If someone would like lower gain the feedback resistor R22 could be lowered to 100 Ohms for about 6dB less gain.
This of course changes the feedback and maybe the sound but it will be stable.
The two box solution is the best from a noise standpoint of course. I am running one box with an Amgis 25 VA toroid and a Zu Denon103 and it is fine.
With a Vandenhul modded Ortofon MC2000 I do have some noise ear to the speaker and would prefer the two boxes.
The J112 bias isn't super critical as long as you can bias up the output transistors, 2-8 mA is fine and the LEDs will last years. This current changes the distortion via lowering the second harmonic about 5-6 dB. It is a bit hard to see among the total Thd+n but you can see it. My simulation shows it pretty well without the noise.
This of course changes the feedback and maybe the sound but it will be stable.
The two box solution is the best from a noise standpoint of course. I am running one box with an Amgis 25 VA toroid and a Zu Denon103 and it is fine.
With a Vandenhul modded Ortofon MC2000 I do have some noise ear to the speaker and would prefer the two boxes.
The J112 bias isn't super critical as long as you can bias up the output transistors, 2-8 mA is fine and the LEDs will last years. This current changes the distortion via lowering the second harmonic about 5-6 dB. It is a bit hard to see among the total Thd+n but you can see it. My simulation shows it pretty well without the noise.
John Curl produced an iconic phono stage, the Vendetta Research, which basically had completely separate units, one for each channel, from AC power wall outlet to the I/O jacks.I’m interested in what JC did…
I was thinking about channeling Curl wrt to the separate power supplies, each feeding one "Wayne" board here... especially if I use the cookie tin where I would have these board mounted on opposite sides of a dividing wall.
The separate power supply umbilicals would exit the cookie tin at the bottom on either side stabilizing the vertical enclosure.
If one is building their own chassis the way the 8 pin cartridge loading bus and inputs are arranged
means you could butt the pcb against the back panel and flip the cartridge loading 90 degrees ( with short wiring ) for outside
adjustments and have very short rca/bnc connections to boot
means you could butt the pcb against the back panel and flip the cartridge loading 90 degrees ( with short wiring ) for outside
adjustments and have very short rca/bnc connections to boot
Drats. I was hoping it was something nefarious…
. The Vendetta is still a superb phono stage. I’m really digging the cookie tin idea!
Or, you could cut holes in the bottom of the chassis and mount the DIP switches on the bottom of the PCB, like I did here.
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Hello,
I see this and wonder if there is a sweet spot?
Years ago I built a SRPP circuit with a 12AU7 vacuum tube and measured it with my then AP 2522 analyzer.
If you sneak up on the 12AU7 applied load there is a sweet spot where the 2nd HD all but disappears.
Just for fun, I will adjust Q9 current and watch what happens on the APx555 FFT at 1kHz.
Thanks DT
Hello, out there,
a first listening session with the PEARL 3... very promising. Testing if all values are in the ballpark.
Waiting for a lot of parts. But it plays.
Thorens (with Ortofon MM) - PEARL 3 - IronPre - 6-24AXO - BA-3 (bass/mid) - ACA-mini (high) into 2-way speakers
Cheers
Dirk
a first listening session with the PEARL 3... very promising. Testing if all values are in the ballpark.
Waiting for a lot of parts. But it plays.
Thorens (with Ortofon MM) - PEARL 3 - IronPre - 6-24AXO - BA-3 (bass/mid) - ACA-mini (high) into 2-way speakers
Cheers
Dirk
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Yeah, but some cartridges are more like 7mV at 5cm/sec. That is 2V out (about the same as a cd player), but records can easily be cut louder, so 4V out is not out of the question with those cartridges. Ticks and pops will be even worse. Older integrated amps often had 150 or 250mV input sensitivity for full output.
P3 could be made an "MM only riaa" by selecting appropriate feedback resistors (e.g. like 43 / 49 dB) for those only using MM cartridges.
Maybe some "tweaking" could make more gain settings possible or an easy way to swap out the feedback resistor.
I guess care should be taken to avoid bad contact to avoid open loop gain.
Maybe some "tweaking" could make more gain settings possible or an easy way to swap out the feedback resistor.
I guess care should be taken to avoid bad contact to avoid open loop gain.
@rhthatcher
...on the subject of XLR...
i thought pin 1 was supposed to be connected to chassis ground not signal or PSU ground?
Does the board make any distinction between these three? Is there a discussion about grounding in the build guide? Thanks.
...on the subject of XLR...
i thought pin 1 was supposed to be connected to chassis ground not signal or PSU ground?
Does the board make any distinction between these three? Is there a discussion about grounding in the build guide? Thanks.