BBX feeding a SS amp

[Marvel]

I know we have talked about this before, and thought I would bring it up again to hear what others have done to solve the problem.

I had tried using my Merlin with a SS amp, but found almost NO bass. Even the LaScalas have more bass than what I was hearing.The SS amp I was using (Alesis RA-100) only has a 7k input impedance. Mark Deneen pointed out that the higher output impedance of the Merlin tube pre was causing the two to make a filter that was rolling off the bass. I had the tube amps here, so just put them back in the system. So what solution is there?

Some have used the little impedance matching buffer boxes that are available. I think ART has one (the names are escaping me at the moment). ROLLS has a quad direct box with a 100k input impedance that might work. But that means spending more money. I checked out some transformers from Jensen, which would also do the trick, and add no more electronic noise to the mix. But the Jensens aren't cheap either.

So... for a while I have had the BBX in the system (nice to be able to listen to the old vinyl again). I started thinking about the SS amp once more. Still have the same problem though. I am trying to think of what I could use to match the impedance without buying something new. Well, most of the other SS equipment I have has a higher input impedance than the Alesis. I grabbed my Tascam cassette deck (50k input), put it in between and lo and behold, I still have bass with the SS amp. But it is big and I need to leave a tape in it to pass the signal through. So I grabbed my 1U high compressor out of the rack and put it in. Made sure it was in bypass mode, and it is working great. Now I also have meters that I can watch from across the room, too. With the Alesis working at 75 wpc into the LS, it doesn't even begin to warm up. Maybe with winter coming I should put the tubes back in place!

It's a nice switch, at least for a while. I will stick the Moondogs back in the bedroom on the Heresies for now.

Bruce

[Guest " "]

Interesting...keep in mind that some impedance matching devices can make the lack of bass problem worst.  An impedance matching device that is autoformer or transformer based which has a low DCR will act like a low pass filter across the load.  Higher quality passive pre-amps will have this filtering effect occur below the usable audio range.  This is what makes the SS black boxes attractive...they perform better at lower price points...at higher price points...the autoformer or  transformer based devices are favored.

 

 

 

 

[Marvel]

Mark,

I have two of the Alesis amps, and use one in my rack of recording gear. Yeah, the amps have a ridiculously low input impedance.

I originally tried it when I first got the LaScalas, and had the Merlin back in the living room. Just didn't work well, for the above stated reasons. I was using the Merlin with the Moondogs, and it a a beautiful match. I bought Cullison's BBX back in the summer, but had trouble with the 6922 being noisy and oscillating. Finally got around to getting some EH 6922s and the don't cause near the problem. A little noisy (hiss), but I can't hear it from my chair.

So I have the BBX in the mix and decided to try it again with the Alesis amp. I didn't even try it straight into the Alesis, but first used the Tascam deck and then the Alesis compressor (again, I will point out that it was in bypass so I am not compressing the signal any). It works great.

Bruce