Mullard 3 Tube 3 watt amplifier Question - diyAudio
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Old 28th November 2013, 04:53 AM   #1
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Default Mullard 3 Tube 3 watt amplifier Question

Going to be building the Mullard 3 tube 3 watt amplifier from the mallard book.
Here's the print. Mullard 3-3. Three Watt Amplifier

question-

I have a pair of single ended 5k transformers that have 4/8 and 16 ohm taps. In the print they have a 1k resistor across the output of the output transformer to ground, Which if you look at the print is R14. If I have 4/8 and 16 ohm taps do I omit that resistor or just put it between 16ohm to ground?
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Old 28th November 2013, 05:13 AM   #2
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I suspect its there just to ensure there is some load in case a speaker goes open circuit. In which case it needs to be across the OPT outputs - any will do.
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Old 28th November 2013, 05:41 AM   #3
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Mullard also published a similar amp of lower power based on the 6BM8/ECL82. I worked with member Jeff Yourison in revising that design. It may make sense to contact him for some notes and building experience.

You definitely can save quite a bit of money by emulating the B+ supply Jeff and I used. "Full wave" voltage double the O/P of a low cost Triad N-68X isolation transformer. As the N-68X has dual primaries, it is useful just about everywhere other than Japan. The 100+ mA. of B+ that can be extracted from a N-68X should be more than adequate.
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Old 28th November 2013, 02:23 PM   #4
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Gotcha aardvarkash10, Thanks That makes sense.
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Old 28th November 2013, 03:21 PM   #5
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Thanks for the link, seldom is there a clearer picture of what proper wiring should look like.
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Old 4th December 2013, 12:18 AM   #6
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Look at how linear that amp is!?!?!!
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Old 16th December 2013, 02:13 AM   #7
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Default feedback question

Ok another question if you don't mind. I have an output transformer that has 4/8/16 ohm tap. Can I just connect the feedback circuit to the 16 ohm tap or do I have to have the feedback connected to whatever tap I'm using at the time?

Mullard 3-3. Three Watt Amplifier
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Old 16th December 2013, 06:48 AM   #8
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You can connect NFB to the 16 ohm tap, but you would have to adjust the NFB voltage divider resistors accordingly.

I would forget about the Mullard 3-3, it is a very poor and outdated design.
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Old 16th December 2013, 11:47 AM   #9
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Default If that's the case

If that's the case, Could I see the best sounding modern SE EL84 print?
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Old 16th December 2013, 10:08 PM   #10
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I'm told not to try building this amp and then I hear Crickets? If this is a bad design what's a good one?

Any help would greatly be appreciated, As it's a lot of work putting amps together. Thank you very much in advance.

I did the Mullard 520 before and it's a great sounding pair of monoblocks. That's why I trusted this circuit would work.
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