Hello 
after a long abstinence from the web and electronics (but while gardening a lot), I feel as if I have forgotten everything concerning electronics...
Anyhow, before I spent too much time reading and thinking, now I want more practice!
I have four LT1210, and from the datasheet it looks ok for a (low power) chipamp.
To feed 4ohms, it looks like I'd better parallel two of them.
As from the datasheet (and my spice simulation) it looks that a gain of 2 would be a good choice, so I'll put an op-amp in front.
It won't be very strong, but 16W at 4ohms should still sound ok.
Spice gives me the least distortion for the global feedback version. Maybe in practice distortion numbers may look different, but I tend to realize the version below.
About the op-amp in front, I'm not sure yet, but it's by far less important than the main amp anyway. Maybe I'll use an OP227 or an OP132, or even an AD8620 (ok, in this case I'll be aware of the supply voltage, it has to be less than +-15V).
I'll probably replace R5 with a pot for volume adjustment.
I think that R2 should be in the range of 1k to 10k, I think that 1k should give me less dc offset, but I'm not really sure, as the LT1210 is a current FB op-amp and if I remember well the offset isn't really calculable here.
Any objections?
Thanks for your interest,
Dominique
EDIT: oops, I've forgotten to put resistors in the signal paths just in front of both LT1210! How big should I make them, maybe 1k?
after a long abstinence from the web and electronics (but while gardening a lot), I feel as if I have forgotten everything concerning electronics...
Anyhow, before I spent too much time reading and thinking, now I want more practice!
I have four LT1210, and from the datasheet it looks ok for a (low power) chipamp.
To feed 4ohms, it looks like I'd better parallel two of them.
As from the datasheet (and my spice simulation) it looks that a gain of 2 would be a good choice, so I'll put an op-amp in front.
It won't be very strong, but 16W at 4ohms should still sound ok.
Spice gives me the least distortion for the global feedback version. Maybe in practice distortion numbers may look different, but I tend to realize the version below.
About the op-amp in front, I'm not sure yet, but it's by far less important than the main amp anyway. Maybe I'll use an OP227 or an OP132, or even an AD8620 (ok, in this case I'll be aware of the supply voltage, it has to be less than +-15V).
I'll probably replace R5 with a pot for volume adjustment.
I think that R2 should be in the range of 1k to 10k, I think that 1k should give me less dc offset, but I'm not really sure, as the LT1210 is a current FB op-amp and if I remember well the offset isn't really calculable here.
Any objections?
Thanks for your interest,
Dominique
EDIT: oops, I've forgotten to put resistors in the signal paths just in front of both LT1210! How big should I make them, maybe 1k?
Attachments
... you might relabel your power supply voltages on the diagram ... all labeled +15 VDC (yes, I see the battery symbols are there, correctly, but I'm old school). ( http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1154,C1009,C1146,P1329,D2461 ) I know you are thinking the right way, but us old timers look at the drawings first, and the comments after.
" ... About the op-amp in front, .... but it's by far less important than the main amp anyway. ..."
Well, I would say just the opposite: The input stage (op-amp) is very important to the over all quality and results. This is the point where most noise can creap in, where wiring practices and impedence matching are most important ... Pick the best quality input stage possible and the rest of the parts will natually work better, sound better. (This is why so much attention is paid to pre-amps. No matter what the power output may be, it would not matter much if that power is simply amplifying a noisy signal. Garbage in = amplified garbage out.)
" ... About the op-amp in front, .... but it's by far less important than the main amp anyway. ..."
Well, I would say just the opposite: The input stage (op-amp) is very important to the over all quality and results. This is the point where most noise can creap in, where wiring practices and impedence matching are most important ... Pick the best quality input stage possible and the rest of the parts will natually work better, sound better. (This is why so much attention is paid to pre-amps. No matter what the power output may be, it would not matter much if that power is simply amplifying a noisy signal. Garbage in = amplified garbage out.)
you absolutely rights!
repeat, recommend to do on offered amplifier, without any change (particularly MC33079)
"Waft-HomeHaney" was made by many people, all of them are very complacent
Look yooree's site, it is author
repeat, recommend to do on offered amplifier, without any change (particularly MC33079)
"Waft-HomeHaney" was made by many people, all of them are very complacent
Look yooree's site, it is author
MC33079 (ON semicon only! Not SGS-Thompson!!!) is unique for it design.But if you not find it - recommend OPA404 (TI) , TLE2144, TLE2074 (TI) - it is free sample on www.ti.com
and LT1356 (is free sample on www.linear.com)
I has got samples from all it supplyer.
