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Hybrid Amp Project (inspired by nzCdog's Lil Watter and Orange Micro Terror)

Started by Ettore_M, November 10, 2012, 11:10:28 PM

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Ettore_M

November 10, 2012, 11:10:28 PM Last Edit: November 10, 2012, 11:17:14 PM by Ettore_M
So guys, here's a thought about a hybrid amp project I'm working. I was interested in an portable hybrid guitar amp, working out of a single 12V DC supply (like Lil Watter), but with the 12AU7 tube preamp's plate running on higher voltages for more headroom and higher output wattage on the power amp.

So, I started searching for ideas..
I found TDA2040. It looks good and works with a wide range of supply voltages, producing around 15-20 W with 4 ohm speaker. For the voltage multiplier, I think it's what Renegadrian posted on DIYSB (got it from juansolo's stompage). Then, for the tube preamp, I used juansolo's Boobtube and nzCdog's BT80 (where I got the idea of running the plate voltage higher). Finally, power fitering and polarity protection from nzCdog's Lil Watter and input buffer is jimmybjj's Klon Buffer.

Please, don't start yelling at me for the various bits and pieces I got from your projects!  :-\ I know I didn't ask for your permission, but I was hoping you're ok with me using them..  :)

Bear in mind that this thing is not even on the breadboard yet so I don't know if it will work properly. The schematic is just thoughts!  ;)

https://www.dropbox.com/s/axiy1eznyqbag8h/Hybrid%20Amp%20Project.png

So what do you think? I don't know many things about practical electronics, so I ask for your opinions and advices to make this work.  :)

Thanks!

Hector

EDIT: I hope I posted on the right subforum. Only here, it seems appropriate for it..
" I would first try what I call The American Approach, which is simply this: "If X is good, then 2X simply HAS TO BE twice as good."  ;D "
- Culturejam

jkokura

#1
November 11, 2012, 03:17:17 PM
(it's fine here)

Jacob
JMK Pedals - Custom Pedal Creations
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nzCdog

#2
November 11, 2012, 08:17:36 PM
First problem I see is using the boobtube as a preamp for a solid state circuit.  The boobtube is an overdrive that outputs a huge signal.  You're going to need to read the datasheet for your poweramp and find the input voltage saturation level and do some serious attenuation I should think....

Corey

Ettore_M

#3
November 11, 2012, 10:38:46 PM
Quote from: nzCdog on November 11, 2012, 08:17:36 PM
First problem I see is using the boobtube as a preamp for a solid state circuit.  The boobtube is an overdrive that outputs a huge signal.  You're going to need to read the datasheet for your poweramp and find the input voltage saturation level and do some serious attenuation I should think....

Corey
Seems logical.. I've been thinking about it, but I said "let's make a draft first and then we see"..
I'll take a look at the datasheet in the morning, and I'll try to calculate how much is the gain of the Boobtube. If it's too high for the TDA, I'll try to reduce it. I got to read the AX84 manual for tube amplification again!  :-\

Corey, do you see any other problems? Thanks for your contribution,BTW!  :)

Hector
" I would first try what I call The American Approach, which is simply this: "If X is good, then 2X simply HAS TO BE twice as good."  ;D "
- Culturejam

nzCdog

#4
November 12, 2012, 03:16:34 AM
No problem. Generate a test signal of 1 kHz, feed it into your preamp and do some AC voltage measurements using your multimeter.  Then you can have a think about where to do some attenuation and by how much.

Ettore_M

#5
November 12, 2012, 02:21:34 PM
Quote from: nzCdog on November 12, 2012, 03:16:34 AM
No problem. Generate a test signal of 1 kHz, feed it into your preamp and do some AC voltage measurements using your multimeter.  Then you can have a think about where to do some attenuation and by how much.

Thanks. I'll do that. What's your opinion on the idea of this amp? I mean, all these things I got together, do you think they'll work? Sorry for the questions. I have no experience on designing a circuit.  :-[
I'll be ordering parts for this soon to build it on my breadboard and start expirementing! I've heard it's sometimes the best way.
Thanks for your advice!  :D That's why I posted it here. Anyone who can help, please chime in.
I hope I'll have my results posted soon!  ;)

Hector

BTW, could you take a look at the datasheet? It says for the input voltage that it can be the same as the supply voltage at absolute maximum ratings! Is this thing possible or am I reading something wrong? I uploaded it to Dropbox: https://www.dropbox.com/s/onl6mnem8mjpoh8/TDA2040.pdf
" I would first try what I call The American Approach, which is simply this: "If X is good, then 2X simply HAS TO BE twice as good."  ;D "
- Culturejam

nzCdog

#6
November 12, 2012, 07:00:48 PM
I read that too.  Vi max = Vs.  That'll be the point of saturation, you'll probably get an increase in distortion as you approach the limit.  So you may find the boobtube doesn't cause problem after all.  It requires a +- power supply, and the total power output of the amp will be limited by the supply voltage you choose.  Get it on the breadboard and have some fun

