1. The premise .
I state that I have never been, in my passion for hi-fi, particularly interested in tube amps. I had always regarded as a thing of the past, a sort of Jurassic universe created by old fans, unable to give evidence of progress, represented by FET transistors, and various amenities.
I've never even been a fan of electronics, except in fairly superficial, searching in the solid construction and good sound equipment, rather than the refinements circuit at any cost.
so happens, quite by chance that one day last year (2003) find me to read web pages of the site www.audiocostruzioni.com , a site that shows very young then several pages of DIY, doing, as they say, drop the eye on the achievements of Giuseppe Marotta, enterprising fan from Sardinia, with an obvious passion for the valves and circuits OTL (Output Transformer Less ).
The enthusiasm that the few lines they are send to the player who decides to contact him, helped by the interest in this plant from hearing a friend of Brescia, made with ARC tube pre, tube monoblocks Unison Research (with 845) and high-efficiency speakers DIY.
The interest of the undersigned is directed (God only knows why) on two monoblocks based circuitry and power valves Cyclotron 6C33C-B, valvoloni Russian military dimensions exaggerated. But maybe the size is, unconsciously, in making decisions.
are taken the necessary agreements between the parties and the project starts with the basic requirement tied to the construction of an amplifier (two, but ...) capable of driving the best two speakers B & W Nautilus with 90 dB sensitivity.
Here are a few clicks on the initial draft, with the description of the designer.
OTL 6C33C
I've always been attracted to the readings on the tube amp otl, describing amplifiers with low distortion, with an extremely wide frequency response with low damping and extraordinary. Otl amps are significantly different from all other valves, starting from their typical pattern used by most of the output transistor and the highest technical level due to its lack of output transformer. Of course, in a spirit of DIY I switched from reading the facts and as the first prototype I built using a final four 6AS7 OTL stereo per channel the scheme used has been published in Glass Audio 02/90 by Bruce Rozenblit.
The end result was considerably above what I expected! so much so that when I did listen to its present owner, my friend Antonio who wanted aIl'istante, the prototype is working for about four years and drives a pair of BW 801 series in the first suspension of 85 db efficiency, and notoriously difficult to drive, the sound is the highest level.
Encouraged by the excellent results I have gone to study a scheme and to build my final two otl monoblocks using Output configuration Cyclotron patented Electro and recovery from atmasphere and Graaf.
I used as an input 12AX7 preamp-sfasatrice followed by a voltage amplifier and 5687 as a pilot in that 6S4A cathode follower configuration 6C33C finals, the first three stages are DC coupled and ' single coupling capacitor is between the 6S4A and 6C33C.
otl Configuration is pure, without capacitors between the power tubes and speakers, and how to use a fast fuse protection that stops in the unfortunate event that it inhibits one of the final.
The sound is immediately striking for a bandwidth very extensive, with significant benefits in mid-high range and bass amp with a damping from a transistor. Among the great qualities of sound and space and depth with incredible detail, listening to the lyric soprano voice is exciting, with no inflection in moments of high dynamic range.
After I listened to the various configurations of tube amps are my favorites and have been operating for two years without any failure or replacement of valves.
2. The implementation of the project.
The project therefore originated from the preliminary draft, but will the small adjustments during gestation (long enough for different problems).
12BH7A A valve replaces the original 6S4A (from single to double triode) and 5751 (selected) replace the 12AX7. For the rest of the pattern remains unchanged.
Discussion "aesthetics" of the project is large and involves a variety of choices which will then be abandoned for the sake of simplicity and cleaning circuit.
Carry some photos of the construction of the final.
3. and there was light ...
Finally, after much discussion with regard to the final product and a long wait by the undersigned, the finals are completed in May 2004 after a long test of goodwill on the part of Joseph to fully evaluate the functionality and meet the design parameters.
