For a few years now I have been trying to make a high quality low voltage amplifier for students at my school to build. Each year I get a number of students who ask me to show them how to build audio stuff after they hear the DIY tube gear I use in my office. Concerned with liability, I tried to design something that the students could make without being exposed to 120ac voltage and high current. With help from people at Audioasylum last year, we made a Jfet driven push-pull battery operated tube amp. It was too complicated for all but a couple of students. This summer I tried to figure out a Gainclone using 12v ac wall-transformers (wall-warts).
The reason I am posting this is because I think the readers of this forum might be interested in this project because it is a bit different and within my goals successful. The chip I used is an STmicroelectronics TDA7384. The 12v STmicroelectronics chips TDA7376 or later were recommended by Alan Hulsebus at Orca Design. He seems to think they have some design advantages over the LM3875, and sound better within their power range, although they are not nearly as powerful. About 4X20/25 watts for the TDA7384, although they make more powerful chips. I picked one that could be ordered with all the parts I needed from DigiKey in one order.
The cost of this amplifier with the power supply will run $40-60. For us it was less because we had giant boxes of left over wall transformers in our computer storage room. I used Shotkey diodes bypassed with Panasonic PPS film caps, Panasonic FC capacitors in the power supply and Panasonic PPS film in the inputs. Alan Hulsebus also recommended the Panasonic PPS film capacitors. I also built another using premium caps. I tried both film and foil, and oil caps at the input signal and for power supply bypass. The Panasonic PPS sound surprisingly good.
Comparing this amp to my tube gear, no compromise SE 2A3, 6V6 SE and 2A3 PP, and two vintage PP tube amps, this amplifier is really quite amazing; serious bass, good high frequency extension, and very fast transient response. Getting close to the tube like midrange required some experimentation with the power supply caps. I can say without doubt that it sounds much better than a newer 135 watts per channel Rotel solid state amp I compared it to using the same speakers and source. Sorry I cannot compare it to an LM3875 amp, but I am going to build one just for that purpose very soon. With only a 12v 1.5 amp wall transformer the TDA7384 amp has much more than twice the power of my 2A3 PP amp.
Today we got out the oscilloscope, signal generator, and regulated power supply to start testing the amp. We will be posting the details of our tests and the construction details very soon on our web page. The web page will also have the PCB image I made for those who might want to try it out. The students are making their own PCB's. I will post the web address when the site is complete. Feel free to email me if you are curious or have any questions.
This is my first Gainclone; I am now a believer. A friend from school who is working with me on this project came to my house to listen to the amp. He says his new Adcom may be on Ebay very soon.
Thanks for all the info I got from this forum
The reason I am posting this is because I think the readers of this forum might be interested in this project because it is a bit different and within my goals successful. The chip I used is an STmicroelectronics TDA7384. The 12v STmicroelectronics chips TDA7376 or later were recommended by Alan Hulsebus at Orca Design. He seems to think they have some design advantages over the LM3875, and sound better within their power range, although they are not nearly as powerful. About 4X20/25 watts for the TDA7384, although they make more powerful chips. I picked one that could be ordered with all the parts I needed from DigiKey in one order.
The cost of this amplifier with the power supply will run $40-60. For us it was less because we had giant boxes of left over wall transformers in our computer storage room. I used Shotkey diodes bypassed with Panasonic PPS film caps, Panasonic FC capacitors in the power supply and Panasonic PPS film in the inputs. Alan Hulsebus also recommended the Panasonic PPS film capacitors. I also built another using premium caps. I tried both film and foil, and oil caps at the input signal and for power supply bypass. The Panasonic PPS sound surprisingly good.
Comparing this amp to my tube gear, no compromise SE 2A3, 6V6 SE and 2A3 PP, and two vintage PP tube amps, this amplifier is really quite amazing; serious bass, good high frequency extension, and very fast transient response. Getting close to the tube like midrange required some experimentation with the power supply caps. I can say without doubt that it sounds much better than a newer 135 watts per channel Rotel solid state amp I compared it to using the same speakers and source. Sorry I cannot compare it to an LM3875 amp, but I am going to build one just for that purpose very soon. With only a 12v 1.5 amp wall transformer the TDA7384 amp has much more than twice the power of my 2A3 PP amp.
Today we got out the oscilloscope, signal generator, and regulated power supply to start testing the amp. We will be posting the details of our tests and the construction details very soon on our web page. The web page will also have the PCB image I made for those who might want to try it out. The students are making their own PCB's. I will post the web address when the site is complete. Feel free to email me if you are curious or have any questions.
This is my first Gainclone; I am now a believer. A friend from school who is working with me on this project came to my house to listen to the amp. He says his new Adcom may be on Ebay very soon.
Thanks for all the info I got from this forum
So I guess that the old "chip amps are crappy by definition" is really falling apart, even for tube guys?
I haven't build any of these gain-thingies myself yet, but it seems worth a try...
There are a few chips, all mush spoken of. What's the difference between them (only the power rating?)?
Jennice
I haven't build any of these gain-thingies myself yet, but it seems worth a try...
There are a few chips, all mush spoken of. What's the difference between them (only the power rating?)?
Jennice
Just for the record LeBob, I made a small amp with OPA548 chips and two single voltage 15V/3A trafos for a friend of mine.
He uses this with his PC, with a pair of small B&W speakers.
It happens that he sells high-end at a big distributor here.
