My_Ref Fremen Edition RC - Build thread

[bcmbob]

Actually, I don't have a clue

That is what the whole experiment is intended to discover. Paraphrasing Andrew from an earlier dialog - a chip will function best when most distant from both its temperature and electronic self-protection triggers. This just caries that concept to the extreme.

I suspect if there is a sonic benefit it will only appear at high volume levels and/or in a situation where the FE is driven with a gain device like the JC-2 preamp. Conventional air flow cooling has been sufficient with properly built amps. (Though I have been thinking about us taking up a collection to buy Mr. Inserra something more presentable )

Since this is experimentation week I'm going to try to get the Visual Analyzer software up and running to go along with listening tests. Liquid cooling works well in eliminating noise and helps when "over-clocking" PCs. Whether there is any similar benefit for amps is to me, unknown at this time.

[lehmanhill]

Consider this an official withdrawl of all measurements and comments in post #355.

First there was the helpful critique from Bill and Andrew, followed by some calibration work and comparison of the software measurement tool, an attempt at my Dad's old oscilloscope, and measurement with my DVOM. Basically, I have concluded that I am picking up noise somewhere other than the FE's when using the software tool. The oscilloscope comes closer to the measurements of the DVOM, but it has a noise floor which is a bit high to be useful. Assuming the DVOM measurement with the input shorted to be OK, then the good hum performance that I hear is backed up by that measure.

Boy, this measurement stuff is hard.

Jac

[bcmbob]

Jac, you're not alone. In my last post I mentioned a promising software called Visual Analyzer. Come to find out the supporting thread on this forum stopped in July due to problems similar to what you describe and have experienced. I'm as anxious as you to gain some knowledge and experience with measurements, but it appears not as easy as one would hope.

You are to be commended for your efforts and encouraged to continue the quest.

[lehmanhill]

Bob,

Good luck with your cool chip approach. It sure is ambitious. I agree with you on Dario's interesting looking heatsink. I think he spent all his money on the R-core transformers and didn't have any left for heatsinks.

Jac

[ClaveFremen]

Originally Posted by bcmbob

Though I have been thinking about us taking up a collection to buy Mr. Inserra something more presentable

Originally Posted by lehmanhill

I agree with you on Dario's interesting looking heatsink. I think he spent all his money on the R-core transformers and didn't have any left for heatsinks.

Those silly aluminum plates are, actually, hard disk heatsinks from an old Fujitsu-Siemens server...

Ok, Ok.

I'll finally buy a case for the amp...

BTW the R-Cores were buyed 3 years ago... the big expense for the FE has been for all the alternate parts...

[bcmbob]

[dtses]

finally fixed the problem with the grounding noise, now the board is dead silent!
the cause was one of the smd resistors (replaced them all).

So there are actually one thing is left to be solved - very poor bass reproduction. The speakers are ASW Genius 100, quite big for bookshelves and connected to my Restek make me feel the bass with my guts. FE sounds opposite - everything below 70-80hz is cut I would say.

Tried replacing 1uf Russian cap with 2x0.47uf Wima mkp - no difference at all. Then I had an assumption that smth could be wrong with these big 15y old Philips cap in PS, replaced them with 2x2200uf BC per rail (know it's not enought, but all I had) - again same bass I felt. As for C9, tried Tonerex, FC, MUSE - same picture.

So I feel really desperate now, don't know what else to check... Any guess or piece of advice would be very appreciated

[dtses]

Originally Posted by dtses

I'll try later swapping my reverse C9 R10 configuration and playing with R13 (also Takman).

found no difference here as well regarding the bass issue I have

[bcmbob]

Can you post some pictures showing your current component choices? Also, do you think the SMD resistor failure was due to exessive heat when soldered to the board?

[dtses]

hi Bob,

some pics are here, but will make more close ones later.

R10, R13 - Takman
R3 -2x 1R Dale 1%
D4 -1N5819 SCHOTTKY
C10 - 22pf Silve Mica
C30,32,12 - Amstar
R11 - Vishay 1%, 0.6W 1R
1uf cap is K71-4
C16 (Tonerex), C15 (Silmic)
other resistors on top are Vishay 1%
for 0.1% smd Rs I used Panasonic


Not sure about the heat, could be or could be another mistake in the shop as I've already reported several pages earlier when I had a relay issue where R2 was 100 or 1000 times less than in should be. Will be more careful and check every component I buy from now.

Regarding the bass issue forgot to say that R10 & R13 were swapped with Vishay 1% metal film resistors to be sure that the cause is not in Takman. Anyway I was unlucky again. Different directions also didn't make any bass changes.