System edited: Just acquired two more chassis, transformer, and assorted caps to build preamp to four chassis status.

bruce_weiland May 25, 2013 13:37

Two additional chassis, transformer, and big A** caps ordered to further beef up the PS for the JP-200-12B's

bruce_weiland May 11, 2013 00:29

Birth of the Jadis JP-200-12B

Ok, I know, I know, there has never been a "12B" model. I will get to that in a bit. First let me get the shields up captain.

I must confess to my rudimentary electronic skills. I can use a VOM, am only moderately good with a soldering iron, and know the theory behind caps, resistors, diodes, etc. Yes I know Ohm's law. Other than that I am just an audiophool/phile tweaker.

Therefore you real engineering types that KNOW putting in (rolling) a tube type that a circuit was not designed for makes no sense without a change in values of resistors, and caps can stop reading now.

And those of you who know/believe that caps, etc. cannot make any difference in the sound, except to us audiophools, can stop reading too. Spend your time doing something you enjoy more, except if those activities include attacking phools like. You don't need to waste your time doing that. I won't respond.

OK. Shields are up. :-) Now let's get started.

I have been spinning vinyl since I was 3, and chasing audio nirvana since returning from the Corps at age 22, 44 years ago. I am sure I will continue for many decades to come.

The preamp I am about to describe sits in a system using big tube amps, big electrostats, powered subs, and massive AC power conditioning.

It started life as a Chinese Jadis JP-200 "clone". I use the term clone somewhat loosely, because it had only two chassis, not four as a real JP-200 would. The chassis, unlike most two chassis preamps, were not line section, and separate power supply, but rather a left chassis and a right chassis. Additionally, it had/has a 3310 chip based remote input selector, volume, and mute. Which is not unlike many very expensive preamps, Roland to name just one. Because it consists of a left and right chassis, and therefore separate volume controls, that can be used for balance too.

There were two owners before me. I was able to pick these preamps up for $630.

Each chassis has four separate boards and two R-core transformers. They contain an LS-DY tube rectifier, regulator board, supposedly patterned after an ARC design. The tube complement consists of a Chinese 6Z4 rectifier (similar to 6X4 but different pin out), a US made NOS/used(?) 12B4A, and a Russian, new production EH 12AT7. The R-80-31 transformer supplies this board. It also has a LM317 for 12.6 or 6.3 filament regulation (it is set for 12.6) for the line stage board.

The Jadis cloned line section board contains three EH 12AX7's. To shorten the story some, and not bore you with all the tubes I rolled, suffice it to say I tried a lot of 12A*7 types and brands, AU and AX, Bugle Boys and others. AT's did not work well.

Knowing that many had said that most 12BH7's were every bit as good as the best 12AU7's in most circuits, and that being my experience too, I decided to put two in the output positions. As the younger generation would say, OMG! Talk about ambience recovery, and filling out the lower midrange and bass, while still maintaining excellent image. WOW! It did it. And more nuances were coming through too.

I eventually rolled 12BH7's into all three locations, with improvements with each 12BH7 added. The power supply has sufficient filament current to supply all three 12BH7's at 12.6 volts, with current to spare. The three tubes need 0.9 amps. The LM317 is protection limited to 1.5 amps.

There are two boards dedicated to the remote volume and digital display and a separate R-core transformer for those two boards.

While rolling 12AX7 types I inadvertently rolled 12AX7's into the 12AT7 position on the power supply board with resultant better dynamics and separation. I went back and forth several times with different AT's and AX's. The AT's always seemed to compress the dynamics and homogenize the image some.

After a few weeks of listening I had a hair brain idea. What if I put a 12BH7 in the AT position of the power supply? Oh, I forgot to mention that I had purchased a pair of adapters so that I could use US made NOS 6X4's in place of the Chinese 6Z4's. I put in 6X4's from day one.

Anyway, 12BH7's in the power supply worked their magic again. This is where the "12B" model name comes from, four 12BH7's, one 12B4A, and a 6X4 in each chassis.

One further mod. The pair I have has Solen SCR pp coupling caps at the output. I paralleled two NOS US made PIO 1 uf, 500v caps in each chassis. Nice improvement. :-)

I have had both active and passive units in my system through the years. I have had SS and tube units in the $5,000 to $6,000 range. My current preamp setup is synergistically MUCH better than anything I have listened to in my system, so far.

Now, what is next for these preamps?

Well why not four chassis as the original $30,000 to $60,000 Jadis. So, I have order two more chassis with power buttons only.

Taking the PS out of the line section box has the potential to further lower the noise floor, which is already very low. However, there are some additional benefits. The chassis are all full sized, 16x13x4. By moving the two transformers and the power supply board out of the "main" chassis I get the additional space to play around.

I have ordered an additional pair of transformers for the tubes to give me twice the potential current capabilities. I have also ordered enough capacitance to increase the PS reserve by a factor of 10. Of course there would not have been enough room in the current chassis to add such big caps. I will also have more room in the line section to play with more interstage coupling caps.

Stay tuned (pun intended) for further developments.

