Tubes vs. solid state.

Guido,

I have. And although my sample is limited, I have found a very strong correlation between zero feedback designs and my long term satisfaction with the equipment.

Non-zero feedback designs that I have dealt with and discarded because of aural issues:

1. Rowland capri
2. Rowland Synergy 2i
3. CJ MV-60SE
4. Linn Klimax
5. Nagra PLL

Besides the CJ above, which I lived with for a year, I got rid of the other equipment within a matter of months, if not weeks.

Equipment, I have had a long term relationship with:

1. CJ Premier 14 (3-4 years)
2. Nagra VPA (bought it and never got rid of)
3. Ayre A7 integrated
4. Ayre KX-R
5. Dartzeel nhb-108

I did not start out with any biases towards non-zero feedback designs ... in fact it was the other way around. I would always (and still do) peruse the distortion measurements of equipment in Sterophile, Soundstage, and I had a strong bias against zero feedback designs, as they showed up poorly in the measurements department.

My ears simply lead me to the equipment that I now have.

Of course it is also possible that I am highly suggestible, and I am the one with the tin-ear.

Pinkus, the only issue with transistors is that without feedback, they will make more distortion than tubes will. However, if the design is competent, the higher orders will not manifest nearly so much as they will if feedback is applied. Its my opinion that in time we (as designers) will sort out what must be done to make them work properly.

One of the best amplifiers I have heard is transistor, made by Ridley Audio. It was zero feedback and class A and fully differential. It employed a heater to heat the output devices to a fairly high temperature (and then regulated the heat) and made as much heat as any tube amp of the same power. The amp made 100 watts and cost about $100,000 for a pair (they could drive a 1 ohm load); a bit pricey for my blood but proof that the extra distortions of transistors can be tamed if handled right.

For the time being as I mentioned earlier, it is a lot easier to use tubes to keep the distortion down. It might be cheaper too. If one looks at the whole amp/speaker thing from the point of view of obeying human perceptual rules, the issue of higher output impedance of zero feedback amps becomes moot- that is 'what is' so you deal with it in the design.

Pinkus, Our tin ears must be forged from different pewter alloys. . . I have never liked KX-R, but as you know have used lovingly a Capri for a year and a half.

BTW, I was not aware that feedback or lack there-of even applied to pre designs.

G.

Is hard to decide between them because each person has different sound tastes, the tube lover will rather tubes and the same will happens to solid state amp lovers.

Guidocorona, feedback is very definately a factor in preamp design. A very famous Ampex recorder (model 351-2), used by RCA and Mercury as well as many others, featured a zero feedback record circuit.

EQ of phono preamps is often handled in the feedback loop of the preamp. The Dyna PAS-3 is a good example as is the ARC SP-3. If not, you will often see the term 'passive equalization' used by the manufacturer. Harmon Kardon used passive phono EQ in their famous Citation 1 preamp decades ago. IMO/IME passive EQ is harder to execute, but allows the phono preamp to sound better- smoother, with less ticks and pops. Refer to my prior posts as to why that is.

Chatta, there is of course an intellectual preference that each audiophile carries. Despite this conscious preference, the human brain apparently knows when it is being fooled, whether we consciously acknowledge it or not. Dr Herbert Melcher, a famed neuro-chemical scientist, has proved this recently in tests using audio playback- its fascinating stuff: as the brain detects violations of how reality actually sounds (false noise floor, slow waveform delivery, etc.), the processing of music moves from the limbic centers to the frontal lobes of the human brain. When we are comparing cables or listening to MP-3s, the processing is entirely in the frontal lobes.