Take a look at my schematic?

[Jeremy]

Hey, folks.  I drew up a schematic for a dual booster I want to build, but I just moved and I don't have anyplace to build it yet...  In the meantime, does anybody want to check it over and see if it makes sense as a circuit?




It's based heavily off of Tim Escobedo's Utility Boosts. 

First, there's a common source amplifier with a gain of -1, and a switch that changes it into a variable gain.  The range of gain should be from 0dB to 26dB, with these transistors, I think.

Then there's another common source amplifier with a gain of -1.  Why?  Because I have a crappy power supply.  I figure that the first amplifier will inject 100% of the power supply ripple into the signal.  The second amplifier will turn the signal over and inject the same ripple again, cancelling it out and leaving my signal ripple-less.  Anyway, that's what I hope.  That idea came from The Tube Cad Journal.  http://www.tubecad.com/

The third and fourth amplifiers are the same as the first two; one that switches to achieve gain, and the other just to cancel power supply hum.

The biasing of this circuit should, if I understand it right, set the Vbias at around 1/4 of the power supply, minus 600 or 700 milliVolts for the diode, no matter what the power supply voltage is.  This is because my crappy power supply is switchable between 9 Volts and 12, and I think that I'd like to use 12.

The 2N5484 transistors that I have generally bias with a Voltage of around 800 mV between the source and the gate.  I figure that that puts the source DC level [within a few tenths of a Volt] at 1/4 of the power supply, which seems good for this circuit.

When the circuit is in "bypass mode," nothing is bypassed.  The gain just goes to one.  This is done by means of those switches.  I did things this way so that I'd have LED indicators with DPDTs.  If I find that having the signal go through four unity gain amplifiers while in bypass mode is too noisy, then I'll consider 3PDTs. 

Any comments?  They'd be appreciated!

[disantlor]

Could be (nay, probably am) very wrong on this, but wouldn't the ripple in the second stage be slightly out of phase with the first.  Then when the one is inverted it wouldn't be exactly 90deg out of phase, resulting in weird or incomplete cancelation, or is the difference negligible?  Pretty cool idea.  Don't know enough yet to comment much further on it unfortunately.

[KerryF]

what kind of booster is this?  Volume?  Gain?  Treble?  Bass?  Mid?  Full?

also, you know that copyrighting doesnt mean you just write it on there and its copyrighted, right? 

[Jeremy]

From my Copyright class, I recall that in the U.S., simply having drawn the schematic makes the drawing copyrighted, although I may choose whether or not to register my copyright with the government.  Regardless, I own the copyright, and may claim it.  The circuit is not, however, patented, and I'm not claiming that it is.

It's a volume booster.  :-)

:::edit:::

Oh.  The name?  The name's not a registered trademark by any means.  The copyright notice was referring to the drawing. 

[disantlor]

what kind of booster is this?  Volume?  Gain?  Treble?  Bass?  Mid?  Full?

also, you know that copyrighting doesnt mean you just write it on there and its copyrighted, right? 

well with music, a song is protected by copyright the moment it is in any tangible form.  Of course its difficult to prove unless you register your copyright (or do the sealed mailing thing).  Is it different for this kinda thing?  

err.. sorry to derail this thread

edit: haha you must have been writing that at the same time as me.

[Jeremy]

Anyhow...  thanks for the responses...  does anybody else want to weigh in on whether or not the power supply ripple rejection scheme will work?

[KerryF]

Ok sounds awsome man.  I wasnt sure about copyrights with schematics.  I know that for music, I have copywritten a few things with the govt.  Cant wait to see if it works.  I have 2 schematics written I am in the process of prototyping.

[Jeremy]

Before this thing totally shoots under the radar, I really would appreciate some more opinions on whether or not my power supply noise suppression scheme is going to work.  Really.  Like, swing by central Illinois and I'll bake you a cake I'll be so happy.

[Paul Perry (Frostwave)]

To get back to the amp, I really think the best thing to do, is improve the power supply! I mean, how hard can it be?? These preamps take little current, so a regulated supply is easy-peasy.

[Jeremy]

I guess you're right, Mr. Perry.  Regulating the power supply would be pretty simple.  The idea came from tube circuits that were using a heck of a lot more current.