My Location Recording Mixer

[emrr]

Many if not most of the RCA tube preamps do not have cathode bypass resistors.  Given the era, likely for reliability purposes, they designed around as best they could. 

 

[alexc]

... learnt a few new things here, re cathode bypass ..  thx to the tube guys, who have a way of explaining stuff so it 'sticks' 

Also, a big fan of the simplicity of the original poster's tube circuits - nothing says audio 'love' like UTC and RCA traffos, some US nos tubes and  'old time'  quality wiring work.

 

[abbey road d enfer]

David Manley would have agreed with that assertion but used a lot more expletives in its expression.

Cheers

Ian

I wonder on what grounds he would have demonstrated that... I'd be curious to examine his arguments. Unfortunately I'm not clairvoyant...

 

[lassoharp]

I built a 3 stage tube preamp and put cathode bypass switches on the first two stages.

The real world differences are often a matter of audio aesthetics - and isn't that almost always the case?  As long as it's not furring up or gritting out to gross levels all those hours you spent measuring the small db differences in total noise can feel like lost causes and often reminders not to spend so much time ever doing it again.

With the cathodes unbypassed you lose about 5-6db of gain and the signal sounds a little skinnier and cleaner. Bypass and you get the reverse of all the previous parameters.  The noise increases slightly as you'd expect with the increase in gain but it's not a deal breaker by any stretch.

 

[ruffrecords]

I wonder on what grounds he would have demonstrated that... I'd be curious to examine his arguments. Unfortunately I'm not clairvoyant...

I had several very long telephone conversations with him a few months before he passed. We were working on a joint development project. During the many hours we spent on the phone he spoke about his ex-wife's prowess in more than one area. Nothing he said about her was complimentary. Difficult to know how much truth was contained in what he said but he definitely felt she was technically light weight.

Cheers

Ian

 

[abbey road d enfer]

With the cathodes unbypassed you lose about 5-6db of gain and the signal sounds a little skinnier and cleaner.

That is to be expected, less gain and a little les THD.

Bypass and you get the reverse of all the previous parameters.  The noise increases slightly as you'd expect with the increase in gain but it's not a deal breaker by any stretch.

In fact noise should not increase as much as gain, so S/N ratio ends up better.