Adding circuits to an amplifier head build

[Shrimpfarmer89]

I am in the process of learning about amps and circuitry etc, my question is this

if I was to make several extra circuits for example

an equalizer circuit
an extra gain circuit
a prescience circuit

How would I tie them into a build that I’m building from a schematic of an amp I have found online?



thanks so much! Godspeed and good luck

[Enzo]

If I wanted to add something to my car:

turbocharger, airlift shocks, automatic high beam dimmers

How would I go about that?

MY point being, those are way overly general questions. We'd need to know what you wanted to put these thing INTO, and what specific examples of them do you intend to use?


Just as on my car, you'd want to know what make and model was the car, what brands of accessories involved.

I am interested in the prescience circuit. Does it anticipate what I am about to play ? (I am teasing, you meant presence)

[Shrimpfarmer89]

Let’s say a Soldano.

There isn’t just a way you can build a circuit outside of the amp like a presence circuit or put together a 10 band eq Circut that you can find scenarios for on Google, there’s no way to make the circuit, and drop it into an amp head somewhere along the circuitry line of the amplifier?

what do I have to do voltage wise to run it? Is there a certain place I need to put it? And how do I add it into a pre existing schematics draw up?

[J M Fahey]

1) Welcome to the Forum

2) many of the circuits you suggest are not something that "you build outside and add to an existing circuit" but are "mods" or "parts of" the original circuit, and get "built in" the original one.

For example, there is not a little box called presence which works on its own (as if it were an effects pedal) .which then you can use on any amp, but a modification on the existing negative feedback circuit which allows it to do 2 things, besides its normal duty:
a) increase mid-highs
b) do it in a controlled way


Same happens with many other circuits.

To be able to do that, you must know enough Electronics to *design* , a tall order for a beginner.

You have 2 paths, which can be run at the same time:

c) practice building already designed circuits, as-is.
As an example, my first tube amp was a Gibson GA-5 , their version of Fender Champ

KILLER little amp, I was (justifiably) very proud.
Then go on, and on, and on, the Sky is the limit.

d) at the same time, start learning Electronics, at your own pace.
Again, the sky is the limit.

[vintagekiki]

https://www.scribd.com/document/372777403/Randall-Aiken-designing-tube-amplifiers

http://guitar-gear.ru/forum/index.php?app=core&module=attach&section=attach&attach_i d=14475

http://www.guitarstudio.tv/documents/Designing-V-T-Amplifiers.pdf

http://guitar-gear.ru/forum/index.php?app=core&module=attach&section=attach&attach_i d=13646

1)
www.n5dux.com/ham/files/pdf/Electronics%20for%20Dummies.pdf
2)
https://music-electronics-forum.com/forum/schematic-requests/25212-links-to-books

[loudthud]

The SLO-100 has a gain circuit and a Presence control.

On a difficulty scale of 1 to 10, a Soldano is about 11. That means even an experienced builder only has a 50% chance of building something that works from some schematic found on the internet. Same goes for a Mesa Mark whatever with it's cheesy little graphic equalizer.. Your money and your time are better spent on an amp with not so much gain like a JTM-45. Sorry to burst your bubble.

[vintagekiki]

To get satisfactory answers to all your questions, you need to give minimal starting data
So
- Tube or solid state device.
- Upload schematics that you have and want to merge into a whole.

Or visit adress with technical literature to help you in choose.

https://music-electronics-forum.com/forum/schematic-requests/25212-links-to-books

Otherwise this is like wandering in the dark with a high probability that you will disappointed in electronics at the beginning.

[Helmholtz]

Apart from presence (if missing) most effects are best looped in via a send/return interface - rather than built-in.

[Shrimpfarmer89]

I am thinking of building a tube amp from scratch, however I want to add another circut that runs on around 18-20v of power, to power this section should I just add another line with some capacitors and resistors off the b+ line near the fx send? Or do I have to add another line off the b+ and add another 12ax7? Let me know!

