Quite a few popular amplifiers use the EL-34 output tube, which is traditionally a bit warm sounding, with a lush midrange, but not too strong in the lower registers. The major competing design concept features the 6550 output tube, which usually has a bit more power at the bottom end and allaround punch, but a little less midrange "magic." Put a few audiophiles in a room together, and there will be a major argument over which approach is "right."
Over the years I have owned many amplifiers based on the EL-34 , and expected the JoLida JD 1000A to have a big EL-34 sound. Much to my surprise, assessing this amp was a most interesting experience; the JD 1000A is definitely more than the sum of its parts.
The JoLida JD1000A is a 100WPC all-tube integrated amplifier that uses a 12AT7 and a 12AX7 tube in a standard configuration driving two pairs of EL-34 output tubes per channel. Thanks to a beefy power supply and equally beefy output transformers, the JoLida tips the scale at 50 pounds (when unpacking, be aware that all the weight is at the back half of the box). The design is straightforward, with the preamplifier and amplifier sharing one big circuit board. The wiring to the inputs, outputs, and controls is neat and orderly throughout. The front panel features a power switch, input selector, and volume control; the rear has four sets of goldplated input jacks along with 5-way binding posts for one set of speakers with a 4- and 8-ohm tap. A standard IEC power socket and substantial power cord are supplied.
One of the big advantages to an integrated amplifier (especially one with tubes) is the assurance that the preamp is matched to the power amp, and so a gain or buffer stage can often be eliminated, allowing for a simpler design. It also eliminates the quest for the perfect interconnect between amp and preamp.
My review sample was new, and it sounded pretty dry out of the box. It continued to sound that way, however, even after about 100 hours of burn-in time. While many of us do not read instruction manuals, I suggest you read this one; here you will find the instructions for setting the bias on the output tubes. On second reading, I noticed that JoLida suggests that you check the bias settings for the amplifier shortly after installation; and this was most of the answer to my dry-sound dilemma. Bias voltage for the JD1000A is 44mv, with a tolerance of +/- 10 percent. The trusty Radio Shack multimeter revealed the actual bias to be at 9-12mv on all of the output tubes. Returning the bias to factory specs made a world of difference, so if you purchase a JD1000A, and don't have a multimeter, plan on a stop at Radio Shack or get your dealer to check the bias before you take the thing home.
I did about 70% of my listening through CD sources, and had the best results with JoLida's CD 100 player, which also features a tube output stage. These two components had a nice, warm synergy, giving a sense of listening from about the 15th row back in the concert hall. I also used the new Sumiko Primare CD21 solid-state player with good results, but this player pushes you forward about ten rows, with a much more upfront sound.
Initial listening through the warmup period was done at my desk with a pair of ProAc Tablettes and then I moved the system out to the big room with Vandersteen 2Ce's. Both of these speakers are in the $1000-1600 range and could be a reasonably priced consideration for a system built around this amplifier. Both speakers are a little bit on the low side of the sensitivity scale at 86dB, but the JD1000A had no problem driving them to more than adequate levels.
Stepping up to the 100 Wpc level really helps, even if you don't listen to music terribly loud, because of the extra dynamic range it offers. Whether I was rocking out to Led Zeppelin or listening to Miles Davis, the JoLida offered a neutral relaxing sound that had a good measure of airiness—not always a given with amps in the $1500 to $2000 range (the JoLida runs $1699).
The biggest surprise with the JD1000A came when I realized that, instead of just sounding like a traditional EL-34 design that got louder, this amp provides was a nice compromise between EL-34 and 6550 designs, retaining the midrange liquidity of a good EL-34, but offering a lot of punch and impact. One of the biggest treats with the JD1000A is its powerful bass performance, which made listening to Mickey Hart's At The Edge [Ryko] a much different experience than with lower powered EL-34 amplifiers because there was so much more weight to the bottom end. A good friend who owns a 6550 amp couldn't believe an EL-34-based amplifier could generate so much low bass performance.
Not sacrificing anything in the area of speed and transient attack, the JD1000A did a great job with Steely Dan's Two Against Nature [Giant] and that old school audiophile favorite, Discovered Again by Dave Grusin [Sheffield Labs]. While some tube amplifiers sacrifice leading edge transients in the name of musicality, the JD1000A has a nice balance between the two, again offering a bit livelier sound than I have heard with this tube before.