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 (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..
(it's fine here)
Jacob
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
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
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.
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 (https://www.dropbox.com/s/onl6mnem8mjpoh8/TDA2040.pdf)
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
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
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
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
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!
So, I'm still working on it! All boards are ready for testing!
Wish me luck! :)
(http://i1023.photobucket.com/albums/af360/Ettore_M/Build%20Photos/ALIM2031_1_zpsd6ab0c14.jpg)
Hector
Very cool. Love to see the outcome of this project.
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... :-\
(http://i1023.photobucket.com/albums/af360/Ettore_M/Build%20Photos/ALIM2033_zpsc8da67ac.jpg)
The schematic is some posts above! ;)
Thanks!
Hector
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 (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
Looks cool hector... good luck fine tuning things! :)
Hi there! :)
I'm quite excited today, because I discovered that all the boards are working! The pre-amp board causes a little hum, but it's not in a box yet so I think this will stop once I box it. ;) BTW, with a 12AX7 at 100 volts, there is a whole lot of headroom available. Or so it seems to me!
However, it seems like an overkill having a full tonestack on soemthing like this. So I think I'll maybe get back to the Boobtube as a preamp stage.
The past days, the pre-amp didn't work, when I tried it in front of the TDA power-amp. Today, I tried it in front of my amp (like a pedal) and it works! So now, I think that this little thing needs more than 850mA that my 12V supply can give.
Also, the heaters are now working on 6.3 volts supplied by a LM317 and the tube doesn't get really hot and the tube will have a longer life. However, the LM317 does get really hot, even with a heatsink!
That's all for now! If there is someone with a little more knowledge than me on tube preamps, and wants to give an advice or two, you're welcome to chime in!
Hector
Holy F#%K! :o
This thing works! I am surprised. The picture below shows why! ;)
(http://i1023.photobucket.com/albums/af360/Ettore_M/Build%20Photos/100_0014_zps26dedf70.jpg)
It actually works. At least, I didn't expect it to behave well at all. But I got great sound from it. It sounds very tube-like, because of the tube preamp. And the TDA2050 gives a lot of power! I think it can get to volumes equal to my all-tube VHT Special 6!
However, I have a lot of noise.. :-\ I'll figure it out later. But as a proof of principle, I think this little amp can be a great amp project, and could be used, not only for practice, but for gigs too. I know a little optimistic, but with a mic'ed 12" speaker cab, you could cover the needs for a little bar gig.
Hope you can actually understand my words. I'm too tired even to think. I'm excited, though! ;D
Here's a sample! It sounds like crap. I put the mic too far away from the cab, and there's an extreme amount of noise. But, I hope you like.. ;)
[soundcloud]https://soundcloud.com/ettore_m/hybrid-amp-test[/soundcloud]
Hector
Very cool. Looking forward to seeing more of this. Looks like a fun project.
Sounds really nice and I happen to need a new practice amp (my Mark II Boogie is to loud for home). If only the noise could be reduced somehow...
Hi guys! I'm happy you like it. I'm going to fix some things that may cause noise, and I'm going to put it in a box, as now it's out and a circuit like this catches a lot of RF or 50Hz noise. I think it's gonna be just fine.
Note that the schem is not right as it is, as I changed a couple things. So, wait a little for the new one, if you wanna build one! ;)
Hector
Finished at last! And it sounds huge! 8)
(http://i1023.photobucket.com/albums/af360/Ettore_M/Build%20Photos/1545768_10200919303337723_41343132_n_zpse9db38c2.jpg)
I like it a lot. And volume-wise, I think it gets really close to my VHT Special 6! Pretty awesome! ;D
I'll record a sample for you! I think you'll like it a lot too! ;)
Hector
Awesome, great job.
nice...very nice!!!
we need more updates on this! hehhe
Well done mate... the demos sound great! ;D
I know its an old thread but how did this project now. did you update it? Im very interested