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Old 21st March 2008, 09:42 PM   #2121
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Old 22nd March 2008, 05:04 AM   #2122
lykkedk is offline lykkedk  Denmark
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Old 22nd March 2008, 08:24 AM   #2123
dwRK is offline dwRK  Malaysia
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Originally posted by jacco vermeulen

Rework the transformer to 4 x 15Vac secondaries.
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Originally posted by Blitz
Or design a choke-input-Filter, that will bring you down to 23-24 V. But it is easy to buy new transformers I guess.

Thanks for the suggestions.

How do you rework it to 4 x 15V? Is it to rewind it?

I've thought about a variac/choke, and also triac control for the AC but decided to have less parts in line with the Zen philosophy.

Also I'm not sure if using a "capacitor bridge? for a floating ground?" will work (i.e., 2 caps in series tied to 0 and 38V, tap in the middle for 0V...so I can have -19V 0V +19V... sorry I don't know the correct name for this circuit)

My question still is will I blow something up with +-38V rails? Thanks.
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Old 22nd March 2008, 11:05 AM   #2124
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Originally posted by dwRK


My question still is will I blow something up with +-38V rails? Thanks.

Most likely you will fry the Jfets as these have a breakdown voltage of ~25V. If I know NP only a tiny bit, it is not by chance that the F4 uses a 23V rails.....
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Old 22nd March 2008, 01:00 PM   #2125
steenoe is offline steenoe  Denmark
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Originally posted by lykkedk
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Great looking speakers How does they sound?

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Old 22nd March 2008, 02:19 PM   #2126
lykkedk is offline lykkedk  Denmark
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Great looking speakers How does they sound?
Thank's Steenoe ... I guess they sound like your''e abbeys, but perhaps, with a little more punch. Well theyr'e not completly finish yet, still missing final coat, edge banding and some wooden phase-plugs

They are very heavy, as i filled the room beneth with drysand (The kind used to blow paint on walls off)

Jesper.
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Old 22nd March 2008, 02:33 PM   #2127
Magura is offline Magura  Denmark
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Originally posted by lykkedk


Thank's Steenoe ... I guess they sound like your''e abbeys, but perhaps, with a little more punch. Well theyr'e not completly finish yet, still missing final coat, edge banding and some wooden phase-plugs

They are very heavy, as i filled the room beneth with drysand (The kind used to blow paint on walls off)

Jesper.

Looking forward to audition them

....and nice work BTW.


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Old 22nd March 2008, 05:37 PM   #2128
Zen Mod is offline Zen Mod  Serbia
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Originally posted by Magura



.......

....and nice work BTW.

.......

naah...... fugly!

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Old 23rd March 2008, 02:33 AM   #2129
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Originally posted by Zen Mod



just pump the gain of Pumpie
15x (23,5db) is completely same as 10x , for Pumpie ......... but not for F4
I might just have to do that ... so, 23.5dB gain... anyway to convince me with numbers that this will make these hard to drive speakers sing loudly? Extra points for using acoustic watts
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Old 23rd March 2008, 02:38 AM   #2130
Magura is offline Magura  Denmark
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With a balanced F4, yes it will make just about anything sing at 23dB gain


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