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I think I might be back in on this. I'm torn between a pair of these vs a pair of Sony xm-gs4
 

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Delta,you'll be receiving my amps in the mail for complete overhaul and you'll be paid handsomely for the work.
 

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Delta,you'll be receiving my amps in the mail for complete overhaul and you'll be paid handsomely for the work.
Thank you for the offer, however, there are shops out there that are equipped with the tools and the knowledge and available for these types of services, even listed in this thread and quite affordable. If I make a mistake and damage my equipment, then I have myself to blame. If I damage someone else's equipment, that is a liability that I am neither insured or bonded to do, and quite honestly would make me feel horrible.
 

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Delta,you'll be receiving my amps in the mail for complete overhaul and you'll be paid handsomely for the work.
Thank you for the offer, however, there are shops out there that are equipped with the tools and the knowledge and available for these types of services, even listed in this thread and quite affordable. If I make a mistake and damage my equipment, then I have myself to blame. If I damage someone else's equipment, that is a liability that I am neither insured or bonded to do, and quite honestly would make me feel horrible.
So I know much of this discussion is formed around the NVX amplifier.How can those of us who own different brand amps be able to tell if ours could benefit from an overhaul? I personally have a JL XD500 and a Fosgate PunchP400.
 

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So I know much of this discussion is formed around the NVX amplifier.How can those of us who own different brand amps be able to tell if ours could benefit from an overhaul? I personally have a JL XD500 and a Fosgate PunchP400.
There is no doubt that virtually any car audio amp can, with the current options we now have, find some significant SQ improvements. And this is something we as a community of end-users can try to help each other with possible recommendations.
 

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Hey Fcarpio,see what you started here!! Now everybody on the freakin' forum will begin to envision ripping their amps apart with dreams of better opamps,sexier resistors and stellar caps.Then they'll be going to Home Depot dropping some bread on a soldering gun with visions of clearer voices,a concert like soundstage that is ready to shatter the windshield by the sheer crispness of the highs! Gary Summers asking for their autograph after they blow the field away at the Meca world finals.........then they get home and begin to dissamble the amplifier and the fear starts to set in,heartrate starts to go up and the forehead beads up with sweat as they realize...."I don't know what the he#$ I'm doing,I've never soldered a dam thing in my life!"
Hey I never thought about the sexy resistors...LOL. I personally think this is a great discussion and at the end we will have quantified results and a complete parts list with suppliers. At that point if someone whats to press ahead with this mod it really comes down to if they have the experience and tools or it can easily be outsourced.

I do think it worth restating that this amp has received very good reviews as-is and can hold it's own with any other amp in its price range. So this is by no means a turd that were trying to obtain the new pro glow from.

I do believe that the changes will give a satisfactory result and we are lucky that those results can be verified (Big Thanks bnae). Believe me you don't want me telling you it now has a oak flavored mid with a subtle hint of Jasmin up high...LOL. We could also find out the risk is not worth the reward either way I see it as a win.

And any time I can play mad scientist you can count me in. :z:
 

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So I know much of this discussion is formed around the NVX amplifier.How can those of us who own different brand amps be able to tell if ours could benefit from an overhaul? I personally have a JL XD500 and a Fosgate PunchP400.
The JL amp utilizes the JRC2068, (bi-polar) which a mid-level desktop radio quality buffer, and would see some improvements. The Punch uses the TL072 (JFET) and would certainly see a loss of hiss, much better phase control, and a much better high frequency response. For the JRC2068, I would use an OPA1602, (bi-polar) and the Punch the OPA1642 (JFET)
 

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Hey I never thought about the sexy resistors...LOL. I personally think this is a great discussion and at the end we will have quantified results and a complete parts list with suppliers. At that point if someone whats to press ahead with this mod it really comes down to if they have the experience and tools or it can easily be outsourced.

