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Old 17th February 2005, 05:49 PM   #1
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Default 2a3 layout

This is my first amp , after reading Jones "Buildin Tube Amplifiers"
I have come up with this layout.
* note : the OPT will be Hammond 1627SE






Can anyone offer some advice before I carv up a chasis ?



Jeff
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Old 18th February 2005, 01:17 AM   #2
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Default layout update

Here is a better pix, My concern is the choke and the rectifier
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Old 18th February 2005, 04:01 AM   #3
ALBQ is offline ALBQ  United States
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Default 2A3 Amp Layout Questions

Tenderland,
After doing this for a while, I have found that it usually makes sense to prototype your design on a board before building a chassis. This will allow you to test various components and play with your design before settling on a final configuration. Besides the obvious benefit of being able to listen and tweak your design, how to layout your final amp will be immediately apparent.
Good luck - ALBQ

http://mywebpages.comcast.net/gillespie147/2A3-Amp.html
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Old 18th February 2005, 06:55 AM   #4
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Tenderland,
you might try orienting the choke's laminations 90 to the OPTs and see if you get lower noise/hum that way. Airgapped chokes inevitably spray leakage flux, but the relatively small AC voltage across them usually means this doesn't present as much of a problem. The problem here is that orienting it 90 to the OPTs places it in alignment with the power transformer - but this appears to be quite far away. Probably something that you will just have to try (unless you can mount the choke horizontally, of course). Moving the 2A3s closer to the edge may aid cooling, and the chassis tends to be more rigid at the edges. Do not forget to tightly twist heater wiring and push it into the edges of the (hopefully metal) chassis if you can.

ALBQ,
I know I'm doing a little nitpicking here, but I had a look at your amp and there is a mistake in the wording. Your amp is not valve regulated, and the 5U4 is not a valve regulator - it's a rectifier. Hence the amp has a valve rectified power supply, but is not valve regulated. Apart from that, a very nice amp. Those perforated anodes sure make the valves look nicer
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Old 18th February 2005, 07:15 AM   #5
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Default Re: 2A3 Amp Layout Questions

Quote:
Originally posted by ALBQ
Tenderland,
After doing this for a while, I have found that it usually makes sense to prototype your design on a board before building a chassis. This will allow you to test various components and play with your design before settling on a final configuration. Besides the obvious benefit of being able to listen and tweak your design, how to layout your final amp will be immediately apparent.
Good luck - ALBQ

http://mywebpages.comcast.net/gillespie147/2A3-Amp.html
Yep, and rotate the power tx and the choke till you find the position with minimum 50Hz at the output with the input shorted. Sometimes 90* isn't quite right. I don't generally like iron sitting on the top plate so it doesn't bother my aesthetic sense if components are at angles, so long as everything works perfectly.
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Old 18th February 2005, 01:27 PM   #6
ALBQ is offline ALBQ  United States
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Default 2A3 Amp Layout

audiousername, tenderland,

Thanks, - as a note about the chassis. Was meant to be temporary so I could have the amp safely in my livingroom until I could make an exotic wood base (current base is Oak) - small children + pets + exposed 300V do not mix. That is why I did not trim all of the transformer leads. But alas, that was 2yrs ago. Still, building it on a test platform first (large soft pine board) meant that I could voice the amp how I wanted it and its dead quiet w/ 93db speakers. Other things I think are key to getting a quiet amp are 1) how the filament wiring is run - I do the same thing you do - twisted and close to chassis and 2) Grounding - a couple parts here a) I like to use a heavy gauge cooper wire to create a bus that everthing connect to that is ultimately tied to the chassis in a single location. This is also a good rule of thumb for safety and b) make sure that the grounding scheme never has a loop in it that might allow a signal path or potential difference
Cheers - ALBQ
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Old 18th February 2005, 02:29 PM   #7
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Thumbs up layout

Thanks all , very good advice


Iwould be interested on more info about iron not on top plate
in particular the wiring and mounting
Jeff
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Old 19th February 2005, 02:33 PM   #8
ALBQ is offline ALBQ  United States
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Default 2A3 Layour

Quote:
Iwould be interested on more info about iron not on top plate
Tenderland,
Can you be more specific what about what you want to know?

Bottom mounted iron on my amp are the big 2.5V filament transformers for each 2A3 and choke in the HV power supply
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Old 19th February 2005, 07:41 PM   #9
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Default mounting

DO you mount the choke and fills on the bottom side of the top plate ? Did you mount youre choke horizontaly? Thanks ALBQ
for youre response .


Jeff
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Old 20th February 2005, 01:21 AM   #10
kmtang is offline kmtang  Canada
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Default Hammond 302AX power transformer

Hi tenderland,

If you still haven't bought the power transformer, you may take a look at the Hammond 302AX which provides all the HV and filament supplies to the stereo 2A3 amp.

302AX
300-0-300 200mA
2.5V CT @ 2.5A
5V CT @ 3A
6.3V CT @ 6A
2.5V CT @ 2.5A


Then, you don't need a separate transformer for the two 2A3 filaments.
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