OK, here is one question:
Why doesn`t I get any more bass from my GC when I use a variac to lower my ac voltage to get less than +/-27V DC to the chip?
As mentioned earlier I have 2*24V ac trafo, 240VA and 44800uF after the rectifier and 2*1000uF on each LM3875 chip.
I use a pair of B&W 801 (Matrix) and I know they are not known as an easy load...
Why doesn`t I get any more bass from my GC when I use a variac to lower my ac voltage to get less than +/-27V DC to the chip?
As mentioned earlier I have 2*24V ac trafo, 240VA and 44800uF after the rectifier and 2*1000uF on each LM3875 chip.
I use a pair of B&W 801 (Matrix) and I know they are not known as an easy load...
Back to the gainclone
Interesting thread except for the last few OT pages. I'm keen to hear others subjective evaluations when trying different components. I'm looking at building a 5 channel amp cheaply using Peter's simplified gainclone. When investigating the black gate filter capacitors which many people rave about, I have found the cost of these capacitors soon add up to a considerable sum.
In previous posts, Peter mentioned using 2 4.7 uF N black gates on the diode bridge, as well as using the 1,000 uF black gates on the power rails of the LM3875. I'm thinking to save some $$, what about using 2 x 1,000 uF on the diode bridge, and 4.7 uF next to the ICs? With 5 LM3875s in my amp I will need 10 x 4.7 uF rather than 10 x 1,000 uF, saving $$$$. Any comments on the difference in sound this will make?
My thinking on the power supply for a 5 channel amp is to use a larger VA toroid, perhaps 800 VA (the surround channels are never driven as hard as the mains), but separate diode bridges for the front 2 channels (as per Peter's circuit) and the other 3 surround channels.
It also strikes me that the gainclone with its tiny power rail filter capacitors and a toroidal transformer will be susceptible to hash on the mains. The LM3875 has a pretty decent PSRR, but I'm wondering if the use of a good mains filter or possibly even a power regenerator like the audio power plant will help the sound? (BTW - a DIY audio power plant would make a good project...)
Regards,
Dean
Interesting thread except for the last few OT pages. I'm keen to hear others subjective evaluations when trying different components. I'm looking at building a 5 channel amp cheaply using Peter's simplified gainclone. When investigating the black gate filter capacitors which many people rave about, I have found the cost of these capacitors soon add up to a considerable sum.
In previous posts, Peter mentioned using 2 4.7 uF N black gates on the diode bridge, as well as using the 1,000 uF black gates on the power rails of the LM3875. I'm thinking to save some $$, what about using 2 x 1,000 uF on the diode bridge, and 4.7 uF next to the ICs? With 5 LM3875s in my amp I will need 10 x 4.7 uF rather than 10 x 1,000 uF, saving $$$$. Any comments on the difference in sound this will make?
My thinking on the power supply for a 5 channel amp is to use a larger VA toroid, perhaps 800 VA (the surround channels are never driven as hard as the mains), but separate diode bridges for the front 2 channels (as per Peter's circuit) and the other 3 surround channels.
It also strikes me that the gainclone with its tiny power rail filter capacitors and a toroidal transformer will be susceptible to hash on the mains. The LM3875 has a pretty decent PSRR, but I'm wondering if the use of a good mains filter or possibly even a power regenerator like the audio power plant will help the sound? (BTW - a DIY audio power plant would make a good project...)
Regards,
Dean
>a DIY audio power plant would make a good project...<
Something along the lines of this would be more efficient and elegant:
http://www.exactpower.com/
Nice way to put differential circuit to good use...
regards, jonathan carr
Something along the lines of this would be more efficient and elegant:
http://www.exactpower.com/
Nice way to put differential circuit to good use...
regards, jonathan carr
Re: Back to the gainclone
The 4.7u caps (after bridges) were added later and they only provide further refinements to the amp's sound. If tight on budget don't use BG N but regular electrolytics or film caps. But I believe that the big advantage is gained when using 1000u BG very close to the chip. I wouldn't do it the other way as you suggest. Use at least good caps for main channels and if you want to save use Panasonic FC or Nichicon on the surround channels.
