[jimbo900custom]

Hi All,
A few weeks ago I purchased a used factory built blue Cornet Classic.
To say I love it and am having fun listening would be a major understatement.
I have been tube rolling like crazy and have even tried a few different power cords.
I have a replacement fuse coming (thanks tubesforever).
My question is: Would it be worth changing the power transformer from the 270BX to the 370BX?
If I did that what other parts would have to be changed?
In sonic terms what do you feel I would gain?
Would I be further ahead to get a Cornet 2?
I know......more than one question.....would appreciate any advice or guidance.
Thanks
Jim

[GRD]

Jim,

I'll jump in mostly with my opinions.  I would also be interested from hearing from anyone who replaced the 2 series with the 3 series on their classic Cornet.

I have the classic Cornet with the 270 transformer.  Several of these failed when the Cornet was introduced.  Jim then revised the Cornet to use the 370 series.  I never had to change to the 370 - mine still works fine. 

There are a few small resistor changes as the 370 delivers a little lower B+ and heater voltage.  Jim stated that he thought the 370 transformer sounded better when he made the change.  The Cornet and Cornet2 circuits are essentially the same but the C2 board is easier to work with and makes adding the CCS much easier as it's designed into the board (versus some tweaking with parts off the board). 

The reason the 370 has a little lower voltage than the 270 is that the 270 is designed for 115 volts primary and the 370 is designed for 120 volts.  So the 270 delivers a little more voltage when run at 120v which seems to be the norm these days. 

The 270 in my opinion is not a very good transformer.  It runs hot after awhile and that seems to change the sonics - maybe the internal resistance goes up and drops the voltage (guess).  The 300 series are heavier, run cooler, and seem much better made.  I use a 372 (300 volt version of the 370) in another project, so that's my reference.

My Opinion: If you've got the time, you're into soldering and tweaking and you're an Audioasylum type of fellow with a Steve Jobs mentality (it's not right unless it's perfect) - replacing  the 270 with the 370 is a good move.  It's stable (sound won't change over the listening session as the transformer heats up), and Jim says it sounds better.  If you're happy with your current Cornet (as I am) and you don't have much time, pass for now.

The C2 board is bigger than the classic board, so going C2 means starting at square 1 and building your own. 

Final point - if you have the classic, does it have the CCS?  I built my Cornet with and without the CCS.  The CCS is a definite addition.  You'll see two transistors on the board if you have the CCS (flat, 3 legs).

Grant

[jimbo900custom]

Hi Grant
Thank you for responding and sharing your thoughts.
I know my ignorance is showing.....but what is CCS?
I don't see a flat, 3-legged transistor....but then again I don't know what to look for .
I'm very pleased with my Cornet Classic....and somewhat feel like if it ain't broke don't fix it,
But..........I'm always open to improvements, especially the cost effective variety.
I will now attempt to post a pic of my Cornet innerds:

[GRD]

Jim,

You have the CCS - those 2 black metal pieces in the middle of the board.  Those are heat sinks and you'll see 3 legs coming out from the transistor.  Whoever assembled this board did a really good job.

Don't know if it's worth moving to the 370.  I'll let others post their opinions.

Grant

[GRD]

Ooops - a CCS is a Constant Current Source.  Instead of a resistor on the tail of the last tube (the cathode follower), you can put in a transistor that "demands" a fixed current.  The Cornet uses the heater voltage as a reference and a resistor that measures the current coming out of the tube (voltage = resistance times current).  The CCS uses it's gain or amplification factor to balance these two inputs and deliver a stable current through the tube.  It makes the tube very linear.  I tried a cathode resistor and the CCS in my Cornet build and the CCS definitely sounded better - more sold, less distortion, cleaner.

[jimbo900custom]

Hi Grant
Thanks again for the reply.
The person from whom I bought it from, said it was factory built.....so maybe Mr Hagerman himself(?) was the builder.
It sounds glorious, and is by a fair margin the best phono pre I have owned.
I do own a soldering iron, but my experience is limited to repairing my son's guitar cables and making a few interconnects, and terminating speaker cables.
I have noticed a slight, and I do mean very slight change in the sound after several hours of listening, but nothing about this preamp disappoints me in any way.
I hope to hear from someone who made the switch from the 270 to 370, and if they felt the diferences were worth the effort.
Thanks for  the info on the CCS..... I am learning alot, thanks to you and this board.
Jim

[hagtech]

Yeah, I built that one.  If the 270BX is working fine, then there is no need to change.  The upgrade was mainly for reliability (the 270 runs hot). 

The caps have already been upgraded.

jh

[jimbo900custom]

Hello Mr Hagerman....thanks for the response and the great phono pre!
The 270  tranny is functioning perfectly with no issues......I'll just sit back and enjoy it.
Regards
Jim