I finally arrived at my house in June, ready to be tested on my system. In fact, compared to damage caused by the transport of cargo to our place (sic), the first week will be spent as a self-test on the installation of my son, to verify that the damage found is the one and you will not others are ... Trust is good, but ...
Here are some photos of the finals, in order to highlight also the circuitry interna.
4. listening and judging.
my total inexperience in the field tube led me to believe that a tube amp, needed a break after all modest to express their credentials and their sonic characteristics, as well as experience in transistor led me to believe.
It took three months instead because the amplifier could be considered stable in performance, without significant changes in overall timbre and detail ... You learn something new.
should be noted that in the meantime, I was also equipped with tube preamp (Conrad Johnson). But its origin from the flea market had apparently made no use running in, sviandomi from these fundamental aspects of amplification and tube.
The impact of the two units was therefore absolutely intense, deep, and extremely long time to get to give a serious assessment and ultimately to the units.
I require a final warm-up "important" by about half an hour, to express themselves better. Early plays can only raise concerns and stomach aches ...
The most immediately striking feature is the great sense of breath that the two objects return a scene open, airy space with a significant. Excellent reproduction of the depth of the stage and location of the various musicians and performers, of course, where records permit ...
This feature is one that puzzled me more, giving me a feeling of three-dimensional scene to which I was not accustomed ...
The mid-range, as expected, I think, by any tube amp, is wonderful, with an impressive sense of reality and dream at the same time. The voices, both male and female, are reproduced beautifully, with fine detail impeccable. I think the voices of Freddie Cole and Diane Schuur, rather than Allison Kraus or Dee Dee Bridgwater, absolutely real.
The treble is slightly behind the average, but with good extension and detail. This feature certainly helps to balance the issue in mid-high range of Nautilus, while giving a very convincing sense of depth. The extension above is absolutely correct, but how to give it to the listener is very gentle and never annoying.
The bass is the element, in my opinion, more convincing. After 30 years of solid state and a series of convictions related to the rubbery and the low accuracy of the low range of tube amps, I was absolutely thrilled by the quality of the lower end of these amps. Extension excellent, very good control and the "right" roundness in the reproduction of acoustic instruments, which means that even a musician to recognize the sound of their instrument as if he was playing. I do not think I can say that the bass is extremely fast, but I can say that have never been convinced that the low range, with particular reference to instruments Acoustic is faster. The important thing is that it is well controlled, without queues and unnatural that it is "real." I would say that in this case, the objectives are fully achieved.
Turning to an analysis of the behavior with the different musical genres, I can say that the traditional jazz and electro, with a preference for small groups, is the death of these amplifiers. I think the impressive realism of the Riverside recordings of Bill Evans with Scott LaFaro on bass seems that there in front of me ... Just as the trumpet of His Majesty Miles Davis' Kind of Blue "or the poignant sadness of that of Chet Baker in "Chet". The Realism is, once again, gorgeous, with an almost perfect reconstruction of the stage. Even incisions less efficient as the latest Diana Krall ("The Girl In The Other Room" or "Live in Paris") are still played with great consistency and realism, giving the voice of the Krall a little more ...
With serious music, classical to speak, the yield is also excellent, again, above all, the ability to create a virtual scene totally believable. Listening to one of my reference discs (Rodrigo - Concierto De Aranjuez - Carlos Bonnell - Decca) implies an emotional high. Bonnell's fingers move over the strings with a new grace, restoring the soul of the musician and his guitar. Also excellent performance of the reference discs Audio Review (Stork bravo!). Excellent performance of "Bolero" by Ravel from Reference Recordings, a growing absolutely perfect. With these tracks, turning up the volume to levels of risk to the health of the ears, make some sign of deterioration in sound performance, which is manifested by an increase in grain, a loss of fine detail and a slight hardening of the treble. Probably the limits of power combined with the sensitivity of the speakers play their role in this. Excellent yield piano, which has a breathing space and an absolutely remarkable. Also excellent yield of old instruments, from the excellent CD attached to a recent Audiophile Sound. As I said, are the major weak point of the full orchestral instruments, but only when played at insane levels of listening. Limitations intrinsic to a house, there are no problems ...
