[Wire Nut]

Now this one returned lots of hits! Thanks.

[steveblezy]

If you do decide to swap out the Opamps, do your self a favor and spend a few bucks and buy an IC puller. It is basically a little set of tweezers with a small horizontal tongue. The IC section in the Jolida is a little tight as there are disc caps (if I remember correctly) on either side of the IC's so it is a little tight. The IC puller would cost less than $10 but makes the job easier. Also, pay attention to the orientation of the chips. These chips have either a white dot or a detent molded into the plastic that will indicate which end pin 1 is. Also, if you are feeling a little nervous regarding the job, drop into Radio shack and buy the cheapest 8 pin chip and practice putting it in the socket to get the feel. It is a very easy job. Unplug the preamp from the mains and let it sit for an hour or two to allow any caps to discharge just to be safe.

The big difference that I heard with the 637BP was the leading edge or transients were more defined. Bells, cymbals, percussion etc all sound more defines. Overall, better tonality and more precise high frequencies.  Bass improved also but overall, everything was not precise. Once you are finished with this, changing the output caps would be the next mod. It has been noted throughout this thread and they play a huge part of the sound.

[Wire Nut]

Steve,
What is the output of the cart you are using? Doroner said he got noise with the high output Op Amps with a low output cart (.3) The Denon I am going to use is even less at .25
Thanks, Nut

[steveblezy]

I am using a Blue Point Special EVO III which is a very high output (Output Voltage/Channel 2.5mV).I tried out the Van Den Hul MC10 Special from the other table as it is sitting beside it to see if I hear and noise. The MC10 Special is Output Voltage at 1 kHz at 5.7 cm/s eff.:0.65 mV RMS so that is quite a difference between the two. The VDH is a little higher then yours.I had no noise coming out with the VDH cart. Beyond that, I have no suggestions for you. At 0.65mV, all sounded great

Steve

[steveblezy]

I went back through the thread and found the post that Doroner made

"The Op-amps recommendations did not work for us - for what ever reason the top of the line AD843KN increased the noise floor in our units (it started hissing on stand-by) without really improving the dynamics. The Burr Brown OPA637BP did not work for me at all - it produced a very high pitched squeel (like a TV would do sometimes) and I yanked it out before there will be damage. Could be a faulty batch of OPA637BP. "

Something sounds a little miss there. AD843KN made a hiss on standby and the OPA637BP squeeled. I would consider asking Doroner if he made other mods before trying to chips. Something just does not sound right.
Steve

[steveblezy]

Regarding the OPA637BP squeal, ask him if he felt as if it was 'self-oscillating". I am just curious at this time.

Damn I love this thread
Steve

[Doronor]

I think it did oscillate and that caused the squealing.
Between you and me Discrete components sound much better (more relaxed and less pinched) so those who went there must be noticing bigger improvement than replacing one op-amp with another. I am using the stock op-amps for now.

[Wire Nut]

Guys, I have started a thread on the Vinyl Engine about the JD-9 mods: please feel free to take a look:
http://www.vinylengine.com/phpBB2/viewtopic.php?t=39598
I am using the OPA627 in the middle and am having good luck. I will post pix and details this weekend.

[Wire Nut]

I can't read resistor values, can anyone tell me what these two resistors are? They are both in the third position in thier respective groups:
http://www.audiocircle.com/index.php?action=gallery;area=browse;album=5862

I couldn't get these photos to load to the post so I just included the URL

Thirdeye- I will let everyone on the Engine know about your excellent updates

[undertow]

By the way I will answer a few issues above as well for posters... And see below for 2011 upgrade updates to this unit.

-One is about the Op amp 843kn, DON'T use it...

The burr brown op637 works fine, not sure why somebody would have a problem with the op637bp version, I think they said they put Op 638bp or something stated in a response above, which I don't know if it even exists? If it does and it squeals its obvious its not an opamp to work in this unit.
_______________________________________ _______________________________________ _____
- FORWARD Midrange....

I believe of course the main output caps can help this, I am using Duelund, Clarity MR's are great too which I originally used.

However, Tubes can somewhat as well change the mid's but not to an extent that might correct it.

Maybe the most effective is getting those SUPER generic Power supply caps out of the unit all together!

The main ones on the board by the transformer for sure, this should help tame the mid glare, as these caps are so generic I don't think they cost 15 cents and they are sizable values.

Go Nichicon at least, and make sure you buy the correct "Metric" sizes and leg spacing to fit them properly.

Also all Nichicon replacements on the input board will help, which there are like 26 caps on it as seen in photos, for sure will make the sound "Richer" and right in the mid's.

If you need better HI's and extension then the AD797 opamp will help over the Burr browns and sound is similar to the AD843kn which is the wrongtype, but the 797 are DEAD silent, and excellent balanced sound. And luckily they are cheaper, but still an expensive op amp if you can even find them, they run about 8 or 9 bucks each.

