| 4 Pi Pro's and pp6BQ5's [message #35762] |
Tue, 02 April 2002 06:07  |
Sam P.
Messages: 307
Registered: May 2009
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Grand Master |
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in my fisher 500-S are a match made in heaven. Driven into the aux inputs by my sand preamp...absolutely ZERO hum...this is a 40+ year old tube receiver...only cap changes were the voltage doubler ones...replaced with minature ec's that fit inside the original cardboard "can".
MIDRANGE/vocals sound BETTER than the sand amps. I think the tube amp can't supply extra current, so the zobel is acting to suppress the woofs rising response better. OR the 14 year old monster cable interconnects are well broken in, contributing considerable "magic":)
Regarding tube friendly Z characteristics, the Fl peak is only 22.5 ohms/26Hz, Z min. near Fb is 6.3 ohms/48Hz, Fh was 20.5ohms/80Hz. Calculated system tuning was 48Hz...I'm not cutting the tubes again...ended up at 3.0idx1.5long...the 2.5cu.ft. net enclosure volume acts like about 3.3cu.ft. once the 1.2cu.ft. of 'glass was added, according to boxplot and ausberger(sp). Aside from the normal zpeaks, everywhere else the Z stays between the absolute min. of 5.8ohms/195Hz. and 9.0ohms/1500Hz. From 3kHz to 20kHz, the Z stays between 8.2 and 7.1 ohms.
NO HUM! Who stole the hum??? Sam
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| Ahh, those were the days! [message #35764 is a reply to message #35763] |
Tue, 02 April 2002 10:59  |
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Wayne Parham
Messages: 18705
Registered: January 2001
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Illuminati (33rd Degree) |
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Some tied the left side to the chassis, but electricians sometimes didn't pay attention to the standard, which is to make the left side neutral. So it is just as common to find the chassis at line voltage as neutral. Since it's AC, "neutral" really isn't relevant to the operation of the circuit, but when you touch the chassis, you sure find the relevance! It can also make connecting equipment togetyher very exciting.I'm sure you recall the "floating ground" that was common in stuff made in the 50's and 60's. That was the first attempt to make household electronics safer. If one side of the line is connected to the chassis and you touched the chassis of two devices together - one plugged in one way and the other plugged in opposite - the two chassis would be at opposite potentials and sparks fly. So with floating grounds, that doesn't happen but it still means the chassis would "float" to about 70 volts. These are why most guys use an isolation transformer on the old stuff - Trying to keep from letting the smoke out of the scope. Remember those 1-to-1 isolation transformers?
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| Re: first of many silly qestions... [message #35773 is a reply to message #35765] |
Wed, 03 April 2002 10:20 |
bmar
Messages: 346
Registered: May 2009
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Grand Master |
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When i first hooked up the mono blocks to the speakers, I hooked nothing to the inputs. I thought this would tell me if they had a hum or not. Well they did! and a ton of hum to boot. it was ugly.
now i figure these things are going to be needing some service, but let me try and hear music over all this noise.
hook them up to a source, turn them back on. no hum. a wee bit but you have to put your ear to the driver.
one side was worse than the other also. but i'm in search of an explanation.
while I'm at it. what is the prefered method for changing speakers hooked to an amp?
it MUST be turned off?
it reallt doesnt matter?
no problem as long as you do the left side first?
Bill
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| Re: Ha! [message #35784 is a reply to message #35775] |
Wed, 03 April 2002 16:36 |
bmar
Messages: 346
Registered: May 2009
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Grand Master |
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lets see,
i can be right winged, drink beer with my left hand and smoke a stogy with my right.
shit, how my going to change the remote now......
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