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Old 17th February 2013, 04:34 PM   #3691
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I guess the biggest issue is still the environment that the caps live in... We need to make sure they will live long and prosper...

Here is a first attempt of what I will try to build.
The transformer and the rectifier will be on a separate chassis to minimize vibration and e/m interference.

The rest of the chassis will be made out of wood and I will probably add a small separately powered fan on the back to allow good ventilation in the small box.

Click the image to open in full size.
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Old 17th February 2013, 04:40 PM   #3692
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You putting both channels in there? Seems like too much sink for one Fet, although you can never have too much sink. You will definitely have option of more bias. In truth. Having more space around caps and getting them away from sinks would help, but if you ventilate well, it should not be an issue. They have 85C rating and only improve lifespan below that.
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Old 17th February 2013, 04:46 PM   #3693
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Quote:
Originally Posted by buzzforb View Post
You putting both channels in there? Seems like too much sink for one Fet, although you can never have too much sink. You will definitely have option of more bias.
No just 1 channel in there. The sink is the one I mentioned above, so 1 for each fet with some headroom for additional bias or cooler operation.
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Old 20th February 2013, 08:46 PM   #3694
ianc13 is offline ianc13  United Kingdom
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Default It works

So I recently took delivery of some F6 PCBs from Tea-Bag. Firstly I must say that these are really fabulous boards!

They got stuffed the night that I got them and after a small break from building on Valentines I managed to get them up and running in my old F5/F2J case.

I have a touch of hum, but mainly because of the layout. The CRC boards are very close to the F6 boards which isn't ideal. The CRC boards are from my (long time dismantled) F5. I am going to change the PSU to something more compact so that I can separate the transformer and CRC boards from the F6 boards with some thick aluminium sheet with MuMetal shielding.

I also need to flip the heat sinks over in the case. The JFETs are mounted quite high on the heat sink. The tops of the sinks get pretty hot, while the bottom is only slightly warm. Hopefully flipping them will help dissipate the heat a bit better.

I am running conservative at 1.2A and have 0.05R source resistance in the bottom JFET.

The only problem that I have at the moment is a bit of channel imbalance, I think this is because I have 2 very well run in JFETs (pulled from the F2J) in one channel and 2 JFETs with only a few hours in the the other channel. Worst comes to the worst I can compensate for this.

So how does it sound - apart from the little bit of hum - fabulous. My F2J was warm and rich, maybe a bit too warm. The F6 is a little less voluptuous but (for now) my favourite so far....

I have attached a couple of pics, you can see how close the rectifiers are to the Cinemag xformers. This will be resolved!
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File Type: jpg DSC_0143.jpg (97.9 KB, 284 views)
File Type: jpg DSC_0142.jpg (87.0 KB, 281 views)

Last edited by ianc13; 20th February 2013 at 08:51 PM. Reason: Adding pictures - doh.
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Old 20th February 2013, 10:07 PM   #3695
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congratulations !!!
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Old 20th February 2013, 10:43 PM   #3696
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Nice!! Enjoy man I m so jealous right now

If I had to guess about the hum, I would put my money on those secondaries running so close to the jensens.
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Old 21st February 2013, 04:56 AM   #3697
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Quote:
Originally Posted by Backbones View Post
A question relating to how the F6 sounds when
you are playing with the pots/phase thing: Is it possible in any amp to get
maximum sense of space and depth in the soundstage whilst at the same
time enjoying pinpoint accuracy of instrument position or do we always have
to sacrifice one for the other?
I think it depends one what you mean by "space and depth" on the one hand
and "pinpoint accuracy" on the other. At the very best, I have seen lots of
space and depth and also have been able to drill down to the particulars of
a given instrument in a group and focus on it, somewhat to the exclusion of
the others.

It takes a lot of things working right to get that, but I am not sure that
it represents "pinpoint accuracy"

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Old 21st February 2013, 05:18 AM   #3698
PKI is offline PKI  United States
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And how close you can get to F6 sound by tuning P3 in F5/F5T? Isn't it the same phase shift and playing with H2/H3?
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Old 21st February 2013, 05:32 AM   #3699
6L6 is offline 6L6  United States
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Tuning the distortion character will not be able to add that certain 'something' that transformers can sometimes do...

'Magic' is a pretty good word, although rather subjective...
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Old 21st February 2013, 05:38 AM   #3700
PKI is offline PKI  United States
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I thought these are SS, not transformers what give you this signature.
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