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Old 26th October 2010, 03:05 PM   #41
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Originally Posted by Zen Mod View Post
fair enough

sorry - I can't help you with any particular finished product ;



perfect .
Listening to some of my own albums without the LS25. I know the sound very well on these records as I mixed and mastered them as well. The sound without the preamp is much better. It is addicting. I've done some research into quality passive attenuators and this sound just might inspire me to make a passive preamp! I suppose I need to deal with a bit of the learning curve though. I am sure there are some concerns with impedance and the quality of the attenuator and the source selector. I heard Shallco makes good ones? Also cable length becomes an issue. Plus I know nothing of drilling holes and cutting cases to fit the parts... But it is not rocket science and if I can understand the theory of Schoenberg and Messiaen, I suppose I can learn this as well.

I need 6 inputs with a tape loop. It would be nice if I have a choice of RCA or balanced as well on all ins and outs.
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Old 26th October 2010, 04:19 PM   #42
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so - it's time for new thread
if you choose DIY route , take it as fun , not cheaper way for having a new box ;

look for relay based selector , it's more convenient for placement at back plate where connectors usually are ; you can use ALPS pot for start and later try some more seductive one
same for buffer - you don't need it on tape out if you're using tape rec occasionally ; on/of rec out relay is perfect substitute so you're loading signal route with rec only when you're really recording
if you need that rec out permanently - you must place buffer there

main out - if you're careful enough with cables you don't need buffer
if your fave wires are capacitive , you need buffer - either Jfet based or decent tube one
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Old 26th October 2010, 04:22 PM   #43
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idea - if you're in music biz - you probably know some studio techs

ask them what they're using for pots and signal switching ;

that way you can maybe scavenge/buy some decent predrilled box , few penny-giles 10K faders and any pro switch
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Old 26th October 2010, 04:30 PM   #44
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Default Passive Pre

Would this help?

FS: Silk Audio Transformer Volume Control (TVC) with Seiden Switch

Looney
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Old 26th October 2010, 04:36 PM   #45
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Originally Posted by Looneytunes View Post
if they're on par with Dave Slagle's and some DIY autoformers/xformers I had opportunity to play with - that's certainly good route
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Old 26th October 2010, 05:16 PM   #46
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Originally Posted by Zen Mod View Post
idea - if you're in music biz - you probably know some studio techs

ask them what they're using for pots and signal switching ;

that way you can maybe scavenge/buy some decent predrilled box , few penny-giles 10K faders and any pro switch
I do know a bunch of studio people. I say people because I can't think of any that are very tech oriented. It's funny. Most just use commercial gear and not too much into hifi. But I'll ask around.
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Old 26th October 2010, 07:04 PM   #47
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some of them must be used to tweak/repair their own stuff .

tech geeks are the same all around the world
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Old 27th October 2010, 02:20 AM   #48
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some of them must be used to tweak/repair their own stuff .

tech geeks are the same all around the world
Not a studio guy but I met a tech today. I learned a whole lot and was very enjoyable to speak to someone who is passionate about audio electronics. I am always inspired by people who do what they love in their lives.
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Old 27th October 2010, 05:23 PM   #49
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Resolution:

After taking measurements of noise in both SE and differential and consulting with ARC, this LS25 II is indeed within spec. So it comes down to my expectation and the high sensitivity of the Focal speakers. ARC's reference speaker is 88db efficiency.

However, there is a 6db gain reduction mod which a tech I consulted here in NYC tells me is the ticket for me. This preamp being high gain @ +18db on high setting, I think.

It is still interesting to me that a Arcam solid state preamp costing less that the 2 6h30 tubes from ARC is dead quiet in my system. Although, sound wise, there is no comparison... Compromise is part of audio life as well, I guess.

Looking forward to doing the mod.

Last edited by GeneJazz; 27th October 2010 at 05:30 PM.
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Old 27th October 2010, 06:56 PM   #50
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noise will go down for 6db , too .

in any case - be sure that preamp gain is on lowest setting , or first up - depending of nature of all sources you are using
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