[christarak]

Hmm…I’m not quite clear on the requirements of your new circuit. Does it require a 12AX7, or have I misunderstood you? The 18-20v leads me to think it’s a solid state requirement, so I’m not clear on the role of the 12AX7.
Any idea of the current requirements of your new circuit? I don’t suggest it would be a good idea to drop such a large voltage from say 300v to 20v without knowing your current or would be looking at an extremely hot dropping resistor. Do a V²/R or an I²R once you estimate the current, and you’ll probably decide against it.
Does your transformer have a bias winding you could use...once again, what's your current requirement?

[Shrimpfarmer89]

That’s partly what’s I’m asking, I don’t completely know, I’m trying to ask questions to round out an answer.

I have a graphic eq circut I want to add to the amplifier. The circut schematic says that it needs 18v dc.

I am planing to put it into the amp before the fx loop.

Part of what I am asking is DO I need another 12ax7 to power that circut. Or should I use a transistor or a line off the power transformer straight to that part of the amp?

I could use several caps to drop the voltage of the b+ and smooth out the dc as well, but it’s probably not the safest?

I really don’t know! I’m shooting in the dark here. This is the closest I’ve come to getting an answer so far.

[nosaj]

That’s partly what’s I’m asking, I don’t completely know, I’m trying to ask questions to round out an answer.

I have a graphic eq circut I want to add to the amplifier. The circut schematic says that it needs 18v dc.

I am planing to put it into the amp before the fx loop.

Part of what I am asking is DO I need another 12ax7 to power that circut. Or should I use a transistor or a line off the power transformer straight to that part of the amp?

I could use several caps to drop the voltage of the b+ and smooth out the dc as well, but it’s probably not the safest?

I really don’t know! I’m shooting in the dark here. This is the closest I’ve come to getting an answer so far.

Well its the cart before the horse here. Your asking us to postulate on the unknown(what schematic)?
12ax7's do not power circuit what they do do is amplify.

You provide a schematic that everyone can work from the same page and you'll surely get your wish.

nosaj

[Shrimpfarmer89]

It’s a soldano.

thanks for the tidbit of info I didn’t know that they just amplify. That helps figure out other questions I’ve had.

here are the schematics.

will I need to change the overall power of the amp to supply power to that circut?

what if I have two 18-20v dc circuts in it? Let’s say one powers a pcb distortion circut and the other is a graphic eq? Will I have to re adjust the entire amp for more output or can I just run these off the b+ with a voltage drop to either of them?

thabks for the help!

[christarak]

That’s partly what’s I’m asking, I don’t completely know, I’m trying to ask questions to round out an answer.

I could use several caps to drop the voltage of the b+ and smooth out the dc as well, but it’s probably not the safest?

I really don’t know! I’m shooting in the dark here. This is the closest I’ve come to getting an answer so far.

I am concerned for your safety where such high tube voltages lurk in dark corners, waiting for your fingers to walk past, whereupon they will leap out and bite you...hard. I'm not sure if are aware that Capacitors don't drop voltages. The resistors between the capacitors will do that role. The capacitors are there to be your reservoir of energy, a reducer of ripple and a stop sign to all miscreant DC voltages.

As Nosaj suggested, post the schematic of the amplifier, including the power supply, and that of your mod, and we may be able to offer some advice on whether its a practical mod, or whether you should just put a graphic pedal in your effects loop or in front of your amp.

Do you have a voltmeter that you know how to use? If not, slowly...carefully...put the chassis back in the cabinet and say a few "hail Mary" equivalents in the religion of your choice.

Please be careful of fuse connections, power switches, standby switches, all pins of all tubes, lots of resistors, capacitors (especially the big ones) ... and watch out for things in dark shadows.

[Shrimpfarmer89]

These are the schematics, I want to put the eq at the fx loop, and possibly a pcb distortion circut as well.

what do I have to do to power it? Run a line off the b+ and put a multi capacitor voltage drop infront of it to power it?

what if I want to add another circut as well in the amp that also runs on 18v of electricity so now I have 2 new circuts? Can I still run them off the b+ or do I have to reconfigure the power of the amp to cover the new voltage needs of the new amp?