Quote from: Stompin_Tom on April 19, 2006, 10:30:43 AM
That looks easy... but no mid eq? hummm...

If you want a mid boost then turn down the treble and bass, if you want a mid boost then turn them both up.

Rock'n'Roll,
--Andy

Quote from: joecool85 on August 02, 2006, 07:54:50 PM
How'd you make the schematic?  It looks great.

http://www.expresspcb.com/ has a bundle available for a free download.  ExpressPCB is the PCB maker, and ExpressSCH is the schematic creator.  It took me a while to get it so all the components looked the way I wanted them too, but using the ones from the library that comes with the software works just as good.

But anyway, does that circuit look like it would function decently?  I'm out of town at the moment, but i'll be home next week and would like to start breadboarding.

Rock'n'Roll,
--Andy

Here's a schematic for the idea so far...

Rock'n'Roll,
--Andy

In that case, the 470nF will be changed to a 10uF.  Using Duncan's Tone Stack Calculator, I did in fact find a way to get the Baxandall's output really close to being linear, so here's my idea:

Input -> Gain Stage 1 -> Baxandall Controlls -> Volume Controll -> Gain Stage 2 -> Output

Gain Stages 1 and 2 would be identical and all coupling caps would be around 10uF.  I'd probably end up using a TL072.  I'd like to run it into a phase inverter and then a bridged power amp (using a LM4780... or two).

Does that look like it'd work out?

Rock'n'Roll,
--Andy

Decoupling caps are essentially the output cap, right ('cause coupling caps surround the gain stage and "de" implys the end, right)?  How large is a  large decoupling cap?  What value cap provides a flat frequency response for a bass? 

What's the easiest way to match impedances?

Do you think that two opamp gain stages with a Baxandall tone stack in the middle would still be fairly transparent?

See the attached schematic.  I think I did it right...

Rock'n'Roll,
--Andy

Just th einput cap?  I thought alll of them would need to be changed...

Rock'n'Roll,
--Andy

Could this bad boy be tweaked to work nicely with a bass?  You know: more emphasis on the lower frequencies?  Also, could you put a tonestack after/before it and still have enough of a signal to push a LM3886 poweramp?

Rock'n'Roll,
--Andy

...Anyone?  I need some help with a transparent bass pre-amp here!

Rock'n'Roll,
--Andy

If I used a high voltage to increase the headroom of the transistor/FET/OpAmp then couldn't I get away with using fewer parts and not having to deal with the distortion at all?

Rock'n'Roll,
--Andy

What is the key to making a transparent preamp?

Let's say it's for bass.  The point is that no matter what bass you plug into it, it still sounds like that bass.  A P-Bass sounds like a P-Bass, a Jazz Bass sounds like a Jazz Bass, and Derek Smalls's doubleneck BC Rich mockingbird sounds like Derek Smalls's doubleneck BC Rich Mockingbird.  No fancy sound alteration, just the true natural sound of the bass but loud enough to pump it thru a poweramp.

I'm assuming that the fewer parts in the signal path, the more transparent the circuit will be, so a minimal amount of amplifying untils such as transistors and opamps as well as a minimal number of knobs should be used.  Am I right on this?  If not, please tell me what I'm wrong about/missing/forgetting/confused about.

Thanks!

Rock'n'Roll,
--Andy

Quote from: RDV on June 11, 2006, 10:08:04 PM

Quote from: RDV on June 11, 2006, 09:40:29 PM

Quote from: SECONDandBOWERY on June 11, 2006, 09:38:14 PM
Instead of just using the 18watt tone controll with the BMP output stage, i'd actually try to clone the 18watt preamp but just using two Jfets in parallel instead of the two tube triodes in parallel.

Be sure and post a schem when you get it working!

RDV

You might want to check the Eighteen at Runoffgroove.

RDV

Yes, I've seen that.  In fact, once I get thru the RAT project and now the LM3886, I think I might try a circuit like a Blackface Fender Deluxe Reverb version of their tube inspired Jfet pedals (I have so many circuits I'd like to build, it's rediculous).  But, not to get too off track, my suggestion way to run two Jfets in parallel, and use the Lite IIb tone controll (also found on the tremelo channel of the amp) instead of the regular one.

Rock'n'Roll,
--Andy

Instead of just using the 18watt tone controll with the BMP output stage, i'd actually try to clone the 18watt preamp but just using two Jfets in parallel instead of the two tube triodes in parallel.

Rock'n'Roll,
--Andy

Check out the 18watt Lite IIb volume/tone controlls.  Very simple and apparently, very effective.

18watt Lite IIb Schematic:
http://www.18watt.com/storage/18wattLite2b.gif

Here's a quote from a boutique builder after I asked him about his thoughts on the 18watt Lite IIb tone controll vs. a TMB:

Quote from: A boutique amp builderI personally don't really like the TMB tonestack. There isn't anything dramatic in its correction I am missing in the one knob tonestack. But that's only me...

Rock'n'Roll,
--Andy

Yeah it came in fine.  Don't worry - I have enough solder.

A few questions before I start putting this thing together:
1) Should I seperate the Power Supply PCB from the LM3886 PCB?  There is a scored line between the two and it doesn't look like any traces would be broke it I snapped it.

2) Do I need to heatsink the LM3886 while I'm soldering it?

Thanks again!

Rock'n'Roll,
--Andy

Just got the kit and soldering iron in the mail!

Golly gee willikers - I sure am excited!

Thanks Joe!

Rock'n'Roll,
--Andy