I should have known better.
Putting this device between my DAC and my amp was, by far, the biggest step down that I have experienced since embarking on my DIYaudio journey.
If you are an audiophile of any sort, do not waste your money. I would feel guilty selling it on, so I'll just eat the cost and chalk it up to experience
Sorry HLLY, but your pre-amp sucks. My wife and kids all agree.
Putting this device between my DAC and my amp was, by far, the biggest step down that I have experienced since embarking on my DIYaudio journey.
If you are an audiophile of any sort, do not waste your money. I would feel guilty selling it on, so I'll just eat the cost and chalk it up to experience
Sorry HLLY, but your pre-amp sucks. My wife and kids all agree.
Now the more interesting question would be: Why is that, and how could one fix the problem? "It sucks" is not too informative, now is it?
I'd definitely want to take some measurements before giving up on the unit. After all, given what's inside and what it costs, there really is no reason for it to be particularly bad unless there were some sort of defect.
Now I wouldn't want to bet on perfect workmanship in a Chinese-made unit, so a look inside may already reveal the problem. For example, I imagine operating a unit wired for 230 V in 115 V territory wouldn't work too well...
I'd definitely want to take some measurements before giving up on the unit. After all, given what's inside and what it costs, there really is no reason for it to be particularly bad unless there were some sort of defect.
Now I wouldn't want to bet on perfect workmanship in a Chinese-made unit, so a look inside may already reveal the problem. For example, I imagine operating a unit wired for 230 V in 115 V territory wouldn't work too well...
I have to apologize for not being very descriptive. I was in a foul mood when I posted.
By "sucks" I mean, primarily, extremely veiled, cloudy almost. In its default state, it sounds more muddy and boring than my Yamaha solid state receiver. In short, it sounds like a mid-fi stereo system. Flat, lifeless, held back... nearly every negative "audiophile" descriptor applies.
After a restless sleep, I woke up this morning with a mission and in true DIY spirit I began disassembling the unit.
I had a couple of surprises:
1) The unit is advertised as having CS3310 + dual AD797. Instead, it has dual "National" branded L49710. I assume this is equivalent to TI LME49710, so not a terrible substitute I suppose. But, are they genuine parts?
2) Between the CS3310 and the input pins of each of the L49710 opamps, there was a generic 470pF capacitor at positions C402 and C405.
As you can see in the photo, I removed both of the capacitors from those positions (you can see one sample of the generic cap in the photo, for reference).
I had some WIMA FKP3 470pF caps on hand, so I used my meter to find a matched pair. Here are the old and new caps:
I chose to solder them on the back of the board:
Then, I tested the unit again:
To my surprise (I am a pessimist) the sound quality has improved immensely!! I cannot believe it, to be honest. My system still sounds better when the source is plugged direct to my amp, however the AMK-II is now actually tolerable to listen to. Much less veiling, much more of a "live" feeling, "presence", etc. It no longer sounds like a mid-fi, more like a different flavour of hi-fi.
I suspect there is more that I can do to get the most out of this unit.
For example, I'd like to know why they opted to not install caps at positions C404 and C408. It seems obvious by the traces that those caps would be in the signal path if installed, but I do not know what their function would be. Part of an incomplete zobel?
By "sucks" I mean, primarily, extremely veiled, cloudy almost. In its default state, it sounds more muddy and boring than my Yamaha solid state receiver. In short, it sounds like a mid-fi stereo system. Flat, lifeless, held back... nearly every negative "audiophile" descriptor applies.
After a restless sleep, I woke up this morning with a mission and in true DIY spirit I began disassembling the unit.
An externally hosted image should be here but it was not working when we last tested it.
I had a couple of surprises:
1) The unit is advertised as having CS3310 + dual AD797. Instead, it has dual "National" branded L49710. I assume this is equivalent to TI LME49710, so not a terrible substitute I suppose. But, are they genuine parts?
An externally hosted image should be here but it was not working when we last tested it.
2) Between the CS3310 and the input pins of each of the L49710 opamps, there was a generic 470pF capacitor at positions C402 and C405.
An externally hosted image should be here but it was not working when we last tested it.
As you can see in the photo, I removed both of the capacitors from those positions (you can see one sample of the generic cap in the photo, for reference).
I had some WIMA FKP3 470pF caps on hand, so I used my meter to find a matched pair. Here are the old and new caps:
An externally hosted image should be here but it was not working when we last tested it.
I chose to solder them on the back of the board:
An externally hosted image should be here but it was not working when we last tested it.
Then, I tested the unit again:
An externally hosted image should be here but it was not working when we last tested it.
To my surprise (I am a pessimist) the sound quality has improved immensely!! I cannot believe it, to be honest. My system still sounds better when the source is plugged direct to my amp, however the AMK-II is now actually tolerable to listen to. Much less veiling, much more of a "live" feeling, "presence", etc. It no longer sounds like a mid-fi, more like a different flavour of hi-fi.
I suspect there is more that I can do to get the most out of this unit.
For example, I'd like to know why they opted to not install caps at positions C404 and C408. It seems obvious by the traces that those caps would be in the signal path if installed, but I do not know what their function would be. Part of an incomplete zobel?
An externally hosted image should be here but it was not working when we last tested it.
