JC-80 eBay PCBs

[Wolfsin]

Guess I'll start rooting up the other odds and ends while things are in transit from East Asia.

The sad part izThat you might well finish ahead of Wolfsin. As Do points out above, he beat me by more than a year to the tunez enjoyment part

Glad you decided to give the JC-80 a try.

I am considering using a single screw in each heat sink (leaving the pin on the other side) rather than soldering them in.

 

[pinnocchio]

The sad part izThat you might well finish ahead of Wolfsin. As Do points out above, he beat me by more than a year to the tunez enjoyment part

Glad you decided to give the JC-80 a try.

I am considering using a single screw in each heat sink (leaving the pin on the other side) rather than soldering them in.

Screwing the sinks will make it much better for maintenance. I couldn't do this since the pins didn't align. Those shtupid pins

Do

 

[ticknpop]

Yes the heatsink pins don't line up with holes on the JC 80 board, i believe the holes were layed out by a Mr. Dremel who is now vacationing in the south of France on the money he has made selling me small drill bits to fix layout errors on PC boards. Au Revoir

 

[Wolfsin]

@ticknpop A shineze guy got tired of seeing those profits flow to Mr. Dremel and makes heat sinks that fit! Less that a dollar each but not as tall as Do's. I don't think he will ship to eastern Canada

My WaveIO i2s interface arrived but I am not ready to turn my attention away from JC-80 yet so I just connected the SP/DIF (it supports both). My Apogee clock does the cleanup. WaveIO is beautifully built and is the subject of another diyAudio thread.

I plan to build the second Kubota today after I clean up a little more of the two feet of fresh snow. 'tiz beautiful.

 

[pinnocchio]

@ticknpop A shineze guy got tired of seeing those profits flow to Mr. Dremel and makes heat sinks that fit! Less that a dollar each but not as tall as Do's. I don't think he will ship to eastern Canada

My WaveIO i2s interface arrived but I am not ready to turn my attention away from JC-80 yet so I just connected the SP/DIF (it supports both). My Apogee clock does the cleanup. WaveIO is beautifully built and is the subject of another diyAudio thread.

I plan to build the second Kubota today after I clean up a little more of the two feet of fresh snow. 'tiz beautiful.

Yeah! I can relate to that... Last night at 1am I was on my roof taking out the snow and ice mixed together... 2.5' of snow on one side of the house and it was so heavy that I was starting to hear my roof making some weird sounds... Hence the reason to go on the roof!

Winter is otherwise "enjoyable"...

Do

 

[Wolfsin]

Perhaps you might consider shipping some of that gear to Colorado where we build to carry the load. The TPA DACs would allow Wolfsin to verify the WaveIO and would be much safer here. We actually like the snow!

You guys convinced me to attach the heat sinks with screws. That way whenever crazy thoughts about climbing on the roof in Winter come my way I can simply replace the output transistors on the JC-80 and consider it 'maintenance'.

 

[pinnocchio]

Perhaps you might consider shipping some of that gear to Colorado where we build to carry the load. The TPA DACs would allow Wolfsin to verify the WaveIO and would be much safer here. We actually like the snow!

You guys convinced me to attach the heat sinks with screws. That way whenever crazy thoughts about climbing on the roof in Winter come my way I can simply replace the output transistors on the JC-80 and consider it 'maintenance'.

Sure why not ship it to you! You can do a cross ship of those two the Wire amp boards at the same time. They would feel very comfortable here with the good care and attention they would receive!

Ciao!
Do

 

[Wolfsin]

Something simple -- heat sinks from Sunelectronic available on eBay, qty 8 shipped for less than US$8 total and the pins fit into the pcb holes.

Nota Bene: If you solder (or screw) the heatsinks for the output transistors to the intended pads on the JC-80 pcb then they will be grounded. If you then choose IRF9610/610 output transistors you must isolate their tabs from the heatsinks or the center pin will be grounded.

 

[ticknpop]

Pinnochio - just made hotel reservations for Montreal Son y Image show, so hide the liqour.
My preamp just lost an EI core transformer. Lucky i bought a spare when I got them from the surplus store. Looks like we need spares of more than jfets to keep things running.

 

[pinnocchio]

Pinnochio - just made hotel reservations for Montreal Son y Image show, so hide the liqour.
My preamp just lost an EI core transformer. Lucky i bought a spare when I got them from the surplus store. Looks like we need spares of more than jfets to keep things running.

Yeah! That will be quite a fun day!

Wolfsin, you should fly in! 'Tis a great show in Mtl

Do

 

[pinnocchio]

JC-80 loud pop issue...

I've had this loud pop for quite some time using R2R ladder attenuators

I've tried two of them and always have this issue. An example would be from 63.5dB to 64dB "POP" then ok and same pop at louder volume. It only happens twice in the ladder...

The input impedance is 1M and my ladder Zload is set as such.

Here's Stanton's suggestion and would like to know John's feedback or anyone with suggestion on this...

"If there is DC coming out of your R2R then there will have pop noise. If your R2R is dc coupled, then the DC is very likely from your source. You may try to reduce JC-80 input impedance to 10K so as to speed up the DC discharge."