Yea its also possible.
But TI dont send free samples to Turkey (I dont know the rason).
For Linear, they already sent me a lot of free samples (like LT1210s, LT1083, LT1014) and I hesitate to request more. Theyre like National guys. Very very kind friends.
So I will buy them with my finance possibilities. I guess I can find them from futurlec or farnell.
Thx again.
But TI dont send free samples to Turkey (I dont know the rason).
For Linear, they already sent me a lot of free samples (like LT1210s, LT1083, LT1014) and I hesitate to request more. Theyre like National guys. Very very kind friends.
So I will buy them with my finance possibilities. I guess I can find them from futurlec or farnell.
Thx again.
" ... if you not find it - recommend OPA404 (TI) , TLE2144, TLE2074 (TI) - it is free sample on www.ti.com and LT1356 (is free sample on www.linear.com) ... "
Good advise ... and if not free to Turkey, then quite inexpensive ...
....
How to get US semiconductor stuff inexpensively in the middle east = Turkey, Jordon, Israel, Pakistan, Iraq, Saudi Arabia and Persian Gulf:
1) Get a DHL or FedEx shipping account.
2) Make sure that the semiconductor item you want to get is not a "restricted" part, like a semiconductor that may be banned from export by the US military or DOD. Most semiconductor makers indicate such on their data sheets.
3) Buy your desired semiconductor parts on line and use your shipping account to indicate "recipient pays" the shipping charges and customs duties, etc..
I ship to Jordon, Israel, Turkey, Pakistan and Baghdad, Iraq regularily and Saudi Arabia and Dubia irregularily. With your own shipping account activated, the shipping costs are ultimately reduced and many local customs complications are removed.
Good advise ... and if not free to Turkey, then quite inexpensive ...
....
How to get US semiconductor stuff inexpensively in the middle east = Turkey, Jordon, Israel, Pakistan, Iraq, Saudi Arabia and Persian Gulf:
1) Get a DHL or FedEx shipping account.
2) Make sure that the semiconductor item you want to get is not a "restricted" part, like a semiconductor that may be banned from export by the US military or DOD. Most semiconductor makers indicate such on their data sheets.
3) Buy your desired semiconductor parts on line and use your shipping account to indicate "recipient pays" the shipping charges and customs duties, etc..
I ship to Jordon, Israel, Turkey, Pakistan and Baghdad, Iraq regularily and Saudi Arabia and Dubia irregularily. With your own shipping account activated, the shipping costs are ultimately reduced and many local customs complications are removed.
Dominique's circuit looks fine, multiloop is a very good way to improve amplifier performance
make sure the current sharing Rs are noninductive
I would add some series impedance between the output and the speaker terminals, 1 uH air coil, maybe paralleled with a 10-20 Ohm noninductive damping R
The input op amp is important for performance, but it shouldn't be too fast without some additional compensation components - unity gain stable op amps with <10 MHz GBW should be very stable in Dominique's circuit without more compensation
I'd leave the LT1210 feedback R at 1K - this gives some “overcompensation" - slowing down the amp but making it less susceptible to ringing with load C
there is no need for + input resistors with the LT1210 - as a current feedback op amp the +/- terminals have very different impedance and input currents don't balance
The Lt1007 is fine, or a 5534 with 20 pF comp terminal cap, fet input op amps are often used too: OPA134
even the lowly TL07x have amazingly low distortion when they don't have to drive heavy loads
make sure the current sharing Rs are noninductive
I would add some series impedance between the output and the speaker terminals, 1 uH air coil, maybe paralleled with a 10-20 Ohm noninductive damping R
The input op amp is important for performance, but it shouldn't be too fast without some additional compensation components - unity gain stable op amps with <10 MHz GBW should be very stable in Dominique's circuit without more compensation
I'd leave the LT1210 feedback R at 1K - this gives some “overcompensation" - slowing down the amp but making it less susceptible to ringing with load C
there is no need for + input resistors with the LT1210 - as a current feedback op amp the +/- terminals have very different impedance and input currents don't balance
The Lt1007 is fine, or a 5534 with 20 pF comp terminal cap, fet input op amps are often used too: OPA134
even the lowly TL07x have amazingly low distortion when they don't have to drive heavy loads
Dear jcx,
As to me it is more important which circuit SOUNDS fine, not just looks.