I do think it worth restating that this amp has received very good reviews as-is and can hold it's own with any other amp in its price range. So this is by no means a turd that were trying to obtain the new pro glow from.

I do believe that the changes will give a satisfactory result and we are lucky that those results can be verified (Big Thanks bnae). Believe me you don't want me telling you it now has a oak flavored mid with a subtle hint of Jasmin up high...LOL. We could also find out the risk is not worth the reward either way I see it as a win.

And any time I can play mad scientist you can count me in. :z:
While I appreciate the posting, an op-amp that is $0.20 each will not sound like a high quality op-amp that is $3.00 each. Just sayin'
 

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I totally agree with you DeltaB. I actually expect some really good things to come out of these mods. By the way I did opt for the OPA1602 as replacements for the JRC4558. Should have them tomorrow.
 

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I totally agree with you DeltaB. I actually expect some really good things to come out of these mods. By the way I did opt for the OPA1602 as replacements for the JRC4558. Should have them tomorrow.
Are these mods difficult to do?How long does a typical amplifier take?
 

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Hardest part is waiting for parts to arrive...LOL. Truthfully its not that bad if you can replace the 8 pin SMD Op-Amps. That probably comes down to experience and practice. Plenty of tutorials out there. Oh and Removing those damn heat sink clips. Again there are You Tube videos on that. Besides that its probably a solid evening. Involves Replacing 11 TL072 Op-Amps (I also replaced the 4 JSC4558 Op-Amps) and probably close to 50 Caps (That might be a little high - I don't have it in front of me at the moment). I'll be glad to put up a parts list (Maybe Tomorrow) and we can edit it as needed. I can also toss up some pics latter as I should be working on it this evening.
 

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Hardest part is waiting for parts to arrive...LOL. Truthfully its not that bad if you can replace the 8 pin SMC Op-Amps. That probably comes down to experience and practice. Plenty of tutorials out there. Oh and Removing those damn heat sink clips. Again there are You Tube videos on that. Besides that its probably a solid evening. Involves Replacing 11 TL072 Op-Amps (I also replaced the 4 JSC4558 Op-Amps) and probably close to 50 Caps (That might be a little high - I don't have it in front of me at the moment). I'll be glad to put up a parts list (Maybe Tomorrow) and we can edit it as needed. I can also toss up some pics latter as I should be working on it this evening.
Easiest way to remove clips is use a allen wrench, size it to just fit hole, short end in the hole, long side pointing up. Gently use it like you would a crowbar and easy-pop off. Super easy. To replace, simply position and push towards the heatsing with your thumb and pop, it in goes.
 

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All this bashing of the opa2209 (deltaB) made me wonder.. why did they use the 2209 in the pre's of our flagship mixers instead of the opa1602.

Knowing the bossman, first thing i checked was noise. Voltage noise is close, 2.5 vs 2.2 nv/Rt.hz. But current noise isn't even close.. 1.8pA vs 500fA..

At the end of the day, the 1602 is actually cheaper so suite yourself. But look at all the information ;)


Much of this stuff is a trade-off when playing around. But anyway..


Keep in mind, just because TI didn't label the opamp "sound plus" doesnt mean it's not able to excel in audio use!


Regarding slew.. i need to find the article, but iirc anything above 6v/us is moot based on how music is recorded. Even with uhd source material.. I think it was nwavguy that wrote it.


Fwiw the company is listed in my profile and the mixers are black. I'm not posting that here. ..even though anyone who owned one could pop the top and see the opamps lol.. i'd rather not go there. ;)
 

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All this bashing of the opa2209 (deltaB) made me wonder.. why did they use the 2209 in the pre's of our flagship mixers instead of the opa1602.

Knowing the bossman, first thing i checked was noise. Voltage noise is close, 2.5 vs 2.2 nv/Rt.hz. But current noise isn't even close.. 1.8pA vs 500fA..

