Pearl Phono with 2SK30

DJG · 31st March 2007, 05:08 PM

Hello,

I was wondering if it would be possible to build Pearl Phono with 2SK30 instead of original 2SK170 and 2SK389. So I went and build just that. I made a circuit just as seen on Fig. 5 in DIY Manual but with BC337 instead ZTX450 and 2SK30 instead of 2SK170 and 2SK389.

The damn thing actually works but with some problems. I believe that RIAA filter is quite off because it does not deliver almost any bass line. And it does not have as much gain as it should. It is quite clear that the used fets are to blame...

Now I would like to hear from some experts what is it possible to make of this? Modifying the values, changing the circuit, ect?

Thanks,
DJG

cviller · 1st April 2007, 06:54 AM

I think your problem with gain is related to the lack of transconductance of 2sk30 (1.2mS) compared to 2sk170 (22mS). If you are determined to use 2sk30, I think you should try replacing R19 with a higher value to increase the gain. Try with 1-3k and see if you get higher gain. If you go too high, you'll hear clipping.

DJG · 1st April 2007, 10:27 AM

Hello,

I have tried changing R19 as you suggested and found that 850E is sufficient value for those few dB's.
So the gain problem is solved but the sound still isn't good. It sounds like there was no riaa filter present. I recon that the cap values should be recalculated? Sadly I don't know how...

Regards

cviller · 1st April 2007, 10:46 AM

How bad is the lack of bass? Have you tried measuring the voltages? Are they similar to those measured by wayne? Any chance you have short or open somewhere on your board?

I think you should be able to find a spreadsheet online or formulas for calculating the values, if you want to change them. If you prefer soldering and testing, you could
decrease R23 (try this first)
increase C11 or C12
lower C10
lower C13
increase R22

DJG · 1st April 2007, 10:51 AM

Hey,

the voltages are identical to those measured by wayne now that I have changed R19 to 850E.

I will try this and report back next weekend. Thank you for your help!

regards

31st March 2007, 05:08 PM	#1
DJG diyAudio Member Join Date: Aug 2002 Location: Slovenia	Pearl Phono with 2SK30 Hello, I was wondering if it would be possible to build Pearl Phono with 2SK30 instead of original 2SK170 and 2SK389. So I went and build just that. I made a circuit just as seen on Fig. 5 in DIY Manual but with BC337 instead ZTX450 and 2SK30 instead of 2SK170 and 2SK389. The damn thing actually works but with some problems. I believe that RIAA filter is quite off because it does not deliver almost any bass line. And it does not have as much gain as it should. It is quite clear that the used fets are to blame... Now I would like to hear from some experts what is it possible to make of this? Modifying the values, changing the circuit, ect? Thanks, DJG

1st April 2007, 10:27 AM	#3
DJG diyAudio Member Join Date: Aug 2002 Location: Slovenia	Checked Hello, I have tried changing R19 as you suggested and found that 850E is sufficient value for those few dB's. So the gain problem is solved but the sound still isn't good. It sounds like there was no riaa filter present. I recon that the cap values should be recalculated? Sadly I don't know how... Regards

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
PCB for Pearl Phono Pre	sonix	Pass Labs	2	4th March 2006 11:41 PM
pearl phono	bernification	Pass Labs	2	7th February 2006 08:44 PM
Pearl Phono Done (almost)	Gregorio	Pass Labs	0	16th January 2006 01:42 PM
Pearl Phono PCB´s	Weil	Pass Labs	9	22nd May 2005 10:40 AM
pearl phono	hsort	Pass Labs	5	2nd March 2002 09:26 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

1st April 2007, 06:54 AM	#2
cviller diyAudio Member Join Date: Dec 2005 Location: Copenhagen Blog Entries: 2	I think your problem with gain is related to the lack of transconductance of 2sk30 (1.2mS) compared to 2sk170 (22mS). If you are determined to use 2sk30, I think you should try replacing R19 with a higher value to increase the gain. Try with 1-3k and see if you get higher gain. If you go too high, you'll hear clipping.

1st April 2007, 10:46 AM	#4
cviller diyAudio Member Join Date: Dec 2005 Location: Copenhagen Blog Entries: 2	How bad is the lack of bass? Have you tried measuring the voltages? Are they similar to those measured by wayne? Any chance you have short or open somewhere on your board? I think you should be able to find a spreadsheet online or formulas for calculating the values, if you want to change them. If you prefer soldering and testing, you could decrease R23 (try this first) increase C11 or C12 lower C10 lower C13 increase R22

1st April 2007, 10:51 AM	#5
DJG diyAudio Member Join Date: Aug 2002 Location: Slovenia	Hey, the voltages are identical to those measured by wayne now that I have changed R19 to 850E. I will try this and report back next weekend. Thank you for your help! regards

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)