It can be run off of phantom power. Put an XLR on the jack! hehehehehe

JUST JOKING!

[Mark Hammer]

The little FET preamps with little gain have very low current requirements, and in some cases the real constraint is the shelf life of the battery not the current draw.  One worries about the battery just giving out because of age, or worse, leaking inside a control cavity.

The variety of lithium watch and calculator batteries that can be gotten from a dollar store these days is truly surprising.  One can easily and cheaply construct a little stack-'o-dimes lithium battery pack that can supply 12v and fit just about anywhere in a guitar, safely, for a few years.  They may not be able to supply vast amounts of current, but your computer can attest that they have a VERY long shelf life, and generally don't leak.  I've also seen little 12v batteries for a buck in the same stores.

FWIW, The little 2N5089-based preamp I have in my Epi Coronet has been powered by the same re-animated 9v battery (I rescue discarded batteries and recharge them) for well over a year now, and shows no signs of letting up.  Admittedly I don't play it a lot anymore, but this is one of those cases where the real threat is shelf life.

[vanhansen]

Speaking of current draw on circuits like this.  Last night I was swapping JFET's in my Marsha Valve and for the heck of it I decided to check the battery voltage since I've been using it a lot for the past 4-5 months.  Not every day but at least a few times a week and on a weekend, a 6 hour jam session, sometimes longer.  The battery was fresh when installed after being built, a little over 9v as expected.  It measured last night at 8.92 volts.  That made me happy, especially since it has a bright blue LED in it with a 10k limiting resistor on it, but the draw of the LED is less than an amp, very very small draw.  The circuit could easily be put in to a guitar but I like it better in stompbox form.