Tír Na HiFi

cybot wrote: ↑Thu Oct 05, 2017 6:36 pm

Rob wrote: ↑Thu Oct 05, 2017 2:14 pm

cybot wrote: ↑Thu Oct 05, 2017 11:49 am If truth be told I was more interested in the passive pre option as I've never heard what a passive pre can bring to the table. When I think of passive I think airy highs, transparency and no bass ;) Anyway I honestly can't see a use for either in my system. So I don't really know exactly where they actually fit into a system that's already been assembled with care......and, more importantly sounds good!

The conventional wisdom is that passive pre-amps can be very good if well matched without long interconnects. I think I read on your link that the Tisbury has a 10k pot so should match well with quite a few power amps except some lower input impedance transistor and Class D amps, as long as they have a high sensitivity, perhaps below 1 volt for use with CD or phono stages, or a much higher sensitivity if using cassette decks (remember them?) and tuners because they tend to have a fairly low output. If bass is an issue then another option is to use a transformer volume control which have a low impedance output. These can be especially pricey but recollect that the Hifi Collective had a relatively inexpensive model.

Thanks for that Rob! It's all starting to make sense....

I would see the issue as one of context - you're probably aware of the issue of impedance matching so if you have a CD player/DAC and/or phono-stage with a decent amount of output voltage and a low output impedance, and the signal will meet a very high input impedance on a high sensitivity power-amp, then a passive pre-amp may be a good solution because the source(s) can drive the power-amp satisfactorily provided the interconnects aren't very long. The one thing I would say about buffers is that they are controversial to some audio sorts because emitter-followers or cathode-followers (the tube equivalent) treat the signal to 100% local negative feedback where all a given active device's gain is traded for a commensurate reduction in impedance. They are probably worthwhile in most instances though and some firms make dedicated tube buffers, e.g. Musical Fidelity a while back.

Again thanks for the tips Rob. I think I'll stick with my actives :)

cybot wrote: ↑Fri Oct 06, 2017 6:44 pm Again thanks for the tips Rob. I think I'll stick with my actives :)

Out of curiosity what preamp qnd amp are u using

nige2000 wrote: ↑Fri Oct 06, 2017 8:25 pm

cybot wrote: ↑Fri Oct 06, 2017 6:44 pm Again thanks for the tips Rob. I think I'll stick with my actives :)

Out of curiosity what preamp qnd amp are u using

All Croft's - Micronaut pre/Polestar 25 watt - both hybrids. Also a Micro 25 pre/Series 7 45 watt..

Rob wrote: ↑Fri Oct 06, 2017 10:30 am The one thing I would say about buffers is that they are controversial to some audio sorts because emitter-followers or cathode-followers (the tube equivalent) treat the signal to 100% local negative feedback where all a given active device's gain is traded for a commensurate reduction in impedance.

One of the noisiest exponents of the 'I hate the sound of feedback' meme I reckon is Charles Hansen of Ayre. He does use emitter followers in his power amps so I figure they're given a pass.

cybot wrote: ↑Fri Oct 06, 2017 6:44 pm Again thanks for the tips Rob. I think I'll stick with my actives :)

Hello Cybot, I hope it didn't seem that I was trying to pressure you into getting a passive - my post was a response to the discussion between yourself, Nige and Abraxalito, with my two cents about the way in which passive designs could (at times) be a good choice.

abraxalito wrote: ↑Sat Oct 07, 2017 12:31 am

Rob wrote: ↑Fri Oct 06, 2017 10:30 am The one thing I would say about buffers is that they are controversial to some audio sorts because emitter-followers or cathode-followers (the tube equivalent) treat the signal to 100% local negative feedback where all a given active device's gain is traded for a commensurate reduction in impedance.

One of the noisiest exponents of the 'I hate the sound of feedback' meme I reckon is Charles Hansen of Ayre. He does use emitter followers in his power amps so I figure they're given a pass.

Yeah probably - I think Ayre amplifiers use a lot of local negative feedback specific to each active stage, rather than the global equivalent across the different active stages of a circuit. Doubt there are many true zero negative feedback transistor amps although maybe the First Watt SIT is an exception. My own triode power amp doesn't use any global and local negative feedback but I didn't follow through philosophically because I found that using the very high gain/high current/very low impedance pre-amp stage of a massive integrated amp sounded a lot better with the triodes than my old direct-coupled Audiolab 8000Q (!!) so never got around to trying a passive but hope to try a TVC or variable autoformer at some stage.

Rob wrote: ↑Sat Oct 07, 2017 10:09 am

cybot wrote: ↑Fri Oct 06, 2017 6:44 pm Again thanks for the tips Rob. I think I'll stick with my actives :)

Hello Cybot, I hope it didn't seem that I was trying to pressure you into getting a passive - my post was a response to the discussion between yourself, Nige and Abraxalito, with my two cents about the way in which passive designs could (at times) be a good choice.

Your two cents were informative, fun and harmless :)

nige2000 wrote: ↑Thu Oct 05, 2017 10:12 pm so its not a bad idea to know what that is when looking at tvc
personally if going with transformer volume control id be looking at a large step down 3:1 or greater
meaning its input would need to be amplified to maybe 4 or 5v

on my list of stuff to try

Although not nearly as dramatic an impedance drop as with a buffer, the nice thing about TVCs is that the impedance drop is the square of the voltage winding so a 3:1 would give a nine-fold drop in impedance from a three-fold cut in voltage, and there is very little inherent resistance in the device - perhaps just from the resistance of the wire windings, but good ones would be way more costly than a volume control. Auto(trans)formers are a realistic option because a large winding ratio isn't required unlike say in a valve amp's output transformer, and reputedly suffer less from sound degradation, with wider bandwidth and less internal resistance - there are a few about such as http://www.tnt-audio.com/ampli/townshend_allegri_e.html but aren't any less expensive than conventional TVCs so still bound to be a speciality item unfortunately.

If you can diy
Intactaudio has a low cost option
http://www.intactaudio.com/atten.html
Dave Slagle the owner has a very reputation for winding iron

Not sure about his international shipping

One of these days I would like to try one of his autoformers

Randy