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K120 Monoblocs or Budget 300B build

Hi guys,

I am soooo in love with the sweet sound of my A10 that decided to keep going in my learning journey and take another step in this path. What would you suggest as a next step: Try to build the K120 monoblocs or the budget 300B?

As a newbie, is the challenging too big for any of these projects? What are the sound characteristics of each one of them? And also in terms of budget, is the K120 much more expensive to build? I had a look on the K120 transformers and only them will cost around 2,000 AUD, on the other hand the 300B valves cost a fair bit as well.Thank you so much for any inputs.

Kind regards,

Alex.

7 answers0 replies

7 Comments

alexmp01

May 07

Hey, George!!

What exactly do you mean by gut the A30?

I can read schematics and follow them asking questions here and there until complete a project. However, I do not know tube electronics to understand how to change the A30 into a 300B. In that case I will need your guys help.

After saying that, this could be a great project as the price for the A50, delivered here in Austrália is around AUD 1,470.00 and the A30 is around AUD 790.00.

Depending on the costs of the change, that could be an incredible bargain.

If you and/or Skunkie will be interested in such a project, I will be happy to be a guinea pig for the development and adjusts along the way, following your steps.

Does it make sense?

Alex.

Junkman George

May 07

Replying to

The 2A3 and the 300b both live in approximately the same place, working with the same voltages, so you would study both schematics, and build a 300b in place of the 2A3.

Once you understand the working parameters you just juggle the components until you have what you want...................

So, study up on the A-50 mods, look at the schematics, review the videos a few times, and once you feel confident get ordering some stuff.

Skunkie has done the heavy lifting, she has verified the output transformers are useful (instead of outright junk) and has given us a workable 300B circuit.

It's winter there and summer here, I am not dependable in the summer because for me it's motorcycle time.

alexmp01

May 07

Replying to

Sounds like a good plan and great learning experience !! I am in!!!

Can I be a bit lazy and ask you, if possible, for a schematic of the A30/2A3? I was trying to find it but not successful so far.

Enjoy your rides.

All the very best!!

alexmp01

May 07

Ahhh....I just forgot to mention...I almost could see in your forefront the stinging drops of sweat....:-)

Thank you again, George

Junkman George

May 06

Alex.................

I am an old fella, I have pushed my share of big rocks up steep hills, and I'm not doing that any more.

I have both an A-10 and an A-12, the A-10 runs 6v6 output tubes, and the A-12 KT77 output tubes.

If I had the urge for a 300B SE amp I would buy an A-50 and mod it as per the instructions here.

KT120-150 tubes cost me as much as some 300b tubes. Skunkie reported trouble getting KT120 tubes, or getting dependable KT120 tubes.

I don't currently own the tools and workspace to make/modify a chassis.

So to me it's a no-brainer.

alexmp01

May 07

Replying to

Hi George,

Thank you so much for the heads up. I will have a look on the videos for the A50 mods, which will be the most cost effective for sure, even compared with the budget 300B project.

My best wishes,

Alex.

Junkman George

May 07

Replying to

Hi Alex..................

The A-20 is a KT88 Se amplifier (I'd have to look it over closely but it is likely you could run KT120's)

The A-30 is a 2A3 Se amplifier (cheaper than the A-50 you could gut it and build it as a 300B amp)

The A-50 is a 300B Se Amplifier (this is the one Skunkie mods)

You still have to get your speakers sorted out.