The yield with the pop-rock music is, as you can imagine, quite variable, depending on the gender play. Certainly fans of hard rock and heavy metal certainly prefer muscular final solid state, able to provide the infamous "slap in the face" but with other genres more "educated" the yield is still a high level. I think the inevitable TDSOTM or the beautiful voice of Peter Gabriel in "Selling England By The Pound" or "So", but also to the West Coast of CSN & Y or jazz-rock of Joni Mitchell. Also excellent yield with the music of our local author and I think Exalted "Anime Salve" De André or the beautiful "Songs crank" by Capossela, where the final two are able to re-create a sound space absolutely real and musicality.
At the end of all this talk, what to say? First an observation: the Audio AM my beloved are off since August, with a little 'of sorrow, but with no regrets or failures of type "music".
The two final OTL has improved greatly over time, demonstrating to the present quality music from all over: a great ability to reconstruct the virtual stage, excellent frequency extension, control, realism and ability to involve the listener ... What to say ? I am convinced that to treat one of the most well-chosen purchases of my career as an audiophile.
THE THORENS 124
(DI SIMONE PADLOCKS - ROME)
What can I tell him that do not already know? It 's my favorite turntable, I love its shapes, its complexity, and nothing in its construction, in my opinion, it was left to chance.
His system of combined belt-pulley is extremely reliable.
Upon ignition the engine begins to rotate, transmitting the rotation of its shaft by means of a strap, keyed to a satellite. At the same time the pulley rubber, which off a record player is in position, goes to rest on the satellite motion and the inner edge of the plate, allowing rotation.
This is roughly the operation of the turntable .
This is a subject where precision mechanics plays a fundamental role, and if you do good maintenance, a turntable is virtually indestructible.
The first and most important parameter to control the temperature of the engine.
Let me explain. By varying the temperature of the engine tends to vary its speed to that reached its operating temperature stabilizes. If the engine has never been revised, the internal friction means that it quickly reaches its operating temperature, but it is also true then that will tend to cross it. In other words, make the engine work without adequate review results in engine overheating and slow "cooking" of the windings, which in the long run due to engine failure. An experiment you can do is turn on your TD124 and touch the engine after a couple of hours, if the contact heat is high, it means that the engine presents an anomalous situation of friction.
Sometimes even after a thorough review can not solve the problem, partly because of damage to the engine.
The review is therefore a task that the engine to last longer over time in optimal conditions.
I think it is useless going to invest a lot of money for such a machine, looking after just make sure you use the correct oil for the post, having replaced the pulley or the speed of rotation is perfect if you do not you review the heart of turntable (motor).
maintenance operations described below require some manual dexterity and familiar in the disassembly and reassembly of parts. However, we recommend great care in the conduct of operations that will be described below, in order to avoid errors that could be irreparable.
We accept no responsibility for the operations described, nor about the possible risks to humans caused by operations carried out under conditions of non-security personnel.
First you need to PULL THE PLUG IN THE POWER.
REMOVE THE ARM WITH THE BASE ON THE PLATE AND FINALLY THE MOBILE internal part of the
NOT REMOVE THE PLATE WITH ALL YOUR PIN, YOU may scratch .
THE TIME NEEDED FOR THE OPERATIONS IN THE FOLLOWING DEPENDS ON HAND 'OPERATOR. FOR AN AVERAGE PERSON EXPERIENCED THE TIME is around 3 hours.
1. The maintenance of the pin
removed first of the three screws at the seat pin (1) and remove the bottom plate of the turntable spindle gently pressing down the turntable. Without the lower plate and then proceed to wash the seat of the pin, using a lubricant / degrippante Svitol type.
