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Pearl phono PCBs Group Buy

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R

royville

Member
Joined 2007
Spares

Hi all,

I have a set of 2 Pearl PCB’s, and a semiconductor Q-pack which are surplus to requirements (From Passlabs USA) if anyone is interested.

The Q-pack (stereo) includes:
2 off IRF9610
10 off ZTX450
2 off 2SK389
8 off 2SK170BL

Not sure how much these are worth but I would be open to any reasonable offers, and can split if required.

Roy
 
R

royville

Member
Joined 2007
Re PCB + Q-pack

Hi all,

I have a set of 2 Pearl PCB’s, and a semiconductor Q-pack which are surplus to requirements (From Passlabs USA) if anyone is interested.

The Q-pack (stereo) includes:
2 off IRF9610
10 off ZTX450
2 off 2SK389
8 off 2SK170BL

I can sell all for £25 + p/p or:-
PCB's £10 each + p/p
Q-pack £10 + p/p

Does this sound reasonable?

Roy.
 
lgreen

lgreen

Member
Joined 2003
HiFi Si said:
Woo hoo! I have ordered my HiFi2000 cases - that French website had the best postage rates

I am a little confused about the earthing and would really appreciate comments from the collective wisdom..

This is my interpretation of how it should go together:

Chassis Grounds:

Chassis of the PSU case will be grounded to mains earth. This earth will be carried along the cord to the Pearl case and then connected to the Pearl chassis earth.

Signal Ground:

Each input and output will be grounded via the respective PCB connection points. Of course, each phono socket will be insulated from the chassis.

The point of connection between signal ground and chassis ground will be a star earth that connects the chassis to the earth point in the centre of each Pearl PCB.

Does that make sense, and is that the correct way to do it? My rationale is to keep the signal and chassis earths isolated until one central point, to keep the potential of earth loops and hum at a minimum...
Click to expand...

You forgot to decouple the chassis from the star ground with a disconnecting network. In other words you don't want the electronic junk picked up from the chassis from getting into your circuit. Pass Labs circuits use a CL-60 thermister to connect chassis to circuit ground; or some of the Zens have a 3W power resistor (25 ohms or less). Make sure your disconnecting network can carry the amount of current of your AC fuse or it will not do much good (and be dangerous).

link

That said- the question is how do you connect the turntable ground cable to your phono preamp?

I have not seen anything on this. On my Pearl I have a terminal for the turntable 3rd wire (ground) isolated from the chassis. It connects via a first wire to the star ground. I also have another wire that connects the terminal to the chassis. I just didn't know which way to go so put in both options (using only 1 at a time).

Listenting to it, I cannot tell which provides a better grounding, there is very little hum from either option. However there was a lot of hum before the disconnecting network was put in.
 
C

cantskienuf

Member
Joined 2004
Cartridge Loading

Just want to make sure I have this right. The original Pass DIY article states "R27 is the input load resistor..." Since R27 is a 47k resistor, am I correct in thinking that the basic circuit loads the cartridge at 47k ohms with nothing placed in the R1 position? If that belief is correct, and 47K is my desired resistive loading, must I jumper R1, or do I leave it unpopulated? The "Jumper" stencil on the board has me a bit confused. I would think that a jumper in parallel with R47 would change the loading to 0 ohms, wouldn't it? The article goes on to say "The phono cartridge can be loaded with lower impedances by simply placing resistors and capacitors across R27." Am I correct in thinking that the R1, C16 and C14 positions in the board do indeed place resistors and capacitors across R27? Any idea what capacitive loading is present with C14 and C16 unpopulated? I see that the word "Jumper" is stenciled above each of C14 and C16 also. Must they be either populated with a capacitor of some value or jumpered? Is the circuit broken if these are left unpopulated? Thanks in advance.
 
R

royville

Member
Joined 2007
Is the circuit broken if these are left unpopulated?
Click to expand...

Hi cantskienuf, - I'm pretty sure the answer to your question is no, - you must not jumper with a short circuit link. You should only jumper with extra resistance and/or capacitance using values according to your cartridge manufacturers recommendations. ie If your recommended cartridge loading is 47k then no extra resistance is needed. Hope this helps.

Now to my problem :bawling:
I have just completed building my Pearl (no m/c ) and it sounds awful.
With a Dual 505 turntable & standard m/m cart its 'thin and tinny'!
And when I use my 'Linn' with a high output m/c (dynavector DV10x4) it isn't any better, and also has a lot of noise and hard buzzing sound.
Now I am not 100% sure that I have wired the earths properly. So I was wondering if anyone would be kind/brave enough to produce a correct wiring diagram for all us novices here to follow. Its a pity there was never one in the pass article.
Hope someone can help!
Thanks
Roy.
 
2

24valveman

Member
Joined 2006
pearl burn in

I've had mine for about 6 months and used it quite heavily. It took just a few hours to reach peak performance. It now challenges some of the best names in "high end" hi fi. I've teamed it with a Stevens & Billington TX103 silver transformer pair and find it superb

Regards
Andy
 
R

royville

Member
Joined 2007
Thanks for the reply's folks,

I don't think its anything to do with running in. I am not at that stage yet as its to noisy to listen to.

I will attempt to draw a wiring diagram and post it here for your comments, and I will check the 'check point' voltages and component values are all correct. (Should have done that first I suppose :eek: ).

For the case I stripped out the guts of a Nad cassette deck and used the case. Just need an aluminum front panel for it now. I will try and post some pics.
Regards
Roy.
 
R

royville

Member
Joined 2007
Hi Folks,

I think I've found the problem.
When I power the Pearl off I noticed it stayed on for a while, but the buzzing had completly gone and it sounded quite good.
So as an experiment I tried a completely separate psu on it, and it worked ok with no hum or buzz (unfortunately it was only a 24v supply but it worked).
So now I'm in the process of removing the psu boards to a separate case and I'll report back on my results when done.
btw all voltages measured correct and components checked out ok.

Regards
Roy.
 
A

Alabama978

Member
Joined 2008
noise

Hi Roy,

When I first tested mine on the breadboard I had the same problem but not the PSU. It seemed to be caused by the source (turntable) probably a ground loop. Considering the gain of the phono stage especially with the ONO MC stage added it if no wonder it picks up some stray noise form the PSU in some layouts. My basic understanding is that noise is also more possible if the PSU is a standard transformer type and not a toroidal.

Good luck anyway, I am soon to switch on after building it all into two cases so anything could happen :spin:
 
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