Jolida JD9 op amps and gain experiments

[Jim Pittsburgh]

Just thought I'd share:  ordered four OPA 627s and two OPA637s thru eBay / China supplier, after reading such rave reviews about this "upgrade" to the JD9 phono pre-amp on more than one of the boards..... Don't get me wrong,  I'm basically very happy with the sound of the Jolida with the current tubes I'm using, but figured "what the heck" after having had such good results with the op amp replacements in the dbx cd player.....  Needless to say, this time things didn't go nearly as well lol 

Although they were clearly marked as 627s and 637s I'm not at all sure what I actually received. But the resulting change in sound was just terrible.... I tried every possible combination of the existing six matching op amps and the three pair of new ones... with not the slightest improvement in sound.....actually all I got for the effort was varying degrees of muddiness, over emphasis of portions of the audio spectrum and even a bit of distortion.... back to the originals.

Also, a big thing on a number of the boards was to use the high outputs without any gain switch turned on for MM cartridges, and some saying it's the best settings for everything (bypasses a circuit) ... with my ClearAudio MM cartridge the result was that it sounded like the phono pre amp was over driving the inputs at anything beyond background levels....  I even played with a number of other settings on the Jolida and within the receiver to try and make the most of the change...... but again ended up right back where I began....

I know it's a function of different ears, different equipment and maybe for part of these experiments, bogus op amps, but the internet / boards and the sheer number of insistent "best thing since sliced bread" posts,  never ceases to amaze me... lol   

[Anders]

I wouldn't trust parts from China.

[AdamG]

I guess that's part of the thrill of the chase! At least you were able to tell a difference, for better or in this case for worse. Now you know 1 more thing not to try!

[Sir Thrift-a-Lot]

I'm not sold on op amp rolling anyway.   Some of the specs specific to one amp can be very different on another.   I don't know about just throwing anything in.

[Jim Pittsburgh]

Adam and STAL.... agreed/ understood.... but I found it funny, and frustrating, particularly after all the reading I did.... Most likely it's bogus op amps.... or all those posters on Audiogon, Audiokarma, DIYaudio etc etc have seriously bad hearing .... lol

[Jim Pittsburgh]

and Anders..... sorry, didn't mean to leave you out.

[Jim Pittsburgh]

Update

Replaced the 627 with ones that OBG got
Played with every possible combo of the
originals, the new 627s and the 637s. And actually
Came up with an excellent combo that is a real
improvement; viewed from the back left to
right. Originals, 637 and 627... OBG can attest
Sounds pretty sweet !

[Anders]

I'm all for op-amp rolling just like tube rolling but you have to be careful.

[OldiesButGoodies]

Agreed with Jim, not sure what the magic is but this particular combo worked great on the Jolida JD9.   Cannot be placebo effect, we tested the ccmbos back to back and the diff was more than obvious on both preamps.

[scorpio333]

Update

Replaced the 627 with ones that OBG got
Played with every possible combo of the
originals, the new 627s and the 637s. And actually
Came up with an excellent combo that is a real
improvement; viewed from the back left to
right. Originals, 637 and 627... OBG can attest
Sounds pretty sweet !

After many hours of fighting with my JD9 I put 627, 637 and the original 37G's in just like Jim and I like it. I made a chart of the opamps I had on hand, there were 20 possible combinations. My OCD agreed it was a great idea until I tried Jim's setup. No need to go any further, at least for now.

I cured the hiss I was fighting by using an SUT and the MM side of the JD9. No combination I tried on the MC side cured the hiss, there's just way too much gain on that side. If I had two more 627's I'd try them in the middle (gain) position, but that's just based on hours of reading about opamps and a few posts claiming the 637 may be a little hot for that spot.

[Jim Pittsburgh]

nice    glad you found a good combo. I'm still puzzled by the gain noise/ hum . I use the low output side of mine , otherwise too much gain.

[rgpit]

I've been in industrial electronics distribution for over 30 years as a Field Sales Rep. Trust me, never buy components from Chinese sources! The chances that they are fake, gray market rejects, or relabeled inferior parts is VERY high. Buy real parts from a legitimate franchised supplier like Digikey, Mouser, or Arrow Electronics. You'll pay more but you will have the real deal.

https://www.allaboutcircuits.com/news/how-to-spot-counterfeit-electronic-components/

[gdv]

Not that I buy much, but I use Parts Express & Newark (old MCM) & at times Digikey...

Are PE & old MCM still reliable?


Thanks,
George

[rgpit]

Newark is a reliable source, but they are usually pricey compared to others. Newark is owned by a large European electronics distributor called Farnell. I would say Parts Express is reliable although I'm not sure they are an actual franchised semiconductor distributor. My guess is that they buy their semiconductors from one of the suppliers I previously mentioned. Avnet is also a good legit source I left out.

[Sir Thrift-a-Lot]

Newark is a reliable source, but they are usually pricey compared to others. Newark is owned by a large European electronics distributor called Farnell. I would say Parts Express is reliable although I'm not sure they are an actual franchised semiconductor distributor. My guess is that they buy their semiconductors from one of the suppliers I previously mentioned. Avnet is also a good legit source I left out.

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