I didn't try real power regenerator, but I tried my 600w UPS which does similar thing (and BTW improves the sound of my DAC) on gainclone and the sound degraded.
deandob said:
The 4.7u caps (after bridges) were added later and they only provide further refinements to the amp's sound. If tight on budget don't use BG N but regular electrolytics or film caps. But I believe that the big advantage is gained when using 1000u BG very close to the chip. I wouldn't do it the other way as you suggest. Use at least good caps for main channels and if you want to save use Panasonic FC or Nichicon on the surround channels.
I didn't try real power regenerator, but I tried my 600w UPS which does similar thing (and BTW improves the sound of my DAC) on gainclone and the sound degraded.
10000 caps, that are quite a lot 
Peter: do you think that your amp is very stable now? I am not yet completely convinced about the stability of my amp. Could be the 100 k att. I use. Sometimes I experience not so good sound from my amp. When I turn off the amp for a few seconds the sound is good again!
BTW: would it not be a nice idea to add a new forum group for gainclones? There are so many threads about gainclones now, it would be nice to assemble them like the Passlabs threads. Just an idea...
Fedde
Peter: do you think that your amp is very stable now? I am not yet completely convinced about the stability of my amp. Could be the 100 k att. I use. Sometimes I experience not so good sound from my amp. When I turn off the amp for a few seconds the sound is good again!
BTW: would it not be a nice idea to add a new forum group for gainclones? There are so many threads about gainclones now, it would be nice to assemble them like the Passlabs threads. Just an idea...
Fedde
I don't experience any problems of that type. But I noticed that when the case was not grounded I was picking radio freguencies. I also think that lower value pot makes the amp less prone to oscillate. The amp is a bit less stable when positive input to ground resistor is removed, but it sounds better without it.
I used 10000 caps, because tis is what I had handy. I also used additional 1000 BG right after bridges, but prefer 4.7 BG N there. It is less vivid sound, but I prefer it this way. The bass is good both ways.
I used 10000 caps, because tis is what I had handy. I also used additional 1000 BG right after bridges, but prefer 4.7 BG N there. It is less vivid sound, but I prefer it this way. The bass is good both ways.
Peter Daniel Gain Clone Power Conn.
Hi Peter. I found the distributor of the Power Connector you are using on your Gain Clone. They are made by Mode Electronics, under microphone connector. Available from Electrosonic,
4 pins Chassis Part No: 25-734-0, price 1.26$ CAN
4 pins Inline Part No. 25-724-0, 1.24$ CAN
Bye...
Hi Peter. I found the distributor of the Power Connector you are using on your Gain Clone. They are made by Mode Electronics, under microphone connector. Available from Electrosonic,
4 pins Chassis Part No: 25-734-0, price 1.26$ CAN
4 pins Inline Part No. 25-724-0, 1.24$ CAN
Bye...
Let's try again... 
Anyway, it's time for a complete rebuild of the amp I guess. My amp is maybe a little bit messy after months of tweaking. Maybe, this time I will use mini pcb's. I didn't like the idea before, but after I realized that I could potentially match my channels better I liked the idea more...
And my cute 23 step att. is still waiting for me...
Now I only have to buy 92 resistors, and solder them... sigh...
I think that I will take metal film, I don't see my self matching the 200-300 resistors for these 92 chosen ones...
Fedde
Most have taken some time to solder all those caps
Anyway, it's time for a complete rebuild of the amp I guess. My amp is maybe a little bit messy after months of tweaking. Maybe, this time I will use mini pcb's. I didn't like the idea before, but after I realized that I could potentially match my channels better I liked the idea more...
And my cute 23 step att. is still waiting for me...
Now I only have to buy 92 resistors, and solder them... sigh...
