2A3 finally finished

Been planning / dreaming of building a 2A3 for so many months. Money, time .... these are all my scarce resources. Finally, I managed to gather enough resources to try a DIY 2A3 by point to point soldering. It is a great challenge for a person who doesn't know how to read schematics.

Well, money has to be spent wisely -- maximizing my total gains. After all, I am an Economist.

都唔知想咗幾耐切部2A3, 又無錢, 又無時間 .... 等了半年有多, 終於集到一點重要資源, 一於開工.

對一個連線路圖都唔識看的人來說, 搭棚切機是幾有難度 .....

已盡可能將D錢用在應用的地方, 奉行自家經濟學人的理論.

Dear Icefireman,

As Accphoto has said, what for?

You mean a relay type ON / OFF switch Power switch to make turning on and off the Pre-amp safer in a sense?

I use this relay type ON/OFF switch just because it has been sitting around for over 8 months. For my M7, I only got a power switch to turn on the separated Power Supply (Transformer), no ON/OFF switch for the main part.

CAT

Dear AP,

原先是好一點的, 但搭錯了位, 唔電死已偷笑. 再改兩下已無咁好.

Dear WINDWSS,

What is a Passive Volume Control? Can you explain a bit?

CAT

Andy, 你說的是. 好彩我是貓, 有九條命 ... 哈哈.



whh1234, welcome here.

My 2A3 is based mainly on the Sun Audio 2A3 SE schematic. However, I changed the driver tube to 6SL7 instead of 6SN7. The GAIN is less than 6SN7 but should gives better details (hopefully, ha...ha)

Whh1234,

That is why I have to save up $$$ for more than 6 months before I can do it. Actually, it still exceeds my budget a bit.

I have, next to me, an original Sun Audio 2A3 from the local dealer. However, it is also modified using Tango Output Transformer (807 -- old model) and Jensen Ceramic Caps. The filtering is also BG 47uf + 47uf.

After running in for 10 hours, the difference between the two is not that significant already. As my 2A3 uses 6SL7 instead of 6SN7, the gain is definitely lower. I was still busy these days so I haven't much time to do a thorough A-B comparison. Will do that for sure after running in the 2A3 for around 100 hours.

Put it this way, DIYing saves a lot of money. I have heard that a new Sun Audio 2A3 now sells for over HK$ 15,000. Mine is, I think, HALF of that sum.

Oh, I see. Really interesting.

However, I would rather have separated ones ... since I won't be keeping too many "toys" around at the same time.

Thanks for your info.

CAT

whh1234,

Hashimoto is nice as well. I haven't got the chance to listen to one of them but I have heard some good comments about them.

Unfortunately, the Jap Yen is going up and up these two years and the prices of good Japanese products keep rising up.

How much did you pay for the Hashimoto? You got the ones for 2A3, 300B or something else?

昨晚將 D 機搬過吓位, 再開部 2A3 出現 "拍拍" 聲 .....

Power off, 再開, 無 "拍拍" 聲, 但右面隻 2A3 紅到發光 ...

出了什麼問題???

下午再研究 ....出乎我意料 !!

:cry:

Ha...ha..

原因好簡單. 我得閒得滯 .... 將枝5U4G換了5V4...燒咗粒 Black Gate 100uf / 100V.

一看見現藍光我就估電壓有問題 .... 因parts少, 較易 check出來.

Thank God, 我重有一兩粒 spare. 換番之後唔會再發神經了.....  :

再整靚 D 線 ... 現在可以用埋對 16 Ohm 全音 Diatone 了!

    

Make the wiring even better. Now, this 2A3 is capable of connecting my 16 Ohm Diatone Full Range speakers.

過獎...

其實重有不完善之處, AC / DC 電未能分開. 但上了電, 沒明顯有交流聲 .... 算了,唔再改.

現附上線路圖.

CAT

Bong,

個 Hum Port 唔使點較 ... set 去中間聽到無 deee... deee 聲就算. 我無話上個 scope 去 check.

一樣東西要提, 這個線路唔係對對 speaker 都推到. 我建議最少要 9x db 先好. 因線路設計上個 gain 好似是較為細 .... 如果對 speaker 無咁 sensitive, 就用回原來線路

CAT

BongCalifornia,

Do you have DIY experience? If yes, the 2A3 is VERY easy for you.

Fostex are good speakers. I like them too. The 2A3 should be able to drive them as their sensitivity is also high. Correct me if I am wrong.

My choke is just 5H, a Tango one. You can check Tango info., I can't remember which model it is but 100% sure it is 5H only.

Ha..ha.. the 47uf+47uf is hard to find. You can try ALP Audio, the one selling Audio Note products in HK. My guess is, HK$ 1800 for one or so. I don't think it is worth that price at all.

Yes, 6SL7 is cheaper. Frankly, using the above 6SL7 circuit should give you more details and the amp tends to a bit sweeter.

For tubes, try to see if you can locate RCA 5691 at eBay. For 2A3, go for RCA VT-95 BLACK Plates. If you find them too expensive, go for the USN or CRC 2A3. Save your money to buy one good pair. Don't waste your money on other things else.

CAT

Accphoto 講的沒有錯, RCA 2A3 Mono Plate 是最好聲.

價錢今日已很高 .... 一對有80% emission 最近見到也約 US $800. 值唔值就見人見智. 比起舊整 WE 300B重平一半以上.

CAT

Dear Bong,

Ha..ha... I am an Economist. "Value" is something which is different to everybody. We share the same time in that $2K BG cap. If I am going to construct a new one, I won't buy BG for sure.

45 can be used in the 2A3 amp. Someone said it needs some minor adjustments. I just plug them in.

