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Old 1st September 2011, 11:08 AM   #1
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Default Jensen JT-11P-1 on tube amp input

Hi everyone.

I recently upgraded my system to a balanced source and I bought a couple of Jensen JT-11P-1 to use with both the amp described here: My experience building a DRD d3A/300B amp and a PASS F5 amp.

Jensen recommends a damping network consisting of a 13k resistor and a 620pF cap before my 47K input resistor on the tube amp and 100K on the Pass F5.

I was wondering if any of the members here had experience with input trannies to help me out figuring what would be the best way of hooking these things up. Is Jensen´s damping network OK for my amps or there could be another way of doing it (without that cap in there would be cool...) I´ve seen some interesting stuff like Thorsten´s way of doing it on the attached image...(granted with a different input transformer)

Any help would be greatly appreciated!! Thanks for your time.

Luis
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Old 1st September 2011, 12:08 PM   #2
kmaier is offline kmaier  United States
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The Jensen units are excellent... I've used them for years. As you've changed your source to a balanced one, is it pro or consumer level? If consumer then you have the right ones, if pro, the JT-10KB would be the correct choice as it's a 4:1 step-down.

Referencing the following App note:
http://jensentransformers.com/as/as087.pdf

The JT-11P1 is designed to run with 10K load impedance. As the typical tube amp will have a much higher input resistance, the RC network applies. If you're building the input transformer into the amplifier chassis you could just change the input resistor value.

Regards, KM
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Old 1st September 2011, 02:14 PM   #3
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Where can you Jensen stuff from ? Sometime ago I submitted a technical query and No-one from the company replied. So I presume they only supply via outlets. Correct or not ?

richy
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Old 1st September 2011, 02:52 PM   #4
SY is offline SY  United States
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I ordered direct from them. I think that they just don't like you.
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Old 1st September 2011, 03:29 PM   #5
kmaier is offline kmaier  United States
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I've ordered from Jensen direct and also from Markertek in the US, which usually have it discounted.

Regards, KM
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Old 1st September 2011, 03:52 PM   #6
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Hello,

Richy, I´ve ordered directly from Jensen. They are efficient and fast.

Kmaier, my source will be an Apogee Symphony IO. It has sofware controlled variable analog trim on the outputs, so I think I´m fine with the JT-11P-1.

Yes, the transformers will go inside so should I just wire a 10K resistor on the transformer secondary and remove the 47K input resistor on the tube amp and the 100K input resistor on the Pass F5?

Thanks and regards,

Luis
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Old 1st September 2011, 04:01 PM   #7
kmaier is offline kmaier  United States
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Well, if the transformers are inside the amp chassis, then sure, use 10K input resistors on both amps. Apogee make some nice gear

Regards, KM
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Old 1st September 2011, 04:19 PM   #8
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Quote:
Originally Posted by SY View Post
I ordered direct from them. I think that they just don't like you.
Jein.....perhaps...being Teutonic bred technically, I was being "nasty" and sniping awkward in my coming old ways....This time with a glass of the red peculiar, I'll try again...may just be the wretched email never sailed.

richy
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Old 1st September 2011, 09:46 PM   #9
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Thanks KM!
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Old 2nd September 2011, 12:17 AM   #10
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Next time, buy from CineMag.

se
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