Tube preamp with SET questions.

[Ray_pierrewit]

Hello all,

 

A couple of weeks ago I purchased a 2A3 SET amp built in Canada. http://fluxion.biz/B-6TK power amplifier.html . The builder has several youtube videos where he shows the construction of said amp and I was mesmerized watching them. He has an EE background and some pretty sophisticated testing equipment, he also winds his own transformers specifically for his circuits. Having said all of that, he also is of the measurements camp and does not believe in exotic caps and such, which I'm not certain to be able to discern one way or the other.

 

For the price of the amp the quality is top notch, all PP with hefty chassis and I'm really enjoying discovering SET amplification in my setup: Lascala in dedicated listening room which alternately is driven by a nosvalves rebuilt 299B. The 6BTK amp is dead quiet, barely gets warm after a day full of listening and has great tone and dynamics. It has a volume dial and can be used as an integrated with one input, which is how I'm currently using it. The same fellow who designs and builds them, Young Ahn, has a tube preamp with phono input which interests me. http://fluxion.biz/BL-2 preamplifier.html

 

Now for the questions! I've never had a preamp, always opting for integrated amps for simplicity. Having said that, what can I expect by adding said preamp? I have no electronic knowledge, so numbers mean nothing to me. I've read his description of the preamp and it fits the bill inasmuch as the inputs/outputs, but besides that I'm at a loss. Is the preamp purely to add the inputs and phono stage, or does it play a role in the actual amplification or general sound of the system? Really basic questions here that I've not been able to answer by searching the net, I'm counting on some of you knowledgable users to help me out with that!

 

Daniel

[rplace]

There really is no one size fits all answer. But long ago there used to be Tuners, preamps, and amps, among other things. Those things were a lot bigger. As things got smaller and peoples tastes changed integrated "amps" came along. Integrating the tuner, amp and preamp functionality into one handy box. Think of the evolution of Reel to Reel >> Cassette Player >> Walkman >> iPod>>Phone. They sure got smaller. One could very well argue the sound got worse.

 

As a general rule (not always) most people that are into audio would argue and accept the fact that "separates" sound better; or at the very least give you more flexibility. Lots of amps don't have volume/gain control. So if you had one of those you could not connect a device in and speakers out as you would need the volume control. The preamp is like a traffic cop providing the switching for various input devices as well as providing volume control. It also adds gain. Surely there are some that sound both better and worse then a mid-fi integrated. Having separate amps and a preamp lets you pick and choose what you like. You could, for example, have a tube preamp and solid state amps. Flip side is that if you have more things in the audio chain, more plugs to plug in, more points of failure, more cables, more clutter, need for more space in your audio rack or side table.

 

Preamps can impact the sound. Up to you to decide better or worse. I happen to really like a 6SN7 tube based preamp. I also Like a passive preamp that does nothing more that provide (in a perfect world) volume control.

 

If you only have one device, I'm guessing DAC, and not a turntable, tape deck, Reel to Reel, BDP, Mini-disc, CD, DVD, etc. you don't really need a preamp because you have the volume control on your particular amp. Phono input is another discussion. Many need only a dedicated phono input on the preamp to magnify (step up) the weak signal. So a preamp from days gone by always had at least one marked phono where all the others were "line" inputs. You can hook up a CD player to a premp's tape input and visa versa but you should not hook up a "regular" phono cartridge to CD/Tape/Aux/etc. The best, IMO, phono cartridges are so weak that they need an external phono stage just to get to the line level that you can in turn hook up to CD/Aux/Tape.....but no "regular" Phono  . Of course there are preamps that have the necessary bits to actually step up those really weak phono signals and not have another dedicated box between the turntable and preamp. Obviously there is no universal one rule and surely one size does not fit all when it comes to amps, preamps, integrateds. Turners are pretty much dead but I'm sure there are plenty of people still using them...connected to their preamp of course.

 

Hope this helps.

[Ray_pierrewit]

Thanks for the reply. I am using several sources, Phono, CD, Tuner, Bluetooth streamer and have been using a quality source selector for all but the phono. I'm encouraged by your 6SN7 tube based preamp observation, as the above linked preamp uses them.

 

When you say that it adds gain, does that mean that the amp will play louder than without? I ask because even though the 2A3 amp is 3w/ch, I rarely go above 11 o'clock on the dial.

 

Would anyone be kind enough to look at the previously linked preamp information and "decipher" the specs for me? I'm not asking for advice on whether or not it will sound nice, of course that can only be heard to be decided. 

