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Old 22nd August 2012, 12:09 AM   #1
TP143 is offline TP143  United States
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Default LM4780 Questions

Hi everyone,

I am considering my first amp build, the LM4780 in parallel, to power some 4 ohm speakers. Before I purchase everything I have a few questions:

1. If I purchase the kit from P Daniels what suggestions do you have for part replacement/upgrades?

2. I have seen some LM4780 kits online that are sold with preamp boards/parts. If I want to make my amp integrated what options do I have (tube verse other) and what parts/kits would I need, in addition to the P Daniels kit? Has anyone compared the different types of preamp with the LM4780 for SQ differences?

Thanks!
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Old 22nd August 2012, 02:47 AM   #2
SoIL4x4 is offline SoIL4x4  United States
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I have the standard kit from audiosector and I am very happy with it. The only thing I added to the amp was some larger power supply caps. At some point I may upgrade some other components, but I think Peter puts together a great sounding standard kit. As for the pre, I could not say, I am using a alps(that went haywire, soon to be replaced with a TKD). In parallel there is plenty of power and it drives my 4 and 6 ohm speakers with ease. You wont be dissapointed.

Last edited by SoIL4x4; 22nd August 2012 at 02:53 AM.
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Old 28th August 2012, 11:48 PM   #3
TP143 is offline TP143  United States
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I have a few more questions before I purchase all the parts. I will be running the LM4780 in parallel.

1. I have read that increasing the capacitance values on the supply caps can improve the sound. The kit comes with (2) 10uf caps and most recommend increasing to (4) 6.8uf caps. What voltage should I be looking for in the 6.8uf caps and are there any other specs that I should pay attention to, such as heat rating?

2. Similarly, I have read that increasing the capacitance values for the input caps can improve sound. The kit comes with (4) 1500uf caps and most recommend increasing to (4) 5700uf caps. What voltage should I be looking for in the 6.8uf caps and are there any other specs that I should pay attention to, such as heat rating?

3. I have read great things about the TKD potentiometer. Is this pot a bit overkill for the LM4780 or would you think the benefits of the pot would shine through on this basic amp? I guess, given my amp selection, would the extra dollars be better spent on upgrading the power supply, capacitors, etc?

Thanks!
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Old 29th August 2012, 12:22 AM   #4
SoIL4x4 is offline SoIL4x4  United States
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I did not change the 1500uf caps on the amp board, I don't know what value peter uses for his premium kit so I can't comment on that. I did add two 6800uf caps per rail for a total of eight caps. They are rated at 63v and a temp of 85c.

I received the TKD pot today so I don't have any listening impressions yet. Hope this helps.
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Old 29th August 2012, 02:22 AM   #5
Einric is offline Einric  United States
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I left the 1500uf caps alone and increased the PS caps to 10kuf.
If you plan on using two toroids then use two power supplies, don't try and run two PS's off of one toroid.
The included rectifier diodes are plenty for running two parallel amps off of one PS.
If you end up running a single Power Supply I would recommend going to 15kuf PS Caps.
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Old 30th August 2012, 08:10 PM   #6
TP143 is offline TP143  United States
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SoIL4x4 - Can you explain how you ended up with eight caps? There must be four "rails" between the two chips for this to work out. I figured there were two rails if only two caps were supplied in the P.Daniels stock kit. Also, I was noticing a post in your dual mono build thread where you were considering changing the stock 1500uf caps to 4.7uf, but I presume you did not make this adjustment?

Einric - I was planning on a single power supply for the entire amp and was going to increase the PS caps to 13,600uf according to a few build threads I found. Is there any benefit to going with one larger cap (as you linked above) verse the two in series that SoIL4x4 recommended? Can the P.Daniels boards accomodate either?

Thanks everyone!
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Old 30th August 2012, 11:33 PM   #7
Einric is offline Einric  United States
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What limits you on the power supply bulk capacitors is physical size.
I believe that you are limited to 30mm diameter, over that and you will need to run jumper wires (no biggie).
If you go with the large PS caps you might want to use the power supply "snubber" circuit like I did.
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Old 31st August 2012, 01:34 AM   #8
SoIL4x4 is offline SoIL4x4  United States
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I used multiple smaller caps in my power supply for a few reasons, price, size and to reduce esr. How it was explained to me is as follows; multiple small value caps will work better in a low current power supply like a chipamps because it allows the caps to recover faster, helping demand peaks. Also these are wired in parallel not series. I used 8 caps because I used two power supplies, one for each channel. Each + and - rail for each power supply has two caps in parallel. Some day I may try even more caps in parallel of an even smaller value to see if there is any difference, but for now I am happy.

I can also now recommend the TKD potentiometer! I installed it today and all is well. It is a great improvement over the alps.
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Old 31st August 2012, 08:46 PM   #9
tsiros is offline tsiros  Greece
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Quote:
Originally Posted by TP143 View Post
(...)

1. I have read that increasing the capacitance values on the supply caps can improve the sound. The kit comes with (2) 10uf caps and most recommend increasing to (4) 6.8uf caps. (...)

2. Similarly, I have read that increasing the capacitance values for the input caps can improve sound. The kit comes with (4) 1500uf caps and most recommend increasing to (4) 5700uf caps. (...)

3. I have read great things about the TKD potentiometer. Is this pot a bit overkill for the LM4780 or would you think the benefits of the pot would shine through on this basic amp? I guess, given my amp selection, would the extra dollars be better spent on upgrading the power supply, capacitors, etc?

Thanks!
Are you sure the supply caps are 2*10uF / 4*6.8uF and the input decoupling caps are 4*1500uF / 4*5700uF ?

Anyway, the lm4780 has power supply ripple rejection so upping the capacitance won't improve the performance a lot. But yeah, i plan on putting 2*15000uF in mine. And i won't be using it at 2*60W, either... more like 2*45W, at 8Ω.

the potentiometer better be the best you can find. you don't want to hear what happens when the pot jumps all over the place.
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Old 31st August 2012, 09:08 PM   #10
TP143 is offline TP143  United States
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The stock supply caps are 2@10uf but the recommended mod is 4@6800uf, not 6.8uf. I wanted to make that correction for future scanners of this thread.

Also, I am interested in having two sources connected to the amp at all times and would like to have some sort of toggle/rotator switch on the front of the chassis for selection. What hardware would I need to purchase to accomplish this?
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