Amp Tech Thread / Ask a tech Q

[Hemisaurus]

Ah, well I stated Ohm's Law already, then substituted in, algebra people 

It's very difficult to overload an input section, to the point of physical / electrical damage, unless you do something silly like connect a speaker out of an amp to an input. Connecting multiple line level or instrument level signals together, should be OK, especially, like Ayek said, if you are doing it via a resistive mixer.

Early PA's, were often little more than a resistive mixer connected into a tube amp.

[Baltar]

So I need help with my Screaming Tree, I can't read a schematic so forget that.  I tried running it into a 3dpt, which I have.  I know this is a simple circuit.  I did have it hooked up before, but I was running it through the battery killswitch and it boosted.  I also did have it running throught the 3pdt, but it actually got quieter when I stepped on it.  Can anyone help?  I love this pedal and it was a gift.  I can post more pics or a video if need be.

[Hemisaurus]

You need to figure out your input and output wires, the input should be running to a capacitor, the output will be coming from the pot.

Wire it up as per the diagram. Can I get a shot of the front? It looks like you have a switch and a pot and an indicator?

Oh hang on, Screaming Tree, not Screaming Bird??

Similar rules apply, figure out your input and output, and wire up the switch according to the diagram, get it working without the switch first, is probably easiest, then you know your in and your out. I'll scratch about for a schematic for my benefit.

OK, it's the same unit, with a kill switch? Odd.

That looks like a stereo jack on the input, I'd wire it according to the GG diagram, battery clip ground to input jack ring, sleeve ground to rest of circuit, and not bother with the battery switch.

The cap connected to the orange wire, should be the input cap, one end of it should connect to just the input jack, the other to one end of two resistors and the transistor.

The other cap connects to the top of the pot, the center of that is your output, (black wire).



resistors are the squiggles they are prefixed R
capacitors are the parallel lines they are prefixed C
transistor is the one marked Q1
input jack is J1 output jack is J2

where the lines connect is where the connections are.

[Baltar]

Buggery, I just broke a leg off at the transistor.  Clean off, I need a new tranny now and it says:

2N5952 on it.  Not what most schems say on the Tree.  It's A LOT different sounding than the Bird, really, really nasty.

[Baltar]

[Baltar]

[Hemisaurus]

yeah that won't help

get a NPN transistor from the shack. you can buy an individual NPN 2n3904 for $1.19 or a bag of 15 mixed NPN for $2.99, any of those will do the job for you.

[Baltar]

yeah that won't help

get a NPN transistor from the shack. you can buy an individual NPN 2n3904 for $1.19 or a bag of 15 mixed NPN for $2.99, any of those will do the job for you.

I'm heading back to Detroit this weekend, we don't have the Shack in Canada, we have Sayal's.  I really want to get the 2N5952, I don't want this pedal to sound different.  I want it to hurt people, clear rooms and start dogs barking.  Will the 2N3904 sound different?

[Hemisaurus]

I got into a similar discussion with a bunch of geeks on another board and we concluded the differences between transistors with the same part name is as big as the difference between tranistors with different part names.

Avast and belay that last comment, a 2N5952 is a FET, not an NPN transistor atall, so yes it would sound radically different, it would be the wrong part. Which is odd, because these things weren't originally built with FET's, but if you have a FET in yours and like the sound, keep going with a FET.

[Baltar]

Thanks for the info, I'll lay out the whole damn thing, ID the resistors so we both know what's going where, nab a 2n5952, and figure it out Monday.  I'll probably stop at Sayal's on the way out of town to save some gas and see if they have 'em.  

EDIT:  I'll grab a 2N3904 too, it might be something else in the circuit that makes it so nasty.  Maybe a resistor? Should I nab a socket too, so I can swap them out?

[Hemisaurus]

Err, see changed previous comment

[Baltar]

Ok, weird eh?  I told ya, it's a Fairchild tranny.

[Hemisaurus]

Well Sayal's do NTE's, the corresponding part is NTE312 the Sayal SKU is 148677

[Baltar]

Cool thanks again bro!

[Hemisaurus]

Grab a socket if you feel confident about soldering it into place, you'll have to be very careful swapping transistors though as the socket will be in free air, don't stress the connections when you so that.

[Baltar]

Gotcha, I'll give it a shot!  To be continued on Monday.

[dunwichamps]

For all those wondering where the bright cap is on your gain pot, it is the silver mica cap (brownish) sticking out from the 2 lugs on the pot in the middle of this shot

[Hemisaurus]

load up paint and draw a red circle around it, lazy bugger 

[Baltar]

I'm putting up pics of my Bogen's guts tonight, maybe you guys can tell me some easy mods.

[johnny problem]

Not sure if this is a valid question, but I'll ask anyway. 

When lowering or raising pick ups, can the process affect intonation of the guitar, and thus needing a set up?

[VOLVO)))]

Not sure if this is a valid question, but I'll ask anyway. 

When lowering or raising pick ups, can the process affect intonation of the guitar, and thus needing a set up?

If the magnets are effecting the natural elliptical motion of the string, it may pull it out of tune a wee bit. Lower the pickup a little bit. The guitar ~just~ may need a setup.

[Hemisaurus]

Probably should ask Jake to do a guitar tech thread, but no, intonation is a product of string tension and length, adjusting picup height affects neither.

[johnny problem]

Thank you!

[grimniggzy]

Can anybody hook me up with a step by step on how to wire a cab that can double for bass/guitar and let me know what tools I'll need? (Sorry, I'm totally inexperienced but I should learn how to do this)

I'm thinking a 2X12 & 4 ohms that can pull double duty will work for me.
From google search I can see the speakers I'm looking at are 8 ohms and would have to be wired in parallel

Here's what I'm looking at...
http://www.stagecraftgear.com/servlet/the-30/Blues-Jack-212-%E2%80%93/Detail

http://www.carvinguitars.com/products/single.php?product=PS12-8

Should I be looking into any of these extra options stagecraft offers?
http://www.stagecraftgear.com/servlet/the-Options/Categories

Here's the heads I use:
Sunn Beta Bass
Sunn Concert Bass (Red)
Sunn Coliseum Bass (Silver)
GK 700RBII
Acoustic 370

The 370 & Coli being the most powerful. Do you guys forsee any problems with what I've chosen and these heads? Also the cab is open back, not sure how much that will matter for playing bass since I've never tried one before. There is an option to make the cab switchable from open/closed though.

Many thanks in advance.

[justinhedrick]

Can anybody hook me up with a step by step on how to wire a cab that can double for bass/guitar and let me know what tools I'll need? (Sorry, I'm totally inexperienced but I should learn how to do this)

I'm thinking a 2X12 & 4 ohms that can pull double duty will work for me.
From google search I can see the speakers I'm looking at are 8 ohms and would have to be wired in parallel

Here's what I'm looking at...
http://www.stagecraftgear.com/servlet/the-30/Blues-Jack-212-%E2%80%93/Detail

http://www.carvinguitars.com/products/single.php?product=PS12-8

Should I be looking into any of these extra options stagecraft offers?
http://www.stagecraftgear.com/servlet/the-Options/Categories

Here's the heads I use:
Sunn Beta Bass
Sunn Concert Bass (Red)
Sunn Coliseum Bass (Silver)
GK 700RBII
Acoustic 370

The 370 & Coli being the most powerful. Do you guys forsee any problems with what I've chosen and these heads? Also the cab is open back, not sure how much that will matter for playing bass since I've never tried one before. There is an option to make the cab switchable from open/closed though.

Many thanks in advance.

nothing special in wiring. ohms are ohms. i would worry abou thte open back cab though.