因為部老爺PAS 有輕微電流声，拎咗比朋友check, 最后發現有一粒 AB 碳阻印10k, 度出來係14.9k， 真係離晒譜。

特此多謝華哥~

You're welcome!

Thx 伊雲士兄

Inputs:

3 stereo low level: RIAA phono, NAB tape head (7-1/2"), "Special" (optional second phono, microphone, etc.).
4 stereo high level: FM-AM, FM-Multiplex, Spare, Tape.
Outputs: Tape output. Audio output.

最後修改時間: 2016-04-09 12:32:04

玩咗兩個月全石，換番PAS-3, 膽機既獨特魅力又真係幾及引。
有冇師兄知道個 "special" 輸入應該駁乜?
謝謝!

Jimmy 兄，應該啱~
不過我冇試過。

請問 dynakitparts.com 賣嘅 240VAC kit

http://www.dynakitparts.com/dynakit-products/amplifier-kits

是否唔合香港用?

Thanks!

FYI

http://www.diyaudioblog.com/2011/04/starting-norman-koren-dynaco-pas-preamp.html

Jumie 兄，請問係點改?
謝!

Dynaco精神
大改特改

謝謝鼓勵

小mod小改 小兒科嘢啫 唔鍾意亦可还原
放心做吧

小弟買了回來的機便沒有貴平，駛了的錢多少也是駛了，現值都是零。
希望儘量保留是以欣賞角度去看前人的智慧。
Dynaco PSA 有mod 料，有全新外殼賣，與其大改，不知從頭切一部更好。
當然，有能力改也是樂趣。

不是貴机 "保留原作"意義不大
改得就改 呢D先係DYNACO好玩地方
我都"重生"過好多部了

諗緊換走晒背面d RCA 定改tape 做多組output。因玩喇叭仔冇subwoofer 真係爭好多。
但又想儘量保留原作。

這部連label 也沒了。
后面的輸出輸入其實不用那麼多，但卻只得一組輸出俾后級，玩bi-amp 或subwoofer 就麻煩，要諗下計。

Introduction:
The venerable Dynaco PAS is perhaps the most famous stereo preamplifier of all time, Much like the Dynaco ST-70, it introduced the magical sound of tubes to thousands of audiophiles throughout the past decades. The PAS is still a popular model, both in stock form or as a platform to be tweaked and modified.

The Circuit:
So what is a Dynaco PAS? There are three iterations. The PAS-2, the earliest stereo version, with circuitry taken from the PAM-1 mono unit and a gold faceplate with brown knobs. The PAS-3, with a more modern silver faceplate with matching knobs. And finally, the PAS-3X with improved tone controls. This is a full-function preamplifier with tone controls and inputs for phono, reel-to-reel, tuner, and others. Gain, of course, is higher than modern preamplifiers since this was the days before high output CD players.

All PAS preamplifiers share the same circuit: For the phono stage, one 12AX7 per channel, each section in series, using loop negative feedback connected to a capactior and resistor network to provide the RIAA equalization. For the linestage, a 12AX7 per channel, each section in series, utilizing loop feedback to lower distortion and provide a low enough output impedance to drive cables into a high impedance input of an amplifier. Power supply rectification is handled by a 12X4 tube. Filaments for the 12AX7s come from a voltage-doubler circuit, which - as the namesake suggests - doubles the supplied AC voltage from the transformer and smooths it out to DC. Having DC on the filaments also helps to reduce hum.

Modifications:
The number of changes that can be done to a Dynaco PAS are practically innumberable. There are simple improvemnts on the stock circuit to full-bore modifications that use nothing but the chassis and power transformer. Personally I prefer to keep the general character of the PAS intact, but improve the weaknesses to the point that the preamplifier can be used as part of a high-end system. Some of these mods are simple to perform but many will require experience working with high voltage electronics. Be warned! If you don't know how to solder or understand electronic safety, please have the work done by someone who does.

Bypassing the tone controls [link] is an easy modification with a great improvement on transparency and detail. Since the signal path is shortened and the effect of various capacitors are removed from the circuit, the overall quality take a jump for the better. Bypassing the loudness switch is also a good idea since these older slider switches can be troublesome.

Signal capacitor replacement is another simple change that benefits detail. treble extension, and transparency. The stock green paper capacitors are hardly high-end fodder. As to what capacitor to use, that is up to the individual user.

** copy from web **
http://6streetbridge.blogspot.hk/2013/02/the-most-important-preamplifier-in.html

銅絲刷亦未能把制紋內的污積清除，但經一番功夫後，已比初開箱時好得多了。

謝兩位前輩分享

我經手過廿部以上DYNACO前級 好好彩幾乎全部跟機D德仔X7都重好強冇短命