Wow, this fella rights some extensive reviews for Amazon:
DESCRIPTION:
The "California (Tone Research) SET-5" guitar amp is a low priced 5W amp that has been receiving good reviews from Amazon and, I wondered if it was any good. I also like its looks; at this time, they are available in red Tolex and black Tolex.
IT IS INTERESTING TO NOTE THAT, "CALIFORNIA SET-5", "ARCHER TUBULAR BK 5W" AND "SUNDOWN ST5 COMBO" ARE ALL THE SAME AMP – THE ONLY DIFFERENCE BEING THE CABINET COSMETICS!
I was pleasantly surprised when I got the amp. The cabinet looks solid and well built – bottom, sides and baffle board are plywood; top and back are MFD (kind of particle board but better). The cabinet also has internal plywood gussets for reinforcement. This is one of few amps that has cabinet vent for cooling. I am considering to add plastic cabinet corner protectors like the ones on the little Marshalls.
Looking inside the amp, I realize that its circuit is almost the same as the Epiphone Valve Junior plus a Baxandall tone control, normally used in Hi-Fi tube amps; it allows for greater tone control flexibility than the conventional tone control designs. The amp is built with good quality components, fiberglass PCB and ceramic sockets – same as Fender Champ 600 reissue amp.
It has one, channel, one input; volume, treble and bass controls. It has two 1/4 in. outputs for 8 & 16 ohms speakers. The OT has also a 4 ohms tap but, it is not connected (no available chassis jack).
OPERATION:
The amp is quiet and hum free, even at max volume. As the Epiphone Valve Junior, the California SET-5 has VDC to power the vacuum tubes heaters which helps a lot. However, like most new amp designs, it gets hotter than it should, especially the power supply transformer, approximately 15 minutes after turned-on.
TUBES:
The amp came with no brand, Chinese tubes - 12AX7B, short plate, preamp tube and EL84 power output.
Similarly to the Fender Champ 600 reissue, the tube sockets are good quality ceramic and flush to the chassis, allowing for experimentation with several tube brands. Additionally, tube sockets flush to the chassis allow for easier installation of preamp tube shield and power tube retainer.
I tried JJ Electronics, Mullard reissue and Sovtek tubes. I usually favor the Mullard reissue tubes but, for this amp I opted for the Sovtek 12AX7LPS and Sovtek EL84. They have slightly higher gain than the other brands and help to bring the tubes current down. To my surprise, the OEM Chinese tubes were not bad.
Further circuit investigation, shown that the power supply voltage is more than 50 volts higher than the necessary to run the EL84 output tube. This excess voltage causes the EL84 to operate above its maximum design values and probably will shorten the tube's life.
The power supply transformer label shows 250VAC but, actually it measures 285VAC!!! With solid state (SS) rectifiers, the power supply transformer high output, should be somewhere between 225VAC and 240VAC to provide proper operation voltage to the EL84 tube.
As an improvised solution, I increased the power supply resistor that controls the EL84 screen grid voltage (R16), from 4K7 ohms – 2W to 10K ohms – 5W. This mod, reduces the tube's plate current and dissipation from 14W right down to its maximum design value of 12W.
Additionally, when the 6 VAC winding is rectified and filtered, it elevates the heaters supply voltage to 7 VDC, which is also above the tubes design limits. The excess power transformer voltage could be easily correct by the manufacturer without any increase in production cost.
SPEAKER:
The amp comes with a 1x8 in. ELECA – 8 ohm, 30 watt speaker, made in China. This speaker has a large size ceramic magnet for an 8 in. driver – 18 oz. (estimate). The amp sounds OK out of the box but, I wanted to try different speakers to see if I could get it to sound better.
As additional info, it is important to notice that, the speaker frequency response has to complement the amp's response in order for the lows, mids and high notes to be "perceived" as same loudness level.
As a rule of thumb, in order to sound good, guitar amps with a flat frequency response, like most Fender Tweed, need speakers with scooped mids response, typically most Jensen speakers. On the other hand, amps with tone stack circuit, which provides a scooped mids frequency response (think Fender Blackface and similar designs), need speakers with flat frequency response curve, typically Celestion and Eminence speakers.
If amp and speaker are mismatched, that is, an amp with scooped frequency response is equipped with a speaker that also has a scooped frequency response, will make the combo sound "thin". That means, a speaker that sounds good in a particular amp might not sound good in another one and vice-versa.
SPEAKERS EVALUATION:
I tried 5 different speakers with this amp. They are list in order of my preference, 1 being the one I liked the most. Before evaluation, all speakers went through a break-in period of 8hrs @ 6 VAC – 60 Hz from a power supply transformer.
Here are my impressions:
1. WEBER AlNiCo Signature 8S – 8 ohms, 15W. Crystal clear notes from lows to highs – Fender Tweed like. I like this better than the WAREHOUSE G8C.
2. WAREHOUSE G8C – 8 ohms, 20W, heaviest ceramic magnet. Very balanced response with this amp. However, it has a hint of muddiness when a full chord is played. This is my second favorite.
3. CELESTION Eight 15 (G8C-15, made in China) – 8 ohms, 15W. Marginal improvement over OEM speaker. Nice mids and highs, mudded lows.
4. ELECA (OEM speaker, made in China) – 8 ohm, 30 watt. This speaker looks a lot like the Celestion Eight 15, specially the basket, cone and dust dome. It has a slightly heavier ceramic magnet than the Celestion. Sounds muffled; no clarity on the high notes.
5. JENSEN C8R – 8 ohm, 25 watt. Sounds too thin, scooped with this amp. Good speaker, bad fit. It works very well in another amp I have.
6. FENDER OEM for Frontman/Bronco – 8 ohms, straight cone (Fender P/N 0994808002, made in Taiwan). Distorted lows at very low volume similarly to the CELESTION Eight-15, thin highs.
CONCLUSION:
Replacing the California SET-5 OEM tubes and ELENCA speaker with Sovtek tubes and WEBER AlNiCo Signature 8S speaker, makes this little guitar amp to sound really good – exactly the way I wanted! And all for less than U$ 200.00!!! This is my favorite little amp so far.
I also bought a nice red with white sides, vinyl cover from "amplifiercovers".
I am taking one star down because the power transformer is producing excessive voltages and, this will certainly shorten the vacuum tubes life. Despite of this, I highly recommend this amp.