Hello,
First thanks a lot for the information.
I have arrived at this product reading that the 3310 is used also as a volume control in the Jeff Rowland Synergy preamp, very well reviewed.
I know implementation also counts ... anyway it seems a good start indeed.
I have some kind questions.
Is your opinion changed about the unit ?
Have you performed any other modification ?
If i understand well the CS3310 is the volume control and then the signal is buffered by the 49710 ?
Do you think that an electrolytic caps replacement with something better grade could be beneficial ?
Thanks a lot and kind regards,
gino
First thanks a lot for the information.
I have arrived at this product reading that the 3310 is used also as a volume control in the Jeff Rowland Synergy preamp, very well reviewed.
I know implementation also counts ... anyway it seems a good start indeed.
I have some kind questions.
Is your opinion changed about the unit ?
Have you performed any other modification ?
If i understand well the CS3310 is the volume control and then the signal is buffered by the 49710 ?
Do you think that an electrolytic caps replacement with something better grade could be beneficial ?
Thanks a lot and kind regards,
gino
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You are welcome.
Interesting. I did not know about the Jeff Rowland pre-amp. Yes, the surrounding circuit and components can make a big difference, as I am learning.
Yes. I do not hate the unit anymore and I am using it happily now.
Yes. I removed the CS3310 and replaced it with TI PGA2311 (drop-in replacement with better specs/performance). It sounds more open and transparent to me. Combined with the above capacitor modification, the unit performs very, very well.
This is the way I understand it.
I do not know. I don't think the signal path travels through the electrolytics, so probably not worth changing. Just my opinion and I could be wrong.
Regards to you as well.
Hi and thank you very much indeed for your kind and valuable reply.
The review i am referring to is the following
Jeff Rowland Design Group Synergy line preamplifier | Stereophile.com
in this case the buffer opamps used are the AD811.
Very interesting indeed. Thank you again.
I also read great things of the PGA2311 and its" bigger" brother PGA2310.
Honestly i have this one myself
http://www.ebay.com/itm/New-version-PGA2311-Stero-Remote-Volume-Controller-Preamp-with-case-/140865254355?pt=US_Amplifier_Parts_Components&hash=item20cc3933d3
a version with the PGA2310 on board. It sounds clean
In the review of the JR preamp at some point they mention how an alternative battery power supply improved the overall sound remarkably (i.e. better soundstage, lower noise, etc.).
Maybe this is the next thing to address to get even better sound.
I understand that the volume chip needs +5V while maybe the buffers operate with +/- 15 V ?
This complicates things a little.
Thanks a lot anyway.
Kind regards,
gino
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Hello again !
honestly i do not know. I have a great respect for Jeff Rowland brand.
If they have select that volume cheap there must be a reason. They make cost no object equipment.
What impressed me reading the review of the JR preamp on Stereophile magazine was the statement that using a battery power supply the sound imporved drammatically ...
So i think that the quality of the power supply can have a significant impact on sound.
i will address this issue in the near future.
Maybe they are right ... i have a fascination for batteries ...
Thanks again and kind regards,
gino
P.S. by the way i have been advised, and i did, to go for the PGA 2310, a better chip than the 2311 .. for little more.
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For this to be true, there must be something wrong with BOTH the Amplifier AND the PSU.
Hi, if with the batteries the sound was good maybe the PSU was not up to the task ?
Anyway i have limited experience with line stages. Well in general not only with line stages.
The most impressive improvement i heard was after replacing a normal Alps Blue Velvet with an attenuator.
At the point that when i see a preamp without these i wonder if they are working at their full potential.
An externally hosted image should be here but it was not working when we last tested it.
¨
Instead for a line stage i would prefer a "discrete" solution ... maybe minimalist but still discrete. I think that a minimalist circuit with good selection of parts can sound sublime.
I had this impression listening to a Pass Bride of Zen but with generic components ... and a soso power supply. Very soso actually.
But i had a good impression anyway. From just one mosfet.
Thanks a lot.
Kind regards,
gino
Member
Joined 2009
Paid Member
Hi ! well no ... what is it ?
Is it good ? do you have a link to some pages about it ?
Thanks and regards,
gino
Member
Joined 2009
Paid Member
http://www.diyaudio.com/forums/analog-line-level/80194-lightspeed-attenuator-new-passive-preamp.html
http://www.diyaudio.com/forums/swap-meet/139113-poor-serbian-man-lightspeed-packages.html
OptiVol (fyi - Greg is a bit of a strange guy to deal with, from personal experience and from others)
http://www.diyaudio.com/forums/swap-meet/139113-poor-serbian-man-lightspeed-packages.html
OptiVol (fyi - Greg is a bit of a strange guy to deal with, from personal experience and from others)
Thank you ! i will read the 3D trying to understand the concept
Am i a beginner.
Nevertheless i think that latest volume control chips must have reached a quite high quality because they are employed in very expensive commercial units.
Anyway i will study the solution you mention.
Kind regards,
gino
Very interesting read, Ive had one of these for the past two years in constant use - I don't have a whole lot of experience with different systems but I do know that I love this pre - I would however like to modify it to the specs that you have, is there any chance you could re-upload the pics on page one, as this would help me massively. Thanks
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