Pearl Two

Funny. I would say I learned a lot with this project. Definitively not the best project for a beginner. Glad I at least did an ACA and F5 first. I thought I would have the Pearl 2 it up and running in a week when I bought the boards. F5 taught me it takes time and patience.

I am ready to bring it to the main room and spin some records. I have the Mobile Fidelity "Grateful Dead - Live Dead, Dark Star" to christen. Do you think I will hear the Fillmore West? :)
 

6L6

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LOL, yes, this hobby isn't for people without patience. :)

(Or for people who don't mind blowing up transistors once in a while)

That seems like it would be a great album - I bet you will hear the Fillmore!

Oh, if you ever are searching through the used record stacks somewhere and see "Virgil Fox, Heavy Organ Live at the Fillmore East" buy it. I will bet you a bottle of your favorite whisky that you will really enjoy it.
 
There is a near mint copy for $4.99. The trick is to find 4-5 others from the same seller to get shipping down. It can take an hour to surf through a sellers inventory to find a half dozen worthy. I may have to pick up later.

I had been using "Yes - Going for the One" as my Pearl 2 test record in my shop. Rick Wakeman plays a big church organ on a few tracks. Good recording with a lot of ambiance.
 
Got home at a decent hour and brought the Pearl 2 into the main room. WOW. Happy Camper! Coltrane is in the room. Bob Marley. Grateful Dead. Clarity is amazing. Definitely a lot of gain with the Rega 2 but no problems, just need to turn down volume a bit. I think my speakers (Polk TSI 300) are the bottlenecks now.:) Also using preamp outs from Yamaha Receiver to an F5 probably move on to the B1 next.
 
I have now replaced R21-24 with 20R (and put back 10k for R10). Voltages around Q3 are now (L/R):

Vc 8.555 (8.717)
Vb 9.125 (9.260)
Ve 8.466 (8.603)

Is it a problem that Vb > Vc? Should I maybe drop R10 to 8k2 or 6k8?

Voltage drop at R21/24 is 109.9 - 112.7 mV (L) and 112.7-114.1 (R).

With a test record I noticed that the gain of the entire Pearl is less now. Where it used to have around 300mV output with a 1kHz tone cut at 3.54cm/s it now has around 200mV (and this is with R14 = 680R in stead of 1k).

Sound-wise I cannot really say I hear a difference (you can't really A/B them of course). I will do some more testing before I decide to keep it this way or to go back to 10R.
 
For some fun, I have simulated this ckt using Pspice, below are the DC bias values that I get.Since I have not fab'd this ckt, I'd be interested to hear, what the actual ckt bias values are? I see some #'s in post # #2043
Q6-9(s)=75mV, 7.54mA, for a total of around 30mA
Q6-9(d)=4.89V
Q3(b)=5.61V
Q3(c)=4.96V
Q1(e)=19.1V
 
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I usually attribute perceived changes to habituation, except for speakers/phones which involve mechanical breaking in. The Pearl does need a bit of time warming up though, you can measure differences in for instance voltage across R21-24right after startup, after 10 minutes, after an hour.

Maybe experts can explain which changes occur in parts after breaking in.
 
I do not profess to be an expert, but I have to agree with Wellerman, I can not understand how nor if there is any breakin period for the components used in this design. You can do some measurements THD, IMD, F response etc, but I doubt that they would change very little from the beginning to after the breakin period. I think it is more psychological than electrical. Bias point change, from initial, would be a result of heat alone, so that is why it should be performed after thermal stabilization
As far as the cascode transistor goes, the measurements show, as well as Pspice, that this device is operating in the saturation region, which I do not see any issues with this.
The I/P stage gate/source voltage measurements look fine as well, There is always going to be some slight difference. Matching IDSS is only one method, and probably the simplest method to match a jfet, but remember that this is not the mode of op in the ckt. Also important is the pinch-off V in matching jfets.
 
I did some searching on burn in of solid state devices - hotly debated subject! The human brain definitely comes into play. I always felt mood and mindfullness impact taste perception when eating, no doubt music.

I was also reminded that the Pearl 2 inverts the phase. I did some before and after listening switching polarity on speaker terminals. Better definition of bass with correct phase. Easy to hear the difference listening to the first 2 tracks of Massive Attack - Protection. I will likely change polarity at cartridge and switch speakers back.
 
helpful suggestions pls

my pearl II is finished and has had moments of greatness, thank you Wayne.
But one thing keeps happening, I lose gain in one ch, -3~6 db. I change the zvp 3310 and it fixes it. then it goes again. I measure voltages and they are very close, .x nothing sugesting trouble. feed back resistor are .1% and measure the same. any thoughts or questions?
Thanks in advance if you answer.
 
my pearl II is finished and has had moments of greatness, thank you Wayne.
But one thing keeps happening, I lose gain in one ch, -3~6 db. I change the zvp 3310 and it fixes it. then it goes again. I measure voltages and they are very close, .x nothing sugesting trouble. feed back resistor are .1% and measure the same. any thoughts or questions?
Thanks in advance if you answer.

Mine is doing something similar, and just pulling and re-seating the output RCAs resets it back to normal.