can the leads of the LM4780 be extended by short wire lengths of say 2ins?
if this method works well without any negative impacts ie temp runoff, oscillation etc. then it provides total flexibility in mounting to heatsink.
if this method works well without any negative impacts ie temp runoff, oscillation etc. then it provides total flexibility in mounting to heatsink.
Upupa Epops said:Probably it will cause instability...Why do you can do this monkey business ?
for 2 reasons:
1 - you may want the pcb and the heat sink to be parallel to each other (as opposed to the usual 90deg) for space reasons and may not want to bend the LM4780 leads.
2 - for those who want to use vero perforated boards as pcb, the pitch is 2.54mm versus the LM4780 leads at 1.00mm pitch. again the mismatch of pitch can be linked with short wires of the same gauge as leads.
as this been done in some examples????
The pins on these chips are fairly easy to break off at the area where they meet the package. Avoid stressing them there and you shouldn't have a problem bending the pins further away from the package.
puginfo, if you want to use LM4870 without any pcb, I would recommend LM3875, 3886 instead. LM4780 is two LM3886 in the same package you know.
thks for the inputs guys. ill lookup the 3886 maybe the pitching is close to 2.54mm there.
so are the short wire extensions are a complete no-no for the 4780? still interested to know the impacts in doing so as its also applicable in other packages ie TO220 or TO3.
so are the short wire extensions are a complete no-no for the 4780? still interested to know the impacts in doing so as its also applicable in other packages ie TO220 or TO3.
how does a pavel dudek's lm4780 amp compare to your other DIY amps like possibly Peter's and the aleph series?
Thank you for the reply.
Thank you for the reply.
Hi everybody,
While I wait for my Digikey order to come in, I was wondering if anybody has tried using LM4562 instead of OPA 134. If so how does it sound?
Pavel, PA,
I was thinking of putting a resistor on the opamp outputs to V- to bias it to Class A. Would you recommend doing it? Would 10 ma (1.2K resistor) do the trick?
Thanks,
Dinesh
While I wait for my Digikey order to come in, I was wondering if anybody has tried using LM4562 instead of OPA 134. If so how does it sound?
Pavel, PA,
I was thinking of putting a resistor on the opamp outputs to V- to bias it to Class A. Would you recommend doing it? Would 10 ma (1.2K resistor) do the trick?
Thanks,
Dinesh
The opamp output will probably never leave class A when the load is LM4780 (100k) and the feedback network (10k). If you insist you can try to draw 3-4 mA or so. 10 mA would heat the opamp.
P-A,
Thanks for clarifying this. One more question.
At some point in time I will be replacing the output stage of my DAC (Zhaolu 2.5C) which will significantly improve the ability to drive a power amp. The input opamps at this point are in unity gain configuration right? Essentially acting as an input buffer, not counting the low pass filter made up of C3 & R3,R4 along with R1,R2 & C2. Would the input opamp still be needed when my DAC is adequately capable of driving the 4780 directly. If possible I would like to eliminate unncessary active stages such as the input opamps. Is this recommended? If so, for the next version of the PCB would it make sense to provide a tap at C10 to bypass the opamp. Or is the low pass filter function important enough that it should be retained.
Regards,
Dinesh
Thanks for clarifying this. One more question.
At some point in time I will be replacing the output stage of my DAC (Zhaolu 2.5C) which will significantly improve the ability to drive a power amp. The input opamps at this point are in unity gain configuration right? Essentially acting as an input buffer, not counting the low pass filter made up of C3 & R3,R4 along with R1,R2 & C2. Would the input opamp still be needed when my DAC is adequately capable of driving the 4780 directly. If possible I would like to eliminate unncessary active stages such as the input opamps. Is this recommended? If so, for the next version of the PCB would it make sense to provide a tap at C10 to bypass the opamp. Or is the low pass filter function important enough that it should be retained.
Regards,
Dinesh
jarthel said:
I have several chipamps and Pavel's, together with the Lightspeed Attenuator, is the best I have. That includes the MyRef.
I hope that answered your question.
The input of the LM3886/4780 is rather high-ohmish and if you have a low impedance signal source (< 1 kohms) it will work fine. Have you checked the datasheet for LM4780? All info is there.dviswa said:
Best or not, compactness and a good grounding scheme (on the pcb) will create good results. I think noone can deny this.Bearman said:
A problem we all see here is when people want to make stereo amps made of of mono boards and a single power supply. Pavel's design (and also mine) eliminates the connection between to channels and the ground. This is already done by the pcb designer. One thing less to worry about. How many have had problems with hum and mono Gainclone pcb's? Hands up!
More or less! It may work, you may also get a lot of trouble. Nothing I would recommend.puginfo said:
P-A is correct, my first idea was to eliminate grounding problems, which I have seen on many questions of DIY's in other designs... 😎
1. Is it possible to use this amp in a car stereo system (with DC-DC transformer)?
2. If this amp will sound as said, It will have a major impact on my system(s) as I've never had an (very) high-end amplifiers.
In the future all my speakers (diy) will be active crossed (meaning amp channel per driver) but my current setup is still passive.
2. If this amp will sound as said, It will have a major impact on my system(s) as I've never had an (very) high-end amplifiers.
In the future all my speakers (diy) will be active crossed (meaning amp channel per driver) but my current setup is still passive.
BNK said:
You mean DC-DC convertor? Such devices are not known to give out a clean DC supply, have large ripple messing up the sound. Are you sure you can find a device capable of >100VA, 40-50 V DC?
P-A, Pavel,
I have been having trouble. Somehow the Berquist insulator I used for the 7912 failed, shorting the tab to the heatsink. This blew out a couple fuses. After much trouble shooting, I found this, removed the heatsink, replaced the 7912, I still blew it out. The opamps were never populated, so there should be very little load on the reg. Also I do not find any short to the ground from TP3. The Zener D3 had failed some time back which I should have suspected, still, I do not understand why the reg blew out. The input is about -28 VDC (the trafo is giving out 20-20 V AC, rated to be 18-0-18) well within the tolerance of the device, even with a bad zener, it should still function.
Any ideas? Please help.
I have ordered new parts, it will take some time to come.
Regards,
Dinesh
I have been having trouble. Somehow the Berquist insulator I used for the 7912 failed, shorting the tab to the heatsink. This blew out a couple fuses. After much trouble shooting, I found this, removed the heatsink, replaced the 7912, I still blew it out. The opamps were never populated, so there should be very little load on the reg. Also I do not find any short to the ground from TP3. The Zener D3 had failed some time back which I should have suspected, still, I do not understand why the reg blew out. The input is about -28 VDC (the trafo is giving out 20-20 V AC, rated to be 18-0-18) well within the tolerance of the device, even with a bad zener, it should still function.
Any ideas? Please help.
I have ordered new parts, it will take some time to come.
Regards,
Dinesh