Telefunken tube is over price

later i will post my tube rolling

hi cuore boy, hows the yaqin tube rolling going? which tube you preferred?

iam using Mullard CV4010 military

yes, mullard nice, i like them too.
western electric tube sound good with my friend ss amp.

Well, i've been messing around this little "magic" buffer and i came to a conclusion that it has a "cathode follower" design.
From the Valve Wizard i quote: " The cathode follower also produces a unique quality compression when DC coupled, which is to be found in most of the classic amp designs. When overdriven the cathode follower clips fairly hard, adding a satisfying "bite" and tasteful mix of odd harmonics to the sound."

And from what i understand in simple terms of this intriguing circuit is this:

Imagine a really big garden hose connect up to your house's water system. If you don't open your spray gun the pressure at the gun will reach the same pressure as your household water supply. If you turn your spray gun on the pressure will start out high but immediately drop to a much lower pressure.
Even with a lot of pressure at the house end of the hose (high B+ voltage) you won't get much water (current) out of the hose (plate resistor). This is how a voltage amplifying preamp tube works with the output being the variation in voltage (pressure). In this hose analogy the tube's grid is the spray gun trigger which requires little power to control a big variation in pressure at the output of the hose.

With this cathode follower you don't have a plate resistor. It's like your hose is huge, and if you turn the spray gun on you can get as much water (current) as you want out the end. This the "secret" behind this "magic buffer".

A couple of interesting articles:

http://www.transcendentsound.com/cathodefollower.htm

http://300guitars.com/index.php/articles/a...phase-inverter/

Another interesting opinion about tube buffers ( cathode Followers ) by Steven Rochlin when reviewing the Conrad Johnson 17LS Preamp, and i quote:

"There are two reasons that it is important that a preamplifier have a relatively low output impedance:

1. The output impedance of the preamp should be not more than 1/10th of the input impedance of the power amp(s) it is connected to in order to avoid degradation of performance due to overloading the preamp's output stage. (Most amps range in impedance from 20kohms to 100kohms. A few are as low as 10kohms. Below that is irresponsible).

2. The output impedance of the preamp forms a low-pass filter with the capacitance of the interconnect cable (rolling off the high frequencies). The 3dB down point of this filter is inversely proportional to the product of the source resistance of the preamp and the capacitance of the cable. Accordingly, the lower the source resistance of the preamp, the wider range of types and lengths of cable the preamp will work well with.

Even high-conductance triode tubes (such as the 6DJ8 and 6922) would normally have too high an output impedance. The traditional solution is to add a buffer stage (cathode follower) to the circuit. What we have done instead is to construct a composite triode made of several sections of 6922. Each doubling of the number of sections reduces the output impedance by a factor of two. The ART uses 10 sections... the Premier 17LS uses 4. In the case of the 17LS, the resulting output impedance is about 800 ohms.

An important feature of this circuit is that it uses no negative feedback of any kind (there is neither loop feedback, nor local feedback). The result is a temporal accuracy that we think is unique to this approach.

The rest of the circuitry includes three discrete power supply regulators (an input regulator followed by separate regulators for left and right channels), and the switching and control circuits. Note that the power supplies use polypropylene and polystyrene capacitors exclusively (NO electrolytics in the audio circuits or related power supplies).

The control circuit is interesting in its own right. Level control is effected by microprocessor selection of combinations of discrete Vishay resistors via sealed relays. Way better than a traditional potentiometer."




Of course he's talking about of one of the best pre-amplifiers ever made ( well maybe the last one from the Pass Labs, the Pass XP-10 could be a little better...?! ) even though, it's intriguing to notice that Mr. Rochlin reffers the use of a tube buffer as "traditional solution" and he was talking in the year 2000 .... I find this funny because the first time i'd mention the use of a tube buffer a few years ago in another forum - AK to be precise - the guys up there find it so weird seems like i was talking about some kind of UFO or something....

You can read the entire review here:
http://www.enjoythemusic.com/magazine/equi...0900/cjls17.htm

That post is worth it's weight in gold.

I'd never heard of one either but put into those terms I'm surprised they aren't all over the place! Thanks for the info!

Tanx mate.
These little things sometimes makes all the difference in "equilibrate" an already good hi-fi setup. I’ already modded ( few months ago) my other tube buffer from Musical Fidelity and adding two NOS Siemens ECC85 for substitute the Russian's 6H23p-EB (6922 type). I’m using it in my computer audio system and I’m also very pleased with it.

I not sure if these tube buffers are suposed to be left on all the time or if you should be switching them on and off when needed. I know the MF x10 is designed to be on all the time is the yain the same? it doesnt say in the manual.

I choose not to switch them on all the time. Even on the MF buffer i unpluget it overnight because the valves i use are not cheap. So, imo you should switch them on before listening to music only 5 to 15 min, just to warm up the valves heater. the reason for this is because the cathode cannot emit electrons until the heater has warmed and that's the reason why valves need a warm-up period to get started.

You should be able to hear when your particular tube (and SS!) gear is warmed up and ready for serious listening. It ranges from around 10 minutes to an hour for most.

Cheered,
Ian