 

 

 

[rplace]

1 hour ago, Ray_pierrewit said:

When you say that it adds gain, does that mean that the amp will play louder than without?

 

I'm not all that well versed in the actual electrical theory end of things. There are much smarter people on the Klipsch forums than me, for that, and I'm sure they will chime in. Hopefully we can both learn something.

 

This is how I think it works or at least net result. That volume knob is not really making things louder it is making it quieter when it is not turned up all the way. This is called attenuation. Attenuation lowers or makes things "less", i.e. quieter. Forget your amp for a second and think of one that only amplifies with no volume knob, a more traditional amp if you will. An attenuator in its simplest form would do nothing but let you control the volume. I, and many others, would call that box with a volume knob and its small collections of electrical bits inside a passive preamp. Signal in >>> volume control >>> altered (attenuated) signal out >>>Amp >>> noise >>> smile on face (unless nose = country music).

 

I think that an "active" preamp or non-passive preamp....lets just call it a "preamp" can be built such that along with attenuating the signal input and controlling the volume can "add" something to the signal that was inputted. Preamp specs will often mention gain. I'm not really sure how it works because it is not a power amplifier so it is not amplifying but it is adding something. This is where I need help from those more well versed in this stuff.

 

I in addition to about a million other preamps I've had/have I currently have a Schiit Freya + and their web site says this

Quote

Freya+ is a refinement of the original Freya, with higher performance, more features, and enhanced ease of use. But it’s still a true no-excuses, balanced, remote-control preamp. Switch between passive, differential buffer, and differential tube gain modes, enjoy the fine control of a 128-step relay-switched stepped attenuator volume control with perfect channel matching, and control it all from the comfort of your favorite chair.

 

If I am listening in passive mode and do nothing with the volume but I do turn it to "tube mode" it gets a LOT louder. If I am initially listen to it in tube mode at a volume I like and switch to differential buffer or passive it is a lot quieter. Some how that tube stage is adding gain or telling the amp here is some more juice to my signal that I want you to amplify.

 

This is the specs on the same model

Quote

Compound Differential Buffer

Gain: 1 (0dB)

Frequency Response: 20Hz-20Khz, -0.2db, 3Hz-500KHz, -3dB

THD: <0.004%, 20Hz-20KHz, at 1V RMS 

IMD: <0.0055%, CCIR 

SNR: >120db, A-weighted, referenced to 2V RMS 

Output Impedance: 75 ohms SE, 600 ohms balanced

Topology: JFET differential amplifier compound pair with equalized-gm followers 

 

Tube Gain
Gain: 4 (12dB)

Frequency Response: 20Hz-20Khz, -0.2db, 3Hz-200KHz, -3dB 

THD: <0.01%, 20Hz-20KHz, at 1V RMS 

IMD: <0.01%, CCIR 

SNR: >115db, A-weighted, referenced to 2V RMS 

Output Impedance: 75 ohms SE, 600 ohms balanced

Topology: differential triode input with semi-circlotron follower stage

 

See the 12db of gain on the tube end of things and zero on Compound Differential Buffer? That has to be what is making my music louder with the volume in the same position.

 

I once had a PrimaLuna preamp with a lot more gain and I cold barely turn the knob up at all. Since my amp(s) don't have any volume control on them I was stuck with a very limited range I cold turn the knob and not very fine control. It probably would have been fine for less efficient speakers. Klipsch are typically very efficient meaning they don't need much power. That is why you 3Watt 2A3 can power them just fine. They might not work so well on a pair of Magneplanar speakers needing 400Watts. If you always have the extra gain of the preamp and don't need it you can potentially introduce other undesirable things.

 

In your case you could use both the volume on your amp and volume on your future preamp to do what (I think) is referred to as maximize your signal to noise ratio. Find that sweet spot between fine control of the volume while also minimizing any background noise. I don't think there is any free lunch in audio. The gain has to come at some price and I think that is noise...maybe some other things as well.

 

See the SNR above? That is Signal to Noise Ratio. I can see they are different, and I'd bet (someone else please chime in) that at least on paper the tube stage is "worse" as SNR goes.

 

Since you have more than one source you might want a preamp. I'm no expert on Gain and noise so really can't tell you what to look for beyond what is the fun part of all this madness - buying and trying different things. If you get a bit more info form others you can probably make a better guess at what you need and what will work best for  you. Or just keep buying things and selling them for less than you bought them for. What could possibly go wrong with that process?

