In the feedback network around U1B, C8 increases the impedance of the shunt leg to infinity at very low frequencies, and DC is the lowest frequency of them all. C8 is after all a capacitor, and capacitors function as open circuits at DC. Open circuit ---> infinite impedance.
U1B and associated components are arranged in a noninverting amplifier topology; like all other noninverting amplifiers, this one's transfer function is: gain = 1 + (Zseries / Zshunt) . . . {after making the usual assumptions about the ideality of amplifier U1B}
Thanks to C8, Zshunt = infinity at DC. Therefore gain = 1 + (SomeNumber / Infinity) = 1 + 0 at DC.
D. Self's book "Electronics for Vinyl" goes over this in some detail.
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Just finished my P3 and a big thanks to @Algar_emi for the boards and @olen for some matched parts for the RIAA and JFETs.
I’m using OPA1656 and been comparing it to my Pearl 2. The P2 does have a more Analog sound while the P3 is more exciting and has more top end detail. I noticed the P3 has opened up more as I play it. When I first turned it on for a listen I was concerned with the bass.
I moved it to my main listening room and just turned my subs up a bit more. Hoping more hours will continue to help it balance out.
I’m using a Hana SL and it requires a cartridge load of >400. Is there a way to get around 400 or 500 ohm from the resistor dip switch? There is a big gap from 249 to 892 and 892 is what I have it at now. If I change the 1K to 1.5k I can get it there.
I’m using OPA1656 and been comparing it to my Pearl 2. The P2 does have a more Analog sound while the P3 is more exciting and has more top end detail. I noticed the P3 has opened up more as I play it. When I first turned it on for a listen I was concerned with the bass.
I moved it to my main listening room and just turned my subs up a bit more. Hoping more hours will continue to help it balance out.
I’m using a Hana SL and it requires a cartridge load of >400. Is there a way to get around 400 or 500 ohm from the resistor dip switch? There is a big gap from 249 to 892 and 892 is what I have it at now. If I change the 1K to 1.5k I can get it there.
Attachments
Finished my Pearl 3 it is amazing, a step up from the Pearl2 and my Bottlehead Eros 2. Listening to Ludovico Einaudi, one of my favorite composers. I listened to it with two different turntables, a Rega P6 with a Rega Ania Pro and a Sota Saphire with a vintage Kiseki Purpleheart cartridge. The Pearl 3 sounds very detailed and has a very immersive sound stage I am hearing more than I have with other Phono pre's. I tried a few different op amps. The OPA 2604 (came with the kit), Sparkos SS3602 discrete opamp, Muses01 and Muses02.
My favorite is the Muses01. This gives the best balance between clarity and warmth. The Muses 02 was little less warm, but still amazing. The stock op amps came in third and I really didn't like the Sparkos, sounded less "clean" to me. Take this all with a grain of salt, as i have gotten older I realize I listen to 1000's of $ of audio equipment with $200 ears.
I would like to thank Wayne , 6L6, and Rhthatcher for making this kit possible.
My favorite is the Muses01. This gives the best balance between clarity and warmth. The Muses 02 was little less warm, but still amazing. The stock op amps came in third and I really didn't like the Sparkos, sounded less "clean" to me. Take this all with a grain of salt, as i have gotten older I realize I listen to 1000's of $ of audio equipment with $200 ears.
I would like to thank Wayne , 6L6, and Rhthatcher for making this kit possible.
One other thing I had to adjust the bias resistor. Very close to what you had to do in the build guide. I had a 523R resistor and this gave me aprox 5ma bias
Getting me all excited, I have an Eros 2 which I like quite a bit. Some nice analog stuff, never heard a Kiseki, but from what I've read it sounds realy nice. Looking forward to being able to do my own comparison.
I prefer a filter that does attenuate the audible range from 20Hz on up as little as possible, but falls off quickly below that. I played around with an online calculator and found C8 = 100uF and R18 = 270R to give a nice compromise (-0.35dB @ 20Hz, -3dB @ 5.9Hz). Only question I have: will changing the value of R18 change something about the feedback loop around U1b (my lack of electronics knowledge shows here).
Thank you for your listening impressions. Seems to confirm other reports that the P3 has a less warm and livelier sound. Personally I'm a bit worried that I won't prefer it as the tweeters of my B&W's do not lack treble. Only one way to find out: build it and compare.
