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-   -   Octal Hagerman Cornet Experiences (http://www.diyaudio.com/forums/tubes-valves/66191-octal-hagerman-cornet-experiences.html)

fergs1 18th October 2005 04:20 AM

Octal Hagerman Cornet Experiences
 
Calling all octal cornet builders, an invitation to post piccies and share experiences building this phono stage especially the scratch builders as I am leaning towards this design to build. Other octal phono designs most welcome infact a definitive octal thread would be great.Lead on McDuff! cheers fergs

thevoice 18th October 2005 11:34 AM

I've been looking at building one of these also, with the added variable phono eq mod (I have 78's I want to play).

Do you have a reasonably priced local source for the transformer? The hammond stuff usually costs about twice the price of the US out here, I'm in Melbourne also.

fergs1 18th October 2005 01:15 PM

the only local source I know of is black art trans. keep an eye out on ebayau as lots of pt's and chokes apppear cheers chris

Bas Horneman 18th October 2005 03:45 PM

I reckon it would be worthwile for you guys to get a custom transformer wound. Since a phono stage can do with extra measures to keep noise out of your phono stage..Such as electrostatic screens between primary and secondary. And then go DC on the filaments with a seperate (maybe surplus) transformer.

markgall 18th October 2005 07:23 PM

I am in the planning stages of building one also. Actually a Claricorn ( Clarinet and Cornet 2 ) in the same chassis with one power supply for both. I am also leaning towards wiring PTP instead of using the boards and building the Cornet side as a hybrid, ( miniature/octal ). I'm trying to keep the costs low. I have the power transformer already and I think I can source the rest of the parts for around $150.00 without the tubes and chassis. I will make the chassis myself. I would be very interested in pics and comments from others that have gone this route also.
Mark

milosz 21st May 2011 09:00 AM

Cornet2 - octal Cathode Follower
 
7025's and 6SN7

http://www.audiocircle.com/index.php...=view;id=59544

http://www.audiocircle.com/index.php...=view;id=59545

Copper Semi-octal Cornet2

Richard 23rd May 2011 02:15 AM

Hi Guys,

You can try Voller transformers in Highett. Paul is great to work with and his transformers are reasonably priced. Turn around time is also quick. I got a surplus transformer from him for my cornet project, so also check if he has any lying around. There is also ses transformers in Dandenong:
http://www.southernelectronicservices.com.au/home.htm

In my cornet I have used a 12BH7 and 6n6p for the output tubes. I'll try the 6sn7 or even a pair 7193's at some stage. The 12BH7 is easy to implement since it's a noval and if you're using a ccs on the cathode it's easy to change the current set resistor and use a 12AU7 or 12BH7. The heater connection was different for the 6n6p and its use also resulted in a hum, so I went with the 12BH7.

What I'm doing now is building the power supply separate to circuit boards and adding in a choke.

Cheers,

Rich

djn 23rd May 2011 02:44 AM

3 Attachment(s)
Here are pix of my Octal Cornet. I love it. I think it is the best phono pre I've had in my system and I tried a number of high end pres before I built this one.

devilsindetails 23rd May 2011 05:53 AM

Please excuse the intrusion. But I`m fascinated by this and the fact that at least one of these variations unashamedly uses the 7025 tube (which is a 12AX7 variant) and 6sn7.

I keep hearing the 7025 (12AX7) is such a poor tube for phono stage designs and yet here it is used again. I posited the use of 6sn7s as well in another thread and was met by deafening silence...so your opinions please regarding this topology.

milosz 23rd May 2011 08:16 AM

7025
 
This is what Hagerman says about the Octal "hybrid" version of Cornet, hybrid in that it uses an octal 6SN7 cathode follower and 9-pin 12AX7's for gain:
I think the 6SN7 makes the best cathode follower. More current, better linearity, better voltage ratings. I like the tube. I also like the 12AX7 for high gain amplification.

Keep in mind, a LOT of the sound has to do with topology and circuit design, not just tubes. I can make no claim that octals are superior to novals, nor the other way around. Each tube has to stand on its own merits.
He's the engineer who's responsible for the design of this preamp - as well as several other very well-regarded designs- and if he says he likes using the 12AX7 in this design, I'll go with his expertise over opinions of people whose engineering pedigree is unknown to me.

The 7025 is a low noise / low microphonics version of the 12AX7. It is otherwise identical.


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