Bruce

bruce_weiland May 05, 2013 17:29

System edited: Remote controlled two chassis

bruce_weiland April 09, 2013 21:35

System edited: New preamps

bruce_weiland April 09, 2013 20:46

System edited: Added second preamp for dual mono. Removed ribbon tweeters.

bruce_weiland March 31, 2013 15:15

I LOVE THE PRODIGYS

jazzkid February 07, 2013 03:51

System edited: New digital playback software. Already using jPlay 4.3a. Just upgraded from Windows 7 to Windows 8 Pro, and from MC17 to jRiver Media Center 18. :-)

bruce_weiland December 23, 2012 18:54

System edited: No longer using ribbon super tweeters. Damping back wave directly behind the stat panels with double thickness of bath towel. Tighter image focus, more depth, width, and focus. :-)

bruce_weiland December 16, 2012 16:16

System edited: New Analog and Digital Source picture

bruce_weiland December 04, 2012 14:27

System edited: Almost done updating.

bruce_weiland December 02, 2012 16:16

System edited: Looks like I inadvertently deleted my computer server. I still need to update the phono cartridge and will ad the server then. Plus the overall system pictures need updating.

bruce_weiland December 02, 2012 15:53

System edited: Warspeed and Fosgate signature sold. New (really old) Conrad Johnson PV-5 used as a phono section now.

bruce_weiland December 02, 2012 15:30

Absolutely beautiful system. Martins really bring fantastic transparency and quickness as I've come to know. Will put that WS right on my SET 300B powered A7's for a test drive. Ron

beanstocks November 29, 2012 18:13

System edited: description updated

bruce_weiland November 02, 2012 15:36

System edited: Added Blue Box and Behringer SRC 2496

bruce_weiland October 30, 2012 15:01

System edited: Added Warpspeed V4 and Wyred4Sound DAC-2

bruce_weiland May 04, 2012 15:08

Tpreaves,

Your "first glance" is partially correct.

The speakers are angled in more than 45 degrees. They don't point directly at each other, but do point at me. I sit almost between them. The inner third of the panels (the preferred listen portion of most Martin Logan's) are pointing right at my ears, and each ear is about 24" from that stat.

Obviously this is an EXTREME near field listening position.

The Prodigy are 5 feet from the wall behind them and 3 feet from each side wall. When using the system for background listening (since the audio room connects directly to the family room) the speaker placement is not a problem. When listening critically, or for the "bathed in the sound" experience it is of course a single listener system. Very much like great big electrostatic & ribbon headphones, but with balls (a pair of powered subs) and whole body enjoyment.

While the single person nature of this setup may not be everyone's cup of tea, there are a number of very distinct advantages to near field listening.

The first is system/room interaction. Because the back wave and the front wave have to travel such a long distance to reflect off of surfaces before returning to the listener and the ratio of that time delay compared to the initial wave to listener ear is so great, room interaction with the system is GREATLY reduced.

As you can see from some of the pictures, I have still treated the room for acoustics. EVERY system benefits for treating the room. You will see many on this forum state that treating the room should be done before, changing a piece of equipment, or a cable, or treating AC, etc. I have to agree with them. A room can certainly ruin a very good system. I have seen/heard it happen more times than I care to remember.

Another benefit of near field is total system headroom. Speaker efficiency, or more accurately "sensitivity" is generally stated at 1 meter and 1 watt at 4 ohms. For every meter one sits further from the speaker an additional 6db of power is needed to achieve the same volume. And of course for every 3db of dynamics above whatever the stated sensitivity is one needs double the power to attain that volume. Put these to realities together and you find that many amps are clipping with the dynamic peaks in the music. And that thousand watt per channel amps DO make sense, just not "cents" for most peoples pocket books.

Near field listening, especially with big amps, give most systems a great deal of "easy". When one is efforting to create an experience of being there, effortless dynamics are very important. This system has them in spades. :-)

Bruce

bruce_weiland March 23, 2012 13:17

Well Bruce, at first glance they look mighty close together and darn near pointing at each other with what looks like not much room behind them.I hope you didn't take my comment as a downplay on your system,it wasn't meant to be, you have some top notch stuff there.I was just taken by the unorthodox positioning of the electrostatic speakers. If it sounds good to you that's all that matters.

tpreaves March 10, 2012 22:04

System edited: Added links for DIY BAC (Big A** Cords), AC power cords. :-)

bruce_weiland March 10, 2012 16:49

Tpreaves,

I don't imagine you live in the LA, CA area, but if you do or are in the area at sometime, you can hear for yourself.

I believe you would be amazed. Everyone, including several "audiofools" I mean "-philes" (I include myself in that group) have been, and are.

Why is it that you think they could not sound good?

Bruce

bruce_weiland March 10, 2012 16:16

I have update the descriptions. More picture edits to come.

bruce_weiland March 10, 2012 16:10

System edited: After several attempts over the past few days, and a half dozen today, I was some how able to get into my virtual. I tried a number of work around's. I am not sure if I an reproduce the work around. I will try tomorrow. Audiogon has finally contacted me about this problem. Good for them! :-)

bruce_weiland March 10, 2012 16:09

Surely those MLs can't sound good positioned like that.There, I said it.

tpreaves March 09, 2012 00:26

Looks like it is all working. Updated pictures soon.

bruce_weiland March 03, 2012 23:58