I think that I will take metal film, I don't see my self matching the 200-300 resistors for these 92 chosen ones...
Fedde
Oh my god, i dont belive i have actually finished reading the 65 pages of this tread and now i can post. 
I have read every single post, and i have taken in about 95% of it 
after reading 30 pages of posts in one go, your brain falls asleep (long after your limbs have ).
ok, down to the point. I am so jelous of your amp Peter! i have decided to make one of my own. now, loads of questions:
which chip would you recomend? the LM3875 seems the most popular. i like bassy, rock, industial etc. music.
what are the differences between the inverted and non-inverted circuits (apart from them being inverted )? and which should i make?
which manufacturers of capacitors/resistors should i use? ive heard alot about Black Gate Capacitors.
will i be able to use my dual 0-30V 1A power suply to power my gainclone in the testing stages (before i make a power supply)? i can use the dual ouputs to make +-25v.
what is a 'star ground'? ive heard loads about them but i cant find any info on what they are, is it just where all the grounds connect?
could someone please explain the classes or point me to a document that does?
what does bridging/parrelleling do to the output?
off the subject but, what circuit drawing software do people use, and where can i download it ?
the only thing i can say about Peter's amp(s) is: WOW!!!
I have read every single post, and i have taken in about 95% of it after reading 30 pages of posts in one go, your brain falls asleep (long after your limbs have ).ok, down to the point. I am so jelous of your amp Peter! i have decided to make one of my own. now, loads of questions:
which chip would you recomend? the LM3875 seems the most popular. i like bassy, rock, industial etc. music.
what are the differences between the inverted and non-inverted circuits (apart from them being inverted
)? and which should i make?which manufacturers of capacitors/resistors should i use? ive heard alot about Black Gate Capacitors.
will i be able to use my dual 0-30V 1A power suply to power my gainclone in the testing stages (before i make a power supply)? i can use the dual ouputs to make +-25v.
what is a 'star ground'? ive heard loads about them but i cant find any info on what they are, is it just where all the grounds connect?
could someone please explain the classes or point me to a document that does?
what does bridging/parrelleling do to the output?
off the subject but, what circuit drawing software do people use, and where can i download it
?the only thing i can say about Peter's amp(s) is: WOW!!!
Fedde, based on my experience you will probably only use about six positions of your attenuator anyway. Of course, you won't know which six until you have used it but when you do know, simply replace the resistors in those six positions with something better like Welwyn RC55's (either .1% or .5% - I can't hear the difference).
I've done 3 stepped attenuators now and all that soldering doesn't get any less tedious! Good luck.
Nice quote
I use a lot of different volumes during the day. In the morning medium loudness. In the afternoon loud to *very* loud. In the evening loud and during the night very soft. And also, my music has a lot different volumes so I need many steps...
Fedde, who is now wondering when he actually sleeps...
I use a lot of different volumes during the day. In the morning medium loudness. In the afternoon loud to *very* loud. In the evening loud and during the night very soft. And also, my music has a lot different volumes so I need many steps...
Fedde, who is now wondering when he actually sleeps...
Matttcattt, welcome from Burnham-on-sea!
Well, you have come up with an awful lot of questions many of which are already answered in this thread.
Anyway, if you're completely new to this game then play safe and copy a tried and tested design. You like Peter's amp so why not start with that and I'm fairly sure that Peter has posted the circuit somewhere in this thread.
That will mean going with the LM3875 to answer the chip question.
As regards components, again Peter (and others) has talked about his choice in more than one post. You can build a Gainclone with any component so long as you stick to the correct value and power ratings. Obviously some components (usually the more/most expensive ones sound better).
It's really a question of trying different components and fine tuning your design to suit the sound that you prefer bearing in mind the variable factors like your source and speakers.
I'm not sure what you mean about your transformer. If you do get 25 volt rails then yes it should be OK. Note, two rectifier bridges are used in Peter's design.
