03 September, 2010

Review: AES SE-1

Even though they make reasonable products, I am not a great fan of CARY. What most people don’t know is that, early on, Cary made kits, named AES (they still have that branch, but finished products only). They at the very least were great values and frequently gave their finished products (of higher gloss) a run for their money. Sounds familiar? Think Audio Note. Think of the AN Kit-1 vs Conqueror.
And the best product of that time was the 300B SET amp SE-1. My first one was about 10 years ago, thoroughly tweaked out, sold to me by a nice fellow from Slovenia! It had good power, able to drive my Klipsch and Tannoy Lancaster to thundering levels. But I had too many amps and marginally preferred the Sun Audio and ICL, so I sold it, even if I preferred it to the AN Kit 1 (which I sold too). They have discontinued this model long ago. I doubt it was making much money for them.
Recently I bought this amp again, in stock form. At its current ridiculous second-hand price, it’s a true bargain. The sound, without upgrades, is still much like what I remember. It is musical. Parts are really superb. High quality diodes, resistors and caps, including Kimber caps. As a matter of fact, recently E lent me the flagship Cary 300B Signature monoblocks, and the parts are similar!
The SE-1 features beefy trannies, likely from Magnequest given that this is from Cary. Solid state rectification. DC filament. 1x 6SL7 (cascaded) driving 1x 300B per channel. This is a fixed bias design. In the back there is a phono jacket in which you can plug in a phono pin and measure (with a multimeter) the combined plate currents of the 2x 300B tubes, which should be in the vicinity of 130 ma. The current is adjusted by the pot next to the phono jacket. Of course, you can bias it lower or higher as you like. I prefer lower.
One cautionary tale. Some people buy it used and just plug their 300B’s in without bothering with the bias procedure. This is not good, even dangerous. The sample I bought this time sounded weak at the seller. When I got home, I measured the bias, and it was in the low 80’s, no wonder. After proper biasing, the amp sounded a lot more powerful. Another caution: The bias measures the COMBINED currents of the 2x 300B tubes, not individual bias. If you’re sure your tubes are a matched pair, there’s no problem. But, if the pair is not matched, it’s better to have lower bias current, as one tube may draw too much current and the other too little.
Aside from using ss rectification, the design is not much different form the flagships. And a good feature is separate switches for on/off and operate/standby. This allows for pre-heating of filaments to ensure better life for the 300B.
This amp can be easily converted to use other tubes, like 2A3. If you change the sockets, tubes like 6B4 can be easily accommodated with minor changes. A manual is essential. If you need one, contact me.
The sound? It’s as good as the 300B SEI and perhaps even the Signature monoblocks (not as powerful in this case). For best result, use Ken-Rad VT-229 silver plate.
Addendum (April 20, 2010)
Finally, I have loaded the Schematic and some pertinent info. Thanks for your patience and I hope the info helps.


Humayun said...
Thanks for the review. I've just bought one, and I need a manual. How can I get one? I'd like to try 2a3 tubes. Thank you.
doctorjohn said...

Where are you? My manual is in the USA and I shall not have access to it until the fall. I can send you a copy then. Can you leave me your email address?

If that's too long to wait, please contact Cary. They may be able to help you.
cruzd2 said...
I am considering this amp, I would also like to run 2a3's (for more bass, any truth to that)? Also when installing 2a3's should they be re-biased, what should my setting be? How about their signaure version, worth the price? I have B&C M15 speakers(98db)that house a large horn and a 15' woofer, I need to move that air for personal bass satisfaction would this amp be a good match? Thanks for your time and insight!
doctorjohn said...
cruzd2: 2A3 is surely more bassy than the bass-lean 300B. You cannot just plug it in. You need to change to the lower filament current of 2A3 and re-bias is absolutely needed (lower total current). As my previous reply says, I don't have my manual with me right now but shall have access sometime in the fall when I return to the US.
tubeornot2b said...
To use the 2a3 tube you do not really have to change the filament voltage circuit. The SE1 was set up to accept either via a voltage dropping resistor. You will have to rebias.

Cary/AES recommends using the settings of a range of 138-150mA for all 300B tubes and 110mA for 2A3 tubes. I found that I preferred the sound of lower settings. Particularly with the 2A3's 110 ma is pushing them a bit.
Tac said...
Thank you for valuable information on your web pages. And I bought SE-1 also and enjoyed its excellent sound with 2A3s as biased 100 mA as your suggestion. I would like to try different tube type such as 6B4G with adaptor or even 183 tube, but had no access to the manual. If you have the access, could you send me a copy?
fedup said...
Could you send me a manual? Or possibly provide some details on using a dropping resistor to lower filament voltage for a 2a3?


doctorjohn said...
This post generates more interest than I thought. I am going to see if I can put a copy of the manual on the net as pdf file or something. Please bear with me
fedup said...
Thanks doctorjohn. I appreciate taking the time to upload the schematic, etc.

I'm still a bit confused on 2a3 compatibility. Tubeornot2b's comment mentions either 300b or 2a3 will work without changing the filament circuit, but he says it's designed to accept either via dropping resistor. Does this mean you need to add a dropping resistor after the .75ohm 25W resistor to bring down the voltage or it does it automatically. I put Sovtek 2a3's in and they measure 2.5v filament but when I put in 300b's they measure 5v filament. It's as if the tube itself is changing the provided voltage needed. When I measure without output tubes in, the voltage is 4.2 volts. So basically I'm a confused newbie. Any thoughts or advice are appreciated. btw, the 2a3's sound fantastic, and I've been leaving them in. I'm just unclear on their operating points in the base (unmodded) configuration. My 2a3 grid measures -69v and get 354v via blue wire gong to the plate. filament is around 2.4v or 2.5v with no mods.
doctorjohn said...
"Fedup": I am glad it was of use. The Blog interface is not the best for chatting though. I found the "auto-adjustment" strange too. To my layman's view, it shouldn't be. But it's true in the manual it does not mention changing dropping resistor for different tubes anywhere, so I'd trus your voltmeter.

I may be getting some articles on modding the SE-1 to auto-bias and tube rectification!!!!! Of course this would necessitate a separate power supply box, but I'm sure this would take the amp to a different level. It's in Chinese but I'll see what I can do. Check back in a few months...

Meanwhile, enjoy!
carla said...
Very cool. I am very interested in a separate tube rectified ps. I just replaced the rectifier diodes with hexfreds and I think I hear a slight difference, a little smoother, but still nice and tight. Cheers.


  1. just built a se-1 amp and some parts were changed and some missing I did add the missing resistors and noticed that the 500uf 25volt caps were replaced with non polarized 100uf 50 volt. I did a very clean job building this amp triple checked everything even the bias checked out but there is low volume and distortion any updated versions of the manual I would love to hear this thing help me please!

  2. I am sorry to hear this. I am not familiar with the various versions. I just know mine, which is likely an early version.

    Check the resistors and cap values against the schematic. Particularly those you replaced. I am not a technocrat and you perhaps should write in detail the problem you have and post in TUBE ASYLUM, where there are a lot of helpful folks.

  3. To use the 2a3 tube you do not really have to change the filament voltage circuit. The SE1 was set up to accept either via a voltage dropping resistor. You will have to rebias.It was nice seeing the blog.Really informative one thanks for sharing it with us.

    Electronic Components seller | Electronic Parts distributor

  4. i have mine from 1995! it use 2 12au7 and 2 6sn7.
    you should use carbon resistor on the 300b grid, and remove the bipass cap on the big 630uf.
    even with the 300b it is VERY bassy...

  5. Replies
    1. Yes, no harm done, but less drive likely.