He compared my (his) small amp with a shiny new 5-star rating
Rotel 1062 integrated amp on a demo room, with expensive B&W speakers.
It was clear that the little amp had a level of detail and faithfulness to the music that the Rotel could only dream of.
He uses this with his PC, with a pair of small B&W speakers.
It happens that he sells high-end at a big distributor here.
He compared my (his) small amp with a shiny new 5-star rating
Rotel 1062 integrated amp on a demo room, with expensive B&W speakers.It was clear that the little amp had a level of detail and faithfulness to the music that the Rotel could only dream of.
Well,Being a fairly die-hard tube head(don't let my nick fool ya!),I thought I'd share my .02..
I've got a small PP 6V6 stereo amp that I rebuilt,from an old console set,along with a Dynaco ST-70 (stock circuit,except an SDS Labs cap-board.),and a pair of small SE 6BQ5 monoblocks. The ST-70's got the power,but I prefer the sound of the PP 6V6's,with the ST-70 being a pretty close 2nd..The monoblocks aren't bad at all,but theres just not enough power there for my tastes/speakers,so I don't normally use them,but sometimes they are a nice change for some background music.
I also recently made a couple chipamps from the TDA7350 (11wx2 or 22Wx1 ) I plan on building a Gainclone also sometime soon,to see what all the fuss is about. (That's what inspired my experiments with the TDA7350's,I just happen to have 3 sitting around!)
I built two versions of the TDA7350 amps,one stereo 11x2 and one 22Wx2 with two chips (and only 4 parts per channel!) straight off the datasheet.
I've never been a believer in chipamps for Hi-Fi,but It was a bit better than I had expected,It sounded pretty good for what it was.11W isn't a whole lot with my(old,homebrewed,kinda inefficient,but good sounding) speakers,but it's enough to rock out pretty decently.
The 22W version was a bit better,with a bit more power,but it sounded pretty similar to the 11W version.Kinda thin and flat compared to my tubes,but overall really not too bad,and the two amps sure were simple enough to build..
I think my Small 6V6 amp(~8wpc before any clipping) has more "punch" than the small 11Wpc version,and definately beats it sound-wise.The 22Wpc version is probably similar in terms of "punch",but also loses sound-wise.It might be a bit better sounding than the 11Wpc version,simply because it doesn't have any output coupling caps. (something I've personally never liked much.) and a bit more power.(what,3 whole dB?)
Now these chips might not be comparable to the one's I've seen in the various renditions of the Gainclone.I'm sure they must have gotten better over the years.And everyone here seems to like them enough,so what the heck,I'll try it myself and see!
I'm kind of excited!
I've got a small PP 6V6 stereo amp that I rebuilt,from an old console set,along with a Dynaco ST-70 (stock circuit,except an SDS Labs cap-board.),and a pair of small SE 6BQ5 monoblocks. The ST-70's got the power,but I prefer the sound of the PP 6V6's,with the ST-70 being a pretty close 2nd..The monoblocks aren't bad at all,but theres just not enough power there for my tastes/speakers,so I don't normally use them,but sometimes they are a nice change for some background music.
I also recently made a couple chipamps from the TDA7350 (11wx2 or 22Wx1 ) I plan on building a Gainclone also sometime soon,to see what all the fuss is about.
(That's what inspired my experiments with the TDA7350's,I just happen to have 3 sitting around!)I built two versions of the TDA7350 amps,one stereo 11x2 and one 22Wx2 with two chips (and only 4 parts per channel!) straight off the datasheet.
I've never been a believer in chipamps for Hi-Fi,but It was a bit better than I had expected,It sounded pretty good for what it was.11W isn't a whole lot with my(old,homebrewed,kinda inefficient,but good sounding) speakers,but it's enough to rock out pretty decently.
The 22W version was a bit better,with a bit more power,but it sounded pretty similar to the 11W version.Kinda thin and flat compared to my tubes,but overall really not too bad,and the two amps sure were simple enough to build..
I think my Small 6V6 amp(~8wpc before any clipping) has more "punch" than the small 11Wpc version,and definately beats it sound-wise.The 22Wpc version is probably similar in terms of "punch",but also loses sound-wise.It might be a bit better sounding than the 11Wpc version,simply because it doesn't have any output coupling caps. (something I've personally never liked much.) and a bit more power.(what,3 whole dB?)
Now these chips might not be comparable to the one's I've seen in the various renditions of the Gainclone.I'm sure they must have gotten better over the years.And everyone here seems to like them enough,so what the heck,I'll try it myself and see!
I'm kind of excited!Wow. Wish we built something like this when I was in high school. Very cool. Hope you let your students know how good these chipamps can sound.
Here's an idea - building a small pair of affordable but high quality speakers to mate with the chipamp. An extra-credit assignment, of course.
Best,
KT
Here's an idea - building a small pair of affordable but high quality speakers to mate with the chipamp. An extra-credit assignment, of course.
Best,
KT
"affordable but high quality speakers"
We are going to make/design a pair of speakers next semester. The design of speakers was easier. There are quite a few good designs to work with on the Internet.
We will probably use a Parts Express, MCM, or Tang Band full-range shielded driver. Most of the kids want to use the amp and speakers with their computers for music and movies.
We are going to make/design a pair of speakers next semester. The design of speakers was easier. There are quite a few good designs to work with on the Internet.
We will probably use a Parts Express, MCM, or Tang Band full-range shielded driver. Most of the kids want to use the amp and speakers with their computers for music and movies.
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