[rplace]

Took a look at the specs you linked to. No real thoughts good, bad or indifferent beyond below.

 

Quote

- line stage amplification gain : 11(approx. 20dB)
- phono stage amplification gain : 40dB(100)
- MM EQ : RIAA standard by 12AX7 & 6SL7
- THD : less than 0.5 %
- frequency response : 20Hz ~ 20KHz
- input / output : 3 / 2
- residual noise : 0.4mV
- SNR = 82dB
- output impedance : 3Kohm(OUT1), 9Kohm(OUT2)
- input impedance : 100Kohm
- separated volume controls

 

 

Line stage = regular stuff like CD/DAC/Aux, not Phono so that is the gain applied to them

Phono stage = the MM (moving magnet) phono input, the one on the top's gain. Note MM phono is like what everyone was used to growing up. Didn't need anything special beyond your receivers "phono" input. The other is MC (Moving Coil) and needs even more boost before you can put it in a typical "line input" where line input = regular CD/Aux/Tape/Etc.

RIAA = some sort of standard for more or less all phono stuff since the 1930s or 40s. Basically it is what you need. Google is your friend if you need more input

20-20KKhz = what you can hear if you are not an old fart....probably more like 10K to 15K if you are above 40

SNR = 82 - not really clear except it is different than my post above

output/input: 3/2 means three things in, 2 out. 2 out is useful for having one for your amps and another for a sub, or possibly a remote location with some additional work.

 

Separate volume control is the one that stick out to me. Should mean it is like having two mono preamps one for the left and one for the right. I'd ask the seller/builder if it is dual mono (I doubt it is or he would be touting that). If so there is two of everything. I once had a preamp I really liked with separate gain for left/right AND a master volume knob. For me, I'd probably look at two volume knobs as a minus since you would have to turn them both up and get them the same. My OCD would make me always question if they are really the same. Plus side is if you had mono block amplifiers and they were not 100% the same output you could dial them in perfectly. That is why I liked the preamp with individual R/L control and master volume. You could dial the amps in R/L independently, set a reasonable amount of gain (louder than ever needed) and forget them; finally using the maser volume to increase/decrease daily, hourly, record to record, etc. Here you could also use the two volume controls like a balance knob.

 

I also personally don't like the 3 inputs on three different planes of the 6-sided box. I guess the front is handy if you swap things a lot. I'd prefer all input/output on the back....just personal preference.

 

I'll save you 5 years and thousands of dollars. Dump all the input devices, buy a turntable as expensive as a used car with MC cartridge, a great phono stage, plug it into your amp directly and forget about a preamp and all the other devices. Take the savings and buy a semi full of vinyl.

[tube fanatic]

All powered devices in the signal path will add some undesirable quality to the signal.  Since your amp has its own volume control, I would go with an external switch box to select your various sources.  High quality phono preamps are available to go between your turntable and the box.

 

Maynard

[Ray_pierrewit]

Thanks for looking into that for me! The newer version has two inputs on the back and the phono input is still on top. 

 

I'm currently using a MM cartridge so the phono stage and RIAA, I trust, will be sufficient.

 

The two outputs is appealing because of the possibility of adding a sub woofer.

 

As for the dual volume knobs, I had surmised, as you, that it can be used like a balance knob. I could dial it in just right, then use the amplifier's volume knob as a master. 

 

59 minutes ago, rplace said:

I'll save you 5 years and thousands of dollars. Dump all the input devices, buy a turntable as expensive as a used car with MC cartridge, a great phono stage, plug it into your amp directly and forget about a preamp and all the other devices. Take the savings and buy a semi full of vinyl.

 

HA! I love listening to vinyl but it has gotten too expensive. I'll listen to my current collection and add slowly to it over the years. My tuner, as odd as it may seem, is still what I use most. It is totally reliable, I have access to some reasonably good FM stations, and ceding control over what I listen feels good. I've heard so much good music through my tuner, it'll be a sad sad day when FM dies.

 

Daniel

[Ray_pierrewit]

1 minute ago, tube fanatic said:

All powered devices in the signal path will add some undesirable quality to the signal.  Since your amp has its own volume control, I would go with an external switch box to select your various sources.  High quality phono preamps are available to go between your turntable and the box.

 

Maynard

 

Thank-you! I'm already using a great Niles source selector with more than enough inputs for me. Maybe I'll look into a good phono preamp and be done with it!