ترانس های صوتی انواع مختلف دارند که در سه بخش در طراحی بکار میروند ، یک در منبع تغذیه که برای کاهش یا افزایش ولتاژ 50 هرتز برق هست که این ترانس ها فقط تحت یک فرکانس اونم برق شهر کار میکنند و وظیفه انتقال سیگنال صوتی رو به عهده ندارند، در قسمت دیگر ترانس های خروجی هستند که در ترانزیستوری هایی مانند مکینتاش و در اغلب لامپی ها بکار میروند. این ترانس ها هم باید در محدوده فرکانسی 20 تا 20 کیلو هرتز پاسخ خطی داشته باشند و هم امکان انتقال صحیح سیگنال صوتی رو در محدوده خطی توان داشته باشند. نوع سوم ترانس بین طبقات مدار بکار میره (اینتراستیج) که برای تطبیق امپدانس و جدا سازی بایاس دو طبقه استفاده میشه. تا اونجایی که من میدونم آئودیو نت و Sakuma هردو فقط از کوپلاژ سلفی (همین اینتراستیج ها) بین طبقاتشون استفاده میکنند و سراغ خازن نمیروند.
لینک های زیر مطالب جالبی رو در مورد ترانس ها بیان میکنه :
MC Transformer Listening Notes
* I had initially decided that Jensen Transformers would be a great choice because I’m using them in updates for Counterpoint gear. But since there are several choices on the market it would be inappropriate for me to design in the Jensen MC transformer without giving the other offerings a careful listen. After all, I know that power transformers vary all across the board in how they sound, resistors all sound different, capacitors, power cords, tubes and wires all affect the sound. It’s pretty unlikely that a transformer in the signal path would have no effect.
To that end, I assembled a stable of MC transformers from Lundahl, Bartolucci, Stevens & Billings, Jensen, and Sowter — these are the “good ones” as best as I can tell (if someone knows of something else I should try, please advise . . . but it has to be a standalone OEM model in production from a company that is in business). I selected 1:10 (+20dB gain) versions from each manufacturer, which is a good match for the 0.4mV cartridge in my Versa Dynamics turntable. The transformers were mounted in identical boxes so I could not tell them apart. Each box has a set of input and output jacks. The boxes were identified with labels: A, B, C, D, and E, and I did not know which model was in which box.
The results are not complete — there was a problem with one of the transformers and a replacement is being sent.
In terms of what I hear, transformer “C” is the winner. Sonically, it outperforms the others hands-down. It outperforms them in so many ways I can’t even list them all. Suffice it to say that in terms of layering, transient decay, rhythm and pacing, palpability, and sheer musical involvement, this is the one you want in your system, this is the transformer I want to use in the WV. But there’s a problem: it does not have as good a frequency response as the other units: it rolls off rapidly below 20Hz, and has a slight 0.3dB tilt upwards from low to high frequencies. Sonically, the bass was deep, detailed and tight; the treble was sweet and incisive.
Transformer “D” had a very pleasant, mellow sound. Smooth. But compared with C it was a little boring. Transformer “B” was darn good sounding, but after hearing C it clearly comes off as second-best. As mentioned I don’t want to identify the transformer yet, but I will say that Jensen makes darn good-sounding transformers, and they has the most extended frequency response.
Unless the replacement transformer kicks C’s butt, C is staying in my system, and is the one I will recommend in the WV. The amount of pure sonic pleasure it provides is far greater than what the others offer, and if anyone wants a better-measuring part, the other transformers will be available on a per-order basis.
* November 2005. Bit of a glitch in the MC transformer listening tests. The replacement transformer arrived, but it also seemed to have a intermittent fault, which led me on a wild-goose chase until the trouble was traced to a Cardas jack with a low-resistance path from hot to ground was located. The last place I’d expect to find such a fault.
But it turns out that I want to burn in the transformers before making a final decision. According to the Lundahl distributor, transformers with amorphous metal cores, such as theirs, need a few hundred hours of running in before they sound right. So for the past week I have been running pink noise into all six transformer boxes, starting at 1v and slowly decreasing the levels day after day so that by the end of this week they will be down to just a few microvolts. Then I’ll listen again and will be able to make a final determination.
* December 2005. All the glitches are fixed, all the listening is done, and here are the results:
o Two transformers stood apart from the others in how good they sounded. Of the top two, the Sowter 8055 is the winner, but not by a large margin over the second-best. Both this transformer and the Lundahl LL9206 (below) not only had great sound, but unlike the rest of the pack, only these two had focus and pacing and emotional involvement. The Sowter 8055 was the most fun to listen to, had the best soundstaging, the best pacing and slam. The Lundahl LL9206 trailed the Sowter 8055 by only a small margin. If the 8055 is a “100” then the LL9205 is a “90.” I would personally be quite happy with either transformer, but in a direct comparison, the 8055 surpasses the Lundahl in every respect.
o The rest of the transformers were not as good. None of them had any rhythm or pacing, or the emotionality of the 8055 or the LL9206. In this grouping were the Jensen JT-44K-DX, which sounds a bit coarser than the two best units; the Stevens & Billington TX-103, which has a bland unexciting sound; the Sowter 9570, which presented the tiredest-sounding rhythm sections; and the Bartolucci GIBA68, which is notable for having an odd rising frequency response being tilted up .5dB at 10kHz compared to 100Hz — and it sounded that way, offering a lightweight, faster but thinner sound.
I did learn an interesting fact about loading MC cartridges when using MC transformers. There is a good-sounding way, and a great-sounding way to do it. I’m not going to write about it here, preferring to keep it as a trade secret, but I will use it in the WV preamps.
Another interesting tid-bit is that MC transformers, despite how complex they are, sound more alike than tubes, resistors, capacitors and wire. With those other parts, I expect to hear changes in tonal balance shifts, graininess, presence, bass artifacts, and edginess. But with the sole exception of the Bartolucci, which possesses a measurable and very audible frequency response aberration, these transformers sounded very, very alike in those areas. Where MC transformers differ seems to be primarily in terms of emotional involvement, presence, rhythm and pacing.