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Old 25th April 2010, 09:22 AM   #1
56oval is offline 56oval  Australia
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Default 300B SET which chassis design

Hello Diy

I'm in the process of building six 300B SET amps they will be used in an active speaker design .I stuck between 2 chassis designs what would you choose between these 2 designs.
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I'm thinking of placing the caps in the power supplys under the input/driver stage caps ,so all the caps are together .

Cheers
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Old 25th April 2010, 09:59 AM   #2
Yvesm is offline Yvesm  France
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OMG !

Iron mine

What are the 7 other tubes supposed to do
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Old 25th April 2010, 01:09 PM   #3
56oval is offline 56oval  Australia
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OMG !

Iron mine

What are the 7 other tubes supposed to do
Hi
The 3 tubes next to the 300B are 2C22 single triode versions of the 6SN7 and the 4 lower tubes are 6D22 half wave power diodes ,the input/drivers have their own power supply and the 300B has its own reg & power supply .

Cheers
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Old 25th April 2010, 08:51 PM   #4
kevinkr is offline kevinkr  United States
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You might want to rethink the design so that no power supply components are anywhere near the audio circuitry.

I have built a significant number of SE amplifiers (both commercial and for personal use) and for quietest operation I have found that placing the power supply on one chassis and the amplifier on another is hard to beat. There will be no issues of electro-static or magnetic coupling between the noisy power supplies and the audio electronics.
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Old 25th April 2010, 09:05 PM   #5
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Good point kevinkr. I would go with 2 separate chassis scheme, one being power supply unit connected with umbilical cord.
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Old 26th April 2010, 02:32 AM   #6
56oval is offline 56oval  Australia
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Originally Posted by kevinkr View Post
You might want to rethink the design so that no power supply components are anywhere near the audio circuitry.

I have built a significant number of SE amplifiers (both commercial and for personal use) and for quietest operation I have found that placing the power supply on one chassis and the amplifier on another is hard to beat. There will be no issues of electro-static or magnetic coupling between the noisy power supplies and the audio electronics.
Hi Kevin
With chassis 2 the power supplys are 300mm from the top of the power supply and I can flip the filiment suuply power tranny under neither and that will add another 100mm of isolation .I'm also looking at putting dividers in for sheilding .
I could use the same layout but make each section modular and have stand offs connection them .

Cheers
Mal

Last edited by 56oval; 26th April 2010 at 02:37 AM.
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Old 26th April 2010, 04:11 AM   #7
ChrisA is offline ChrisA  United States
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Originally Posted by Evenharmonics View Post
Good point kevinkr. I would go with 2 separate chassis scheme, one being power supply unit connected with umbilical cord.
Use coax with UHF connectors for the high voltage power umbilical cord. Something like RG213 with PL259 connectors. It's not really safe to run B+ volts outside of a metal chassis unless it is inside a very robust cable (like rg223) or a conduit.
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Old 26th April 2010, 05:36 AM   #8
chrish is offline chrish  Australia
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If you are going active with 6 amps, I am assuming you are powering two 3 way speakers? If that is the case, have you thought of optimising your amps to suit the load? The tweeter will require a much smaller amp than the woofer. 300B with associated iron may be wasted on the tweeter and may not powerful enough for the woofer. You may end up with 300B for tweeter and mids with a PP design for woofer etc.

See Rod Elliots site for discussion on bi-amping etc http://sound.westhost.com/bi-amp.htm

Good luck with the project!

Chris
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Old 26th April 2010, 06:43 AM   #9
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I'd like some advice on this question too. I already build on 2 chassis - the power supply and the signal chassis.

But I've been thinking - why not put the filament supplies on the signal chassis? The transformers - which are toroidal anyway - can be tucked away on one end of the chassis away from the tubes, and the diodes and caps and regulators put right by the tubes.

Advantages of this are:
a) no umbilicals for filament supplies
b) keeps the filament supplies away from the heavy iron in the PSU - mains transformers and chokes.

This is important to me since I use DHT input tubes like 26, 01A etc.

Next question - if you have power in 2 chassis, what do you do with the earth? I was thinking of running a secondary mains lead from the PSU to the signal chassis, so that the switch on for both is in the PSU chassis. So where does the earth go in this arrangement - we have options of the mains cable and the B+ umbilical or both?

Opinions?

Andy
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Old 26th April 2010, 06:49 AM   #10
56oval is offline 56oval  Australia
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Quote:
Originally Posted by chrish View Post
If you are going active with 6 amps, I am assuming you are powering two 3 way speakers? If that is the case, have you thought of optimising your amps to suit the load? The tweeter will require a much smaller amp than the woofer. 300B with associated iron may be wasted on the tweeter and may not powerful enough for the woofer. You may end up with 300B for tweeter and mids with a PP design for woofer etc.
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Good luck with the project!

Chris
Hi Chris

I have seperate 300B amps for the Tweeter different circuit .The OPT's are wound to suit the Raven R1 don't ask me how my mate winds all the trans and its his circuits I'm building .

Cheers

Last edited by 56oval; 26th April 2010 at 06:58 AM.
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