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Old 7th January 2013, 08:49 PM   #41
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Quote:
Originally Posted by mogliaa View Post
Hi djn,
I would be more inclined for a line stage providing the right impedance and current driving capability to drive your cables and input capacitance. That and its sound are more important than the gain factor. The gain can better be provided by a well design driver in the amp :-)
Cheers, ale

Tricky if your set on two stages though, suck it and see i guess!
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Old 7th January 2013, 08:54 PM   #42
Magz is offline Magz  United States
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Originally Posted by enzoastro View Post
as i remember the microphonics on my 4p1l's were mainly 2 or 3 resonanses around 1500-2000hz i've tried damping the tubes with limited success and am working on mounting all the gain stages on a highish mass rubber decoupled platform.

all this talk of gyrator drivers is tempting me to dig out my sv811-10's :-) my gm70 stereo chassis started out as an A2 push pull 811-10 monoblock!

enzo
I made a rather elaborate high mass damped mounting unit for the 26 tubes in my preamp (see picture). Chassis vibrations have to go through in order 2.5mm aluminum chassis, wood mounts, deflex washers, 4mm aluminum, constrained Soundcoat damping material and a teflon socket to get to the tubes. The dissimilar materials should help with limiting sound propagation. It's veeeerrryyy quiet.
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Old 7th January 2013, 09:35 PM   #43
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Thats really impressive ;-)
anyone hear the story of harley davidson and their competitor whos name I cant remember in the I think 30s or 40s?
They both had probems with headlights blowing bulbs. The competitor made a sophisticated arangment using spring mounts etc. harle
y just made them heavy and guess who stood the test :-)
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Old 8th January 2013, 04:12 AM   #44
djn is offline djn  United States
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Quote:
Originally Posted by mogliaa View Post
Hi djn,
I would be more inclined for a line stage providing the right impedance and current driving capability to drive your cables and input capacitance. That and its sound are more important than the gain factor. The gain can better be provided by a well design driver in the amp :-)
Cheers, ale
Well I am stumped. I always thought an active pre amp and a line stage were the same thing. My Low Mu only has a gain of 5 but it sure makes a big difference.
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Old 8th January 2013, 06:28 AM   #45
mogliaa is offline mogliaa  United Kingdom
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You just need the right level of gain in the preamp without compromising the output impedance. Your low level Mu is fine but I prefer a different topology and valves for a preamp.
Ale
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Old 8th January 2013, 12:41 PM   #46
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I'll try and do some bandwidth tests of the ccs loaded 4p1l into some of the higher mu drivers and see how it comes out, on its own into my soundcard it was a hardly down at 90+khz I'll cgeck my notes when I get home, I think 0.5 db @ 60khz at normal listening position on 100k switched attenuator.

Enzo
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Old 8th January 2013, 02:32 PM   #47
djn is offline djn  United States
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Originally Posted by mogliaa View Post
You just need the right level of gain in the preamp without compromising the output impedance. Your low level Mu is fine but I prefer a different topology and valves for a preamp.
Ale
Thanks Ale. so is the term "pre amp" and "line stage" the same thing?
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Old 8th January 2013, 03:59 PM   #48
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I'm working under that assumption!

enzo
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Old 8th January 2013, 04:20 PM   #49
djn is offline djn  United States
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I'm working under that assumption!

enzo
I assume so too E. I might want more gain from the pre if my amp driver could not swing enough for the gm70
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Old 8th January 2013, 04:31 PM   #50
palmas is offline palmas  Portugal
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I assume so too E. I might want more gain from the pre if my amp driver could not swing enough for the gm70
2 different things: gain and swing capability
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