To Steve Eddy:
Sure, but not with the famous 1.5K resistor to Vsupply! The gainclone chips' temperature and current safety circuits make it unsuited for high bias (say 25 Ohm to -33V supply).
Regards,
Thijs
Sure, but not with the famous 1.5K resistor to Vsupply! The gainclone chips' temperature and current safety circuits make it unsuited for high bias (say 25 Ohm to -33V supply).
Regards,
Thijs
Peter Daniel said:
FC ps caps, type N input & coupling caps? brand resistors?
I only use cheapo parts (for the momment) in mine
It doesn't sound bad, on my crappy speakers (crappy crappy...)
Peter: when you are about to test an amp's (or anything else) sound, how are you proceeding?
You certainly listen to a perfectly known CD, but what do you pay attention for?
I use a 28 VDC supply with 6800uF per rail in the PSU. In the amp I use 1000uF per channel and per rail, bypassed by a 1uF film cap between + and -.
Miguel
Miguel
It shouldn't be that hard to disonnect 6800 caps. I'm curious on your findings, just use 1000u per rail. And if DC allows, don't use coupling cap.
When I listen to the amp, I have a Zen like state of mind, and I try to find what's my reaction to music is.😉 If I enjoy it, then I look further into details, frequency extention, soundstage and try to listen to familar tracks. But the most important factor is that the music must feel real and not boring.
When I listen to the amp, I have a Zen like state of mind, and I try to find what's my reaction to music is.😉 If I enjoy it, then I look further into details, frequency extention, soundstage and try to listen to familar tracks. But the most important factor is that the music must feel real and not boring.
well, it is anothers amp PSU, and I have not access to the bottom of the board without taking the whole thing apart...
But I can use the transformer's leads and a diode bridge to take out the juice. That is easier.
Of course I keep the inputs/outputs of this amp disconnected when I use the gainclone, so the few mA it draws in iddle should not affect the sound.
Miguel
analog_sa said:
It depends on the value of the resistor and the rail voltage. You can set the resistor to run as much or as little current as you want provided it's within the SOA of the device.
se
tschrama said:
Well, that 1.5k resistor is only meaningful in the context of small signal opamps.
Not sure exactly what you can ultimately get away with using the LM-3875. I'd have to take a look at the datasheet. Certainly you wouldn't be able to get away with something on the order of 50 watts as you suggest above. But I don't see any reason why you couldn't get away with it down around say 10 watts or so.
se
I am more or less gathering that the OPA541 is not good... well, I have two of them lying around, so is it even worth my trouble? Or should I just get an LM3875 and let it be that?
I think I mentioned this before... I am using a Sony CDP-CE375 cd-player RCA outs as my source. I do not know if there is any DC present here. I can check... just run the MM from output ground to output signal with MM on DC, right? What is a safe level?
The amp will be used with speakers I am building (8" Eminence, 1" Selenium tweeter, in 1.1cu.ft. box). I will also be making a sub preout, probably including a preamp there, for a 15" DIY sub I have also. With speakers such as these, which chip would sound best? Overall sens= 97-100dB throughout audio spectrum.
A note on parts, again: The speakers I am using will use Solen crossover caps, the same ones I would have used on the amp input. Iw as planning to bypass the 3.3uF metallized Solen coupling cap with a .22uF polypropylene. would this help anything? Should I source other caps? Is .47uF enough on input, or do I need more?
Also on parts: the Nichicon UPW's are spec'ed basically the same as Panasonic FC. Shouldn't they be an ok subtitute? I cannot order enough from Digi-Key to meet the minimum order, which is why I would like to cut them out. Are 1/2W RN65D Vishay/Dale resistors sufficient?
Thanks
I think I mentioned this before... I am using a Sony CDP-CE375 cd-player RCA outs as my source. I do not know if there is any DC present here. I can check... just run the MM from output ground to output signal with MM on DC, right? What is a safe level?
The amp will be used with speakers I am building (8" Eminence, 1" Selenium tweeter, in 1.1cu.ft. box). I will also be making a sub preout, probably including a preamp there, for a 15" DIY sub I have also. With speakers such as these, which chip would sound best? Overall sens= 97-100dB throughout audio spectrum.
A note on parts, again: The speakers I am using will use Solen crossover caps, the same ones I would have used on the amp input. Iw as planning to bypass the 3.3uF metallized Solen coupling cap with a .22uF polypropylene. would this help anything? Should I source other caps? Is .47uF enough on input, or do I need more?
Also on parts: the Nichicon UPW's are spec'ed basically the same as Panasonic FC. Shouldn't they be an ok subtitute? I cannot order enough from Digi-Key to meet the minimum order, which is why I would like to cut them out. Are 1/2W RN65D Vishay/Dale resistors sufficient?
