Steve,
I always use my own enclosure so I really don't have an opinion as such.
What are the differences between the 7A, 10A and 12A? Is it in the PS, i.e. solid state versus tube? I'm sure there are more differences, as I can see that the 10A is much higher gain.
Best,
Anand.
Sorry I missed your post Anand. My bad.
First, I think it would be advantageous to
provide a framework. This may be over response to your question, but I feel it is necessary for newbies to gain a basic understanding, for knowledge is essential for making wise decisions. Skip to the bottom if what comes next is not of interest.
Some feel that simply throwing together a power supply and
installing a tube is the goal. And if a particular tube sounds better to them, than suddenly it is "the best". However, such a conclusion is built on false premises.
Each tube type offers a different frequency response depending upon
the plate resistance (Rp) of the tube. Each tube type also offers
what is called Gm characteristic, meaning a different amount of
gain, plate current, minus grid voltage etc.
Since each tube type is different, each requires a different type of power supply. So when word is spread about this or that tube being superior, such may not be the case at all. It depends upon the signal circuit design, parts, power supply design etc.
(Also not only does the power supply have to eliminate 120hz and other artifacts, but also has to deal with wide ranging frequencies, musical signals in a linear fashion.)
Some tube types with high plate resistances (high Rp) just cannot function with any sort of load such as interconnect capacitance, or low load resistance. Doing such either dramatically reduces the frequency response and/or dramatically increases harmonic and IM distortion.
As such, each tube type requires a different type of circuitry and
power supply for optimum performance.
Filter capacitors reduce 120hz ripple. However, as the capacitor increases in value, DA, DF and self resonance problems (especially electrolytics, tantalum etc) must be addressed. But even poly caps have problems.
High Rp tubes require a buffer output stage in order keep the high
frequency (HF) response to a respectable level when IC capacitance
and amplifier input capacitance is introduced. However, adding a stage reduces the fidelity further, unless a stage is so poorly designed that adding another stage actually solves a particular problem and sounds better.
Frequency dependent feedback (and phase shifts) also occurs between stages that decoupling power supply capacitors cannot completely eliminate. (RCA Radiotron Designers Handbook, 26 Engineers, 1960 edition)
Another criteria is finding and using the most accurate
sounding parts available. Not doing such can give the false conclusion that one tube type is superior to another when it is not IF accurate sounding parts were used.
With this backround, I found that using
one particular tube for all my small signal components is quite advantageous. It allows for one overall type of power supply with some minor differences, which means my preamplifiers have similar, superior outcomes sonic wise.
The 7A is a result of the R&D of the 10A/11A/12A, but less expensive. The 7A does not have regulation in the power supply, although otherwise it follows the general pattern of my power supplies, with 4 stages. It is designed for optimum operation.
It has a little less depth, width, soundstage when compared to the other three. But very natural and organic. It is designed with one volume control and one balance control whereas the other three have dual volume controls.
The 10A/11A/12A do have vacuum tube regulation in the power supplies which minimizes what little reactance my supplies have.
The 11A is high gain, some 21db of gain and is so natural and very organic.
The 12A is the 11A but with low gain, some 8db total gain, and with lower output Z (750 ohms or so), yet with the same naturalness, very organic.
One last thing. The specs are extremely good, but proprietary listening tests are always the final word.
I hope this answers your questions Anand, but if you have more, or I am not clear, please feel free to ask.
Cheers.
