different audio forum

[rayma]

Many tube preamps have trouble driving under 50k loads. Adding a buffer follower stage would help,
either tube or FET.

 

[Galu]

Most solid state power amps have an input impedance of 50k ohms anyway, so the tube preamp you quote should have no trouble driving one.

Very few solid state power amps have an input impedance that is lower, so a buffer is unlikely to be necessary. Do you have a particular model of power amp in mind?

 

[jimmyjoe]

Perhaps, perhaps not. A local pro-audio dealer has some used amps (Peavey and Crown) for sale at very attractive prices. However, some of them (Crowns) have 10K input impedance. I thought that was awfully low.
I wouldn't be looking at pro audio normally, but some are interesting, with high-pass filters built in and all. Just a thought. jj

 

[Galu]

The 10X rule that is generally applicable states that the input impedance of the power amp should be at least ten times the output impedance of the preamp.

You may get good performance connecting your 800 ohm output preamp into 10k, but some tube preamps may be fickle as cautioned by rayma.

Why not ask your dealer for a demo using your valve preamp - I presume you already have one?

 

[woody]

You may look at the Pass B1 preamp it's not a preamp just a unity gain buffer.



PassDiy

 

[jimmyjoe]

Hmmmmm. Possibly interesting. Might need it, and might not. jj

 

[jimmyjoe]

No, I don't. I'm thinking of getting this one:
PAS-NGCT
However, it's a sizeable investment for me, so I thought to save money on the amps. I know, I know .... not a good idea. But the lure of low prices is powerful, and I NEED to know that everything will work acceptably before I sink money in it. The tube amps that I would use otherwise would set me back $4,500. No way am I willing to pay that much for amplification. I may be profligate, but I'm not THAT profligate. jj