All the audiophiles who have used tube amplifiers know clearly a phenomenon that one Amp would make sounds differently if the the owner use different brands or times tubes on the Amp. Different models of one kind of tubes would make sounds more differently. Doning this is so easy that you just need pull out the old ones and insert the new ones. This is why there are so many tube Amps owners are looking for every models of tubes to chase all kinds of sounds. This has been another fun out of simly listening to the music. But there is a limit to use the other tubes for you just could use the same kind of tubes. You couldn’t use different models of tubes on one Amp. If one wants his tube Amp could use different kinds of tubes, he will meet many technical problems to solve the different bias voltage of the tubes on the same tube Amp. So there is few models of this kind of Amp in the market for a long time.

The new model of Focus-836 of Music Space Time as the world’s first this kind of Amp has been manufactured at present. This one can use directly 36 kinds of different tubs and you needn’t change anything on the Amp. The tubes are include KT88/6550, EL34/6CA7, 6L6, 6V6, etc. All these tubes can work nomally but the push powers are different.

The First Impression

When I open the packing box, I found a very small and exquisite machine lying in the package. Taking out carefully on the table, I found the design was very succinct. There were four tubes in the Amp. The preamp part uses 6U8x2(6F2), the amp part uses KT100x2. There were another 6 tubes in the package. They were EL34x2, 6V6x2, 6L6x2. It was really worth for these attachments. The outer color was black and silver. There was a picture of all silver color in the package. One looked sedate another looked fashionable. A big half-ball volume snob was in the middle of the face board. The power switch was on the left side board. The inputs selecter was on the right side board. There was another switch on the back board use for selecting output resistance. The designer of this Amp must uphold simple style. It was more like a product designed by Audin Sterling. All the covered boards were made by thick aluminium. The face board was even used 10mm thick silk deal aluminium board. This kind of design obviously was not only for good looking but also for reducing interference. The transformers covers were used 1.2mm thick iron.

Looking at the Amp, let me think about another famous Italian single-ended tube Amp, Unison Research. Its EL34 Amp not only had elegant out looking, but also had attractive sound.

Spcifications

Input Impedance 100kΩ

Output Impedance 4Ω, 8Ω

Output Power 18w (max)

T/H/D < 1%

Weight 14kg

Frequency Response 18Hz~38kHz

S/N > 85dB

Preamp tubes can use 1252, 6678, ECF82, 6U8

Amp tubes can use KT100, EL34, 6L6, 6P3P, 6V6, 6P6P, KT88, WE350B, KT66, 6CA7, 12E13, KT77, KT90, 6650, 5932, 5932, E37, 1622, 5881, 7581, 7581A, 5992, EC33, 5871, 7184, KT61, etc

Output Transformer Size 78mm x 68mm x 43mm

Power Transformer Size Model O, 55mm high, Dineter 100mm

Volume Switch ALPS 100K x 2

Main Electrolytic Capacitors WIMA MKS4 0.47/400v

MSTCOP 0.47/630v

Key Resistor FIVE RING USA

Testing

The 6F2 at the preamp part is a tri-pantode which was first used at the “Guanshi” K-6T pull-push tube amplifier a few years ago. The quality of this tube is certified so. As the reason the testing sample had burned in only for a few hours, it sounded a little tight. But the low frequency was good. The coherence and the shapes of the instruments were good. The air feeling was felt less. The characteristics of the class A tube Amp was basicly right.

We all knowed the indicated specifications for an Amp could not represent the real feeling of listening. A transistor Amp which was signed T/H/D < 0.01% did not must be better than a tube Amp which was signed T/H/D < 1% in listening. The transistor amp was working on the high amperage and lower voltage while the tube amp was working on the lower amperage and the high voltage. The working principle was totally different. The transistor amp easily made singles harmonic waves but the tube amp easily made doubles ones. On the other hand, the power storage of the tube amp was always better than the transistor amp. So in normal situation, the listening feeling of the tube amps were better than the transistor amps.

The protection on the circuit of the Focus-836 was simple and efficient. I had let it working for a whole day, but it was still keep the acceptable temperature. It used a circuit board structure, so you must take a little strength to change the tubes. The tube voltage was working on 350v. It was belonged to the transistor half wave supply mode. It was said that this kind of mode had more music taste than the others. But it would also made noises easily if the design was not good enough.

When the KT100 were used on the amp, it had the max power of 18w. According for this, using EL34 the power was about 12w, 6L6, 8~10W, 6V6, 5~6w. It was estimated that the Amp was working ont self-bias mode. This kind of characteristics was also reflected on the preamp tubes. I had a few British Ediswan ECF82 and 2 American Sylvania 6U8A. The ECF82 were new tubes which had been used only for a few hours. This kind of black shield tubes sounded sweet and amooth. The high frequency was better than 6F2, but its strength was less than 6F2. compare to the ECF82 and 6F2, the 6U8A’s presentation was on the medium of these tubes. It has better power, large sound field but it less smooth.

For the power tubes, I had taken a risk to test 6Y6G. its cohesive force and shuttle force was the better but the volume point should be on one clock. I also had used ECF80 on testing, but it looked couldn’t work well.

The amp could push bookshelfboxes which sensitive was in 85dB to 90dB. When the volume was on 9 o’clock, the sound pressure was felt enough in a 15m2 room.

Actural Efect on Performing

Through actural testing, I felt the amp had these advantages: more details, better dense and balance, transparant, fine and smooth, real and relaxing, sweet and natural. Even listening for a long time continuously, I didn’t felt a little uncomfortable. In a word, the amp could represent the characteristics of the class A tube amps.

Using Focus-836 listening, I felt a beautiful and clear picture of the sound. It’s natural and actively. High frequency was both sweet and smooth. I could hear more detail of the strings. It could make the music vigorous and vivid. The sound lines were fine and sharp. The voices expressed sweet and smooth, thick and lustrous, which let me feel comfortable and relaxing. The drum music was was fast and booming when using the powerful tubes. The greatest advantage of the Focus-836 was you could change tubes with your heart. It made me very fun.

Summary

As I was testing, I had not only changed different kinds of models tubes, but also had compared to an other amp of FU7x2(20w) and a DENON 100x2 amp. I had also changed many loudspeakers to listen. Every speakers gave me different feelings of music. The three ways speakers had mor detail than the two ways speakers. If the four ways speakers could be controled well, it was better than the three ways speakers.

Through testing, I felt the amp was really a good design. To the 300B single-ended amp users, I advice you trying the Focus-836. You will feel the power more larger and an other kind of feeling of dignified and elegant charm in the music. For the audiophiles who have many good tubes, it’s a good choice to test them. Don’t miss it. It provides a good terrace to change and play tubes.

Digested From《OVERVIEW OF CONSUMER APPLIANCE》2007.11 Writer: MinSheng