It then builds a big buffer, using wadding quality (which does not lose the fibers) and Spedding wooden kitchen and cleans the seat of the post. With my dough (found on eBay) and then proceed to polish the only spindle, taking care not to deposit the paste at the bottom of the post where is the ball. Replace (or replaced with Teflon element) the tablet. Do not relocate at this stage either the pin or oil, which will be repositioned at the end of the maintenance cycle.
2. The engine cleaning
Now for the maintenance of the engine (3).
must first remove the aluminum upper pulley (5), that, so to speak, attached to the spindle motor and moves the belt. To disassemble, loosen the screw, or screws, side present. It then pulls up the metal pulley using only his hands. Never use tools for leverage. If the pulley were to resist, make sure that the side screws are loosened properly. At this point, it should give small taps, with a piece of wood, to down along the engine axis. Do not hammer the sides to prevent tilt of the axis of the engine. Then remove the metal pulley.
You then unscrew the screws which hold the base of contacts (2) positioned next to the engine so the base of contacts will be free from the frame. This allows you to pick up the engine without having to unsolder all the wires!
us lower then the turntable in the plan and remove the retainers of the engine (these are the three rings in the rubber match of the suspension) while the other hand support the engine, which otherwise would fall. Now the motor is free; You can then lift the turntable as shown. Need to get the thickness to the threaded rods in place, they are able to safely support the weight of the turntable without flexing. Place the turntable vertically and so the left hand resting on the table.
also Get a thick piece of foam.
Getting the right size of a wrench to unscrew the bolts of the engine. Do not try to unscrew the screws with the screwdriver, they are very tight and the only result would be to ruin the screws. Once you unscrew the screws, recompose the screws removed, pointing to the position of washers and long pins.
Open the engine and pull off the underside of the engine if the rotor so that follow you in this down time is what you'll see a disassembled engine.
WARNING! SLOWLY OPEN THE ENGINE! Sometimes it's' Captain WINDING that the sleeves are glued UPPER AND LOWER. A SLOW OPENING ALLOWS THEM TO THE NECK SMOOTH top and bottom.
In the two photos above see two engines with different degree of wear, the left one has a critical condition, while the right is a perfect engine, like new (note how the wires are clearly visible winding ).
ENGINE It consists of 4 parts:
the bottom cover, IL ROTOR, THE PACKAGE IS WINDING, the top cover.
should hours to extract rotor very slowly, taking care not to lose the ball located below it, is extremely small! If not visible, no biggie now! Sometimes it stays stuck inside the home, if that were the case we proceed by filling the seat of Svitol, tap it on a cloth to cover down. In this way the ball will fall into the cloth.
If it still does not free to use a small screwdriver with a magnetized head and try to remove it.
I never happened to find an engine with no ball underneath. If the ball is in his seat on the rotor leave it where it is, without removing it, and place the rotor in a safe place, so do not take shots.
Then close the headquarters of the bush with wadding.
CLEANING LOWER BUSHING
wash the underside of the motor with a soft brush and lubricant / degrippante (the usual Svitol). It does not matter if it gets wet the bush, The important thing is not to dirty the inside of the bushing.
One can also use a small container and wash with degrippante the parts removed.
Now use the cotton swab with the traditional and polishing compound to clean the seat of the bushing. Just a little product, without exaggeration, as the polishing compound has a very light abrasive action. Observing with a small light bulb that the bush is quite clean. not use any type of abrasive paper .
If during this operation, the bush moves, it does not matter, as it has articulated and is chuck.
If there are stains do not try to remove with any kind of tool.
Now take a clean cotton cloth and place the piece above it, and fill the bushing with the Svitol full height and let it soak for at least 10 minutes, slowly and tend to decline in the level percolerà the liquid on the cloth of cotton bush and filled again with the use of compressed air (up to 2-3 atmospheres) try to push the liquid into the seat of the bushing. (I use a plastic gun with a nozzle to avoid damaging the bush), in order to let all the sludge from the bottom and sides the bush.
