Would like to start a mini thread here instead of hijacking the 'Show us your tubes post', together posting with some better photos:
http://www.stereo.net.au/forums/index.php/topic/51808-show-us-your-tubes/page-18#entry1625921
Firstly as all reviews, it's subjective, so if you don't agree please don't be upset
Introducing is the latest invention from Eric Chan, aka McChanson. For a lots of people in the forum the name is not new. He's a local master amp builder in Sydney. Here introducing is the latest product from him, a 3 tubes SET amp using 2 6EM7 and 1 rectifier. According to Eric this's his second made of this kind and was never on public listing.
Spec:
2W
Single End Triode (SET)
Class-A (of course)
Rectifier: (one) Could use any in-direct heated GZ30 / 32 / 34
Driver / Power: (two) 6EM7
Size: 10.5 x 14.5 inch (Junior Chassis in Eric's term)
Functions:
Design:
Now come to the design - firstly please forgive me if I used any incorrect terms etc as I'm not any expert in any tube / amp building.
It is by design a pure Single End Triode amplifier. So obviously it's also a class-A design as it's Single End and nothing to do any push-pull.
As a three tubes amp, it's using one rectifier and two 6EM7 tubes. Since the 6EM7 tube itself is indirect heated and there's no separated slow start circuit, recommendation is to use a indirect heated rectifier to avoid directly powering up the 6EM7. This particular design (on my request) accepts a larger output rectifier and can use any of GZ30, GZ32 and GZ34 or equivalent (like 5Z4, 5ar4 etc). Usage of rectifier is up to your personal taste and some people / amp builder prefer not to. I personally found a good rectifier contributing to a much solid bass and open sound-stage so I do enjoy using it. The standard rectifier comes with Eric's amp is also good as well.
Comes to the 6EM7 is a bit of story and learning for myself. So how's the single tube power up one channel and therefore needing only 2 tubes for 2 channels? The answer is a dual-triode. Normally in a valve you'll see 8-pins, our modern valve designs (KT-88 eg) are using as a pentode for higher power output and you can only fit one set of pentode into 1 set of 8 pins. In the case of triode, since you got 8 pins it's possible and common in the old day design to fit 2 sets of triodes into a set of 8 pins, therefore you got 2 triodes in one tube!!
How is that being used? Then come to the basic of tube design you always need a driver and a power tube for a good stable output. On this Eric's creation, he use one set of triode as a driver and the other set of triode wiring as output all in the single dual triode tube. As a result, since you can only using one tube or not using it and they started / stopped at the same time, there's no need of an extra capacitor in between to safeguard / separate the two and therefore is 'direct coupled'. SET circuit is famous on it's simple design and removing the need on the capacitor further pushing that envelope. Is that sounds better? that's another subjective question but at least it saves you the costs on expensive capacitor upgrades - save your money and invest on NOS tubes!
Conclusion:
Another beautiful creation from Eric Chan!! If you are new to tube amp or using similar tubes on headphone amps and would like to explore into speakers I would highly recommend to give this a try.
- Typical Eric sound signature - warm and open sound
- Sensitive to tube rolling and is inexpensive on this 3 tubes amp design, and fun!!
- Multi-function, can be used as an integrated, preamp or headphone amp
- (Contact Eric for a price) won't break your bank account, with local support
My first review post. Thanks for viewing.