building guitar amp... first project! help

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
hello, I'm a 4th year electronics student and i'm about to make an amp for my guitar... it's going to have tone, volume, balance controls, it'll be stereo, 40W per channel... it'll have a distortion / overdrive pedal. I'm going to use lm4766 for amplification, lm1036 for tone/balance/volume controls and a pedal that i found on this forum... I'm thinking of connecting the guitar to the pedal, the pedal to the lm1036 and it to the lm4766... is it right?? any recommendations, etc?
 
ashade said:
hello, I'm a 4th year electronics student and i'm about to make an amp for my guitar... it's going to have tone, volume, balance controls, it'll be stereo, 40W per channel... it'll have a distortion / overdrive pedal. I'm going to use lm4766 for amplification, lm1036 for tone/balance/volume controls and a pedal that i found on this forum... I'm thinking of connecting the guitar to the pedal, the pedal to the lm1036 and it to the lm4766... is it right?? any recommendations, etc?


Op-amps are supposed to sound absolutely awful when overdriven or abused. (They're the exact opposite for tubes in this respect).

I've got threads both here and in the Tubes thread on a tube-gainclone hybrid amplifier. You could probbably do something similar with a low-power FET amplifier.

http://www.diyaudio.com/forums/showthread.php?s=&threadid=87279

http://www.diyaudio.com/forums/showthread.php?s=&threadid=87447

It's a nice solution - Assuming you use an el-cheapo power transformer (about 3$, less if you rip it out of something else) for the interstage transformer, and can find a cheap transformer for the 200v needed for the tube stage (rip apart another amplifier!), the total cost of the tube stage is well under 50$.

As an added bonus, the transformer eliminates DC offset on the inputs, and you can do some interesting things by oversaturating the transformer by adding a DC offset to the tube stage, and by adding current-limiting resistors on the power supply.

Plus, the tube stage is completely isolated from the power amp stage!
 
ashade said:
tubes?! I thougt i though it was left behind decades ago.... well, thankx for the help, i'll think about it...
PS: are you sure op amps are not goodfor overdrive, even the highest quality ones?

I've heard from everyone I've ever met that they're abysmal, but you don't have to take my word for it.

Tubes are clunky, fragile, and inefficient. However, because they're more or less electromechanical (google the Thermonic Effect), they do many interesting things in very non-linear ways under certian situations. This is generally considered desireable.

(They also do a much better job of distortion. Distortion is bad most of the time, but most of the "effects" on an electric guitar are just forms of distortion. Overdrive is just the preamp overdriving the power amp, fuzz is often formed by adding diodes (with their breakdown voltage and voltage drop) in the signal path, et cetera.)

Of course, because you need a massive output transformer built to exact tolerances and lots of tubes, big tube power amps are tricky; usually, they largest are not above 50w. However, we can take the same signal (with all the distortion intact) and feed it through a Gainclone. If the input is clipped, the output will be clipped, but without sounding nasty. (For example, if you have a 2.5v signal into a gainclone with 30v rails and a gain of 10, the output will clip at 25v, but within the 30v of the gainclone- it will output it like any other signal).

Plus, you can use a cheap-0 power transformer in place of the fancy, expensive transformer, and you only need a very small power transformer.
 
i thought it were different... let me give an example:

input signal: a sine wave with 2V peak
pre amp overdriven signal: the same sine wave, but clipped at, let's say, 1,5V.
power amp output: the same signal multiplied by a gain factor, let's say, 20 times, which means a sine wave with 40V peak, but clipped at 30V... if the power amp is fed from +- 50V for example there will be no problem in my opinion... (the output signal is the same distorted signal from the pre amp).

Am I thinking the wrong way?
 
Some opamps distort better than others....If you want a Chip that has a relitively ok sounding distortion (For opamps) try to get true Fet High impedance input opamps as they clip more gracefully than non-fet input opamps.....

Most distortion pedals are either driven by a Fet opamp or by low noise Fets so you can get a Pretty good distortion useing the right circuit and component combinations.....

You can even try doing a Hybrid amp useing a Tube pre stage with a solid state power amp stage....I actually think I will try that with some 6418 Sub minuature power amp pentodes I have and see how it works.....


Cheers
 
Minion said:
Some opamps distort better than others....If you want a Chip that has a relitively ok sounding distortion (For opamps) try to get true Fet High impedance input opamps as they clip more gracefully than non-fet input opamps.....

Most distortion pedals are either driven by a Fet opamp or by low noise Fets so you can get a Pretty good distortion useing the right circuit and component combinations.....

You can even try doing a Hybrid amp useing a Tube pre stage with a solid state power amp stage....I actually think I will try that with some 6418 Sub minuature power amp pentodes I have and see how it works.....


Cheers

I'm trying to do that myself.

However, unlike you, I'm not entirely sure of what I'm doing.

