DIY Pre-amp help

[GrahamT]

I am stuck at college right now and the preamp section on my integrated HK3375 is acting up. The right channel is almost always choppy and staticy. I dont think it is a dirty pot because it sounds the same no matter the volume and it is consistant. I've had dirty pots on other amps but this sounds much different. The amp is used and a refurb so there is no warranty.

So, I need to come up with a cheap pre-amp. The line out on my Pioneer DV-563a is high enough to connect to the power amp section and drive the speakers much louder than I would ever listen to them.

Can I just make a little box with a couple of rheostats to control the line voltage?

It seems to me that I just need something to attenuation the line level right?

I'm a mech, not an elec so bare with me.

Thanks in advance.

[ThomasW]

Can I just make a little box with a couple of rheostats to control the line voltage?

Yep that's what so-called passive preamps do, they attenuate the signal from the source

[GrahamT]

Yep that's what so-called passive preamps do, they attenuate the signal from the source

Excellent, thanks Thomas. I'll look into that.

[GrahamT]

It looks like a double-gang 10 k ohm potentiometer might be the way to. I may just go with whatever I can find here though.

[Saurav]

10K is usually a good compromise. Lower and your source may be driving a difficult load, higher and the driving impedance to the amp may be pretty high. Get an audio taper pot if you can find one, it'll make your life easier. Keep the interconnects as short as is practical, especially the ones from the pots to the amp.

[GrahamT]

Thanks for the confirmation Saurav. Havn't seen you around here much lately.

I'll look for audio taper pots. Thank you.

[JoshK]

Graham,

Email ken_shih@digitalanaloguediy.com and ask him about his 10K ladder stepped attenuator (they are audio taper). This is about as good as it gets for an attenuator, and at $60 is much cheaper than DACT, etc. I have two of these attenuators, one for SS and one for a tube preamp. They are reasonably nice, although not perfect (some noise while switching, but nothing horrid). They certainly are a nicer solution than most pots.

[GrahamT]

Thanks Josh,

I'll look into that too.