Ettore_M

#7
November 12, 2012, 10:36:31 PM Last Edit: November 13, 2012, 07:03:23 PM by Ettore_M
Quote from: nzCdog on November 12, 2012, 07:00:48 PM
I read that too.  Vi max = Vs.  That'll be the point of saturation, you'll probably get an increase in distortion as you approach the limit.  So you may find the boobtube doesn't cause problem after all.  It requires a +- power supply, and the total power output of the amp will be limited by the supply voltage you choose.  Get it on the breadboard and have some fun
It can work with a single supply, too. Not only bipolar.
Yes, I guess the power output will drop approximately to 10W from 25W, if I use 12V supply. But it won't be that bad. Still, pretty powerful!
I'll order the parts and get it on breadboard as soon as possible. I'll post results, too! ;)
Thanks again, Corey!

Hector
" I would first try what I call The American Approach, which is simply this: "If X is good, then 2X simply HAS TO BE twice as good."  ;D "
- Culturejam

joao andre

#8
March 13, 2013, 01:30:47 PM
Hi!

have you got your amp to work?
I would be very interested in making an amp like yours to attach to a laptop battery and take it to the street. If you got it working, could you share the schematic and experience?

Thanks!
João

Ettore_M

#9
March 13, 2013, 06:46:52 PM
Quote from: joao andre on March 13, 2013, 01:30:47 PM
Hi!

have you got your amp to work?
I would be very interested in making an amp like yours to attach to a laptop battery and take it to the street. If you got it working, could you share the schematic and experience?

Thanks!
João
I didn't get that working! It was left back! But I'm gonna be building it this month. I will have to try different tone stacks and preamp section, to get it working just the way I want to.  ;)
I will inform you guys when I'll have results with this project. And sure thing I'll post a build doc for anyone that wants to build it!  :)

Hector
" I would first try what I call The American Approach, which is simply this: "If X is good, then 2X simply HAS TO BE twice as good."  ;D "
- Culturejam

Ettore_M

#10
August 14, 2013, 11:43:35 AM Last Edit: August 14, 2013, 01:41:18 PM by Ettore_M
Hi guys!

Sorry for reviving this old thread. I don't know if you are interested in this thing anymore. A lot of time passed and this amp remained as only thoughts. But these days, I have a lot of time and I'm considering of doing a single-sided layout and try it at the end of August when I get back to home.

I used another preamp scheme, the AX84 Simple Preamp. It has full EQ controls, so it seems more versatile.

As you see, the tube preamp uses a voltage-multiplier supply, up to 80 volts. The thing is I don't know anything about high voltage supplies. I have a question. What kind of resistors (according to wattage) should I use in the preamp section?? Should I go for 1/2W or 1W ones? Can the 1/2W ones do the job?

Hector

P.S. If this question belongs to the Tech Help forum, tell me and I will start a new topic!
" I would first try what I call The American Approach, which is simply this: "If X is good, then 2X simply HAS TO BE twice as good."  ;D "
- Culturejam

Ettore_M

#11
November 11, 2013, 09:29:57 PM
So, I'm still working on it! All boards are ready for testing!
Wish me luck!  :)



Hector
" I would first try what I call The American Approach, which is simply this: "If X is good, then 2X simply HAS TO BE twice as good."  ;D "
- Culturejam

selfdestroyer

#12
November 11, 2013, 10:03:52 PM
Very cool. Love to see the outcome of this project.

Ettore_M

#13
November 12, 2013, 11:51:58 AM Last Edit: November 12, 2013, 12:21:30 PM by Ettore_M
So, the Multiplier and Buffer & Power Amp boards are working great!  :)
But I can't get the Preamp to work! I built it on a perfboard, and the layout is mine, so I need a second set of eyes to look at the layout. Please...  :-\



The schematic is some posts above! ;)

Thanks!
Hector
" I would first try what I call The American Approach, which is simply this: "If X is good, then 2X simply HAS TO BE twice as good."  ;D "
- Culturejam

Ettore_M

#14
November 13, 2013, 11:05:05 PM
I don't know if it's of any interest for you guys, but I'll keep working on this. Until I get a good result!  ;)

I didn't have time to check the pre-amp board, but I had a good read of Merlin's Heater/Filament Supplies article ( http://www.valvewizard.co.uk/heater.html ). I found out that if you use a DC supply, it must be regulated at exactly the needed voltage (6.3V or 12.6V) or else it will cause a lot of hum! And I did get that in my build! So now, I'm going to run te heaters from a regulated 6.3~ V supply, and I hope at least the hum problem will go away!  :D

Also, I think I used a very small wallwart supply! Current-wise! Think that the heaters eat at least 0.3A. If you count the power amp, I need at least 1A supply! ;)

That's for today! I hope I'll have more news the next couple of days and the weekend!

Hector
" I would first try what I call The American Approach, which is simply this: "If X is good, then 2X simply HAS TO BE twice as good."  ;D "
- Culturejam
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