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Old 18th January 2013, 05:40 PM   #1
suwaned is offline suwaned  Indonesia
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Default choice of driver for RS 241

i have RS241 and planning to make Power.
But i confused to choose the driver for that.
using DHT or Pentode?
i have seen in the web. thas used RE604 /A71/ 10.
how about the pentode like EL6?

please advise
thank you

Last edited by suwaned; 18th January 2013 at 05:42 PM.
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Old 21st October 2013, 02:49 AM   #2
suwaned is offline suwaned  Indonesia
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VT25 for driver RS241
how about is this?
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Old 21st October 2013, 07:13 AM   #3
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hi Edy,

We can help you choose, but you must choose some important features of your design first.

1. What is your expectation of output power? The RS241 is capable of operating with grid positive (class A2). this will give more power, but you will need a FET source-follower, or a high-gm cathode follower to provide the current required into the grid. A2 also means the driver must be able to supply higher [ac] signal voltage.

2. When you have decided about A2, you can draw the load line for your transformer, knowing the impedance that the transformer and speaker combination presents to the RS241.

3. The load line confirms the grid bias voltage you need, and the operating point (eg Va=400V, Ia=30mA, bias= -15V. In this case the driver only needs to swing about 35V or so, peak to peak - class A1, and a little more for class A2 (if required).

4. Finally, what's the output of you preamp or DAC? With this value, you can identify the required gain. This will have a strong influence on what kind of driver to choose.
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Old 21st October 2013, 05:14 PM   #4
suwaned is offline suwaned  Indonesia
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Quote:
Originally Posted by Rod Coleman View Post
hi Edy,

We can help you choose, but you must choose some important features of your design first.

1. What is your expectation of output power? The RS241 is capable of operating with grid positive (class A2). this will give more power, but you will need a FET source-follower, or a high-gm cathode follower to provide the current required into the grid. A2 also means the driver must be able to supply higher [ac] signal voltage.

2. When you have decided about A2, you can draw the load line for your transformer, knowing the impedance that the transformer and speaker combination presents to the RS241.

3. The load line confirms the grid bias voltage you need, and the operating point (eg Va=400V, Ia=30mA, bias= -15V. In this case the driver only needs to swing about 35V or so, peak to peak - class A1, and a little more for class A2 (if required).

4. Finally, what's the output of you preamp or DAC? With this value, you can identify the required gain. This will have a strong influence on what kind of driver to choose.
Hi Coleman,
thank you for your help.
I've tried to make it.
using the circuit the commond cathode SE with auto bias
My reference circuit VT52. but by using the VT25 as a driver, not 71.
but I am not sure what is true.
I do not know what is enough, the driver sends to the grid voltage swing.

my preamp cleo triode dick B406 parafeed with OTL 10K:600 little gain. and amplification.

have given the chart .
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File Type: jpg skema power rs5b.jpg (65.1 KB, 126 views)
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Old 21st October 2013, 06:11 PM   #5
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Hi Edy,

Do you have a 12K transformer? It will be high cost, for good quality.

The bias voltage is probably 12V or less for the RS241. This means, the RS241 grid needs about 30V peak-peak for full power (= 10.6V rms). Maybe a little less will suffice, but assume you need this.

The interstage transformer is 1:2 so with 10Y or VT-25 you will need about 1 - 3Vrms from the preamp, depending on the exact transformers and bias settings.

It's probably OK, but the outcome will depend on the transformers you can use. But a DHT should be possible - no need to use a pentode.

I hope you have high efficiency speakers - the output from the RS241 will only be 2-3W or so.
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Old 14th April 2014, 06:40 PM   #6
suwaned is offline suwaned  Indonesia
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Quote:
Originally Posted by Rod Coleman View Post
Hi Edy,

Do you have a 12K transformer? It will be high cost, for good quality.

The bias voltage is probably 12V or less for the RS241. This means, the RS241 grid needs about 30V peak-peak for full power (= 10.6V rms). Maybe a little less will suffice, but assume you need this.

The interstage transformer is 1:2 so with 10Y or VT-25 you will need about 1 - 3Vrms from the preamp, depending on the exact transformers and bias settings.

It's probably OK, but the outcome will depend on the transformers you can use. But a DHT should be possible - no need to use a pentode.

I hope you have high efficiency speakers - the output from the RS241 will only be 2-3W or so.




Hi Rod,
thank you for your advise.

I have OT Tribute 12K from Pieter.

I've tried to build ,my Power Rs241 dan driver VT25.
Rectifire RGN 4004
Transformer Hashimoto.
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File Type: jpg 20140326_101112.jpg (892.9 KB, 71 views)
File Type: jpg 20140326_100750-001.jpg (341.1 KB, 67 views)
File Type: jpg 20140326_101618.jpg (411.7 KB, 64 views)

Last edited by suwaned; 14th April 2014 at 06:46 PM.
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