300b lovers

But there are choices that affect the sound.  If you need a 1 watt 1K resistor you can use any type on a cathode, but different types have different sounds.  The cathode bypass cap might need to be 100 uF.  Different 100 uF caps sound very different.  All will satisfy engineering standards, but parts and layout choices have profound effect on the final sound. 

When you run zero feedback, the circuit has no ability to reject things like this. So everything makes a difference. However, for something like an electrolytic bypass, I think you'll find that as long as the part is good quality, the big differences you hear will be more about the part forming up over time: they will arrive at the same place sooner or later.

For reasons that are not clear, various brands of metallized polypropylene capacitors sound quite different from each other, and there is little correlation with DA and DF parameters. Based on measurements, they should all sound the same.

Sometimes you have to do your own measurements because the specs of the manufacturer don't always tell the whole story. If you use a precision differential amplifier to drive the caps in question, you can measure how they behave and differ from one another while in circuit.

@atmasphere First off, this thread was started by a fellow who has a rough first prototype of a zero feedback push pull 300b amp, so of course we are discussing that.   I agree that in that circuit you hear everything.   I will tell you that even in circuits with feedback I will not use electrolytic caps in the signal path.  I also do not use them in my power supplies, but only in the filament supplies.  In my experience electrolytic caps make circuits sound grey and hazy compared to a very top quality film cap.  You can wait forever for a lytic to run in, you can bypass it with small film caps, and whatever else.  When I replace them with a very good film cap I hear the difference.  To each their own.  I also hear differences between resistor types in key spots in circuits, whether the circuit has feedback or not.  Again, my experience, so I build amps with the parts types that I favor.

@donsachs FWIW I was referring to an electrolytic cathode bypass cap. I wasn't very specific about that in my last post.

As I read the last few posts, it seems like objective approaches contain a subjective element (the proverbial yin-yang). Designers can perform the same experiment and draw different conclusions based on what they hear or don't hear. Perhaps the ultimate audiophile is the guy who designs his own gear and seasons to taste. :)    

Well, Hawkrising, your last sentence might be correct but I studied Economics, not electronics, so I rely on excellent designers and fabricators like Don and Lynn for my front end gear and, in exchange, I compensate them for their efforts.  

Aspirationally, the ultimate audiophile could take a stab at recreating the something akin the stellar Lampizator DAC's, like the $20K Lampi DAC in the Spatial room in Seattle which was the source for the music they presented.  Totally stunning sound, but likely far beyond the skills of most audiophiles.  I am not sure even Don or Lynn want to tackle building a DAC.  

Don/Lynn vs. Ralph seem to have somewhat different notions of how these tube amps might be best designed and fabricated, which reflects different design criteria.  That's cool.  Lots of designers have different design philosophies... probably all of them.  I haven't heard Ralph's 300b amps which might at some point be an interesting comparison to my 300b amps.  ;-)

Don sent me his pre-pro 300b amps a few months ago which I have been using to power my very efficient Cube Audio Jazzon speakers and the sound is simply ethereal, like nothing I have every heard in my 50 years of audiophilia... a remarkable improvement even in comparison to  Don's  KT88 amp, which is outstanding, a legacy amp for sure, and the 300b mono's are better in every way.  The musical notes simply hang in the air, suspended in the room in front on my listening seat.  Matching of speakers is required for the 300b monos, but I drove some 86 db efficient standmount speakers with alacrity... my ears gave out long before the 300b amps did, with not a hint of distortion so as Don says, the 27 wpc amps rather sound like a 100 wpc SS amp.  That is what my ears tell me so the amps will drive a wide variety of speakers that many other 300b amps simply will not.  

If you have followed this thread, Don and Lynn have made significant enhancements to the performance of the pre-pro mono's I have, yet I just can't imagine how much better the SQ will be after Don gets them back and updates them to the final production version.  However, I have no doubt that I will have one of the finest 300b amps possible at any price so always with Don, it is "promises made and promises honored."   

The final point I'd like to make is that Lynn envisioned this employment of 300b tubes in an earlier iteration of it and he and Don put their collective wisdom together to update the design with these new mono's.  Just as with fleawatt 2A3 power tubes, the 300b power tubes have a sonic signature, to my way of thinking and to my aging ears, are unlike any other tubes in power amps and I have had many of them over the years.  Once you have heard them, you can't unhear them... so long as they are matched properly with compatible speakers which in fact will include a lot of speakers that many other 300b amps will not drive properly .  Cheers.