Ok, got the second channel running. I made the circuit that Thorsten put on amp chip diy, inverted with 22k from + input to ground and 18K from - to ground. Everything is in a L-shaped aluminium bar, 20 cm long and 5 cm square. Neat and clean. I have a nice wood cover that I must finish now. Resistors are metal film and metal oxide, 1/4 and 1/2 W. Feedback resistor is metal oxide 1/2W. BC film caps and Samsung electrolytics. The chip is a OPA541. PSU is from the rotel, that has 2 x 6800uF, +/-28 VDC.
I been listening to it and I have to say that it is not so special as I though. Sounds crisp, clean and fast. And has lots of power too. But my first impression was that each speaker was singing without caring what the other one was doing. So the soundstage was like broken at the middle. I checked for polarity of the thing and it was ok. Bass is good. But again not that good. It seemed that things have improved after an hour or so, so break in can be required or I am getting used to it.
Miguel
I been listening to it and I have to say that it is not so special as I though. Sounds crisp, clean and fast. And has lots of power too. But my first impression was that each speaker was singing without caring what the other one was doing. So the soundstage was like broken at the middle. I checked for polarity of the thing and it was ok. Bass is good. But again not that good. It seemed that things have improved after an hour or so, so break in can be required or I am getting used to it.
Miguel
Nuuk said:
Matt, I use a 1.6AT on the primaries side of my PSU's and that should be sufficient. Depends how many more of the sound degrading little so and so's you want to put in!
I'm a GC picture fan so get them up ASAP
when i make a power supply for my gainclone (im using a variable bench power supply at the moment), should i use fuses on both the primary and secondarys of the transformer?
Asen said:
Using the non-inverting datasheet circuit, with a 50k pot, the input impedance will be 50k.
With the inverting circuit, assuming a 10k input resistor and ignoring the input capacitor, the input impedance will range from 50k (pot turned all the way down) to 8.3k (pot turned all the way up).
I chose to ignore the input capacitor because it is frequency dependent. At 20Hz, the capacitor's reactance will be about 1.7k ohms which adds to the 10k input resistor. Your input impedance at 20Hz will then be about 9.5k rather than 8.3k.
At 20kHz, the capacitor's reactance will only be about 1.7 ohms and the input impedance will essentially be 8.3k.
se
Complex impedance
The impedance is the square root of the resistance squared plus the capacitive reactance squared.
http://www.cvs1.uklinux.net/calculators/
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/impcom.html
amateurs...........
The impedance is the square root of the resistance squared plus the capacitive reactance squared.
http://www.cvs1.uklinux.net/calculators/
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/impcom.html
amateurs...........
Re: Complex impedance
Oops. Brain fart. Was looking at them as two impedances in series. Thanks.
As for amateurs, I guess I'm in good compnay. Perhaps you'll recall this brain fart of yours:
<i>Worse case for a 50K pot gives a gain of 200k/(25K+10K) or 5.7 and the amp stands a good chance of having stablity issues in this configuration.</i>
Have a great weekend, Fred!
se
Fred Dieckmann said:
Oops. Brain fart. Was looking at them as two impedances in series. Thanks.
As for amateurs, I guess I'm in good compnay. Perhaps you'll recall this brain fart of yours:
<i>Worse case for a 50K pot gives a gain of 200k/(25K+10K) or 5.7 and the amp stands a good chance of having stablity issues in this configuration.</i>
Have a great weekend, Fred!
se
Complex Flatulence ?
200k/35k = 5.71428k according to MS Calculator.
Steve Eddy said:Oops. Brain fart. Was looking at them as two impedances in series. Thanks.
As for amateurs, I guess I'm in good compnay. Perhaps you'll recall this brain fart of yours:
<i>Worse case for a 50K pot gives a gain of 200k/(25K+10K) or 5.7 and the amp stands a good chance of having stablity issues in this configuration.</i>
Have a great weekend, Fred!
se
200k/35k = 5.71428k according to MS Calculator.
Re: Complex Flatulence ?
That's because your MS Calculator (or mine for that matter) isn't smart enough to say "Pssssst! Hey Eric, the other 25k of that 50k pot is in parallel with the first 25k."
So instead of 200k/(25k + 10k), it should be 200k/(25k||25k + 10k), or 200k/(12.5k + 10k) which is 8.8888...
And actually, Fred typoed on that. Should have been 220k rather than 200k. So it would be 9.7777...
se
mrfeedback said:
That's because your MS Calculator (or mine for that matter) isn't smart enough to say "Pssssst! Hey Eric, the other 25k of that 50k pot is in parallel with the first 25k."
So instead of 200k/(25k + 10k), it should be 200k/(25k||25k + 10k), or 200k/(12.5k + 10k) which is 8.8888...
