Hi, I have no experience with tubes, so I want to ask you if it really can be as simple as this, or are there missing parts in schematic ?
What I think I have learned is that a single tube like this may have high gain ?
In article 2 tubes are shown .... I guess that would mean they only use half of the tube .... could they be wired different so that tubes could be shifted left to right when they wear out, or are other factor in play with tube wear ?
http://www.electra-print.com/ultrapath.php
What I think I have learned is that a single tube like this may have high gain ?
In article 2 tubes are shown .... I guess that would mean they only use half of the tube .... could they be wired different so that tubes could be shifted left to right when they wear out, or are other factor in play with tube wear ?
http://www.electra-print.com/ultrapath.php
kstagger how did you like the sound?
Ever tried a different tranformer or tube?
I have been curious about this preamp and pondering transformer options. I know Sowter makes some line output transformers but don't know of much else capable of 20-25 ma to be able to experiment with different tubes...
Ever tried a different tranformer or tube?
I have been curious about this preamp and pondering transformer options. I know Sowter makes some line output transformers but don't know of much else capable of 20-25 ma to be able to experiment with different tubes...
never swapped out the transformer... but I did check out different versions of the 12J5 (which is mercifully cheap)...
It's been awhile but I remember it was an all-around good performer - I used an outboard regulated Heathkit power supply supply/. But in the end I preferred some of latter creations and the line transformers were sold off to fund some other projects. Don't get me wrong - it wasn't a bad preamp at all and I sure wish I could hear it again with my (since then) upgraded system. If I was going to build it again, I would have used a stepped volume control pot and a different PS.
There are some pix on my website (behind my screen name) under Projects. It's a cruddy 'free webspace' so beware of the pop-ups.
It's been awhile but I remember it was an all-around good performer - I used an outboard regulated Heathkit power supply supply/. But in the end I preferred some of latter creations and the line transformers were sold off to fund some other projects. Don't get me wrong - it wasn't a bad preamp at all and I sure wish I could hear it again with my (since then) upgraded system. If I was going to build it again, I would have used a stepped volume control pot and a different PS.
There are some pix on my website (behind my screen name) under Projects. It's a cruddy 'free webspace' so beware of the pop-ups.
Re: How good is it?
Sorry - it's been too long since I've heard it so I can't say anything very specific about the sound anymore... at the time I thought it was one of the best preamps I've ever heard - but (at least in my system) I ended up preferring some of my later designs - perhaps it's vanity. I would say try it out.
Nikolas Ojala said:
Sorry - it's been too long since I've heard it so I can't say anything very specific about the sound anymore... at the time I thought it was one of the best preamps I've ever heard - but (at least in my system) I ended up preferring some of my later designs - perhaps it's vanity. I would say try it out.
A bit different solution
It seems that the beauty and fundamental idea of the Ultrapath amplifier is in minimizing this current loop:
Anode - Transformer primary winding - Capacitor - Cathode.
The way that was done in Ultrapath amp was by removing the bypass capacitor from the cathode resistor and reconnecting it to the positive high voltage, directly to the transformer. Thus the loop area was minimized. As we have been told, the principle works. I suppose that keeping all iron away from the loop would be good too. Choosing a good capacitor is another important part of the solution. But this Ultrapath solution caused a problem we allready know: The 120 Hz humming.
We should remember what was important:
1) Keep the current loop small.
2) Have good capacitors in the signal path.
That is the Ultrapath way. But what about the humming problem?
I think there is at least one more possible solution, different than the Ultrapath, but based on the same principle:
1) Keep the bypass capacitor, just like in most cathode biased amps, but let the capacitor be as good as you can get.
2) Take one more good capacitor and connect it from the Ground to the high DC source voltage. You get an AC current loop:
Anode - Transformer primary winding - (DC voltage here) - New capacitor - (Ground here) - Bypass capacitor - Cathode.
3) Take care that the current loop really is small and there are no iron parts inside or near the loop.
The schematics of this solution is nothing special. You can easily draw it. Actually there is nothing new. The new capacitor is just one more filter for the DC. But keep in your mind the original idea of the Ultrapath amplifier. Following the idea you should be able to get desired results.
It seems that the beauty and fundamental idea of the Ultrapath amplifier is in minimizing this current loop:
Anode - Transformer primary winding - Capacitor - Cathode.
The way that was done in Ultrapath amp was by removing the bypass capacitor from the cathode resistor and reconnecting it to the positive high voltage, directly to the transformer. Thus the loop area was minimized. As we have been told, the principle works. I suppose that keeping all iron away from the loop would be good too. Choosing a good capacitor is another important part of the solution. But this Ultrapath solution caused a problem we allready know: The 120 Hz humming.
We should remember what was important:
1) Keep the current loop small.
2) Have good capacitors in the signal path.
That is the Ultrapath way. But what about the humming problem?
I think there is at least one more possible solution, different than the Ultrapath, but based on the same principle:
1) Keep the bypass capacitor, just like in most cathode biased amps, but let the capacitor be as good as you can get.
2) Take one more good capacitor and connect it from the Ground to the high DC source voltage. You get an AC current loop:
Anode - Transformer primary winding - (DC voltage here) - New capacitor - (Ground here) - Bypass capacitor - Cathode.
3) Take care that the current loop really is small and there are no iron parts inside or near the loop.
The schematics of this solution is nothing special. You can easily draw it. Actually there is nothing new. The new capacitor is just one more filter for the DC. But keep in your mind the original idea of the Ultrapath amplifier. Following the idea you should be able to get desired results.
Even better solution
It seems that someone has already thought about this:
http://www.tubecad.com/2006/03/aikido_se_amplifier_2.png
Look at the KT88 pentode, bypass capacitor C2 and the other capacitor C1.
It seems that someone has already thought about this:
http://www.tubecad.com/2006/03/aikido_se_amplifier_2.png
Look at the KT88 pentode, bypass capacitor C2 and the other capacitor C1.
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