Preamp Queston

[littlegreiger]

Can I use a preamp for recording into my computer.  And is the EH LPB-1 really a preamp or is there no difference between a preamp and a booster, because I want to build the LPB-1 and use it to record on my computer.  Please tell me if this will work.

[Paul Perry (Frostwave)]

Yeah, any kind of amplifier will work, if you set the gain so as not to overload the soundcard input.
Generally speaking, preamps & boosters are themselves free of distortion.

[littlegreiger]

So I can use a LPB-1 to record onto my computer as long as the volume is turned down a bit?

[Marek]

Sure you can record the guitar through the booster/preamp/buffer! Why not? You could also record it directly into the soundcard with out any preamp. Really. It's all the matter of personal taste & preferences... and sound quality, of course :-)

If you boost the level of the guitar too much, it will drive the soundcard input preamp into distortion (unpleasant harsh clipping - belive me, you want to avoid this unless you are some kind of s0uNd desIgner fr3aK).

Your guitar will of course sound differently than amped guitar if you don't have the appropriate software...

The best way of course is to try it out yourself. LPB has less than 10 parts altogether, you can easily make it in 10 minutes, if you don't care for being very tidy.

Greetings,
Marek

[littlegreiger]

If I put it right into my computer, don't I have to boost it with software?  What software should I use? and what software will make it sound like it's running through an amp

[Marek]

If you plug the guitar directly into the soundcard, you'll (probably) get a weak signal full of noise, unless you have some DIgidesign 'soundcard' with dedicated guitar input...

Thats why people use this little 'Buffer' or preamplifier, or maybe even better an 'amp simulator': it's an interface which helps you connect otherwise not directly 'compatible' devices, such as a guitar at one end and the soundcard at the other.

Why don't you simply put the LPB together? Or any othe similar thinggy? ( Alembic Stratoblaster, Don Tillmans Buffer,...) The parts for those will cost you less then a pack of cigarettes, and it really takes only few minutes to put together on the perfboard.

Greetings,
Marek

[littlegreiger]

i'm probably going to build it because i have some of the parts laying around.  do you think i could substitute 4x100 ohm resistors for a 390 ohm. and can i use a 2N3904 instead of a 2N5088?

[squidsquad]

Your parts will work...maybe a tad duller & a bit noisier.  You CAN go straight into the soundcard & get decent results....with post tweaking (EQ - compression - reverb).  IK Multimedia makes Amplitude...a fun amp & effect software sim.  As for an LPB...a search here brings all kinds of info.  Since I've already done that...take a peek:


"The schematic link shows the transistor (Q1) as 2N5133 and notes that a
BC239 was also used.  My original LPB1, purchased in the mid '70's has a
2N5088 transistor in it.  I recommend using a 2N5089 or 2N5088, since they
are low noise and readily available."

Gain Changing Modifications
---------------------------
The overall gain characteristics of this circuit can be tweeked by changing the
value of the resistor connecting from the emitter to ground (390 ohm value
resistor in the schematic).

Tone Changing Modifications
---------------------------
This layout can be used to create a "Screaming Bird" by simply substituting
the 0.1uF capacitors with 0.002uF capacitors.  The schematic is directly
below the LPB1 schematic on the schematic link.  I've never heard any kind
words about The Screaming Bird or Screaming Tree. As Art Thompson says,
the Screaming Tree "Should have been called The Sceaming Audience"!  Yeow,
I think these treble boosters are pretty harsh to most ears.  Maybe you
could try something in between the 0.1uF and 0.002uF value for milder treble
boost.  Brian Tremblay reported that 0.01uF caps worked well for a treble
boost without being too ear piercing.
Try changing R1 to 1meg and R2 to 82k

"My LPB-1 cuts highs off of my guitar. Anything I can do?"

There are a few things that you can do to increase the treble response.

1. Switch to a different device. Any bipolar transistor will have a characteristic high-frequency response and gain. Usually the higher the gain of the transistor the more high frequencies it can amplify. Try a 2N5088 or 2N5089 for a start. 2N2222 can work but will be duller-sounding.

2. Increase the input impedance of the circuit. You can do this by changing the biasing resistors on the base of the transistor, keep the same ratio (on an LPB-1/2 it's usually 10 to 1, 470K to 47K - try 1M and 100K) and also by inserting a resistor in series with the base (after the input cap works better but try it both ways.)

3. Decrease the input cap to block low freqs. The stock .1 is too much for my ears unless you're using it for bass. Try a .047 or a .033.

From Torchy:
Here's a list of subbed values:
R 1 1M
R 4 390R
C1/C2 220nf
BC549B transistor ( after an hour of trying EVERYTHING I had ! )

Result, great "clean" and "Full" boost up to 2 thirds of gain pot, then HUGE boost after.

[sir_modulus]

nice mods there, and nice post squidsquad!

I personally use a Eighteen ---> Condor cab simulator for all my recording purposes.
(both available at www.runoffgroove.com)

Cheers,

Nish

[MartyMart]

From Torchy:
Here's a list of subbed values:
R 1 1M
R 4 390R
C1/C2 220nf
BC549B transistor ( after an hour of trying EVERYTHING I had ! )

Result, great "clean" and "Full" boost up to 2 thirds of gain pot, then HUGE boost after.

Erm, sorry but they were MY subs on "Torchy's" layout  !!!
Just wanted to point that out  :wink:
BTW  It sounds AWESOME with those values and tranny.

Marty

[squidsquad]

Oops...RATZ!  Sorry Marty....credit noted!