Please post results!
 
Spasticteapot said:


I'm trying to do that myself.

However, unlike you, I'm not entirely sure of what I'm doing.

Please post results!


Actually I am also pretty new to DIY electronics myself and have only been doing it for maybe 6 months but I seem to have a Good brain for it although i have absolutly no skills when it comes to the math required for computeing the correct values of a particular component for a certain application.....

I get most of my circuit ideas from other Circuits, so If I have a Particular project idea I will look at schematics of other simular projects and use parts of different circuits in my circuit ideas...

I don"t really consider it stealing an Idea because the end result is no were close to the circuits I started with, especially after trouble shooting problems and changeing things so all parts work together properly....

I started makeing Simple Microphones useing electret elements and watch batteries, I then went to phantom powered Mics and then I did my first real project which was a 2 channel Green preamp which worked great and really got my intrest in DIY going...

My next project was me designing a simple Mic preamp based arround the INA103 Preamp chip which had phantom power, 20db Pad, and 60db Gain which worked out great and sounds great and was very simple and was mostly taken from the Datasheet.....

My next project which I am still finnishing is a Much more complex project as it is a self designed Solid state/Tube hybrid amp with 4 Gain stages ,2 of them are Tube stages useing Submini tubes...

In has a NPN/PNP Transistor front end with about 20db of gain which then going into one tube running at unity gain and then into another Tube with an adjustable gain of 8 which then goes into a fet Impedance Buffer to lower the impedance comeing from the tubes...It then goes into a Non-inverting Ballanceing stage with an adjustable gain of up to 18db useing a NE5532 Dual opamp.....

It is powered from a +/-15v +48v supply with the IC"s and Transistors being run off of the 15v rails and the Tubes running off of the +48v power rail.....

I have the design finalized and the PCB Board etched and drilled and Fully stuffed and Just needs to be wired up to see if it works...
I am actually scared to try it because I have put so much work into it and I"m sure that it isn"t going to work right off of the bat and don"t want to be dissapointed.....If it does work though and even if it makes a noise I will be happy .....

My latest design is a 50w Guitar/Bass amp useing a opa2134 for the preamp and the LM3886 for the power amp...It has a Lot of features and I am 98% sure it will work right off of the bat as it is a very simple design and I have allready etched the board and I just need to get the parts.....

If there are any Project that you would like to try let me know as I have a Pretty Big library of schematics...Most of it is solid state but there is also some tube stuff.....


Cheers
 
Something not said here - most all basic distortion pedals on the market use an opamp with a diode clipper circuit to get their distortion. The most popular opamp for distortion pedals is the 4558.

Many solid state guitar amps for decades have used the 4558 with a diode clip circuit in the preamp. So this being said opamps can easily be used to develop a good guitar distortion circuit. Do they sound like like a 12AX7 preamp tube distortion? No not entirely however some are close and there are some tube distortion pedals on the market that sound much worse than an opamp based version.

Many tube amps labeled as hi-gain have also started using a diode clipper circuit in the preamp section.

One of the most popular distortion pedals of all time is the Ibanez Tube Screamer TS9 and it uses the 4558 opamp with a diode clipper circuit.
 
Hi, I have some schematics that show how to use the 6418 Sub mini tubes in a Circuit that might help you to utilize these tubes...

I also have a schematic for a Electret Tube condenser mic useing a 6418 Sub mini...

I also have a bunch of submini tubes and have designed a few things useing them...

An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.



In the First Picture you can replace the 100k resistor comeing off of Pin 1 of the Tube with a 100K Linear pot wired backwards for adjusting the Gain.....


I hop[e this gives you a basic idea how to use them in a Circuit....


Cheers
 
Well these tubes sound tather nice and clean as long as they aren"t over driven too much ,but in a Guitar amp overgriveing the tubes and cause distortion might be a Good idea to get a Nice Crunchy tube sound.....

You could use a preamp Circuit like this:

An externally hosted image should be here but it was not working when we last tested it.




But remoove the 4 Diodes and the Transistor output stage and replace it with the Tube circuit from my First Tube pic and then use a Low noise Fet ot Transistor as a Buffer at the output to lower the Impedance of the Tube Output stage and then use the LM3886 Chip as the Power amp stage.....

Here is what a Fet Buffer looks like:

An externally hosted image should be here but it was not working when we last tested it.


Or

An externally hosted image should be here but it was not working when we last tested it.



Well that is basicly how I would go about it and it should work quite well as the Voltage for the LM3886 is about the same as the Plate voltage of the 6418 Tube and you could use the +15v Rail that is for powering the Preamp stage with a Diode and resistor regulator to get the 1.5v filament Voltage for the tube....

You will have to build a Power supply that supplies+/-15v regulated for the preamp stage and about +/-24v Unregulated for the LM3668 Power amp stage......


I hope this helps.....


Chris
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.