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In Reply to: Re: My real interest is basic. posted by njjohn on February 4, 2007 at 20:07:36:
Hopefully, someone else could chime in if they have any ideas as to the possible impact of running such a wide range of tubes with the same OPTs. I am not questioning the sound of the amps and I am certainly not passing judgement. I am just wondering how that issue is impactful as I have had several amps built and I have always been mindful of the primary impedance, power output and distortion given a specific tube and primary impedance. I am not arguing the virtue of John's amps.
Follow Ups:
Each of the output tubes you have listed have their own plate resistance. In Class A, a triode tube will give good output power and have low distortion with a load a least 3 times it's plate resistance. The higher the load impedance the lower the output power and the lower the distortion.A 45 has a plate resistance of about 1650 ohms. Three times that is 4950 ohms. A 300b has a plate resistance of 700 ohms. You see a lot of people using 2500 ohm transformers for the 300b. A 300b will have less output power and lower distortion if it is loaded with a 5000 ohm transformer.
One size does not fit all. But there is some wiggle room.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
That was my understanding but I was curious as to the possible effects of using a PP OPT, designed for a 2A3, in a SE circuit using 45s, 2A3s, 50s, 300Bs, PX25 and 845s. John Hogan had used a certain vintage Webster OPT with those various tubes and to good sonic effect according to the people that heard them.
That is what I am trying to say. Armchair philosophy is useless to me.Bring over your best amps and let's see what's up.
That's the only way to tell what is really going on.
My guess it that your amps are going to have some sound features or aspects that the websters don't have and vice versa. Because different opts are the real reason for different characteristics, and tubes less so.
> > A push-pull transformer will work just fine single ended as long as the power level, especially the DC component in the primary, is so low that you don't saturate the core. In other words, your eight watt transformer can't put out eight watts single ended, but I wouldn't be the least surprised if it worked just fine single ended at two or three watts. < <I am sure it works fine but I am wondering how it applies to the varies tubes. I think the smaller Webster OPTs were for the PP 2A3.
'Armchair philosophy is useless to me'.You seem to be under the impression that I am questioning the sonic or musical value of one amp versus another. That is a different area exploration that could be taken up at some point. My question is basic and is rooted in fact.
> > Because different opts are the real reason for different characteristics, and tubes less so < <
Not that this reply is correct but has it ever dawned on you that the different characteristic in tubes that is not apparent could lie in the fact that the OPTS have such a strong characteristic as to not have the resolving power to deliniate the changes in tubes, particularly the input tubes?
There ae many things that go into an amp with the OPTs and the PT being critical along with good power supply design and execution and most certainly a good circuit design and execution.
Again, I am not questioning the sonic merits of John's amps. I heard them and liked what I heard and too many other experienced people, including yourself, have heard them and have been impressed with the sound. I chose not to pursue John's amps because I have my own approach to the hobby. Part of your big interest is John's amps and his ability to draw music out of those Webster OPTs. My interest is researching topologies to gain enough knowledge to be dangerous and then seek enough input from enough people to then have an amp that I am interested in built.
The different characteritics in tubes are very apparent. Even different brands of the same tube are very apparent as per Gordon on the asylum.You can basically hear everything you need to hear.
But real character of the amp lies in the opts.
To me the websters are like coming home to a sound that I treasure, sound characeristics that are remarkable.
Will what I am saying ever catch on? I doubt it. It might be too much of a mystery to fathom.
In three years of posting on the asylum, I've yet to hear of another set builder who has tried them.
So it can be left at that. I've been trying to share that's all.
Thanks.
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