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dave slagle
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Joined: Sat Jan 22, 2005 3:54 am
Location: NYC
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RMAF

Post by dave slagle »

hey steve,

Just had a talk with 1/3 of the C3 and it seems a new topic is of merit since they are jonesing to play with your design. I'm game for anything they are up for given the following ground rules.

I'll get all of the iron to you (steve b) so you can get it boxed up and "functioning" properly for your first listen. After the first listen, I have no problems with youse guys (C3+) tearing the iron within apart and regapping for some experiments. My only request is that after you find what sounds best, you document it all and send it back to steve to listen to and measure.

dave
Johnny
Posts: 62
Joined: Wed Jan 26, 2005 3:43 pm

RMAF

Post by Johnny »

Hi Dave,


I like it! So as I understand it, Steve B. will send one power supply that we can use with the different signal boxes. One box would include a version with Sowter iron, another box would include a version with your iron, 80% nickel for the chokes and 49% nickel for the transformers. Finally, you'll send out some amorphous chokes so we can replace them the 80 nickel chokes.
After we have listened and played with the gaps, we'll send the phono-pres back to Steve B. with the optimized gaps in place. Steve B. will then take a look and let us know if he finds anything different in the way of measurements. I really like this plan. It cuts down on the variance between experiements.

Johnny
dave slagle
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Joined: Sat Jan 22, 2005 3:54 am
Location: NYC
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Post by dave slagle »

(revise)

i spoke with sB and as it stands now the best approach is to make a single singnal chasis with the nickel IT's and a switch that will allow swapping between nickel and amorphous inductors in the Lriaa. This will allow for a quick on the fly comparison between two known situations.

The bobbins for the IT versions of the amorphous transformers are not an issue, but i still have a Sept. 27 delivery date of the cores. The general thought is the IT's should roll in with little effect on the riaa curve, so these could be swapped on site if things come together.

ps, maybe we should stock up on d3a's prior to the price increase :-)

dave
dave slagle
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Joined: Sat Jan 22, 2005 3:54 am
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Don't ya hate it when a plan falls apart.

Post by dave slagle »

Hey all... good news bad news...

Me making it to RMAF seems pretty good, but the amorphous Lriaa inductors might not cut it.

I had every intention to get them shipped out tomorrow... bobbins are wound, preliminary measurements looked perfect, cores painted and brackets for stacking made... then things got ugly :-(

i gapped the first 1.8hy version and clamped it down with the stainless band and it went up to 2hy !?!?! hmmm that's odd, i didn't expect that kind of increase but i tapped it a bit and it was a stable 2hy. so off the turns came to get 1.8hy and all was well... or so i thought. Measurement with frequency seemed good. 1.8hy at 100hz, 1.75hy at 1K and 2.4hy @ 10K. which suggested a self resonance somewhere above 10K which is acceptable for a 50hz pole. Then all hell broke loose when i varied the test voltage. My meter tests at 50mv 250mv and 1V and at 100hz i measured 1.7, 1.8 and 2hy respectively. I'm not sure what the variation is all about and i retested a nickel 1.8hy and it measured 1.804, 1.804, and 1.807 as i varied the voltage.

Given the above results, i stopped gapping and will need to think a bit on the cause and how to proceed. the odd thing is all of the numbers and theory suggest that the amorphous choke should be more linear so this one has thrown me for a bit of a loop. This is the first time i have ever seen such a great variation with signal level with such a large gap so i am not ruling out measurement error.

hmmm.

dave
sbench
Posts: 296
Joined: Fri Jan 28, 2005 3:45 pm

Post by sbench »

gapped the first 1.8hy version and clamped it down with the stainless band and it went up to 2hy !?!?! hmmm that's odd, i didn't expect that kind of increase but i tapped it a bit and it was a stable 2hy. so off the turns came to get 1.8hy and all was well... or so i thought. Measurement with frequency seemed good. 1.8hy at 100hz, 1.75hy at 1K and 2.4hy @ 10K. which suggested a self resonance somewhere above 10K which is acceptable for a 50hz pole. Then all hell broke loose when i varied the test voltage. My meter tests at 50mv 250mv and 1V and at 100hz i measured 1.7, 1.8 and 2hy respectively. I'm not sure what the variation is all about and i retested a nickel 1.8hy and it measured 1.804, 1.804, and 1.807 as i varied the voltage.

Given the above results, i stopped gapping and will need to think a bit on the cause and how to proceed. the odd thing is all of the numbers and theory suggest that the amorphous choke should be more linear so this one has thrown me for a bit of a loop. This is the first time i have ever seen such a great variation with signal level with such a large gap so i am not ruling out measurement error.
I am not at all surprised, actually. After looking at the different vendors cores, I can see there being much variation. That translates to different frequency response at different levels... the effect is not unpleasant, but I strongly suspect that's part of the non-relaxed feeling I get with the Sowter inductors... the resolution is still there, but the relaxedness of the original Lundahl is gone. With your nickel cores, the accuracy is there and the relaxation is still there.

Steve
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