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RE: Nah

Posted by Ralph (M) on June 22, 2012 at 08:02:07

In Reply to: RE: Nah posted by Plinko on June 21, 2012 at 16:39:06:

Yes, I would concede that compared to most preamps a good TVC is probably not robbing bass. I'm not sure I would say that about *all* active line stages- for example ours is direct-coupled and has response to 1Hz, which is lower than any TVC I've seen.

I should point out that TVCs are a bit different from PVCs and don't have the same issues of loss of dynamics and bass that plague the latter. The main issues I have seen with them have to do with loading, as loading on any audio transformer is paramount to prevent if from ringing (distorting) and if loaded to heavily, rolled off highs. The issue is different for each position on the volume control! Some manufacturers deal with it better than others. And some play bass better than others as they might have better bandwidth.

BTW for a preamp or TVC to play bass correctly it should have flat bandwidth to 2Hz as a minimum to prevent phase shift at 20Hz; otherwise there will be a loss of impact at that frequency. Many transformers in tube amps are only spec'ed to 10Hz, the better ones maybe 5Hz. This means that they are having problems with phase shift (impact) at frequencies up to 100Hz (in the case of a 10Hz cutoff) or 50Hz (in the case of 5Hz cutoff). If there is a rolloff in the TVC, depending on the amp used you may never know, especially if you are running SETs, as bass is one of the weak areas for many SETs (they get better if they make less power; one of the reasons why the 2A3 sounds better than the 300b and the 45 better than the 2A3).

My speakers go down to 20Hz so I am used to hearing problems in this area if they exist. Regardless I see TVCs as a better solution than PVCs...

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