You may very well run into some technical problems attempting to run a guitar cable (Hi-Z, unbalanced) over 15-20 feet. You will almost certainly discover noises and tone loss unimagineable caused by the loading of the cable and RF interference.
If you are REALLY wanting to play through the combo amp (I can personally understand that desire), try disconnecting the internal speaker and run the resultant "head" to a cab seperated by the 30-ft speaker cable.I have several combo amps (64 Princeton, 65 Supro, a Pro Jr., Kalamazoo 2, Marshall JCM800, etc), and I play them all thru this little Marshall "micro-cab" that I've put a 10" Eminence 60-watt speaker into. That way, I can isolate the cranked-up sound in the studio while playing in the CR. And no noise or tone problems from a longer-than-your-d---- geetar cord. This problem is especially prevalent with single-coils.

Having said that, I need to add this. This past weekend, I recorded a guy with a Fender silverface Pro Reverb from the early 70's. He was adamant that he play through his amp/speakers in the other room. When I explained the distance issue, he pulled out a little box made by Seymour Duncan. It is a "pick-up booster", and it has a very low output impedance and lots of gain. He ran his guitar through that box and used it to drive a really long (30-35') shielded cable to the amp. Now his guitar was a PRS with humbuckers, but it did great. You might try that.PEACE...

moonbaby, great advice about the remotely located heads.

I use the Duncan booster too, its reasonably transparent. There's an internal version for those who want to install it into thier guitar, but I like mine on the floor. It also features a three position resonance switch which allows for use with single coil pickups to fatten out the tone.

Thanks,Tommy...
I liked that combination so much that I bought it! That Duncan box is great ! And the guy with the amp has 2 others (one's a "blackface"), and was wanting to sell it for ...studio time! I thought I died and went to heaven! No Master Volume crap, just a great Fender reverb combo in clean shape...with a nice boost box, to boot! I gave him 50 hours in my studio (48 track digital Tascam) evenings. How much are '73 Pro Reverbs going for where you are?

Thanks for the advice, guys :D . I'll definetly check out the Duncan pickup booster. But for now I'll sit with my combo in the tracking room and have my girlfriend work the digidesign002. This way we can spend "quality time" together and I can finally get some recording done too

Ahh, the old "girlfriend in the CR" trick,eh? You are very wise man, my friend!!! Good luck!!!

The "pickup booster" sounds like a great idea. However, how or does it handle hi-freq rolloff?

In otherwords in an hiZ cable, the cable itself is a crossover where the hi-frequencies are attenuated. This doesn't really become apparent until you reach 15 feet or so. This is where the crossover point becomes low enough to hear. The cable acts as the capacitor where the shield, insulation and signal wire together become the capacitor. The length of the cable becomes the resistor for the crossover circuit. So as you increase the length of the cable (raise the resistance) the attenuated frequencies (which were really high and above 20k) are now low enough to shave of the top end clarity of the signal.

So, my question is does the booster compsensate for this or just boost the gain of the signal? If it doesn't it will still sound great but there would be a loss of highs...

Old trick:

There used to be an old trick that would help with this, however some love it and others hate it... It takes 2 di boxes to do this.

Plug the guitar into DI-1(hiZ) run a mic cable from the DI-1(lowz) over to DI-2(lowz)( (you'll need adaptors/gender changers) now take DI-2(hiZ) and go from its HiZ "input" to the amps input.

This basically converts the gtr signal from hiZ to lowZ for the trip across the room then converts back to hiZ just before it hits the amp allowing the amp to see the impedance it is expecting.

Though, I tend to take a more purist approach (I don't like anything between the guitar and amp if possible and shortest cable possible). I also believe that the signal's journey from the guitar to the amp is one of the absolute most delicate things. Screw up there and everything after suffers. However, it is an option you can try just to see what happens.

Best regards-

Karbo

A simple unity gain opamp buffer circuit can be made using "demos" from BurrBrown/TI for under 5 bucks (including jacks, case, and additional components). Put one every ten to 15 feet of guitar cable, and you shouldn't really have any problems with hi-freq or signal loss.

Thanks for the tip Chris!

If you do go with the free BB demos, be sure to download and read the documentation, as their design often includes many measures that negate the use of conventional op-amp circuit design conventions, like those used to prevent back-current.

Honestly, any audio op-amp should work fine though and have plenty of bandwidth to handle 20 to 20k signals without issue. Keep the traces short to help prevent oscillations, and if necessary, throw in the customary oscillation preventing cap...but it usually isn't needed in this application.

A simple 9 volt can be used to power the thing...current draw will be amazingly low, so a 9 volt could potentially last years. You can enable it with a switch or by cleverly wiring a stereo quater inch jack to connect the power through the sleeve and ring connections...just remember to unplug the cords when you aren't using it.

If I get the time I'll draw up a simple schematic.

If you want a cheap distortion box, toss on a couple of clipping diodes and throw a pot into the feedback loop for gain control. If you want a cheap octave box, throw in a bunch of clipping diodes.

Thanks yet again Chris. I am pretty well versed in audio electronics and am currently researching building some tube mic pres, Tube DI's etc from scratch.

I have been out of the loop for a few years but have been soldering circuits since I was 7 years old and the more you speak on the subject the more what you suggest starts ringing a bell from long ago.

I may have to keep an eye out for you here as I start breaking out my old tools and building stuff!

Speaking of the diodes/distortion. I have a trs jack around here somewhere with 2 diodes wired in such a way that I just plug into an insert for this gritty, narly, ugly distortion. Forgot all about building that thing a few years back.

Best regards-

karbo