Jolida JD9 phono amp hybrid Magic...

Wire Nut · « **Reply #160 on:** 3 Sep 2011, 12:54 am »

I forgot to mention that I have a Rogue Cronus Magnum that uses 12au7's and I have a bunch of tasty NOS tubes to roll in to try - including Brimar 4003's & many others- this will be fun!

undertow · « **Reply #161 on:** 3 Sep 2011, 12:58 am »

Tube rolling 12AU7's that might be to low of gain with the MC no matter what you do not sure. Maybe putting it back to the 33 ohm resistor with a pair of AU7's is possible, you would want to try that before doing anything else at this point or ordering parts if you plan to roll some 12AU7's you have on hand.

As a SIDE note, I highly suggest you might want to run to a radio shack and buy a bunch of the cheap resistors first of various sizes if you feel the 100 ohm is still too much gain or cuts too much gain. You need to be honest with yourself if you are right where you want to be with the volume control on your preamp and its in the sweet spot.

You can buy 120 ohm, 150 ohm, even 200 ohm or something if you think there is still a little more room to clean up volume and still want to have even better control of the gain. That's up to you, so if the 100 is perfect go for it, but the cost of Caddoks at 5 bucks a pop, or Vishays at 15 will burn you if you decide it was not the perfect size!

danska · « **Reply #162 on:** 22 Oct 2011, 09:46 pm »

Undertow,

Would you be willing to share a little more information about modifying the power supply area? Do I just read the values of the stock caps on the power supply board and buy higher grade versions of the same? Bypass caps I can understand easily enough.. The other thing I'm not sure exactly which version to get is the diodes? I notice several different ones on parts connexion, I want to make sure I order the correct ones.

Also for the output cable, am I looking at using interconnect cable specifically? Thanks a lot for your help.

Following recommendations on this thread an several other related ones I've modded my JD-9 with all new opamps (627/637BP, LT1028 input), ClarityCap MRs 1.0 uF, RCA Command blackplates 5751. Going to do some input board work once I get my Ortofon Jubilee back form re-tipping. This phono amp does wonders with both LP-12s my roommate and I have, I'm running it into a very modded Jolida 302b and I'm loving the combo.

rkay5 · « **Reply #163 on:** 26 Oct 2011, 06:48 am »

HI,
I just reading about modification of the JD9 here for the first time.I have one also and BB op-amp chips should be 637AP not the BP that way it doesn't sound right.
I'm using the 637AP for output and 627AP Input and Riaa.Tube are Tung-Sol and I used jantzen audio Superior Z-cap 800VDC 1.0uf +/-2% for output cap,The cartridge I'm using is Denon DL304 LOMC and sounds great!

midfi · « **Reply #164 on:** 31 Oct 2011, 03:46 am »

I'm really starting to like this little gem. This morning I swapped in these http://thetubestore.com/sba-jolida-jd-9.html from some Tung Sols (which ain't bad at all, just rolling....) and moved the 627's over to the from the input to the center and put some 637AP's in the input and left the 1128's in the output spot. I've think I've found the combo for my setup

I put the Obligatto caps in a few days ago as well as some sound deadening material.

I removed the blue caps with my solder suck thingie...
I think I'm gonna leave it be for a while and work out some other areas in my system that needs addressing (my Adcom GFA-750 is humming like a bird!!!

).

undertow · « **Reply #165 on:** 31 Oct 2011, 07:42 pm »

Danska,
As for the power supply, yes just pull the electrolytic caps and replace with equal voltage or higher and values that are in the unit. However, as a warning this could get tricky as many of the caps are lets say 16 mm diameter, or 20 mm diameter etc… depending on the size and value. Some of the higher end Nichicon caps, Elna caps, BLACK gate especially are much larger diameter sizes over the generic capacitors in the unit, so matching exact size might prove difficult especially if you go to the higher cost audio grade types from Parts connexion.

I would say this, anything brand name is better than the 13 cent generic caps that are in the unit stock. Easiest to find that should fit most positions are probably the lower grade I think (VX)? series Nichicon electrolytic caps. I did use a couple Black gates as well, but these don't fit anywhere near the board, they are far to large, and would hit the top if you close it as well, also these have a much larger PIN separation and they had to be modified to fit this unit, I don't necessarily suggest going this route.

The DIODES in the unit are basic ZEENER diodes, I believe they are all 1 amp versions, these can be tricky to fit as well and you need to mind the installation of these and put them in correctly if you flip polartity of the cathode on these they will burn. Basically you can use Cree/Schotkey or whatever fast recovery soft diodes in a 1 amp version.

bluepearl · « **Reply #166 on:** 11 Nov 2011, 05:51 pm »

What is the difference between OPA637AP and OPA637BP ??

Undertow. You recommended the AD797 op amp, there appear to be numerous variations, can you clarify what the suffix is? (EG: AR, AN, AU, ANZ, BR...)

Thanks.

BP

midfi · « **Reply #167 on:** 12 Nov 2011, 06:47 am »

can't remember where I read it but the author said that AP's should be used instead of BP in audio operations. I'll try to find it...

midfi · « **Reply #168 on:** 12 Nov 2011, 06:34 pm »

newsflash, for some odd reason the Tung Sol tubes do not like my AT15Sa at all! Sounds like a $10 fisher price toy. The JAN/Philips mix well with it though. The Tung Sol sounds sweet with my Shure M91ed and the V-15iii though.

Charles Xavier · « **Reply #169 on:** 13 Nov 2011, 08:32 pm »

Quote from: midfi on 12 Nov 2011, 06:34 pm

newsflash, for some odd reason the Tung Sol tubes do not like my AT15Sa at all! Sounds like a $10 fisher price toy. The JAN/Philips mix well with it though. The Tung Sol sounds sweet with my Shure M91ed and the V-15iii though.