Notice in the picture the presence of solidified oil and fat to bring all of the little plastic pill that can not be replaced if not raising the rivets. (Operation strongly recommended !!!). E 'visible even one of the two pads.
repeat this operation, if done properly the fluid input and output will tend to show the same color. When done, sprinkle still air until it comes out more liquid. The bush must be completely clean and dry and, in particular, the felts have to dry interior.
Place the cloth in the lower level. Take the engine oil and, using a cotton swab soaked in oil, drop a few drops in the bush, to fill half the thickness of the bushing itself. After a couple of minutes, the level will drop, meaning that the pads are re-absorbing the new oil. Repeat until the level stabilizes at half thickness. Do not proceed.
Putting aside the piece and then proceed to the cleaning of the upper bushing.
UPPER BUSHING CLEANING
The cleaning of the upper bushing is not simple, it is necessary to lift the top cover by sliding ii motor wires through the hole in the lid
Wipe again with a cotton swab and polish.
degrippante between the spray and the metal around the bush, operating from inside the headquarters of the bush, and dry with compressed air. When dry, the bush should be added to more than a couple of drops of engine oil. Make sure they are now well, since too much oil during use of the turntable (ie hot engine) would fall on the rotor could, causing damage.
CLEANING ROTOR
Now take the magnet rotor with a screwdriver and remove the ball, polished only two pins of the rotor.
If the central part has rust, remove brushing with a medium hard brush, carefully and without polish, and often there is a black stripe: Do not remove it!. Thoroughly clean both sides of the rotor with the polishing paste, clean thoroughly with a cloth, with particular care with regard to the ball seat (using a cotton bud).
Getting so fat viscous medium. No matter what type, because it has only to cement it must, in short, to anchor the bead seat of the rotor. It serves a very small amount, to be applied over the groove. Finally, place the ball.
If the transaction you think you can avoid risky to remove the ball, simply by rubbing the rotor.
If the procedure was successfully performed so far, you will be half full of oil in the bushing bottom cover of the engine; if the level had come down to fill to reach the level of half bush and no further.
Put the ball on the rotor should now be VERY SLOWLY reinsert the rotor in the bush to avoid them losing oil. Should be given time to air out.
If oil comes out when putting the rotor on the inside of the container of the engine, it means that you have put too much. Again, disconnect the rotor, clean the inside of the engine and remove the excess oil, then repeat the operation. To remove excess oil is a perfect cotton bud dry, inserted into the bushing absorbs excess oil. It 's normal, however, that the oil leak from under the engine cover in the initial phase of operation to reposition the rotor.
Do not worry if the bush below the rotor moves while Rethread.
Now the engine is ready!
Close the engine putting the rotor in the top cover, it is important that at this stage the motor and lower the rotor remain in contact, so that the ball can be thrown out.
Replace the screws and the upper pins, tighten by hand.
Replace the top plate, making sure that the notch corresponds to the position of the output cables.
The plate should be mounted in sequence just after placing the screws, because if reassembled with screws tightened, it would be difficult to position correctly. Finally tighten the screws, but not permanently.
The brasses, as mentioned, are self-centering, then take the ends of the rotor and the axis move slightly to the left and right (Not to be pulled up), to settle the bearings.
tighten, without exaggeration, to avoid stripping the screws.
HAND TO TURN THE ENGINE TURNS TO CHECK THAT PERFECTLY.
If all operations are carried out properly, the engine must have a perfect rotation. Replace now the engine in place, reassemble the base of contacts complete with lid.
IMPORTANT! Check the various threads do not touch each loro.Potreste Indeed, while cleaning the engine, some have inadvertently twisted cable.
re-aimed the engine, place the turntable in the horizontal
3. The cleaning system of pulley-satellite
Remove the pulley means of the metal device placed above it. These are two small screws, which are both loose. for the 124 / I; for 124/II should instead remove the screw shown on the bracket.
