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Which amp for Jordan JX92S Tline ?

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founzie

Member
Joined 2002
Hello to all tube specialists,

whet would you recommend to drive a pair of Jordan JX92S (88db) based transmission lines ( similar to Carolina Audio or Konus ones, with some mods that doesn't in my mind affect their relation to the amplifier ).

regards,

François
 
fdegrove

fdegrove

diyAudio Senior Member
Joined 2002
WHAT AMP?

Hi Founzie,

I think that what is said here could also apply to your speakers and amp requirements.

http://www.diyaudio.com/forums/showthread.php?s=&threadid=8578

There is of course plenty to choose from.
If you do not want build from scratch you may be interested in looking at the secondhand market in France.
An Ampliton or Yves Cochet for instance would drive your speakers nicely and with a bit of tweaking can still hold their own to this day.

Ciao,;)
 
F

founzie

Member
Joined 2002
Is a 6W single ended enough for a 88db speaker or is a 15W push-pull recommended ?

My room is 4x4 meters but open on one side to a 4x10 meters room (makes a "L").

On my old technics (class H+, 2x100W), the volume control is between 1/4 and 1/3.

regs

François
 
Brett

Brett

Member
Joined 2002
founzie said:
Seems 15W may be not enough for a 88db speaker.
Click to expand...
15W isn't enough unless you use them like headphones.
15W (or 11.7dBW) gives you 100dB SPL at 1m (90dB at 3m) at clipping. 80dB SPL <i>average</i> is a moderately loud listening level, so 15W only leaves you 10dB for peaks in the music, where IMO 20dB is a minimum or else the music will sound compressed.

Cheers
 
F

founzie

Member
Joined 2002
World Audio has two kits :

one with EL34s (32W per channel)
one with 6550, KT88 compatible (40W per channel)

Both are UL Push-Pull

The second is 20% more expensive.

Is it more reasonnable to go to 40W or is 32W already enough for my 88db speakers ?
Seems to me those are great powers for tube amps...

François
 
316a

316a

Member
Joined 2002
Hello ,
I use a SE 6C33 SRPP amp to drive my Jordan JX92VTL , about 10 watts a side . Similar sized room , I use mine in my 10ft x 10ft workshop . The only problems I ran in to : not enough treble over 10kHz (too warm) . Have added ribbon and currently piezo array (4 per side) tweeters . Also I ran my amp parafeed with self bias for a while : not good , changed to fixed bias , ok . Need fairly good damping to tame these fairly reactive tl's . Yet to try with a push pull amp but would expect far better bass , which is already good !

316a
 
316a

316a

Member
Joined 2002
Re: AND WHY IS THAT?

fdegrove said:
Hi,



Yep...never heard about Miller effect?

...sure have but this does not apply here . The other speakers I use sound a lot less warm than these . Remember the JX92 is a full range driver that relies on controlled flexure of the dustcap region to provide upper treble . I would think the upper rolloff point of my amp is considerably (I hope) better than 10kHz . Others I know who use the JX92 augment with ribbon tweeters , you need something domeless and fast ! If it has a dome tweeter it belongs on someone else's system

...FB
Click to expand...
 
316a

316a

Member
Joined 2002
BrianGT said:


Did you build the TL from the Jordan website? Did you follow it exactly? If so, how do you like it? I am considering building a pair of these soon.

--
Brian
Click to expand...

sure did , got a bit confused at first but after viewing carefully it all makes sense . Not much of a taper and I believe there are some nasty corners which need rounding off . I had the baffles cut then the rest of the sheet of MDF cut into 70mm strips . I just used a mitre saw for the cutting and cutting the angles , which was a breeze !
One point to note : if building these stuff the line up about 30cm from the exit port , then add to taste by stuffing the port gradually

316a
 
316a

316a

Member
Joined 2002
driver valve

...is the handsome 2C50 . A 5watt a section double triode with Ra of 2.9k . Other more 'piddly' drivers I tried like the 7N7 were a bit warmer and woolier . I must admit I was a bit paranoid regarding oscillation so used 4.7k grid stoppers at first , still a safe 2.2k at the moment so there may be a slight amount of rolloff

316a
 
F

founzie

Member
Joined 2002
I use a SE 6C33 SRPP amp to drive my Jordan JX92VTL , about 10 watts a side . Similar sized room , I use mine in my 10ft x 10ft workshop . The only problems I ran in to : not enough treble over 10kHz (too warm) . Have added ribbon and currently piezo array (4 per side) tweeters . Also I ran my amp parafeed with self bias for a while : not good , changed to fixed bias , ok . Need fairly good damping to tame these fairly reactive tl's .
Click to expand...

Damping : Strange that you need so much dampening, I've removed everything ! But I thing the asymetrical shape of my upper chamber removes lots of renonances in the upper mid.

http://www.diyaudio.com/forums/showthread.php?s=&threadid=7951

For the lower mid, I think the amplifier (maybe the too warm ones?) has a great impact. I had no renonances with a mosquito (2x80W Transistor amp with oversized power supply, class A/B running mostly in class A at the listening level). I also tried the baffle step correction circuit (although I don't need any : the speaker is designed to be wall mounted to avoid that) : then I had again this resonance in the lower mid/iper bass, maybe the kind of resonances you get with your amp. But I don't want any dampening know I've listen without : there much more punchy, it's really a live stage sound, much more realistic ( I don't think it's the common taste, anyway it's more the french speaker sound that the english one - more soft - )

So now I've one fear : is the tube amp the right amp for this speaker ? Even if a plan to add a super tweeter later on, I want a very high switching frequency to keep the full voice frequencies on the jordan. So is your mod with the piezos due to the amp or is it a general improvement to add some "air" in the upper treble ? What's the cost of those tweeters and how are they arranged on the box ?


Kind regards.
François
 
fdegrove

fdegrove

diyAudio Senior Member
Joined 2002
GRIDSTOPPERS

Hi,

still a safe 2.2k at the moment so there may be a slight amount of rolloff
Click to expand...

No offense but I don't use them if I don't have to.

Experience shows they roll off the treble and tend to eat up dynamics as well.

May I suggest a value of say 100R to start with?

On semi conductors it is a different story so I won't bore you with that.

Cheers,;)
 
316a

316a

Member
Joined 2002
piezo

I bought the piezo's for a ridiculously cheap price for 10 (about six pounds for the whole lot of 10) . They're just stuck on the front with foam pads at the moment . I'm still playing with the 'crossover' but quite promising . Thinking of trying those Stryke Audio 'Neo' ribbons next . Trouble is finding something that compliments the JX92

316a
 
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