Quote from: midfi on 12 Nov 2011, 06:34 pm

newsflash, for some odd reason the Tung Sol tubes do not like my AT15Sa at all! Sounds like a $10 fisher price toy. The JAN/Philips mix well with it though. The Tung Sol sounds sweet with my Shure M91ed and the V-15iii though.

How are these guys sounding ?

http://thetubestore.com/sba-jolida-jd-9.html

midfi · « **Reply #170 on:** 13 Nov 2011, 11:08 pm »

Quote from: Charles Xavier on 13 Nov 2011, 08:32 pm

How are these guys sounding ?

http://thetubestore.com/sba-jolida-jd-9.html

good, don't seem to take or add anything, they're just there. Not sharp or bright and a little less bass than the Tung Sol's but good overall. Much better than the ones that came with it from Da House...

midfi · « **Reply #171 on:** 15 Dec 2011, 08:08 pm »

video of the Jolida Shenda factory...

http://www.youtube.com/watch?v=GiLKzUURIgU

Lifer · « **Reply #172 on:** 16 Dec 2011, 02:03 am »

Been running my JD9 for about 3 years now (see my entry in this thread on page 1). I've been using an Analysis Plus Oval 14 pc for that entire time I guess. I floated the ground on the pc right away but I did it on the wall side (wrongjavascript:void(0)

and didn't change to floating the amp side until a few months ago - nice change.

Last week I got some Pangea signature 14's and wanted to try one on the JD9, but the connectors on these cords are molded on so floating the ground isn't possible. I tried it anyway and it sounded good but not as good as the floated pc. So I looked inside the box for a solution. The grounding on the JD9 is a single point (a star ground I think) - a screw in the bottom of the chassis that many wires hook to. I disconnected the power ground from that screw and wrapped a bit of electrical tape around the connector at the end of the wire so that it wouldn't reform the ground by shifting position. Including taking the cover off and putting it back on this took all of 10 minutes. I hope this is clear.

Now I put the Pangea cord in place and warmed up the JD9. Excellent, a nice match of power cord to amplifier. These cords are inexpensive and very well made. I recommend trying one, especially after floating the ground inside the amp. I figure a lot of people who read this are skeptical that a pc can make a difference - here is a good opportunity to find out for yourself.

TomS · « **Reply #173 on:** 16 Dec 2011, 03:05 am »

You do realize that's a safety ground right?

Lifer · « **Reply #174 on:** 16 Dec 2011, 06:31 am »

That is SHOCKING!! Well yes, I do. But this is a high risk hobby, right? Seriously, the phono-amp is grounded through the ic's to the pre-amp (which is grounded to the wall outlet) it is also fused.

I run everything (cd, turntable, tuner, phono-amp, and power amps) except the pre-amp with the grounds floated and have done so for decades. It has never been a problem and the sound is far more dynamic and involving this way. Who wants to live forever with dull music. What do you have to lose?

TomS · « **Reply #175 on:** 16 Dec 2011, 07:48 pm »

Quote from: Lifer on 16 Dec 2011, 06:31 am

That is SHOCKING!! Well yes, I do. But this is a high risk hobby, right? Seriously, the phono-amp is grounded through the ic's to the pre-amp (which is grounded to the wall outlet) it is also fused.

I run everything (cd, turntable, tuner, phono-amp, and power amps) except the pre-amp with the grounds floated and have done so for decades. It has never been a problem and the sound is far more dynamic and involving this way. Who wants to live forever with dull music. What do you have to lose?

And it's fine to disagree. With +230vdc B+ in there along with line voltage there is a lot to lose. I buy and sell a lot of gear so if I "forgot" to reconnect it and someone gets hurt then it's on me. In my case I just can't live with that.

Lifer · « **Reply #176 on:** 17 Dec 2011, 02:30 am »

I understand your concern, and agree that it is fine to disagree. But, I would suggest that you can easily float the ground on a spare pc and try it on your JD9. I think that you would be surprised (if not shocked). Good listening to you.

alx_d · « **Reply #177 on:** 29 Dec 2011, 02:29 am »

Hi Undertow....thanks for the new update.....I would suggest that one do one more mod (at least) and that is what I did.....I removed the transformer form the case and put it in a plastic hobby box I got from Frys. This made the biggest change to the sound ( I have done all the mods you suggested and more a few years ago). This is due mostly to the magnetic field that the tranformer produces as well as the mechanical vibration. I used a Oscope probe with the x1 probe and no ground. You can move the probe.around the transformer and wires and see the massive amount of stray AC interference that it produces. Once removed and put in the case I made a umbilical cable that connects the two together (6 feet long). The on/off switch and IEC connector are in the remote box as well. I also removed the LED and wires. The cable that goes.into the phono is shielded and where the wires are outside the shielding I use copper foil tape wrap and made sure to ground the foil to the shield.
If you dont have an Oscope to to try it yourself try getting a stethoscope and place it on the chassis. You will hear the vibration everywhere on the chassis.
Regards
Alx_d

alx_d · « **Reply #178 on:** 29 Dec 2011, 02:30 am »

Undertow...by the way I see the schematic in your post. Any chance of getting a copy? I am sure it would help us all out.
Alx_d

alx_d · « **Reply #179 on:** 3 Jan 2012, 08:37 pm »

Undertow. I got your PM for the schematic and sent you a response but never got an answer. Maybe I got sent to your spam folder. Any cahnce you can send it?

Regards
Alx_d