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Tube integrated with tube pre-amp? Have a few questions.

Discussion in 'Tube Audio' started by HiFiJeff, Dec 7, 2018.

  1. HiFiJeff

    HiFiJeff Well-Known Member

    Messages:
    900
    Location:
    Colorado Springs
    Question number 1.
    So I just recently purchased a nice tube pre/buffer for my system that has volume control. Which I am matching to a TPA chip amp that also has volume control. I am also using my Yamaha dac as a pre for volume control as well since it has a remote. So with the tube pre and the tpa amp with volume control, do Imax them both out and use the Yamaha to turn it up and down? Is that stressing the pre and the tpa amp by having the volume turned all the way up?

    Question number 2.
    I am getting ready to purchase a SET integrated tube amp which also has volume control. Same question there, do I max out volume on it?

    Question number 3
    Is there such thing as too many tubes in the signal path?
    Is it redundant to have a tube pre/buffer and have a tube integrated?
     

     

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  2. Palustris

    Palustris AK Subscriber Subscriber

    Messages:
    813
    Location:
    Cape Cod
    First, let me congratulate you on choosing some really great speakers. I own both the Dirty Weekend Specials (in the office system) and also the Soul Superfly in the main system.

    So, what you have are somewhat specialized speakers because they are an easy load on the amplifier and very high efficiency. They are also very revealing of the electronics that drive them which means that getting the most out of them requires pairing down the electronics to the minimum. If we consider that every component (tube, transistor, resistor, capacitor, volume control, interconnect cable, jack & plug) that the signal goes through alters it in some way (adds noise and distortion), even slightly, then we can begin to appreciate that the less we manipulate the signal, the cleaner the output to the speakers. Another way of saying it is that the signal will never be more perfect than it is at the output of the CD player or phono stage, so the goal is simply to amplify that signal to the point that it drives the speakers to listening levels.

    So what does that mean in the real world? Since all that each of us can do is comment on our own experiences, I will tell you what I have done. For the main system using the Soul Superfly speakers the entire signal chain from the output of the CD player is: cable/jack - volume control - driver/voltage amp tube - EML 320B output tube - output transformer- cable - Zu speakers. OK, let's decipher that. The signal from the CD player goes by interconnect to the volume control on the amplifier; that attenuated signal is fed to the tube that amplifies the voltage necessary to drive the output tube to clipping; the amplified signal is fed to the grid of the output tube by direct coupling (no capacitor); the output tube works into the single ended output transformer which converts the high impedance of the triode into the low impedance (16 ohms) that the speaker needs.

    Consider the signal chain: one interconnect, volume control, one driver tube, one output tube, output transformer, cable, speakers. That's the entire signal chain from CD player to speakers. There are no superfluous stages, no buffers, no extra stages of amplification that will simply be attenuated in the volume control, and all that adds up to a lack of noise and distortion in the signal chain.

    So that's my recommendation: reduce the number of amplification stages, reduce the number of components the signal goes through, reduce the number of interconnects and with each reduction of an unnecessary component you are making the signal cleaner and clearer. These speakers sing with a high quality source into a single ended triode amp that is two stages: driver tube and output tube with a volume control at the input. Naturally, direct coupling between the two stages is preferred since that eliminates one capacitor in the signal chain.

    I would suggest you experiment. If the volume control on the CD player can attenuate the signal in the digital domain without corrupting the signal, then use that directly into your Class D amp with the volume control maxed. Now try maxing the volume on the CD player and using the volume control on the Class D amp. Which sounds better? Eventually, you should get a two stage SET amp to try since they can be extremely transparent.
     
    BassKulcha likes this.
  3. HiFiJeff

    HiFiJeff Well-Known Member

    Messages:
    900
    Location:
    Colorado Springs
    Thank you! One of the best responses and explanations I have ever received on this forum. And yes, ZU's are VERY special. I have heard them at RMAF multiple times, and finally pulled the trigger on a pair last Feb. I just recently bought another pair of DW's with the clarity cap upgrades. The regular ones are going to be delegated home theater duty while the new ones are going to be in my dedicated two channel system.

    So I am going to go through and re-read your response a few more times to get everything you said. But the gist of it is, less I more. Which I have ALWAYS been a fan of. I agree with you that less things the signal has to pass through, the better the sound is going to be. I come from a car audio competition background and I literally had no eq or weird thing in the signal path and my system won multiple 1st place trophies. It was head unit to amp to crossover to speakers. That's it. And also one of my favorite sounding systems was some Omega speakers that was fed by a Decware SET amp. CD player went straight into the amp.

    Now my only thing is this. I am constantly turning up and down the volume depending upon what I am listening to. So having a remote control is a must for me. I don't want to have to keep getting up and down. So is there a passive preamp that I can buy that wouldn't interfere much with the signal? Plus I need a pre for the three different sources I have. CD, streamer and turntable.

    And what is a two stage SET?
     
  4. HiFiJeff

    HiFiJeff Well-Known Member

    Messages:
    900
    Location:
    Colorado Springs
    So this option would be a good thing and a direct path?
    upload_2018-12-7_12-7-41.png
     
  5. Palustris

    Palustris AK Subscriber Subscriber

    Messages:
    813
    Location:
    Cape Cod
    Well, I know I must have blasted you with way too much information, but I am very enthusiastic about these speakers and how I use them.

    Let's get back to basics. You have a CD player with an internal volume control so connect it directly to the class D amp input and crank the volume to max on the class D amp. Use the volume control in the CD player and listen for an hour or so to several types of music you like. Then crank the volume on the CD player to max and use the volume control on the class D amp to control loudness. Listen for an hour or so and see which you prefer. That's where I would start. Now if you have the patience, you could interpose the "buffer" and go through the experiment again with the various volume controls, using just one of them and maxing the other two.

    Next think about the SET amp. Here is a good article about a two stage 2A3 amp with a volume control at the input to illustrate what I am talking about. A SET based upon a 300B tube will have more than twice the output wattage compared to a 2A3 e.g., about 8W as opposed to about 3W for the 2A3. So, in my experience, the Zu speakers can use the extra wattage, particularly in a large room. I would look for a 300B amp.

    I don't have much of an idea what's available for SE 300B commercially available amps, since I have been modifying or building my own for years. However, if you are willing to built a kit, I think the Audio Note 300B kit has all you would need except the remote volume control which you would have to add on as another kit (note the optional 3 input selector switch). The great thing about a kit is that you can modify it, such as adding the remote VC. The Audio Note is a three stage amp that is cap coupled between stages. It is not the ultimate in transparency, but will give you a window into the high end. You could download the manual to get a feel for how it is assembled and if it will be within your own capabilities. Bottlehead also makes a 300B kit that may be easier to assemble, but it is intended to be used with their preamp so requires another purchase.
     

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