My R2R is AMB's [FONT=arial,helvetica][SIZE=-1]δ1[/SIZE][/FONT]
The δ1 Relay-based R-2R Stereo Attenuator

Coupled with AMB's source selector [FONT=arial,helvetica][SIZE=-1]δ2
[/SIZE][/FONT]The δ2 Relay-based Stereo Input/Output Selector

Thanks
Do

 

[pinnocchio]

I've had this loud pop for quite some time using R2R ladder attenuators

I've tried two of them and always have this issue. An example would be from 63.5dB to 64dB "POP" then ok and same pop at louder volume. It only happens twice in the ladder...

The input impedance is 1M and my ladder Zload is set as such.

Here's Stanton's suggestion and would like to know John's feedback or anyone with suggestion on this...

"If there is DC coming out of your R2R then there will have pop noise. If your R2R is dc coupled, then the DC is very likely from your source. You may try to reduce JC-80 input impedance to 10K so as to speed up the DC discharge."

My R2R is AMB's [FONT=arial,helvetica][SIZE=-1]δ1[/SIZE][/FONT]
The δ1 Relay-based R-2R Stereo Attenuator

Coupled with AMB's source selector [FONT=arial,helvetica][SIZE=-1]δ2
[/SIZE][/FONT]The δ2 Relay-based Stereo Input/Output Selector

Thanks
Do

Here's some more feedback

me
"what adverse effect on sound could lowering the input impedance to 10K do if any"

Stanton
"If your source has a high output impedance then firstly the output level will be reduced. Secondly if the source is AC coupled the bass quantity may be reduced."

Do

 

[pinnocchio]

Ti from AMB gave me some explanations

"the transition from -63.5dB to -64.0dB is when every relay changes state (i.e., it goes from 01111111 to 10000000). This is the most extreme case where if the relay timing is not exact (and they will not be), the signal will experience a discontinuity which is perceived as a pop. Similar situation occurs at other places, such as -31.5dB and -32.0dB, but since less relays are changing em mass the pop is lower in level.

This characteristic occurs in every relay attenuator implementation I've come across, not necessarily at the same level (it depends on the number of relays in the system and the step size).

However for the delta1 with 8 relays and 0.5dB steps, at such low attenuation levels the pop should not be readily inaudible. If you hear it, then probably you have too much gain in the system after the attenuator. Or else if there is DC offset from the source it could also pop."

So I guess I need to modify the gain of the JC-80

I tried two sources, my CD player which is a Sony DVP-S7700 using the analog out and them my Opus DAC using the IVY III output stage fed by the SPDIF of the DVP-S7700 with same results.

Thanks
Do

 

[Wolfsin]

So we have ticknpop in Toronto and Do with pop in Montreal. Seems geographical to me.

 

[Wolfsin]

The r-cores are on order from China. A pair of dual 30v secondaries. They may result in a little extra heat but after falling short with 24v dual secondaries I wanted to be certain when ordering a pair.

I am down to a very short list now and the major obstacle is finding a local service capable of measuring resistance, capacitance, and noise with considerable accuracy. I am curious how @imminentdomain is getting along in his sourcing efforts.

 

[pinnocchio]

AMB a10 + JC-80 = Complete orgasm!!!

Finally finished assembling the JC-80 with AMB's o1 and o2 on the a10 backplane.

I can't believe the sound of this thing with the Opus DAC in balanced mode.

Really really GOOOOOD!!!

Now I have to pack everything in the enclosure... Lots of Front Panel Express work to be done!

My previous attenuator was causing a ground loop and thus sound was really not up to par. This setup is dead silent!

JC-80 is really a beast! Now to see what can be changed to make it heaven's sound!

I will post pictures later on, now I'm just paralyzed!

Yesssss!
Do

 

[sean]

Pinnocchio,I’m very glad u enjoy jc80,now I will layout the jc80 pcb again and change smd components and more compact.I’ll try 4 layer FR-4 board if need,any comments?I’m sorry for my pool English.
Thank you!

 

[Wolfsin]

Welcome Sean

Hi Sean, your English is easy to understand. My Mandarin requires apology

When you write 'again', it leads me to believe you did the layout on the board we are using. If that is the case, congratulations on a beautiful product. When do you anticipate having the revised pcb available?

Will you be making major changes to the servo area?

@pinnocchio It is great to see you this excited.

 

[john curl]

Welcome to the sound of quality hi end audio, amateurs! Yesterday, I had the original builder here in my lab. He now is chief operating officer for Constellation Audio (very expensive stuff) and we both looked over a JC-80 sent to me for any repairs that it might need. We were reminded that we built this design, together, over 30 years ago. It has held up pretty well.

 

[ticknpop]

Pinnochio - 10 k is best choice for lowest interaction with cable and JC 80 jfet input capacitance and noise, 50k is highest you want to go.

Wolfsin- the 30 VAC R core should give about 41 VDC after the bridge. suggest to use 317/337 ( or 2 of 317 if you have seperate positive and negative bridges) as preregulator at a minimum.

I used 2 x LM 329 referenced LT 1085 with 36 VDC output , then Borbely super shunts set to 30 VDC out, then the JC 80 cap multiplier on board drops final 6 VDC to 24 VDC. I use selected 2sk246 to be a current source instead of resistor for the cap multiplier. You select the lower resistor to match the IDSS of the jfets you have to get 24 VDC out of the cap multiplier - allow for 4 volts for cap multiplier Fet drop when you select the resistor.

I believe John used 2sk147 jfet for the cap multiplier pass device for Vendetta phono first stage and Toshiba fet for second stage cap multiplier pass device to keep noise low.