Hi it is easy.
Connect XS1A pin 1 to XS3 pin 1. Remove all other connections to either of these pins.
Connect XS2A pin 2 to XS 3 pin 3. Remove all other connections to either of these pins.
Remove tubes. Disconnect PSU. Done. No one needs extra GAIN today certainly when the power amplifier already has enough gain. Sources all have 2Vrms line levels. If it was not silly enough that people still built 1 mV sensitive stuff now the tube ChiFi goes on the same track.
Connect XS1A pin 1 to XS3 pin 1. Remove all other connections to either of these pins.
Connect XS2A pin 2 to XS 3 pin 3. Remove all other connections to either of these pins.
Remove tubes. Disconnect PSU. Done. No one needs extra GAIN today certainly when the power amplifier already has enough gain. Sources all have 2Vrms line levels. If it was not silly enough that people still built 1 mV sensitive stuff now the tube ChiFi goes on the same track.
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Could I just add a circuit that rectifies the input power which would give me about 110~115v DC for the heater supply, or am I over simplifying?
Barry NJ,
I am not sure what you are saying in your Post # 43.
But do Not power anything other than a power transformer Primary from the Power Mains.
Connecting any other amplifier circuitry directly to the Power Mains is a Recipe for the following:
"The Surviving Spouse Syndrome"
Remember, Safety First!
You will not enjoy your stereo from 6 feet under, if you get my meaning.
I am not sure what you are saying in your Post # 43.
But do Not power anything other than a power transformer Primary from the Power Mains.
Connecting any other amplifier circuitry directly to the Power Mains is a Recipe for the following:
"The Surviving Spouse Syndrome"
Remember, Safety First!
You will not enjoy your stereo from 6 feet under, if you get my meaning.
The best possible scenario - is not to add any gain at all between your source components and a power amp, rather to not have any adverse loading on the source and at the same time allow it to be attenuated for audio enjoyment. Quite easily done.
Yes, I now realize what I really want is a tube-buffer with a volume control.
With modern stereo systems, a true "Pre-Amplifier" is not really warranted...
You have learnt something important today. No sarcasm, seriously.
Now also try to think if inserting a buffer with often worse drive capability than your sources wil be beneficial. It is very normal for modern sources to be able to drive volume potentiometers of 10 kOhm without any issue except lower noise.
Things would be different if the sources are tube devices but if not then inserting superfluous stuff won’t improve matters in many cases.
Now also try to think if inserting a buffer with often worse drive capability than your sources wil be beneficial. It is very normal for modern sources to be able to drive volume potentiometers of 10 kOhm without any issue except lower noise.
Things would be different if the sources are tube devices but if not then inserting superfluous stuff won’t improve matters in many cases.
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I like the sound with this tube pre-amplifier in the signal path, I'm just unhappy with the excessive gain and lack of finesse available with the volume control. If the sound I like is due to some increased distortion, then so be it, I like it.
Then a tube buffer is possibly what you need/want. However it is not clear which sound you do and which sound you don’t like. You could do the straight wire test just to check (if only to find out if the line level signals are enough in your setup).The power amplifier itself might just have enough of what you like.
If distortion is what you are after then the tube buffer could be too good for the purpose and you maybe will not like the outcome. It is a possibility.
If distortion is what you are after then the tube buffer could be too good for the purpose and you maybe will not like the outcome. It is a possibility.
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Well, I still need volume control, and source switching, so something needs to go between sources and amplifiers, and I like what the tubes bring to the sound.
Yes but the passives are not the variables. The passives can also be connected directly to the power amplifier if only to check…..
Fair enough, I won’t repeat what I wrote in my previous post. Apparently the device must have tubes whether necessary or not. Technical features seem to be of less importance.
Still, in our small technical world we deal with impedances, standardized line level signals and therefor predefined gain. This to avoid silly high GAIN and mismatching of devices. It works.
Fair enough, I won’t repeat what I wrote in my previous post. Apparently the device must have tubes whether necessary or not. Technical features seem to be of less importance.
Still, in our small technical world we deal with impedances, standardized line level signals and therefor predefined gain. This to avoid silly high GAIN and mismatching of devices. It works.
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For clarity, my current "pre-amp" an Audio Alchemy DLC, generally has its volume control set between -30 and -20dB. If I were to connect a source directly to my amplifiers, I would not be able to listen as the sound pressure would be too high, so I need attenuation to the signal, I need a "pre-amp" of some sort. When my X10-D died, I figured I'd skip the buffer and go right to a tube pre-amp. I purchased this unit without a full understanding of the differing gain structures built into various pre-amps, I figured a pre-amp is a pre-amp...
Yes that is normal. Your situation is a preamp that amplifies input signals a tad to much leading to the power amplifier having full volume very early on the volume scale. Of course a power amplifier will need volume control as it normally has full output with for instance 1Vrms input signal. Sources generally have 2Vrms line level signals so more than enough, even enough to make the amplifier be overdriven damaging the loudspeakers. Now imagine what happens if you amplify that 2Vrms with a tube preamp (with a gain of 30x)...
You will likely be better off with a gain of 1...3x. Issue with many a tube preamp is their very high and today unnecessary gain. In reality this is often because of wrong focus on "it must be tubes" and not looking to a single technical specification or any detail at all. There are some simple rules to make this all function as it should. We do need exact information to be able to determine the chain has normal standardized sensitivity etc. so it would be good to mention the brand and type of power amplifier and/or its input sensitivity.
Please have a read here where many things are explained quite nicely:
https://www.diyaudio.com/community/threads/what-is-gain-structure.186018/
You will likely be better off with a gain of 1...3x. Issue with many a tube preamp is their very high and today unnecessary gain. In reality this is often because of wrong focus on "it must be tubes" and not looking to a single technical specification or any detail at all. There are some simple rules to make this all function as it should. We do need exact information to be able to determine the chain has normal standardized sensitivity etc. so it would be good to mention the brand and type of power amplifier and/or its input sensitivity.
Please have a read here where many things are explained quite nicely:
https://www.diyaudio.com/community/threads/what-is-gain-structure.186018/
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I think I missed the above earlier...
And it's fair, but I don't have one handy to test, and I'm not ready to make the investment. If someone near by wanted to bring one over, to try in my system, I would not be opposed. Supposedly, my current pre-amp is passive until unity gain is reached, and then the amplifier circuitry is called into play, but I'm not 100% on this information, I would need to reread the review from the '90s.
For amplifiers I use both an Audio Alchemy OM150 (Class A/B) and Merrill Audio Thor (Hypex UcD), both seem to have similar sensitivity/gain, since volume settings on the pre-amplifier are similar, though I have not done any real measurements on this.
Who says a cathode follower will have worse drive capability than the source?
A typical CD player will have something like an NE5534 op-amp for its output stage. That will have a very low Zout, but it won't sink more than perhaps 4mA into the load. Stick some high-ish capacitance interconnect and a 'passive preamp', then another high-C interconnect, and one could conceivably degrade the signal before it gets to the power amp. I'm not saying that is likely. I'm saying it is possible.
I see nothing wrong with adding a reasonably well designed cathode follower to the signal chain to buffer the sources and drive the input switching, volume control and interconnects. A 12AU7 cathode follower biased to perhaps 5mA plate current would do a fine job. There are better triodes to use for a buffer, but heck -- 12AU7s are still cheap and plentiful, and will work fine for this. If you want to play with tubes, why not? This will work.
OM150: 30 dB gain, I can not find its input sensitivity though but it will likely be 1Vrms for full output. The situation seems to be as pictured. You know what to do.
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