I need a pre amp...
Aug 3, 2008 at 6:07 PM Thread Starter Post #1 of 4

Navyblue

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For quite some time, I am in need of a stereo pre amp for my 5 channels Carver AV-405 power amp, which in practice I use it as 2 separate stereo amp (front channels for speakers, rear channels for headphone), with the fifth channel (center) left unused.

I see the following options:

DIY passive pre amp

I have been wanting to DIY a passive pre amp for months, but for various reasons I did not act on it. The main reason is the high output impedance, and I wonder if it is worth doing. I measured my power amp input impedance to be about 120K ohms. From what I have read the input with about 10x less output impedance is required, which is about 10k ohms. And I have problem getting hold of a Alps RK27 10k ohms, 20 and 50 k ohms seems to be more readily available. I even bought a casing for it.

Headphone amp as pre amp

Since I don't own a headphone amp. It might be a good excuse for me to get one. I am looking at the cheaper ones like the Little Dots or even Darkvoice. I am also considering DIY options. I could use the casing I bought for the above. I have a question regarding the DIY amps, do I just hook the headphone out to the input of the power amp to use them as pre amp?

I am open to both SS and tube. Would a tube headphone amp "tubify" overall sound when used as a pre amp? If so I am not too enthusiastic about it for my speaker. But for my headphone it is a welcome addition.

Integrated amp as pre amp.

I wonder if it make sense to buy a used old integrated amp as pre amp. They are dirt cheap and readily available, and I have problem getting a used pre amp. Would most of the budget ones be worse than a typical budget pre amp?

DIY speaker switch

This is be the cheapest way. I could split the 2 channels output to the 4 channels of the power amp. I could made a switch box to disconnect the speakers when I don't want them to make noise. But it might not be a good idea to add one more switch in the signal path. though in practice it might not be noticeable and my speakers are pretty mid fi and used mainly for movies and rarely for music.
 
Aug 3, 2008 at 6:19 PM Post #2 of 4

Drag0n

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Aug 3, 2008 at 9:50 PM Post #3 of 4

atbglenn

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Quote:

Originally Posted by Drag0n /img/forum/go_quote.gif
Parasound php850, went for about $250usd new, reviewed very well for the price. Found cheap on Ebay etc., used.

http://www.parasound.com/pdfs/vintage/php850om.pdf



I've been using one for a few years now for my home office system. I think it's great for the money. It even uses an ALPS Blue Velvet volume control pot, and the build quality is pretty good for the money as well. You can probably pick one up for around $125 on ebay.

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Aug 4, 2008 at 12:01 PM Post #4 of 4

Navyblue

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Thanks guys, the Parasound look like a good deal. I'd like to get one locally as I'd prefer to to mess with shipping for an item of this size. For some reason I haven't seen a cheap pre amp lately on the local used market, which made me look at other options. The headphone amp options looks quite interesting to me due to it's dual purpose, while at the same time the simplicity of passive pre amp also interests me.
 

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