Every day, out there in audio land, someone looks at their tired and uninspiring solid state integrated amp or receiver and thinks; ĎWhat is this tube stuff about? Could it be right for me?í Then they look at the prices of the finest triode single-ended amps and cringe. When they see loudspeaker sensitivity requirements 10 or more dB higher than their present speakers, it looks hopeless. The idea of replacing amp and speakers when theyíre not sure tubedom is right for their ears is a big leap of expensive faith. What if there was an integrated tube amp that cost less than $600, and it had enough power to drive less specialized speakers. Then tubes could be tasted without purchasing the whole case.† Would that sway more curious people?
Well there is such an amp, and it is called the Jolida 102B.
I will now state, here at the beginning of the review, that I like this amp. In fact I own an earlier example: the Jolida 101. Iíve owned this amp for about four years and I frequently use it while developing loudspeaker designs and also to take the bite out of my digital satellite receiverís audio signal.
The circuit is very much cast in the mold of smaller late 50s and early 60s American amps. With its tube complement of one 12AX7 and two 6BQ5 / EL84s per channel, it could have been copied from designs by Eico, Pilot, or any number of other classic companies. Many of this amplifierís ancestors are sought-after collectorís items and the prices of such amps in need of full-restoration bear out this fact. If you have neither the time, skills, nor the inclination to restore a classic, this could be your amp.
While Jolida claims a 20 Watt output per channel, my measurements put it closer to 16.5 Watts at the beginning of clipping. This is a small discrepancy and is really of no importance. What is important is that like most any tube circuit, this one can handle transient peaks of twice the rated output without flying into a fit of harsh distortion. This is why many people find tube Watts to be so different from transistor Watts. Itís called headroom.
To be capable of this kind of power for so little money some topology other than the much-loved triode single-ended approach must be followed. Output transformers for 15 Watts of SE can easily cost more than this entire amp. This amp is of a type called: Class AB push-pull pentode. An output section of this type uses one output tube to amplify the positive half of the music while the second tube amplifies the negative half of the musical wave. That is where the Class B portion of AB comes in. The Class A portion is the first Watt or so where both output tubes are ďturned onĒ and waiting for a signal. Above this Class A region the output becomes Class B. Solid state amplifiers are usually designed in the same way, but arenít quite as successful in making the switch from A to B as tubes are. A great number of high-power, well-loved tube amps also use this AB configuration. One design decision made by Jolidaís engineers, whom I agree with, is to use the tiny 6BQ5 output tube. I have long felt that this tube is the most ideally suited output device for AB operation. Most pentodes cannot compete with the 6BQ5 when it comes to sweetness, detail and liquidity when used in push-pull. Iím not saying that 6550s and EL34s sound bad, they just lack some of what I consider the charms of tubiness. This little amp has charm, in spades.
By tubiness, I mean there is a warm sense of flow to the music, a harmonic richness and most of all a pleasant non-clinical presentation. This is due in part to a tubes ďdesireĒ not to be turned off. Listen to a tube amp after it has be switched off and you will hear it fade to nothing. Solid state on the other hand is a switch waiting to be turned on or off and so drops to nothing instantly on shut-off. No continuous flow here.
This switching nature of transistors accounts for the more obvious crossover distortion with Class AB than is audible with tubes. When a transistor amp transits between Class A and Class B it is a sudden and violent transition with no sense of inertial flow. As light as air is it still has inertia and tube amps come much closer, to my ear, to the inertial flow of music in the air than do solid state devices. With pure Class A single-ended circuits, there is no transition from one mode to another so they offer the smoothest and most natural inertia of all topologies (once again to my ears). Transistors used as Class A single-ended sound much better than transistor AB circuits but even they lack the fullness and richness of a great tube circuit.
With the Jolida 102B the transition region is audible but is very low-key. My reference loudspeakers are very highly sensitive at 97dB 1W /1m so I really have to push to high volume levels to cause the transition from A to B to occur. In my system the 102B is usually a Class A push-pull amp. With speakers of lower sensitivity the AB nature begins to reveal itself more strongly. Above one Watt this amp begins to lose some of its liquid-like flow but it doesnít get edgy until closer to clipping.
With this, or any, push-pull circuit much of the even-order harmonic distortion is canceled leaving behind most of the harsher odd-order distortion. This is why even the best push-pull circuits lack the intimacy of an SE amp. So while this is a good amp it lacks the utterly relaxed character of a pure Class A amp.
This amp images well, it has depth, it has warmth, it has fine detail and as tube amps go it has tight, fast bass. It is not the most detailed amp Iíve heard, nor the most liquid, or warm, but it is GOLD at $550.00. I havenít heard any other amplifier in current production, in this price range, that can drive average speakers this well to reasonably loud volume levels. I like this amplifier; it can even dull the razor blade of less competent CD players.
In spite of the problems inherent with push-pull, this amp still manages to portray music rather than information. The sonics do tend toward the romantic end of the spectrum but lack, the harmonic flow of my favorite amps. When pushed too hard this amp can become cruel, but no more so than most AB amps. I find vocal presentation to be very good, but not earth shattering. Extremely complex passages do cause the amp some minor confusion. The circuit manages to be far less sterile than larger more complex AB tube amps by virtue of its very simple design and tube selection. I believe any one who has survived transistor consumer amps will find this amp a true friend.
For every ointment there is a fly. In this ointment it is the stock tubes. While they donít do anything badly, they arenít prime examples of the breed. I canít quite see putting NOS tubes costing hundreds of dollars in this amp right from the beginning so Iíve changed the tubes in my 101 with Sovtek 12AX7WXT and 6BQ5WA matched pairs. This simple, inexpensive change greatly enhanced the listenability of the 101 (after break in of course). With the above tubes in place I turned up the bias from the recommended 35mV to 40mV( true bias is in mA but the meter reads out in mV) with no ill effects to the power supply. Now the amp measures 18.4 Watts at the beginning of clipping and can easily handle peaks of 35 Watts. Not bad for an extra $55, or 10% of the original cost.
The cosmetics of the 102B are superior to those on my 101 and they have added an input selector switch along side the balance and volume controls. Handy! The tubes are left out in the open, as tubes should be, for that electronic fireplace look. Fit and finish is quite good for the money.
Sonically the 102B out classes any solid-state gear anywhere near the price, and rivals quite a few more expensive tube units. If you are hungering for tube sound, without high-end prices, try a bowl full of Jolida 102B. You too will like this sweetie of an amp and Iíll bet you wonít look back fondly on your tired old solid-state stuff. The overall character of this amp is warm, relaxed and spacious. A true taste within the Kingdom of Tubes alchemistís ability to turn lead into gold.
In the end, I prefer my more costly SE amps, but my Jolida is not for sale!
These ratings represent a comparison with my reference system sounding its best after only the amp change.
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