ZERO OSCILLATION from the AD797 and Burr Brown 637's in my experience.

Good Luck

[undertow]

PAGE 10

[undertow]

Wire Nut,
The resistors your looking at are for the Gain in the circuit and in your Jolida book layout those are the gain dip switches for MC-LOW, MC-High, MM. In the photo I think your pointing at MC low. Which means its the smallest value resistor in the bunch. I am not sure look and see which switch its hooked to from the other side.

Anyway MC-Low - switch #3 = 33 ohm

MC-High - switch # 2 = 100 ohm

MM - Switch #1 = 1k ohm(1000 ohm)

Again I think your pointing at switch #3 so just check,

[Wire Nut]

I am using the lowest output cart I know of - the Denon 103r. So I am using the low output in the three DIP series and 100 ohms in the first set of DIPS

[Wire Nut]

Actually I am getting too much gain so if I know the value I can go to the next highest one to get it normalized with the rest of the gear- the Jolida has lots to give!!!

[undertow]

YOU HAVE too much gain?

When it says LOW MC that means its going to give MORE power to make up for the Low output cart you have which somebody at Jolida was Deaf when they designed this unit! Which is why everybody thinks this thing has too much gain, and why your tricked into thinking LOW MC on this unit is useable even with such a tiny signal it has too much power.

If you put it on HIGH MC that means you will get less power.

So you need to turn off switch #3 or Low MC because it is a 33 ohm which is too much power due to too low resistance, and turn on Switch #2 which is 100 ohm and try it, this will cut a substantial amount of gain.

They are all the same by design, MM, MC high or low means nothing, that's just generic Consumer talk, they all use the same circuit and resistors, it just depends how much resistance is needed to cut the gain correctly, every switch and design is identical just with different value resistor attached, all cartridges need the same exact phono amp, just different load and gain resistors ultimately.

12ax7 tubes= 100 % gain in this unit, a 12au7 is ONLY 30% the gain of a 12ax7, so it works with very powerful cartridges perfectly like the MM's and some MC's.

[Wire Nut]

Hay Buddy; the middle output level is the cat's meow for my stereo!
Great advise!!!!!!!!!!!!
Can you tell me what that value is? I would like to replace with Caddok MK's.

[Wire Nut]

Dude, I am fearless... look at my TT project. An AR upgrade expert thinks I have one of the best XA upgrades around-bring it on!
http://www.vinylengine.com/phpBB2/viewtopic.php?t=34945&postdays=0&postorder=asc&start=0

[Wire Nut]

Absolutely right on the skill issue. Can you draw me a picture (art major) so I can get it?

[undertow]

Okay I will try to clearly explain, no photo needed

So first thing is first, turn off and LEAVE off ALL DIP SWITCHES, they will no longer be of USE.

Now when you open the input stage you see the 2 RCA Jacks on the input correct? Right, so you see the ground wire, and the center pin of the RCA, all you do is put your new 100 ohm resistor one leg on the ground and one on the center pin for each channel. Simple, now your loaded direct! And all your switches stay off, because you are in direct contact, if you turned on a switch for example your 100 ohm on the board again, it simply would be 2 parallel resistors, making it 50 ohms. Obviously you do not need this... NO danger in accidentally putting the switches on, it just would not be right.

Okay for the GAIN resistors, the new found miracle you have experienced when turning on the 100 ohm resistor VS. the 33 ohm you were using.

This is just as simple, but harder to do. Look at the board where the 33 ohm resistor is and right next to it all the way on the right of the board if standing behind the unit you see the wires connecting that little board down to the main input board correct?

There are 4 wires, 1 pair is for the right channel, and 1 pair is for the left channel. They look like a ground and hot wire, just like everywhere else right? Well they are not, they are the same HOT pin no ground its simply a loop going IN and OUT on the main input board, this is just simply inserting your resistor in series for the gain circuit to reduce power, if you put no resistor which is when the DIP switches are off, the unit does not operate as there is no connection.

But now if you just BRidge that hot pin to hot pin for each channel the unit will be constantly connected and no need to turn on dip switches because your already in the circuit.

Also, NO danger in accidentally turning a DIP ON, because it will simply just parallel in another resistor on top of your permanent 100 ohm across those terminals DROPPING resistance which would make it much louder again as if you were in the 33 ohm setting. So this is why now if you do these direct solder connections the entire unit will operate with none of the switches on or in the signal path or the load.

[Wire Nut]

I have sent an email to Chris at Parts Connexion about the resistors and will pony up to get them. I am getting a little harshness now that I switched to the middle output & suspect it is from the cr@p resistors that came with the JD9.