BAF 2015 Coverage

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6L6

6L6

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In the talk, he said "these are my normal Jensen transformers" which implies something related to the JT-123, and they are quadfilar 1:1 at 600:600ohm.

But don't quote me on that. I would assume that the schematics and such will be made public soon.

I think the whole point of the transformer was a place to insert the feedback and invert the phase of the feedback loop - and that's pretty clever.

EDIT: I just got off the phone with Dave Hill at Jensen, the JT-112-L (what's on the schematic in the video) is an obsolete part number, the part still exists as the JT-123-FL, and the various mounting permutations of that transformer.

Here's the datasheet for the FLPCH, the PC mount version, the same as used in the F6 - http://www.jensen-transformers.com/wp-content/uploads/2014/08/jt-123-flpch.pdf
 
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wdecho

Member
Joined 2014
6L6 said:
In the talk, he said "these are my normal Jensen transformers" which implies something related to the JT-123, and they are quadfilar 1:1 at 600:600ohm.

But don't quote me on that. I would assume that the schematics and such will be made public soon.

I think the whole point of the transformer was a place to insert the feedback and invert the phase of the feedback loop - and that's pretty clever.

EDIT: I just got off the phone with Dave Hill at Jensen, the JT-112-L (what's on the schematic in the video) is an obsolete part number, the part still exists as the JT-123-FL, and the various mounting permutations of that transformer.

Here's the datasheet for the FLPCH, the PC mount version, the same as used in the F6 - http://www.jensen-transformers.com/wp-content/uploads/2014/08/jt-123-flpch.pdf
Click to expand...

I found this out when I bought my transformers for the F6. I think the reason Nelson keeps referring to it being the JT-112-L is because as he said in the video about using a certain part is because he has drawers full of them. Evidently he has a drawer full of the old part #. We forget sometimes that manufactures buy in bulk. When he quotes a price of a part and it is cheaper than our cost is because he buys 500 or more at a time such is the case of the transistor for the latest diagram, $14 for 500 is the cost but 1 will cost $21, the same with the transformer when he said it is like $29 and when we find the price it is higher.
 
Nelson Pass

Nelson Pass

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Joined 2001
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Classic long tail pair, this and the J2 are the only FW amplifiers using it.

:cool:
 

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famousmockingbird

Member
Joined 2010
Hello :wave:

Is there any stability issues due to phase shift with the transformer in the feedback loop? Maybe I should rephrase my question. If there was no stability issues with the current Jensen transformer used and if another was used in it's place could there be stability issues due to the resonance placed differently by the manufacturer? Will there be a need for possible compensation components?
 
W

woody

Member
Joined 2002
If you look at the Ixfn140n20 that Nelson talks about it has a couple of things going for it besides that whopping 680w power dissipation. That SOT-227b package requires no insulator and the 2 mounting holes have the same spacing as used for our old T03 transistors.
 
2 picoDumbs

2 picoDumbs

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Joined 2013
ci11 said:
I am still hoping that someone has plausible DIY heat sink suggestions for mounting these 196W per channel SOT-227's into less-than-full-size monoblocks.
Click to expand...

What's wrong with monoblocks? This amp deserves the full red carpet treatment.
Do monoblocks using the Deluxe 4U case (ie One case per channel). Mount one SOT-227 on each heatsink.
You can always add pc case fans though.
 
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ci11

Member
Joined 2014
2 picoDumbs said:
What's wrong with monoblocks? This amp deserves the full red carpet treatment.
Do monoblocks using the Deluxe 4U case (ie One case per channel). Mount one SOT-227 on each heatsink.
Click to expand...

Nothing wrong with using the 4U Deluxe case for a monoblock - they just won't fit in my listening area. Was hoping to using something rather smaller than a 19" case for each channel. My speaker is only 9" wide.
 
jacco vermeulen

jacco vermeulen

Member
Joined 2004
No problem, my tooth is aching, the aspirins haven't kicked in yet.

That level of dissipation in a small case size is easiest done with a fan-mounted heatsink.
Modern (plastic instead of metal) PC fans are dead quiet, <10dB at 6.5ft/s air velocity (4.75'' diameter model), also lots cheaper than ancient ones.
 
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