I got the 100Ohm hum pot and the 750Ohm resistor from eBay. They are no longer available. I still have some left but I need to check. I can sell them to you if you wish. Not very expensive.

For the 100Ohm, you can get those cheaper ones at 麥氏. I guess they have 2W. 華輝 may also have 2W ... but no 1W.

CAT

Dear Bong,

Ha..ha.. so you are really "California" as the name implies.

If you are not in a hurry, wait. I search for them for over 1 month before I can finally get hold of those.

I guess the 1W / 2W hum port is not the important, as long as it is solid built.

For the resistor, mine is DALE. I would say the brand is more important this time.

Shipping cost is minimum. What I worried is the TAX.

CAT

Dear Bong,

Yes, it is always good to have good planning beforehand.

Where did you get those Lundahl Transformers? They look nice to me. I have got a chance for an audition but I have heard that they are good, quite musical. That is what I have heard from others only.

How much are they?

I think it is well over 160V. It should measure 167V or so. I have to double check.

CAT

Sorry Bong,

My mistake. Wrong cap I referred to.

I think it should be close to 160V. I blew one of these once since I put in the wrong rectifier tube; used a 5V4 instead of a 5U4.

I "think" the 5V4 gives around 10-15V more ... and the cap blew.

The OPT looks like a good deal indeed. But you have to match the Ohms correctly.

For mine, I think I connected at the 2.5 KOhm.

Yes, I blew the 100uf /100V. I think mine is not 160V. Seems to me that 160V is not available.

I doubt whether we can still find 100uf / 160V.

So when do you plan to start working on this toy?

Dear Bong,

It looks like you do have a lot of project on hand, ha..ha..

I did compared with a Modified SV-2A3. The Amp uses Jensen Ceremic Tube, BG capacitors (47 + 47) and others. I asked my other colleagues and wife / daughter for the audition to avoid bias.

With similar tubes (the SV-2A3 uses 6SN7, mine uses 6SL7), mine out-competed the SV-2A3 in their opinions. I guess it is because of the OPTs. The one with the Sun Audio is the lowest grade OPTs in Tamura. Mine is the mid range one in Tango.

After their verdict, I do the audition myself. My feeling is the Tango is more spacious, the high and the lows are a bit more and more realistic. That is my feelings towards the Tangoes.

CAT

My goodness.

The Tamura OPT from the Sun Audio Kit is not very nice. It is their "bottom" line. That pair of OPT will limit your amp's performance by a lot.

Recently, I have compared some amps across the spec. I "think" the output transformers have a lot to do with the amp's performance. The Tamura high end OPTs are very very good at that price. However, the one that comes with the kit, I have hesitation.

My feeling is, the OPT actually costs the most. But you save yourself a lot of trouble. You can first try the Tamura OPT first. If you can stand them, fine. If you want something else after a while, you can then try the Lundahl or the Tango ones.

CAT

Bong,

Don't be too discouraged. They aren't "BAD". Compared with some other OPTs, they are already okay.

However, there are other better options. Look at it this way, you saved yourself a lot of trouble getting the other stuffs by buying this kit. That is money saved.

The Sun Audio Tamura is OKAY. Listen to them for a while, say 6 months. Then perhaps try something else like Lundahl or the Tango. As you know DIY, it should be of minimum trouble. And this is the spirit of DIY as well, moving from one point to another after a while.

CAT

Dear Bong,

Please check your PM.


CAT

Dear Bong,

Thanks! See if I got lucky ... ha.ha.

I am planning to build a 300B. Well, actually I got everything ready. Just need to finish marking my exam papers and should be able to start next week.

:  :twisted:

CAT

Dear Bong,

Yes, I have decided and got all the gears as well. Will be posting the photos up on a new thread.

Yeah, you are right .... IFF your wife knows about it, ha..ha...

I spent a fortune as well; that is why I have to sell off something to keep the balance.

Me and our "brothers" built the Pass Labs 1.7 last year. As you know, it is a transistor pre-amp. By the time I finish it, I am definitely sure it sounds better than my Marantz 7. But as I upgrade my M7 with copper tubes, the Pass Labs becomes the inferior one. I am not saying it is no good, but for sure my taste changed.

I am not sure whether you would like to have a transistor pre-amp to go with your Sun Audio 2A3. You have to try it out yourself.

Hey, have you start working on the Sun Audio Kit yet? Post some photos up if you have, ha..ha..

CAT

Dear Bong,

Oh, your sister bought the kit already? My colleague knows the owner of Sun Audio's dealer here in HK. We went down just last week to have an audition of his modified 211 power amp.

Mailing the kit to US will be quite expensive! And, of course, the tax as well.

Awaiting your photos.  

I have took photos of my 300B project as well but very busy these 2 weeks. Will have more spare time after next Wed. Will continue to work on  the 300B and post the photos by then.

CAT

Dear Viewer,

I am waiting for the opportunity to continue my work too. Flood with duties these few days. Still got a couple of reports to file after finish entering all those marks, remarks, grades ... etc. into the computer.

Next WED should be a better day.

CAT :

心思思將部 2A3 改行 6SN7, 唔用 6SL7.

牛仔也用了 TANGO.

Modifying my existing 2A3 amp by using 6SN7 as the driver instead of the original 6SL7 design.

Power Transformer changed to Tango as well.

Dear Viewer,

Yes, it sounds different.

Now, it has a bit more power but not as "驕" as before. I will try using different resistance (K) in the Output Transformer later.

Actually, this one is a "re-build" using many old parts. Therefore, not as beautiful as it can be as the resistors / capacitors' legs cut short already.

CAT