Thanks
Dear Peter,
Nice work you are doing on the gainclones. You have inspired other members also. My question is if the gainclone can drive loudspeakers with resistance about 2 Ohms. I am building the Scan Speak Reference Monitors and was wondering if I could use the Gainclones as amplifiers or an Aleph30.
Thanks
George
Nice work you are doing on the gainclones. You have inspired other members also. My question is if the gainclone can drive loudspeakers with resistance about 2 Ohms. I am building the Scan Speak Reference Monitors and was wondering if I could use the Gainclones as amplifiers or an Aleph30.
Thanks
George
gchrist said:
You quite probably can, if you lower your voltage or parallel two or more chips on each channel to handle more current.
If you parallel chips using a +/-24v supply you may get good results with those speakers.
In any case 2 ohms is a tough load for any amp. Let's hope you are not paralleling speakers that are already 4 ohms, because that's nominal and on some cases can dip lower, particularly if they are subwoofers.
Carlos
For 2R loads, I'd advice you to use maximum 20V DC rails, with a LM3875, this would give you a little more than 40W
or, have a look at the datasheet, they show how to bridge them to work nicely with 2R loads
or, have a look at the datasheet, they show how to bridge them to work nicely with 2R loads
If I use the OPA541... do I need the current limit resistor? I plan to make PC boards for this... so, I am limited on room. A big 5 or 10W resistor just won't fit. So, can I just take the current limit pin and connect it directly to the output pin of the amp chip?
trespasser_guy said:
It certainly works that way with the other BB power opamps, but check the data sheet just in case😉
http://focus.ti.com/docs/prod/folders/print/opa541.html
(edit) Sorry, on the other chips the Ilim pin is connected to V-😱
I just spent the past 3 hours staring at the data sheet... I honestly have no clue whether it is necessary or not. I mean... having something there (a .01 ohm resistor) seems to be pointless. .01 ohms! Why not just connect it straight to the output pin. That is just the way I see it... But, I don't really know. I would rather not use it... but if I don't order a resistor for it, then I won't have one if I do need it, but if I don't need it, I just wasted money... I am on a VERY strict budget, where any mistake means the difference in being able to do the project or not. 🙁
I never build anything because I am afraid it won't work... because I really don't know. This project is stressing me out... I may abandon it soon as well. 🙁
I never build anything because I am afraid it won't work... because I really don't know. This project is stressing me out... I may abandon it soon as well. 🙁
A 0.01 ohm resistor should be very easy (and exact) to make diy. But i fear if you soldier it to something the value will change significantly.
I would not order one.
why not 549?
I would not order one.
why not 549?
Hey mate, chill!🙂
Why don't you try the 549 or 548 chips, they both work without the limiting resistor, I know that for a fact as I have built GCs with them both!
They are also a bit easier to mount than the T03 packages, and the only thing you loose on is the slightly lower Vmax, at 60V rather than 80V.
Why don't you try the 549 or 548 chips, they both work without the limiting resistor, I know that for a fact as I have built GCs with them both!
They are also a bit easier to mount than the T03 packages, and the only thing you loose on is the slightly lower Vmax, at 60V rather than 80V.
Sorry about that... I get kinda stressed when I cannot understand...
EDIT: Wait... I just read further in the data sheet and can see what to do with the REF and Ilm pins...
What do I do with the E/S pin? Just leave it unconnected?
And the biggest question of all: How do these chips sound? Do they sound like Burr-Browns, or are they dead, lifeless, ect.
EDIT: Wait... I just read further in the data sheet and can see what to do with the REF and Ilm pins...
What do I do with the E/S pin? Just leave it unconnected?
And the biggest question of all: How do these chips sound? Do they sound like Burr-Browns, or are they dead, lifeless, ect.
No problemss mate😉
Yes, you can just ignore the E/S pin unless you want to implement a Mute function.
Hmm, stand by for subjective comments
IMHO the OPAs sound better than the LMs. Bass is better, the brittleness at the top end is gone, and the sound in general seems more accurate. They certainly don't sound cold.
However now we get really subjective... Peter Daniel agrees with all the above observations, but he prefers the LM chips, so it all comes down to personal taste in the end!
(note- neither of us has done blind testing or objective measurements😀)
Yes, you can just ignore the E/S pin unless you want to implement a Mute function.
Hmm, stand by for subjective comments IMHO the OPAs sound better than the LMs. Bass is better, the brittleness at the top end is gone, and the sound in general seems more accurate. They certainly don't sound cold.
However now we get really subjective... Peter Daniel agrees with all the above observations, but he prefers the LM chips, so it all comes down to personal taste in the end!
(note- neither of us has done blind testing or objective measurements😀)
- Status
- Not open for further replies.