직결앰프

http://www.my-audiolab.com/index.php?mid=KDK_Column&page=5&document_srl=34187

일반적으로 Coupling Capacitor 를 뺀 회로를 말합니다.

Loftin White 의 2A3 Amp 가 원조라고 볼수 있습니다.

 

직결 또는 DC Amp 라고 합니다

일본의 金田 씨 가 전문가 입니다

 

아래 참고

 

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dcamp.biz

http://dcamp.biz/?page_id=13

金田先生 ご紹介文

”For the English , please kindly scroll this page down”

世の中には生の音楽が聞きたくても，なかなか聞けない人が大勢います．その様な人たちの夢を叶えるのが，オーディオであり，DCアンプです．DCアンプは「音楽を再現する」と言うただ一つの目的のために，生まれ，進化して来ました．同じアンプでも利益を第一目的にするメーカー製アンプとは，根本的に音が違うのは，目的が違うからです．

DCアンプで音楽を聞くには，DCアンプを製作しなければなりません．製作には色々ハードルがありますが，特に大きなハードルはケース加工と基板製作です．ケース加工のミスはすぐ発見できます．致命的なミスでない限り修正もできます．しかし基板製作のミスになると，全く動作不能の基板からミスの箇所を見つけるには，ある程度専門的な知識と感，それに根気が必要です．逆に基板さえ確実に動作してくれれば，外部配線を確実にするだけで，必ず完成できます．外部配線のミスは基板の内部と異なり，丁寧に見ていけば必ず見つかるからです．この基板製作の強い味方をしてくれるのが萩尾 正己さんです．

萩尾さんはソフトウエア技術とハードウエア技術の両方に精通している，希に見る貴重なエンジニアです．何よりも大事なことは彼自身，列熱な音楽ファン，オーディオマニアであり，永年のDCアンプファンなのです．彼はDCアンプの音をこよなく愛し，一人でも多くの音楽マニアにDCアンプによる音楽を聴いて欲しいと言う願いから，基板を設計製作し，配布してきました．彼はDCアンプシリーズで最新アンプが発表される度に，基板を独自に設計製作し，試作，ヒアリングテストを繰り返し，確実に動作し，作りやすく，音の良い基板を完成させて来ました．マイコン制御の技術を応用し，D/AコンバーターではDAIをソフトウエアモードで制御し，きめ細かい条件設定と，便利な付加機能を加えて，使いやすさと応用範囲を広げています．

ケース加工ではボール板などの工作機械があると，精度の良いケースが能率良くできるのですが，一般的には難しいでしょう．このような時は「美獅真BF」の中江 清社長に相談してみて下さい．かれの仕事は金属塗装業ですが，熱烈なジャズファン，オーディオマニアで，DCアンプ試聴会を支える重要なスタッフの一人です．迅速に，高精度で美しい加工をしてくれます．詳しくは「美獅真BF」のホームページをご覧下さい．

DCアンプはできるだけ若いうち製作する方が得をします．それだけ音楽人生を楽しむ期間が長くなるからです．一刻も早くDCアンプを製作し，涌き上がる音楽と心を込めた演奏に浸りましょう．萩尾さんがついているから，成功間違いなしです．後はあなたの決意次第です．

金田　明彦　2012年8月

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RECOMMENDATION LETTER FROM PROFESSOR KANETA

In this world, there are a lot of people, who want to listen to live music but cannot due to various constraints.  The solution for fulfilling their dreams is Audio instrument and DC Amplifier.  DC Amplifier was invented and has progressed since its birth for the sole purpose, “reproducing music truthfully”. The sound is totally different with the profit-come-first vendor products. 
This because of their priority differences even though both called simply an amp.

If you want to listen to music with DC Amplifier, you have to make it yourself. In that process, you will face with various hurdles but the amplifier casing fabrication and Circuit-board production will be the most difficult parts.

The case production is relatively easier than the board making. You can find the processing error soon and modify it unless it is a fatal one. But if you make your board wrongly, it requires some expert knowledge, a sort of sense and patience to locate defective point from the completely inoperative board.

In other words, if you make the circuit-board correctly, you can definitely assemble your DC Amplifier by only connecting external wires correctly. Unlike the board-defect locating process, even you connect wires mistakenly, it is easy to detect.  You will find it for sure by only checking each connection carefully.

For the painstaking board fabrication, Masami Hagio is the ideal person to help you. Mr. Hagio is an extraordinary engineer who familiar with both software and hardware technology. Most importantly, he, himself, is a devoted music fan, audiophile, and longtime DC Amplifier advocate. He loves DC Amplifier sound deeply.  He has designed and produced his own boards, 
and distributed them to music fans from his strong desire that is to provide an opportunity listening music with DC Amplifier as much as possible.

