Dual JLM99 question ?

[flaheu]

I've stuffed a dual JLm99 board with 5534 and OEP 1+1:6.45:6.45 input transfo and i would like to understand the jumper config fot the ration og this transformer, see the link to the photo:http://lacave.myphotoalbum.com/view_album.php?set_albumName=album01

Is the red jumper the 1:6.45 and the yellow the 1:13 ? If i move the jumper between these 2 positions I can hear a level difference but when i use the impedance pot (27K + 100k pot) on both config the difference is not so obvious.
If I put a switch to flip between 1:6.45 and 1:13 I can also switch to another value for RL -> xx k + xx pot with a DPDT ? What would be the value for the 1:13 ? I can not find any value in the table for th Jlm BA :http://www.jlmaudio.com/Baby_Animal_Mic_Pre.htm
Also, is that normal if when i turn the impedance pot the sound gets more bass but the level diminishes ?

Thanx

By the way, this preamp has loads of gian :shock: :shock: :shock:
Thanx to Joe :thumb: :thumb: :thumb:

 

[JLM Audio]

Is the red jumper the 1:6.45 and the yellow the 1:13 ?

Your link to the photo doesn't work for me so I am not sure what you mean by yellow and red but for 1:13 you have to fit 2 jumpers vertically (not one) at right angle to the yellow horizontal one shown below in the overlay. So you will need a DPDT switch just to switch between the 2 ratio's.

when i use the impedance pot (27K + 100k pot) on both config the difference is not so obvious

For 600ohm to 3k impedance range at 1:6.45 you need 27k + 100k log pot.
But if you want 600ohm to 3k at 1:13 ratio you need 100k + 500k log pot.
So if you wanted to cover both ratio's use a 2 x 51k resistors in series with a dual 250k log pot and switch the resistors + pots in parallel for 1:6.45 and series for 1:13 and this will keep the impedance range the same for both ratio's.

Also, is that normal if when i turn the impedance pot the sound gets more bass but the level diminishes ?

Your pot is wired backwards. It should get less level and more bass when the impedance is decreased towards 600ohm and more level and brighter as the impedance is increased to 3k.

 

[flaheu]

Joe,

Thanks for your reply, i'll test this evening, but for the ratio and serie/parallel switching i have to order a 6pdt push button, but that's cool.
For sure, i recommend your stuffs to everybody, it's simple, top quality, good prices and the most important , the service :thumb: :thumb: :thumb:

I've ordered dual jlm99v and BA kits, will make some test in situation with different OPA and DOA on several sources to make my choice for my main 8ch preamp , maybe i'll post some sound sample when done..

With my power staion can I power 4 dual Jlm99v, IC version with 2 DI ?

Cheers

 

[JLM Audio]

Thanks for your reply, i'll test this evening, but for the ratio and serie/parallel switching i have to order a 6pdt push button, but that's cool.

Yes use a rotary switch as you can get them in 2 position 6 pole changeover just like you need.

For sure, i recommend your stuffs to everybody, it's simple, top quality, good prices and the most important , the service

:grin:

With my power staion can I power 4 dual Jlm99v, IC version with 2 DI ?

Yes the powerstation will power that easy. Just make sure you have the regs bolted to the side of a case with the insulator kits or use small heatsinks that are not touching each other.