New Posts New Posts RSS Feed - Genera phono cartridge loading
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Welcome to the Graham Slee Audio Products Owners Forum

 

Open to all owners plus those contemplating the purchase of a Graham Slee HiFi System Components audio product and wishing to use this forum's loaner program: join here (Rules on posting can be found here)

This website along with trade marks Graham Slee and HiFi System Components are owned by Cadman Enterprises Ltd


Genera phono cartridge loading

 Post Reply Post Reply Page  12>
Author
Alasdair View Drop Down
New Member
New Member


Joined: 30 May 2012
Status: Offline
Points: 14
Post Options Post Options   Thanks (0) Thanks(0)   Quote Alasdair Quote  Post ReplyReply Direct Link To This Post Topic: Genera phono cartridge loading
    Posted: 18 Aug 2012 at 2:47pm

I recently built a Genera phono stage and have since been exploring the mysteries of cartridge loading. Once it had been burned in, I can confirm that the standard 220pF capacitance gives an excellent sound with a moving magnet cartridge (Sontra 500EX), running either into a Rogers HG88 or HiFi World KEL84 amplifier. 

However my normal cartridge is a Denon DL103 through a HiFi News Blackhead stepup transformer (10x) and this has proved more problematic. I have two DL103s: one with the standard stylus and one with an Expert Stylus Paratrace stylus and lightweight sapphire cantilever. With the standard stylus 100pF capacitance sounded good but a little edgy at the top. At 220pF  the sound balance was too bright; it reduced the edginess but lost crispness as well. 150pF gave a reasonable but not perfect compromise. However with the Paratrace stylus there were problems. At first, tracking was great, detail was great but there was a false brightness on some records and a spittiness and edginess. Also, although it tracked perfectly, it sounded strained and downright unpleasant on some records. The first stage of the solution was to play around with alignment and tracking weight to get the best basic sound out of the cartridge (line contact styli are very fussy compared with a standard spherical). However although this got rid of the spittiness, some records still sounded terribly strained and unpleasant. I knew that CD sounded fine through the amplifier, so the problem had to be something to do with the Denon and the Genera. 

Having run out of other options, I tried adding a parallel 500 ohms on the 'cartridge' side of the stepup transformer, in order to reduce the input resistance seen by the cartridge from 47k/100 = 470 ohms to 240 ohms. The result was miraculous: suddenly the glare and strain disappeared, leaving only sweetness and light. 

I appreciate that it is probably not common to feed a Genera with a low output moving coil and stepup transformer and the Denon DL103 is notorious for its setup and loading foibles. However anyone else who runs into similar problems may find the above experience helpful. 

However what was going on technically? I previously used the Denon DL103 Paratrace and stepup transformer to feed the Rogers HG88 phono input without any problems, so there was nothing wrong with the Paratrace stylus. Also why was the Paratrace DL103 so much worse than the DL103 with a standard stylus? I can only assume that there was something different about the Paratrace DL103's output which was causing trouble - and this was somehow eliminated by reducing the input impedance across the DL103. 

The main effects of lowering the resistance fed by a cartridge are to increase high frequency damping and also (working in series with the cartridge internal inductance) a roll off of output at high frequencies.  

Could it be that, compared with the standard DL103, the lightweight Paratrace stylus was generating more output at supersonic frequencies, e.g. due to record cutter ringing, and either this was upsetting the Genera itself or else it was being passed on faithfully by the Genera and upsetting the main amplifier? If so did the lower resistance solve the problem by reducing the cartridge's supersonic output to a level that did not cause trouble? Any thoughts?

Alasdair

Back to Top
Alasdair View Drop Down
New Member
New Member


Joined: 30 May 2012
Status: Offline
Points: 14
Post Options Post Options   Thanks (0) Thanks(0)   Quote Alasdair Quote  Post ReplyReply Direct Link To This Post Posted: 18 Aug 2012 at 10:10pm

PS

After writing this I found that the problem had not gone away and a rather hard unpleasant sound returned. Following a lot of fruitless fiddling around I decided to try taking out the 150pF input capacitors I had installed in the Genera and put back the 100pF capacitors which had sounded good originally with the conical stylus DL103.  Back came a really nice sound. Sorted!

Therefore rather than an obscure high frequency problem in the Genera, the problem may have been either the 150pF capacitors I had bought (branded Evox Rifa but 400v rating rather than  the 100v rating of the capacitors supplied by Graham Slee) - or else possibly my soldering of them. 

Regards,

Alasdair

Back to Top
Graham Slee View Drop Down
Admin Group
Admin Group
Avatar
Retired

Joined: 11 Jan 2008
Location: South Yorkshire
Status: Offline
Points: 16298
Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 19 Aug 2012 at 9:11am
Alasdair, I see the problem - I think. Could it be possible that the 150pf caps were not the PFR type? True, they would have been Evox Rifa but obtaining 150pf in the PFR range is difficult - they wouldn't be an off the shelf item in the UK. So am I correct in assuming they're non-PFR (it says PFR on the PFR ones)?
That none should be able to buy or sell without a smartphone and the knowledge in how to use apps
Back to Top
Alasdair View Drop Down
New Member
New Member


Joined: 30 May 2012
Status: Offline
Points: 14
Post Options Post Options   Thanks (0) Thanks(0)   Quote Alasdair Quote  Post ReplyReply Direct Link To This Post Posted: 19 Aug 2012 at 12:31pm

Dear Graham,

Thanks for your reply. The 150pF capacitors I bought are marked as Evox PFR 150pK 400-. They look identical to your 100pF and 220pF capacitors, except for the higher voltage rating. 

Regards,

Alasdair

Back to Top
Alasdair View Drop Down
New Member
New Member


Joined: 30 May 2012
Status: Offline
Points: 14
Post Options Post Options   Thanks (0) Thanks(0)   Quote Alasdair Quote  Post ReplyReply Direct Link To This Post Posted: 19 Aug 2012 at 12:48pm

Oops, there was a typo in my message. The 150pF capacitors are marked EVOX PFR 150pJ 400-

Sorry about that.

Regards,

Alasdair

Back to Top
Graham Slee View Drop Down
Admin Group
Admin Group
Avatar
Retired

Joined: 11 Jan 2008
Location: South Yorkshire
Status: Offline
Points: 16298
Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 19 Aug 2012 at 1:12pm
Strange. Higher voltage shouldn't make a difference or if it does it should be better. Probably 100pf plus arm wire capacitance matches your cartridge better. Also there is burn-in time to consider.
That none should be able to buy or sell without a smartphone and the knowledge in how to use apps
Back to Top
Alasdair View Drop Down
New Member
New Member


Joined: 30 May 2012
Status: Offline
Points: 14
Post Options Post Options   Thanks (0) Thanks(0)   Quote Alasdair Quote  Post ReplyReply Direct Link To This Post Posted: 19 Aug 2012 at 3:26pm

Dear Graham,

Thanks for taking a bit of 'weekend time' to think about this. As everything is now sounding OK I am going to leave well alone for the time being and provisionally put the problem down to experience. After all, it could just have been duff capacitors or maybe I was a bit hasty when I soldered them in. If the problem recurs I'll investigate further but otherwise I'll just listen to the music ...

Best wishes,

Alasdair

Alasdair

Back to Top
 Post Reply Post Reply Page  12>
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.01
Copyright ©2001-2018 Web Wiz Ltd.

This page was generated in 0.109 seconds.