Once removed the washer and the pulley should be cleaned with the polishing compound in which the pin is stuck pulley. Clean with cotton buds and usually a bit of polishing the inside of the bearing of the pulley.
The operation v made to gently because the dough into a light abrasive.
Remove now the satellite in aluminum, first loosening the screw 7, the satellite can now be withdrawn. Clean the home of the satellite with the polishing paste and cotton buds.
Wash then spray the home with degrippante and dry the seat with compressed air and cotton buds. Finally, clean the hub of the satellite with the polishing paste, NOT REMOVE THE BLACK PART YOU SEE IN THE SATELLITE! THIS IS NOT THE DIRT, BUT A BAND MAGNETIC!
hours Put a few drops of oil in the headquarters of the satellite and have it down slightly. Then remount the pulley. In Model 124 / I, during reassembly, interposed between the metal device and a card from the pulley 120 gr./m2, this serves to distance the metal device from the pulley, that otherwise might turn braking. Of course, should be removed at the end of assembly. Replace the metal tab 7.
After cleaning the motor, pulley and put the satellite into the seat belt, connect the turntable and make sure everything is okay. In particular, examine it carefully, as I said, that the wires of the engine which do not touch each other.
Turn on the turntable, make sure that everything is in place, turn off and unplug the power again.
hours Put the oil in the pivot of the turntable: it serves an amount equal to one teaspoon abundant. Do not overdo it because too much oil is useless.
again lift the turntable and turn the speed knob end located above the center ignition, until the metal plate underneath is in the middle (the pawl 8 is at the red dot) .
This is the central location of speed control. SO NOW horizontal turntable and mounted the main course, without placing the screws that secure the pin .. Turn on the turntable in position 33 laps. If you run correctly As written the turntable should have a rotation speed higher, sometimes much, it depends on how dirty was the engine.
not attempt to adjust the speed by adjusting the fine-tuning. If the speed is increased, again removed the plate and approached the magnet (9) to the satellite, to reduce the speed of rotation. Take a series of tests until the turntable takes a speed close to the correct value. Only then, turn the fine adjustment of the speed.
Now the turntable is ready, let it run for at least 1 hour and then clean, with no raise, the bottom of the engine. It 's normal that in the first days of use there is a slight oozing of oil. A hot engine, avoid carrying the turntable. This rule is valid forever.
Finally I recommend that you clean the contacts of power, only for model 124 / I and replace the condenser ignition engine, then cleaning the bulb, taking care not to break , strobe and mirror.
All I've read comes from my personal experience. I have reviewed dozens of Thorens 124 and I gained a good skill.
If you feel you can not even remotely of the steps, do not do it!
I do not assume any responsibility for damage to equipment and people .
If you think you need my help, I can carry out the review on your own, or contact an authorized repair center that knows specifically the turntable. This is not a modern turntable reigns electronics, but an object where 90% of the work is purely mechanical.
Piu 'an electronics expert is an expert in mechanical engineering.
For those who are about to perform their own maintenance, so is experience, dexterity, ability to reconstruct any missing parts. Each unit has its own history and its own special problems
Issues such as the breaking of a wire while the engine is overhauled, the switch does not go that speed, the replacement of a bushing of the motor, a broken spring are quite complex to solve, but often to be found.
What I have described in these few rules is the minimum level of maintenance which should be submitted to the Thorens 124 so that it can give you many hours of great music.
Other things could be done, but I prefer to stop here to not make it too complex work.
Usually, the first revision of a motor, shall verify the temperature over 3 hours with a temperature sensor. After I submit the revision to the engine test lasting on average 6 to 8 hours.
I advise you, before starting work to get everything you need to review, in addition to my pasta and my oil, of course!
If you have any questions for me about the maintenance, do them before starting work!
Simone Lucchetti
To contact Simon for more information, write to simoluc@tiscali.it
