[BobM]

Is there a compiled list of mods and tweaks and additions / improvements that have been made to the Coronet phono stage? Can someone please point me somewhere?

I've searched the forum here but found very little. Are these buried inside other topics? I'm guessing some of the following are possible, but I would love to see what has been tried and found successful:

- NOS tube swapping (which brand provides what kind of sound)
- output coupling caps
- cap bypasses
- key resistor upgrades
- other?

Thanks,
Bob

[mgalusha]

Bob,

There is some discussion in the Critcs Circle about various tubes. I believe several owners (including myself) have posted in there about it. As for ca[ mods, since Jim allowed enough room on the baord for various caps I don't know if this is more of a mod or just a personal choice of favorite cap.

Mine has Auricaps at present but I originally built it with Relcaps. I prefer the Auricaps in this case. I have heard Wayne W's unit and I think he has a mixutre of Relcaps and Jensen copper foil in oil and his sounds very nice as well.

I am currently using Sovtek 12AX7LPS, a NOS Mullard for the 12AU7 and a NOS GE 5Y3 (not sure what vintage) and am quite happy with the sound. I installed a pair of Jensen step up transformers inside the chassis as I run a low output cartridge and didn't want to mess with yet another set of cables. Plus this eliminates the cable interaction between the transformers and the Cornet. I have heard the Cornet with the Lundahl step up transformers and with the S&B units. The S&B are very nice but mighty expensive. All sounded good.

mike

[Frank McCrea]

Hi Bob,

Check out the following post from Jim to give you some idea's where to start. http://www.audiocircle.com/index.php?topic=13094

Regards, Frank

[Wayne1]

Here is a shot of the latest Cornet I have built.

It uses Jensen Copper Foil, Silver Lead out, Paper in Oil capacitors in the signal path. RIAA resistors are Riken-Ohm. PS Bypass caps are Multi-Cap.

It has the Jensen JT-44-K moving coil transformers built into it.

I used the constant current source.

The transformer is the 370BX.

Tubes are Sovtek 12AX7LPS, CBS-HYTRON JHY 5814WA, and SYLVANIA JAN CHS 5Y3WGTA

[SHIF]

Here is the definitive list:

http://www.audiocircle.com/index.php?topic=13094.msg112612#112612

[mac]

I don't want to put words into Jim's mouth, but he did hear my Cornet and did say that it sounded better than the typical breed.  Aside from doing all the standard things (Sovtek LPS, Holco resistors, AudioCap Theta coupling caps,  CCS, etc) I used massive, low ESR Nichicon NT caps in the power supply along along with an ASC oil cap.  This unit sounds great and has very good bass authority.  I also use Jensen step-up xformers but have them mounted externally in a well-shielded environment.  Cheers, mac.

[coffeedj]

#1.  Output caps -- Spend the money on some good one.  1.5uF is plenty big.
#2.  Power Supply.  I moved mine external changed it from a resistor drop to double PI filter choke drops.  Massive final filter caps completed the project--it was a major upgrade.  BTW it is not necessary or recommended to change the first and second stage filter caps.  If you do that then you need to change the bypass caps and possibly add a second bypass cap.  Get the power coming in clean--then the downstream stages (power-wise) are fine.
#3. Innerstage coupling cap. I found some surplus Techtronix caps and scored 2 caps that were non-polar, unbelievable quality and matched parameters.  They also had a separate can shield that I tied back to single point ground--cleared up every trace of hum.
#4 Tubes--best you can find.
#5.  RIAA caps.   Don't need to go overboard, but make sure you get high tolerance, closely matched, good quality caps.   The passive RIAA equalization is not really in the signal path, since it 'bleeds' off the frequencies according to RIAA specs.  A bad cap can affect the equalization curve, as well as affect the linearity.  Save your big money for tubes.

[BobM]

Wow. Some of you have really taken the beast and tamed it. Congratulations on your creations.

I'm buying a pre-made unit from a friend. I'm tempted to just let it break in and play for a while, but I've already heard the octal version of this unit and was very impressed. Break-in is such a pain with a phono stage (flipping records) that I'd rather do it only once, so the upgrades may happen sooner rather than later.

There will be 2 sets of NOS tubes included (so I can play with those at my leisure). The RCA's are gold, but the rest of the unit is pretty much stock. I won't have a schematic, so I'll have to go by eyesight, unless someone (Jim?) feels in the holiday spirit and want to share one with me.  

The priorities seem to be:
- output coupling caps (is a 1.5uF value correct, I've always liked the Sonicaps, perhaps I'll bypass with a .1uF Sonicap2 also)
- coupling caps between stages (what are the board locations & values?)
- what is the "370BX" that I see listed in Jim's upgrade list?
- perhaps the power supply caps too, if I can score some Nichicon KG's somewhere (recommended size?)

Thanks for your posts. They were highly informative.

Bob

[BobM]

Nevermind the schematic and owners manual. I found them on the Hagerman site.

Jim, you've thought of everything.

Thanks,
Bob

[Wayne1]

The Jensen transformers are triple shielded. There is no problem with hum pick-up by using them inside the Cornet.

What is more important is the capacitve loading and lead length.

This is from Jim's website referring to his moving coil transformer:

"Output cables are hardwired to chassis not only for convenience, but to optimize reflected capacitive loading seen by the cartridge. Keep in mind here, that at 10:1 gain, every foot of output cable is equivalent to 100 feet of input cable. You wouldn't want 100 feet of cable loading your cartridge! That's why output cables are cut as short as possible. "