And actually, Fred typoed on that. Should have been 220k rather than 200k. So it would be 9.7777...
se
I have finished both channels of my gainclone using the OPA548, and i like how it sounds, i now want to make one with the OPA541 as i have 2 of these. i have two power suplys, one is +/- 15v with 33000uf and the other is 35v with 2200uf, which power supply would be better with which amp?
i also want to try bridging and parrelleling and i want to know which i should try first.
what sort if speaker cable is best suited to gainclones? solid core or stranded cable? thick cable or thin cable? i have some cat5 cable (some stranded, some solid core) and i dont know wether to use a single pair for both or wether to wire all the pairs together.
i also want to try bridging and parrelleling and i want to know which i should try first.
what sort if speaker cable is best suited to gainclones? solid core or stranded cable? thick cable or thin cable? i have some cat5 cable (some stranded, some solid core) and i dont know wether to use a single pair for both or wether to wire all the pairs together.
Help
I just finished two channels of my gainclone based on Peter Daniel's schematic. I left out the input capacitor. I get nothing out!!!
I have checked and double checked my connections. I am currently using a cheap 12 volt power supply until I finish my battery supply.
Is it possible I got a bad batch of chips?
Vic
I just finished two channels of my gainclone based on Peter Daniel's schematic. I left out the input capacitor. I get nothing out!!!
I have checked and double checked my connections. I am currently using a cheap 12 volt power supply until I finish my battery supply.
Is it possible I got a bad batch of chips?
Vic
Good luck Vic. It's great when these things work straight off but perhaps more satisfying after we have solved a problem or two!
I've been tinkering with speaker cables for my Gainclones and thought it time to post a few comments.
I started off with good old (over 20 years actually) 79 strand which was OK but had a flabby bass.
I replaced that with two strands of .6mm bellwire which firmed up the bass but lost the silky smooth mid range (not surprising really as it wasn't burned in and the tinned wire didn't help).
I added a small stranded copper cable in parallel with the bellwire but it didn't seem to make any improvement.
Then I found a cable in my 'box of bits' that is a flat braided design and that sounds the best so far with the bass nice and tight but with a good mid-range/top end. I can't find any sort of ID on it though.
I should also say that the speaker cables that I have used are modified in a way that I am not permitted to divulge but it does make a big difference, especially to the bass. The modification is the subject of a patent and I was only told on the strict condition that I don't pass on the information.
After a couple of weeks of using them, I am more impressed with the Gainclones than ever. A friend who listened to them driving the Mordaunt Short Pageants insisted that I was 'pulling his leg' and using a hidden subwoofer. He claimed it was impossible to get a sound like that from a pair of mid-priced 1980's speakers! Well, we know better, don't we?
I've been tinkering with speaker cables for my Gainclones and thought it time to post a few comments.
I started off with good old (over 20 years actually) 79 strand which was OK but had a flabby bass.
I replaced that with two strands of .6mm bellwire which firmed up the bass but lost the silky smooth mid range (not surprising really as it wasn't burned in and the tinned wire didn't help).
I added a small stranded copper cable in parallel with the bellwire but it didn't seem to make any improvement.
Then I found a cable in my 'box of bits' that is a flat braided design and that sounds the best so far with the bass nice and tight but with a good mid-range/top end. I can't find any sort of ID on it though.
I should also say that the speaker cables that I have used are modified in a way that I am not permitted to divulge but it does make a big difference, especially to the bass. The modification is the subject of a patent and I was only told on the strict condition that I don't pass on the information.
After a couple of weeks of using them, I am more impressed with the Gainclones than ever. A friend who listened to them driving the Mordaunt Short Pageants insisted that I was 'pulling his leg' and using a hidden subwoofer. He claimed it was impossible to get a sound like that from a pair of mid-priced 1980's speakers! Well, we know better, don't we?
just finished gainclone piccies
just finished a Inverted Gainclone using this design http://home.attbi.com/~greggbaker/invertedLM3875.gif
LM3875
Panasonic FA caps
1 160VA 18V toroidal per channel
sounds great! a lil hum needs taking care of and a couple of the caps need to be changed to Pana FAs (as the originals blew up cause of wrong polarity and were replaced with cheapies till the panas arrive)
rest of the pics here : Pics
Amit
just finished a Inverted Gainclone using this design http://home.attbi.com/~greggbaker/invertedLM3875.gif
LM3875
Panasonic FA caps
1 160VA 18V toroidal per channel
sounds great! a lil hum needs taking care of and a couple of the caps need to be changed to Pana FAs (as the originals blew up cause of wrong polarity and were replaced with cheapies till the panas arrive)
An externally hosted image should be here but it was not working when we last tested it.
rest of the pics here : Pics
Amit
I just soldered the two pins, that are side by side on the OPA541. BTW it is sounding better, which means burning in is necessary. If you use the OPA541 let me know your findings.
Vic, have you connected the enable pin (if there is one)? Do you have any short in any place? I made a couple of mistakes on the soldering and the chip protected itself and did not make any sound. Errors corrected and it worked fine. If it was a transistor smoke had evolved in soem misterious ways
Miguel
the connectors are from CPC(UK). isolated phonos and speaker bindings. actually i havent checked if the speaker terminals accept 4mm banana plugs yet.
if you look closely each phono connector is different. They were sposed to be both the same version as the black one, but they were out of stock.
if you look closely each phono connector is different.
They were sposed to be both the same version as the black one, but they were out of stock.- Status
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