Star ground is a method of connecting all the ground wires to a single point (hence the name). Very briefly, this is to avoid creating loops that may lead to hum or other problems. Again, re-read all the threads and you will see how this is done.
If you bridge amplifiers you produce a higher power output. Don't worry about doing that until you have built a simple Gainclone and got it working.
What do you mean by 'drawing circuits'. If you mean producing a circuit diagram then you can use just about any graphics program. Then there is specialist software that produces the actual layout and tracks for making a PCB.
Well, you have come up with an awful lot of questions many of which are already answered in this thread.
Anyway, if you're completely new to this game then play safe and copy a tried and tested design. You like Peter's amp so why not start with that and I'm fairly sure that Peter has posted the circuit somewhere in this thread.
That will mean going with the LM3875 to answer the chip question.
As regards components, again Peter (and others) has talked about his choice in more than one post. You can build a Gainclone with any component so long as you stick to the correct value and power ratings. Obviously some components (usually the more/most expensive ones sound better).
It's really a question of trying different components and fine tuning your design to suit the sound that you prefer bearing in mind the variable factors like your source and speakers.
I'm not sure what you mean about your transformer. If you do get 25 volt rails then yes it should be OK. Note, two rectifier bridges are used in Peter's design.
Star ground is a method of connecting all the ground wires to a single point (hence the name). Very briefly, this is to avoid creating loops that may lead to hum or other problems. Again, re-read all the threads and you will see how this is done.
If you bridge amplifiers you produce a higher power output. Don't worry about doing that until you have built a simple Gainclone and got it working.
What do you mean by 'drawing circuits'. If you mean producing a circuit diagram then you can use just about any graphics program. Then there is specialist software that produces the actual layout and tracks for making a PCB.
thanks Nuuk, that answers nearly all of my questions.
the power supply i mentioned has only got an output of MAX 1 amp, will this be enough?
does bridging double the power output? in this case 56w --> 112w? what does parrelleling do? the same thing?
questions still unanswered:
what are the differences between the inverted and non-inverted circuits (apart from them being inverted )? and which should i make?
could someone please explain the classes or point me to a document that does?
also, can i use a normal petentiometer (0.2w) for the volume, or do i need a more powerful one (2w) or do i need to make one?
what simple loudspeaker protection could i build into the circuit so that i wont blow up my speakers if i make a mistake with the construction.
the power supply i mentioned has only got an output of MAX 1 amp, will this be enough?
does bridging double the power output? in this case 56w --> 112w? what does parrelleling do? the same thing?
questions still unanswered:
what are the differences between the inverted and non-inverted circuits (apart from them being inverted )? and which should i make?
could someone please explain the classes or point me to a document that does?
also, can i use a normal petentiometer (0.2w) for the volume, or do i need a more powerful one (2w) or do i need to make one?
what simple loudspeaker protection could i build into the circuit so that i wont blow up my speakers if i make a mistake with the construction.
Matttcattt said:
Op amp has two inputs: inverting and non inverting. Depending where you connect your incoming signal you got two modes of operation with a chip. Everybody commented that inverting config. sounds better, so that's why I tried this one. After hearing results I'm not even slightly tempted to try the other one.
You can use any pot, if it's no good you will smell it and then you'll have to look for something better but it's unlikely.
I'm not sure, but I think that the chip has some sort of protection built in.
If you want more, check the thread "amplifier and speaker protection circuits."
I'm not using any drawing software, because I'm not designing much circuits. I usually use other people circuits and remove the parts that are not required.
Peter Daniel said:
Op amp has two inputs: inverting and non inverting. Depending where you connect your incoming signal you got two modes of operation with a chip. Everybody commented that non inverting config. sounds better, so that's why I tried this one. After hearing results I'm not even slightly tempted to try the other way.
You mean inverted config. !!!
Highly unlikely...
Yep it has. First measure the output with the multimeter and ensure all connections are firm&correct.
See my page for more info:
http://home.student.utwente.nl/f.s.bouwman/audio/thor-amp.html
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