[GRD]

I’m seeking some suggestions for solving a subtle problem with my Cornet.  It seems a bit harsh in the upper mid-range (ie. Higher versus lower voices, upper range of the cello) and slightly bright overall.  I’ve tried the Cornet in two systems and got the same profile (brightness), so it does not seem to be the TT or cartridge.  I’ve compared CD through the iRIAA /Cornet with CD and the Cornet is slightly brighter and shows some of the mid-range harshness.  At this point, the Bugle is easier to listen to over extended periods, less bright, and seems more balanced in the mid-range.

The Cornet is stock except for the CCS modification and a 0.68 uf Auricap output cap at C6.  I originally had also installed a 0.1 uf Auricap at C5, but later removed that and replaced with the specified C5.  It does seem to have slightly less bass and slightly less glare than with the Auricap in C5.  The Cornet is very good in the lower frequencies.

I’ve rechecked the resistor and capacitor values printed on the components and their location on the board.  I also measured the resistor values with a DVM and they are well within spec.

I’ve tried some tube rolling and the least bright combination has been all JJ.    

I’m looking for suggestions on what else to check and, if indicated, possible components to substitute.  

Thanks in advance for your suggestions.

[Doc Jr 8156]

GRD,

Hi.  Like you I been using JJ tubes for 12AX's and the 12AU, Tungsol for the 5Y3.  I however used Hovland caps in C6 and C5 instead of Auricaps.  I also experienced the brightness when the original Mouser caps where in C5 and C6. I used Auricaps, Audiocap, and Sonic caps before and I like the smoothness and the coherence of Hovlands.  Techtronix and Jensen caps are very good too, but thats another story. I used a .47uf for C5 and a 1uf cap for C6. In this configuration I also replaced all signal path resistors to Riken-Ohms (R6,7,8,9,10,11 and12).  All output wirings are five9's silver and input wiring are OTA coppers.  I'm using all silver interconnects in my system. Not bright at all.  No glare.  In fact the Cornet is a very smooth phono pre.  My comparison was made using my Monolithic + PS1 phono and the Cornet is smoother but more extended specially in the bass than the Monos.  Hope tube rolling can solve your problem.  If you could, try the Hovland caps.  Happy listening

[penance]

how many hours has the cornet got on it?

Mine was fairly bright for the first 50 or so hours and then balanced out after, this was with all standard components.

[GRD]

Doc - Many thanks for the details on your unit and your experiences with different caps.  Good input.

Penance - thanks for your reply.  I have a little over 100 hours on the Cornet.  I did about 50 of those with the iRIAA.  I removed the Auricap in C5 after 100 hours as I thought that might be have a effect.  Not much of a change, but a little smoother perhaps with the standard capacitor in C5.  However, the new C5 has only been in for a few hours.

[GRD]

I've decided to stay away from "capacitors on steroids" for the time being and do some minor tweaking with Riken resistors and a better cap in C8.  Then I'll revisit C5 and C6.  

Thanks again for the feedback.

[Doc Jr 8156]

GRD,

Why is "C-8" cap so important?  It is not directly in the signal path as I recalled.  Thanks.

[Wayne1]

C8 is the output coupling cap. It IS in the signal path.

The better the cap you use for C8 and C5 the better the Cornet will sound.

Mr. Hagerman does suggest using 1 uF 200 V PP for an upgrade to C8.

The Multicap RTX is a polystyrene and tin foil cap that is VERY good sounding. I am partial to the Jensen copper foil, paper in oil caps.

[GRD]

C8 is part of the RIAA equalization if I am reading the schematic correctly.  I think C7 handles the 50 HZ and 500HZ and I like the bass already.  I think C8 handles the 2122 Hz and 50Khz.  But I'm cheating - I saw a Multicap in that position on Jim's tips page for the CCS.  Seemed cheap enough to try if I was going to be in the general area with a soldering gun while changing resistors.  I won't modify the specified value.

[GRD]

And to you master builders out there, can anyone explain how the effective resistance from V1A to C7 is 61K for the 50Hz point, while it is 72k from V2A to C8 for 2122Hz?  Where did the extra resistance for V2A versus V1A come from?  Again, I cheated using the AnyEQ calculator on Jim's web site.

[hagtech]

Easy, R16.

jh

[GRD]

Ah ha!  Textbook time.

[GRD]

I thought I'd pass on an update.  I upgraded resistors R7, R9, R10, R11 and R12 with Riken-Ohms and replaced C8 with a Multicap.  A subtle but definite improvement.  The mids and highs seem smoother yet there is no loss or coloring across the frequency spectrum.   I plan on living with this version for awhile longer and then deciding on whether to do an upgrade to C5, C6 and/or C7.  I'll post my findings if I make other changes.

[TChung]

I saw in this thread that someone upgraded C8 with Auricap or Multicap.  I searched many part suppliers' sites but could not find such value (.001uf) from Auricap or Multicap.  The only things I could find are the Orange Drop from AES and the supper expansive and large paper in oil.  Please advise where can I source the Auricap or Multicap .001uf.

Best regards,
TChung

[Wayne1]

PartsConnexion has the MultiCap PPMFX Metalized Polypropylene in .001 @600V

http://www.partsconnexion.com/catalog/CapacitorsFilm.html

So does Welborne Labs: http://www.welbornelabs.com/rel.htm

[TChung]

I found it!

Thanks,
TChung