question about the 搭棚膽後級

Hi everyone,

Happy New Year!!

I am planning to enrol 膽後級組裝班.  But I have a question wanna someone to answer.  If I made a 套件2A3搭棚膽後級, may I upgrade any parts such as transformer at anytime?
Thank you very much!

You can check with Hi Fi Fever Admin.

It is hard to say in my opinion. I have seen different versions of 2A3 and they all have different Voltage ..... sigh. I got a hard time finding a "suitable" transformer.

I "think" the best way is to find a good 2A3 circuit first as there are so many "modified" ones around. A good one with high resemblance to the "original" may help to save you trouble in the future in case you need to replace the transformer (assuming you are talking about the Power Transformer).

CAT

Because I am a new hand, so that I have no idea about the circuit.  Besides of replacing transformer, may I upgrade any components such as cap, resistor at anytime?  In my mind set, DIY item can be modified anything when I wanna change or ungrade the component.  Am I right?  Thanks Alfcat!

Dear Icefireman,

If you use Point to Point soldering (搭棚), you can change anything anytime provided you construct the set well enough. If you use PCB, the PCB will have to be good enough. Else, you can cause severe damage to the PCB and troubles will then come.

I am relatively new too, just been here DIYing for less than a year. But I learned a lot from the friends around here.

There are people around here who has knowledge of good circuits. If the circuit design is good, it is worth upgrading. Else it will be a waste of money. Putting in good components MAY just "magnify" the weakness of the equipment, instead of curing it.

CAT

Hello Icefireman,

Have you bought the 2A3 power amp kit yet?  If not, I would advise you to hold until you finish the class because you are going to take the course.  You may discuss with your tutor about your project in mind.  There are a lot of points that you need to consider before you pay for the transformers which are very important in a tube amp and are the most expensive parts.  For example, single-ended, parallel single-ended or push-pull would you like to go for?  Should you like a single-ended, it is better for you to have a pair of sensitive speakers, say 90 dB or above because  a 2A3 gives you just 3.5 Watts output.  And, you better choose the output transformer with 2.5k Ohms load or 3k Ohms load for push-pull which will give you a maxium of 15 Watts.  2A3 is a triode tube which is more suitable for single-ended.  Also, you have to consider the driver tube too.  For 2A3, it is better to have a high mu tube for the driver stage, such as 6SL7, 12AX7, 2A6 or EF86......  What about the rectification? Tube or Diode? Self-biasing or fixed biasing?  You have to clear that.  Otherwise, you would not know which power transformer that you need.
Well, do you really enjoy the sound of 2A3?  Please bear in mind that people would have their own taste in music and have different sensitive response to sound quality too.  Or I should say that it is subjective.  Me, I like 2A3 very much.
Hope you enjoy the DIY class as well as your project.

Dear Icefireman,

I strongly agree to what Cheaplow said. As he is more experience, he is able to give you more insight.

Since you said you are new, I would suggest you listening to different tube amplifiers and figure out what combinations you want before upgrading anything. I like 2A3 myself but I have to admit that there are other amp and pre-amp that does not fit my taste. It is like choosing a car. Better test drive (listen with different combinations of speaker, etc) before you actually upgrade it.

When you attend the class, tell Modi Sir and alike what type of music you like best. KK Sir has good knowledge of those electronics stuffs and Modi Sir is very experienced in Tube Stuffs. Willaim Sir can arrange for different package deal for you. Therefore, you have a great team serving you there in the class. ENJOY!

CAT

Thank you Cheaplow and Alfcat again.  I am glad to listen your suggestion.  First of all, I don't have any friend around me fever hifi (tube stuff).  Therefore, I don't have any chance to listen other tube amp or speakers for me to choose which style of tube I like to.  From Cheaplow point of view, I should take the course first, and then tell the teachers what kind of music I like to in order to choose which components (in amp) I should pick.  Am I right?

Now I am using JMLab 907Be speakers, the sensitive is 89db.  So do they fit in using 2A3 amp?  

I think I have a long way to learn.  Hope that course is my milestone for DIY hifi.  Thank you again.  

Dear Icefireman,

My suggestion is the same as Cheaplow. Attend the class first and tell them what music you like and what are your current settings. They can then suggest you to get / try whatever you want.

You don't really need friends with lots of Hi Fi stuffs. You can go to the shops, right? The price there may not suit your budget but at least you know how they sound like. A DIY project usually cost less than 1/2 of the street price of any good brand product. This is my impression.

CAT

2A3 is properly too low for JM Lab 907Be, I am using a pair of 300B monobloack (8W) driving a pair of JM Lab 916 with great success. I think you got to have at least 8-10W to drive the speaker properly otherwise it will not enough power. 2A3 is only good for those speaker with  95- 100db sensitivity like Horn.

Besides of JMLab 907Be, I am going to buy a pair of speakers which sensitivity is around 94db.  Then is 2A3 good enough to drive them?  Anyway, I probably will attend the course because I wanna learn more about DIY.  

Do not really look at the sensitivity at all as a main consideration. Sometimes, I found it hard to drive some speaker eventhough it is 94db. Traditional wisdom saying that Horn and Old Full Range speaker like WE 555 or Altec 604 best suit 2A3. I had a friend who drive a pair of Altec 604 with a DIY 45 tube ampifiier, the sound is really old but of course it will lack high. DIY is really interesting, once you go into it, you will never look back at those famous brand who charge you an arm and an leg.

I checked with my colleague who got a 2A3 as well. He also said that it is not easy to find matching speakers as the power (output) is not that high.

The last time I listen to a 2A3, it was driving a medium size speaker (can't recall the brand). The sound quality is good but it just lacks the "punch" in my opinion.

DIY is always fun. Just go step by step and don't be afraid of making mistakes. Ten years from now, when you look back, I am sure you will be proud of yourself. I myself feel very happy with the products I finished so far ...  :

CAT