However what U wrote, I mean your last post, is really actual and valuable.
There is no need to think much over the compensation method when we speak about LT1210. The datasheed intoduces us with this.
Another thing is one has his own decision on compensation.
As he (or perhaps she
) pleases.
Sorry to say but U mentioned toooo ancient OpAmps to use for the pre. The world is spinning, the time is running those 5534 or TL07x are not the leaders novadays.
As to me it is more important which circuit SOUNDS fine, not just looks.
However what U wrote, I mean your last post, is really actual and valuable.
There is no need to think much over the compensation method when we speak about LT1210. The datasheed intoduces us with this.
Another thing is one has his own decision on compensation.
As he (or perhaps she
) pleases.Sorry to say but U mentioned toooo ancient OpAmps to use for the pre. The world is spinning, the time is running those 5534 or TL07x are not the leaders novadays.
Wow, I'm glad to see the topic finally interested someone!
Sorry, I wasn't here for a lot of months. My girl left me, and I knew I had spent too much time in front of my computer, read too many op-amp datasheets and so on. After that, I didn't like the computer and electronics anymore, it took me too much time of my life and I didn't get back what I invested.
I mean, I used my time ineffectively...
But I want to get back to it finally - just in a more effective way - doing rather small projects and finish them quickly.
And let me say: I got helpful hints here more than once - thank you, everyone!
I once only quickly soldered a very simple version of that 1210 as a gainclone with low gain (possibly 6) after my CD player (which is rather hot) - it sounded very nice. (Though it ws a bit risky to connect my good loudspeakers after a first test, maybe )
Initially, I wanted to use them in parallel because they seemed a bit weak for 4ohms. I think I have used them with a DC of 18V for some time.
After all, I'll possibly only use a single 1210 in a small project, some tiny active speakers?
But also, those fast 1210s could be a good idea for driving the tweeters in 3-way active speakers?
Opa549 for the Bass, and a National chip for the mids, like LM1875?
Would be a funny cooperation, but I'd have to check if the usual power distribution between bass, mids and tweeter to see if that makes sense...
Well, I'm back!
Thanks, cu soon!
Dominique
Sorry, I wasn't here for a lot of months. My girl left me, and I knew I had spent too much time in front of my computer, read too many op-amp datasheets and so on. After that, I didn't like the computer and electronics anymore, it took me too much time of my life and I didn't get back what I invested.
I mean, I used my time ineffectively...
But I want to get back to it finally - just in a more effective way - doing rather small projects and finish them quickly.
And let me say: I got helpful hints here more than once - thank you, everyone!
I once only quickly soldered a very simple version of that 1210 as a gainclone with low gain (possibly 6) after my CD player (which is rather hot) - it sounded very nice. (Though it ws a bit risky to connect my good loudspeakers after a first test, maybe
)Initially, I wanted to use them in parallel because they seemed a bit weak for 4ohms. I think I have used them with a DC of 18V for some time.
After all, I'll possibly only use a single 1210 in a small project, some tiny active speakers?
But also, those fast 1210s could be a good idea for driving the tweeters in 3-way active speakers?
Opa549 for the Bass, and a National chip for the mids, like LM1875?
Would be a funny cooperation, but I'd have to check if the usual power distribution between bass, mids and tweeter to see if that makes sense...
Well, I'm back!
Thanks, cu soon!
Dominique
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