Every time the latest model of the DC amplifier series is published, he always designs its board himself. And after repeated prototype-making and sound quality tests, he creates his unique board which works surely, is easy to make and has good sounds.    

He employs microcomputer control technology to his creation. By applying it, DAI of the D/A converter is controlled with the software mode.  And it also enables detailed condition settings and enables to add convenient functions. Overall, he broadens usability and application range by it.

If you have machine tools such as drill press, you can make a fine amplifier case without an effort. However, it is difficult to prepare such tools in general. In that case, please contact Mr. Kiyoshi Nakae, president of the Misima BF Corp. Although his actual business focuses on metal coating, Mr. Nakae is a devoted jazz hound and audio nut. And he is one of the important staffs who support our DC Amplifier preview meeting. I am sure he will help you by providing fine and beautiful case processing service promptly. For the details, please visit his website.

It is beneficial to start making DC Amplifier as early as possible. This because you can enjoy music life longer. Then, let`s make DC Amplifier immediately and let yourself immerse to the exciting music and hearty performances. You do not need to worry, you have no chance to fail because Mr. Hagio supports you.  The rest is only up to your decision.         

Akihiko Kaneta  
August 2012

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PROFESSOR KANETA/KANEDA, WHICH IS CORRECT?
THE ANSWER IS HERE.

We normally call Professor “Kaneta”(金田　先生) as Professor “Kaneda”.

And this may cause you a confusion because you are not sure which pronounciation (Kaneta/Kaneda) is correct.
So, we would like to inform you his correct name first.

THE CORRECT/OFFICIAL PRONOUNCIATION IS KANETA.

In official places, public places, people call him as “Kaneta”.

Please check below picture.

His name wrote as “Kaneta” in this picture.

Also, his signature on DCAmp.Biz is “Kaneta”.

So, in official writings, people call him as “Kaneta”.

THE REASON WHY HE HAS TWO NAMES TO BE CALLED

In Japan we use Kanji for writing our name.

His familiy name in Kanji is “金田”.
And we can read this in two ways, Kaneta and Kaneda.

This is the reason why he is sometime called as Kaneda.

However, again, his official name is Kaneta.
Only in friendly places, we call him as Kaneda in a friendly manner.

KYJ 2017.06.23 01:22

직결을 2단 이상 하지 않는다면, 즉 한단을 그 다음단에 직결하고 또 그 다음 단에는 직결을 하지 않는다면 크게 어렵지 않습니다. 이런 경우 대개 안정적으로 동작합니다. 자작한 대부분의 암프를 이런 식으로 만들었습니다. 그러면 암프가 총 3단 증폭단으로 구성된 경우 대개 카풀링 캪은 1개만 들어갑니다. 암프를 종 2단으로만 구성한다면 카풀링 캪은 사용하지 않습니다.

KDK 2017.06.23 01:48

제가쓰는 PK 분할형 Phase inverter 그리고 Shishido 808 회로에는 둘째단이 직결입니다.

일부러 직결을 피하는 설계도 봅니다. 득보다 실이 크다는 이유에서 입니다.  충분히 이해가 가는 이유입니다.

커플링 캡을 쓰면 전원이 간단합니다.
커플링 캡을 빼면 B 전원으로 변동한 각부위의 B 전압을 재조정 하게 됩니다. 

전원이 복잡해지고 전압도 경우에따라서는 많이 올라 갑니다. 

6SL7 SRPP / 2A3 Single-Ended Tube Amp Schematic

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Loftin-White 2A3 Single-Ended Triode Tube Amplifier Schematic

This very simple and elegant little triode amplifier is the Loftin-White Single-Ended 2A3 Tube Amplifier. The direct-coupled (no coupling capacitors) two stage circuit was designed as a laboratory amplifier in 1929 by the team of E.H. Loftin and S.Y. The input stage is a 6SL7 SRPP (shunt regulated driver). Use a good quality audio output transformer with a 2.5 to 3 k-ohm primary with a rating of at least 5W. Output power will be about 3.5W @ 2.5% THD (OPT 2.5 - 3 k). We have had good results using using new production Electro-Harmonix 2A3 EH Gold tubes as a lower cost alternative to NOS RCA 2A3 Black Plate tubes.

There are a couple items of interest to note with this circuit.

• The bias for the output tube is provided by the voltage divider created between the driver stage load (upper half of 6SL7), the driver stage (lower half of 6SL7) and the extra large cathode resistor (the three series resistors below the 2A3 tube).
• How high gain, wide bandwidth, and low source impedance are achieved with an absolute minimum of parts with the SRPP front end.

Loftin-White 2A3 Single-Ended Triode Tube Amplifier Schematic

The power supply use a 5V4G tube rectifier and C-L-C filtering. 

For more information about power supply design with vacuum tube rectifiers, see Matt's informative article Power Supply Design for Vacuum Tube Amplifiers.