Loading your Hana: you could jumper C23 and then switch on both 1k resistors to get around 500R. In my P3 I will put socket pins for R37 and C23, so this will become a "user value" position (and I plan 50-100-300-600-1k2 for the other positions).
Re: cartridge loading-
Choose one of the switch positions you think you’ll use the least and substitute the perfect resistor in that spot. Easy!
I have a Hana SL as well, been using it with 1K (switch 4 ON) and am completely happy.
Choose one of the switch positions you think you’ll use the least and substitute the perfect resistor in that spot. Easy!
I have a Hana SL as well, been using it with 1K (switch 4 ON) and am completely happy.
I'm getting close to starting on mine, even though I've had my kit since before Christmas, lol! Needed to finish my new preamp first and with that done I'm ready for this! Need to inventory what parts I actually have and order everything else, including chassis.
Good to see the problems and solutions in this thread, too.
Good to see the problems and solutions in this thread, too.
Hello All,
From the point of view of DC unity Gain: there is no difference between C8 being 100uf and 1000uf.
From the point of view of low pass filters the answer is knowable: If there is very low frequency floating around, R18 and C8 will give us a Time Constant.
https://www.digikey.com/en/resources/conversion-calculators/conversion-calculator-time-constant
A Time Constant gives us a -3dB cutoff frequency:
https://www.digikey.com/en/resource...sion-calculator-low-pass-and-high-pass-filter
So I am guessing that a low pass filter, C8 := 220uf and R18 :=220R with a -3dB cutoff of 3.3HZ is a user adjustable happy middle.
I have been reading Douglas Self for more than a few years about Op-Amps, filters and the like. My largest takeaway is the concept of “noise budget”
Thanks DT
Did you adjust the bias on account of the op-amp rolling?
I assume the P3 needs a pair of Muses 01?
They're not cheap.
Ready to go with the first Pearl 3 opamp rolling test, see (post #1,396) . I'm shipping the first set of blind-listening dual opamps tomorrow.
Attached below is the information telling each opamp's mfg part number, and its serial number label in the blind listening test. It's a .zip archive and it's encrypted.
As soon as the listening evaluations are posted and the rankings from best to worst, I'll post the encryption key and anyone can open the .zip archive. You'll notice I am posting the part IDs many days before the listening review. Which means it's not possible to wait, read the reviews, and then revise the serial numbers to make it appear that opamp-X was the big winner and/or opamp-Y was the big loser. It's all here, publicly visible, ahead of time.
_
Attached below is the information telling each opamp's mfg part number, and its serial number label in the blind listening test. It's a .zip archive and it's encrypted.
As soon as the listening evaluations are posted and the rankings from best to worst, I'll post the encryption key and anyone can open the .zip archive. You'll notice I am posting the part IDs many days before the listening review. Which means it's not possible to wait, read the reviews, and then revise the serial numbers to make it appear that opamp-X was the big winner and/or opamp-Y was the big loser. It's all here, publicly visible, ahead of time.
_
The Hana sounded fine on my previous phono.
I just tried lowering C8 from 1000uf to 100uf to see if I could hear a slight improvement. No major change.
When I first listened to the P3 it was with a Shure V15 Type iii set to 47k and I thought the bass also sounded weak there too.
I just tried lowering C8 from 1000uf to 100uf to see if I could hear a slight improvement. No major change.
When I first listened to the P3 it was with a Shure V15 Type iii set to 47k and I thought the bass also sounded weak there too.
Ugh… I’m dumb. I just realized my XLR pin 3 was connected to shell and NOT pin 3 on my board. My boards have a shell PCB connection where the boards online are just 1,2, and 3.
I fixed it and and immediately the bass heavy Justin Timberlake album (belonging to my wife… wink, wink) blew me away!
Going to reset everything and restart my listening on the other albums I had been testing before.
I fixed it and and immediately the bass heavy Justin Timberlake album (belonging to my wife… wink, wink) blew me away!
Going to reset everything and restart my listening on the other albums I had been testing before.
I just adjusted the bias according to the build guide. I think the Muses sound the best to me, but the stock op amps sounded very good also.