At the end of the day, the 1602 is actually cheaper so suite yourself. But look at all the information ;)


Much of this stuff is a trade-off when playing around. But anyway..


Keep in mind, just because TI didn't label the opamp "sound plus" doesnt mean it's not able to excel in audio use!


Regarding slew.. i need to find the article, but iirc anything above 6v/us is moot based on how music is recorded. Even with uhd source material.. I think it was nwavguy that wrote it.


Fwiw the company is listed in my profile and the mixers are black. I'm not posting that here. ..even though anyone who owned one could pop the top and see the opamps lol.. i'd rather not go there. ;)
Take an op-amp, any op-amp of 6v/µs and place it's gain at 0db on +-15v rails, and play complex content from the DAC and record the waveform. (Take a CD like Margaret Becker's "Falling Forward" for example) Do that multiple times and superimpose the waves, and you will find that none of them will output the same. Then take that same complex content, and run it through an op-amp at 20v/µs at 0db and then superimpose. The result will be axiomatic.

There is a reason DAC companies like ESS do not recommend slow slew rate op-amps, in fact the NE5532 (9v/µs) isn't recommended on any of the 32bit DAC's and only the last choice for the ES9006, which is the lowest performing 24bit DAC in their lineup. Recording a single channel content and audio reproduction is two distinct things. Be careful what you read.
 

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Here's the article
NwAvGuy: Op Amps: Myths & Facts

Don't really wanna be the guy that rains on the parade, but i think these things should be taken with a grain of salt.

Can we get better noise floor, thd, and phase response? Yes. Is that worth it, hell i think so..

Will the difference be mind boggling? I don't know about that..

Getting that last 5% when you're 95% of the way there isn't easy. No question this could be part of it. Just go into it being realistic.

Fwiw
 

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Take an op-amp, any op-amp of 6v/µs and place it's gain at 0db on +-15v rails, and play complex content from the DAC and record the waveform. (Take a CD like Margaret Becker's "Falling Forward" for example) Do that multiple times and superimpose the waves, and you will find that none of them will output the same. Then take that same complex content, and run it through an op-amp at 20v/µs at 0db and then superimpose. The result will be axiomatic.

There is a reason DAC companies like ESS do not recommend slow slew rate op-amps, in fact the NE5532 (9v/µs) isn't recommended on any of the 32bit DAC's and only the last choice for the ES9006, which is the lowest performing 24bit DAC in their lineup. Be careful what you read.
Well, i did read the noise specs. :p

All for the sake of discussion, and two sides to every coin...

The slew difference for complex material (ie we dont listen to sine waves..) makes sense. True enough.

I'm not smart enough to punch out the math, but anyway...


As i've geared up my lab, this was always the endgame... to play around with better components/changes/etc (as well as the repairs i do).


I haven't started yet, but will be playing with my ks900.6 soon. Point being, i dont know how big or small the difference will sound... i'm just programmed to be skeptical first ;)
 

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Glad to see both the TL072 and 4558 were both on NwAvGuy's Don't Bother list. At least makes me feel like we are addressing weaknesses.

Quote from NwAvGuy article:

DON’T BOTHER: While the following parts had their glory days, they’re long gone. They offer no advantage over the above parts and are often much worse:

*TL071/TL072 – These were mainstream audio parts and used in lots of pro gear before the 5532 came along. For all those speed freaks, it’s worth noting they’re rated only slightly slower than the elite chips at 15 V/uS. They were also among the first reasonably priced FET op amps that were useful for high quality audio. But they suffer from very limited output current, they can’t get very close to the rails, have higher distortion, and they’re relatively noisy. Their lower power cousins the TL061/TL062, and the lower spec TL081/TL082 are even worse.
LM833 – This was one a National’s early attempts at a high performance audio op amp like the 5532 but they failed to beat the 5532.
4560 – The 4560 has been eclipsed by the NJM2068, 5532, 4556, etc.
4558 – Same as above
 
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