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Old 12th July 2013, 07:27 PM   #1
apnneto is online now apnneto  Brazil
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Smile Another TVA1 - KT88 power amplifier

Hello,

I'm interested in building a clone of TVA1 - Michaelson and Austin, using a new layout. The attached file contains the new layout. I did a test with this model and now I will send for board production.

The board is double-sided and electrolytic capacitors will be fixed from the bottom side of the plate. All other components on top. The supply for the filaments of the tubes will also be at the top.

Would like some suggestions regarding the layout and whether there is any visible problem which can degrade the sound quality.

Regarding the use of pcb is a personal choice. I will use the Hashimoto transformers, which have already been purchased directly from Japan

Any feedback is welcome.
Attached Files
File Type: pdf Tva-1-bot.pdf (86.9 KB, 348 views)
File Type: pdf Tva-1-tsilk.pdf (63.3 KB, 189 views)
File Type: pdf Tva-1-top.pdf (41.6 KB, 167 views)

Last edited by apnneto; 12th July 2013 at 07:36 PM.
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Old 15th July 2013, 03:19 PM   #2
apnneto is online now apnneto  Brazil
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Smile The prototype is working ...

Yesterday I finished the 3rd prototype. To use the power until the final design is ready, I mounted the amp on a chassis that was here at home. Actually, it was going to scrap in the garbage. Then I decided to mount the amplifier on it. Below are some photos of the power amplifier.

The sound is wonderful. And, at this moment, the otp is not the Hashimoto transformers. They are too big to be used on this chassis.

Now, I've already sent the board to the factory. I just want a professional look for this amplifier.

I'll post all the step-by-step, component lists, etc ... for this project. The sound of this unit is really very good.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.
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Old 19th September 2013, 02:59 PM   #3
gk7 is offline gk7
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Location: Vienna, Austria
Looks like a great project !
A few questions about the PCBs:
Which layout program did you use ? Are you willing to share
the layout (the original files, because pdf is not so well
suited if you have the manufactured) or would you sell PCBs ?
I see you have both channels on one board, is it possible
to cut the board in two halves if one wants to make mono blocks ?
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Old 19th September 2013, 07:15 PM   #4
apnneto is online now apnneto  Brazil
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Quote:
Originally Posted by gk7 View Post
Looks like a great project !
A few questions about the PCBs:
Which layout program did you use ? Are you willing to share
the layout (the original files, because pdf is not so well
suited if you have the manufactured) or would you sell PCBs ?
I see you have both channels on one board, is it possible
to cut the board in two halves if one wants to make mono blocks ?
Yes, it is a great project. Take a look at this link:

http://youtu.be/Bn2U7qfUC_w

I used Eagle software and after testing final project, I will post the geber files here. The channels are designed to operate in separated circuits including earth. It is possible to cut the board into two halves for the construction of mono blocks, with no problems.
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Old 19th September 2013, 07:36 PM   #5
apnneto is online now apnneto  Brazil
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Default pcb double-sided

The images below are of the pcb double-sided. In the final project I will use DC for tube hearts, with the tube sockets mounted on the bottom of the board in inverted position. The hum level is excellent.

Click the image to open in full size.

Click the image to open in full size.

In this project I included a soft starter and delay circuit to the B + (550v). The chassis I would like to use was this:

2U Slimline (Tube-Friendly Configuration) - Full Width with Quasi Heatsinks - Chassis

.. but it is out of the stock. So I bought this one:

Model AL-470R-S

Last edited by apnneto; 19th September 2013 at 07:40 PM.
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Old 19th September 2013, 09:53 PM   #6
gk7 is offline gk7
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Quote:
Originally Posted by apnneto View Post
... with the tube sockets mounted on the bottom of the board in inverted position. ...
So in the final version the tube sockets are mirrored, right ?

From various other posts on the net there seem to be some
confusion about the correct schematic, did you see this post:

Michaelson & Austin TVA-1 info

Would you sell some PCBs too ? (The current version, like in your picture
would be ok for me).
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Old 19th September 2013, 10:24 PM   #7
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the negative feedback is set at a gain of 40
what is the open loop ( no NFB ) gain of this amp
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Old 19th September 2013, 10:56 PM   #8
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Hi apnneto, I would also be interested in a pcb. I have a TVA and every time I look at fixing it I find another problem on the pcb.

Thanks, sp
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Old 20th September 2013, 01:42 AM   #9
lexx21 is offline lexx21  United States
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Count me in for a pcb as well if you have enough. I would be very interested in building this.
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Old 20th September 2013, 08:43 AM   #10
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Hi apnneto,

Nice job, do you intend to sell the boards or any group by ?

i am in for a stereo set,

cheers
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