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For RIAA preamp: Large value caps vs. Regulated/Stabilized PSU
For RIAA preamp: Large value caps vs. Regulated/Stabilized PSU
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Old 31st July 2021, 09:57 AM   #281
dreamth is online now dreamth  Romania
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did the tone change after switching to 12at7?
It's the lack of mids you're experiencing ...now you've left with more of a tipical Fletcher Munson curve that wes lately dimissed by Harman curves iterated for a few times especially when applied to headphones.Do you listen on headphones or speakers?
Equal-loudness contour - Wikipedia
What Is Harman Curve? - HeadphonesAddict

Last edited by dreamth; 31st July 2021 at 10:08 AM.
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Old 31st July 2021, 03:40 PM   #282
rongon is offline rongon  United States
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Location: Across the river from Rip's big old tree...
For RIAA preamp: Large value caps vs. Regulated/Stabilized PSU
Tone changed very slightly w 12at7 instead of 12ax7. However, after R9 changed to 590R, 12ax7 sounds great in there. I may have had a mid boost originally.

Listening thru loudspeakers jbl lsr305 nearfield.

I just received an inverse Riaa today, so we'll see about FR in testing.

3. Harman research for in home listening shows preference for evenly gradually falling hf response in room at the listening position. A slight dip centered around 1khz might be pleasant, but only if very shallow dip. Otherwise would sound hollow and weird
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Old 2nd August 2021, 12:22 AM   #283
rongon is offline rongon  United States
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For RIAA preamp: Large value caps vs. Regulated/Stabilized PSU
I just received a 2 ft (roughly 0.6m) DIN-5 to 2x RCA-M tonearm-to-preamp cable. (There has to be a better name for that type of cable!)

I had it made by Blue Jeans Cable. It cost a little more than $40 USD, which I think is quite reasonable. It's nicely made, looks good, feels good, has high quality plugs on it.

My 1m (3.3 foot) Sonic Frontiers by Cardas cable measures about 130pF.
This new Blue Jeans Cable measures about 80pF.
It seems the best you can do for a DIN5 phono cable is roughly 40pF/foot (130pF/m).

The tonearm wiring adds about 30pF, so the Blue Jeans Cable measures 110pF once connected.

I figure the Cin of the 12AX7 input stage is 150pF to 200pF.

I'm just over the upper limit of the recommended Cin of 250pF for present-day moving magnet carts like Audio Technica, Nagaoka, Ortofon (and Shure too, even though they're out of production now). Somewhere from 260pF to 310pF.

I'll have to do some listening and try to find out if there is a noticeable difference.

The KAB inverse RIAA network box came too. I have to get the signal generator, 'scope and that hooked up and sorted out, so I can see if the response from the preamp's RIAA EQ network is close to what LTspice predicts. That will be a good test...

I've attached a schematic and LTspice predicted freq resp of the current 'state of the EQ' in this preamp.
--
Attached Images
File Type: jpg RIAA-EQ-values_2021-08-01.jpg (84.0 KB, 44 views)
File Type: jpg RIAA-EQ-response-LTspice_2021-08-01.jpg (257.6 KB, 37 views)

Last edited by rongon; 2nd August 2021 at 12:45 AM.
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