Review: Blue Circle Audio Sugarbrie Tube Preamp Tube preamp

No, this is not a Sugarbrie review of a Blue Circle preamp. This is a review of what is known among a small (blue) circle of people as the Sugarbrie Preamp. What is the Sugarbrie Preamp, and how did it come about? The old saying goes "be careful what you wish for, you may get it". Well in this case it has a happy ending.

I was at CES 2003; the consumer electronics show in Las Vegas last January. On Friday morning I wandered into the Blue Circle room and found Gilbert Yeung sitting there alone. Thinking Gilbert would not have a clue who I was, I introduced myself by my real name. Surprisingly, Gilbert shot back with "hey Sugarbrie".

After looking at his new offerings for this past year, I mentioned that I was still using one of his original BC21 preamps. I told him I wanted something better, but was stuck on the sound of octal tubes like the 6SN7's used in the BC21. For me 6SN7 tubes have the right tonal balance. I find that 6922 tubes slightly emphasize the upper-midrange detail (which might be why they are popular). Gilbert's response was; "yeah, I heard you tried the BC3 and were not that crazy about it". Embarrassed; I was now waiting for Gilbert to toss me out on my ear for having an unfavorable opinion of some of his gear.

Instead of kicking me out, Gilbert offered what he had done for some other BC21 owners. He would move the power supply on my BC21 to a separate case, and then would add a Shallco attenuator. When the troublemaker in me responded that I wondered if there was something even better out there; Gilbert smiled and said to contact him or Angela after he returned from the show. He had some other ideas as well.

What Gilbert and I finally settled on was a dual-mono 6SN7 tube preamp built inside a BC3000 chassis and BCG3.1 power supply chassis. Double transformers. The power supply uses things similar to the AG3000, which uses polypropylene caps. The output caps are Blue Circle ture film and foil, which at the time was only use in the BC3000, BC9 and AG3000. Two Shallco attenuators and two selector switches. Same layout as the BC3000 faceplate and back plate. The weakest point of the original BC21 is the power supply.

Foolishly or not, I decided to go for it without even asking how much it would cost.

As a point of reference; subsequent to the making of this preamp last spring; many of the "upgraded" parts built into this preamp and power supply are now part of the regular Blue Circle Mark II line of preamps.

Now the other reason it is called the Sugarbrie preamp other than is was made for me. When I opened the box when it arrived, I found that Gilbert had engraved "Sugarbrie" on the lower left front faceplate of both the preamp and the separate power supply, where it usually has the model number like BC-XX. Quite an ego trip having your own Blue Circle product!

After a very long break-in period, the preamp started to sound very good. To make sure that I was not just getting use to it, I inserted the BC21 back into the rack to do a comparison. I used the same type of tubes in each and the same power cord (a BC61). I left both preamps on and warmed up; and would just shut the power amp off long enough to quickly switch the cables.

What I found is very similar to what others have found comparing Blue Circle's other preamps against the new MkII versions. But more so in this case, since the Sugarbrie preamp is a big step forward from the simple design of the BC21. The biggest difference was in the lower end. The bass in the Sugarbrie preamp is much tighter, more real sounding, with greatly improved detail on individual notes and individual instruments. The midrange has the same character as the BC21 with a little more detail. The overall sound is smoother and more natural to my ears. The Sugarbrie preamp also produces a larger and more focused image. It is also quieter than the BC21, which brings out a little more fine detail in some recordings.

For those familiar with the characteristics of vintage 6SN7 tubes, I find the improved design of the Sugarbrie preamp also results in reduced microphonics. My favorite tube with this preamp is the Sylvania 6SN7W short bottle. Very immediate, with very good low level detail using this tube. For a smoother sound, the Tung-Sol VT-231 is a great choice. I find that the sound coming from the BC21 is greatly influenced by the tube used, due to its simple design. Changing between tubes in the Sugarbrie preamp is closer to a tweak, more than a change. The Sugarbrie preamp still performs pretty well using inexpensive tubes that would sound a little harsh in the BC21.

The Sugarbrie power supply is a dual transformer design similar to the BCG3.1 power supply. For the first few months I used a Blue Circle BC61 power cord. I figured it was good enough for a preamp. Wrong!!! When I later swapped in the larger BC62 cord, I was surprised when the performance improved dramatically. Just about everything I liked about the sound got even better. So if you've have a Blue Circle preamp with a BCG3.1 power supply, I recommend that you do not cut corners with the power cord.

Finally, I should mention that Gilbert has indicated that he will consider making Sugarbrie preamps for others by special order. You should probably contact Blue Circle directly. Unfortunately, you won't be able demo it first (unless you can hunt me down). However, if you like what you hear with the original 6SN7 based BC21 preamp and want something more, I think you will be happy with what Gilbert has created here.

Happy listening,
Sugarbrie (Tom).

Associated gear
Blue Circle power amp, power cords, speaker cables. Modified Gold Link DAC and modified transport. Modified Kenwood KT8300 tuner. Music Hall turntable with Goldring cartridge.

Similar products
Blue Circle BC21 and BC3. Conrad Johnson PV-10 and PV-11. Motif MC8.