Preamplifier power supply

I'm wondering myself, like the Pass First Watt B-1.

Chris, my comments were regarding resistive passive preamps versus transformer passive preamps. Between those, I prefer TVCs.

Most preamplifiers are built the traditional way because people need gain, specially audiophiles with phono front ends, low gain amps and low efficiency speakers. A preamp must be (ideally) able to cope with all kinds of sources, amps and speakers, no easy task.

As for Wadia's integrated preamp, it is active, not passive (I have seen the opamps inside a Wadia). Its attenuation is partly analog, partly digital. It sounds great and it replaces handsomely a preamp + PC + IC, as long as one adjusts the internal analog gain DIP switches in order to use a MINIMUM of digital attenuation. If one goes deep into digital attenuation, there is a clear loss of resolution/detail/soundstaging.
As for active preamps, there are excellent ones, some with gain, some with unity-gain buffers. I am not familiar with the Pass buffered preamp.

In summary, there is no clear-cut BEST solution.

In general, I follow these rules-of-thumb:

-If your system lacks dynamics and punch or you need to use the preamp above 3 in the dial, you need more gain, therefore no passive preamp will do the trick. Buy an active preamp that drives your system to VERY LOUD levels and still has about 6 db spare gain for those quiet recordings.

-If your system has too much gain ( volume pot stays around 8 in the dial, "jumpy" volume control near 9) or you can hear noise/tube hiss, you need a preamp with less gain or a TVC preamp IMHO.

-If you want a minimalist solution, a Wadia or Audio Aero CD player connected directly to the power amp will sound great IME.
Audio Aero has an internal active analog, tube-based preamp followed by a buffer to lower output impedance.
Opus 21 also has an internal solid state active analog preamp (SS) and it sounds great for the money.
There may be other brands of CDPs with internal preamps.

Anyway, my original point about the cap-charging current peaks in a preamp DC power supply reaching 10 times the average current remains (and is validated by engineering textbooks). A transformer that is specified for 10 times the preamp continuous power draw is NOt overkill, it is just sensible design.

I hope this helps

I can think of hundreds of scenarios where an active linestage is necessary (as I can think of just as many scenarios were SETs will sound terrible). But the question remains, if you have plenty of gain, low capacitance cables, 100kohm input impedance on the amps with high sensitity - that is a source and amp/speaker combo where there absolutely no need for gain or buffering to match impedances, under though circumstaces how and it what way could an active linestage better a passive resistor preamp? I have had a CAT, Lamm, ARC, Joule ME, Dodd, and even a Bent TAP and now I use a Lighspeed Attenuator to drive the Music Reference RM10 and RM9 SE amps - I don't hear loss of dynamics, soundstage, texture, PRAT, bass, or anything else, except noise. Though I do use a Atma combo becuase the the passive approach just does not work for me with my Atma amps. I would not draw conclusions about passive preamps unless they are in the right system context, as I would not judge whether 1.5 watt SETs are any good by trying them on a pair of Thiel or B&Ws. And if I needed buffering, I'm sure the TVCs or AVCs would sound better than the resistor-based passives. Now this may all work becuase the power supplies in the EMM Labs gear is pretty beefy.

Casouza - yes, transformer should be oversized since mentioned current spikes, while driving recifier/capacitors, heat up the windings (RMS much higher than Average) and their high frequency content heats up the core but 10x is perhaps overkill. Imagine 40% efficient class AB 200W amp with 5kW transformer. Large amount of capacitors is beneficial providing better filtering but when you think of it - linear power supply is really a bad case of SMPS working at 120Hz. SMPS working at 100kHz will do the same with 10x smaller toroidal transformer, is line and load regulated and is quiet since higher frequency is easier to filter out, non-audible and switching is done (in modern SMPS) in zero voltage/zero current. For that reason Jeff Rowland uses SMPS in Capri preamp (where efficiency is not important). SMPS got such bad rap from cheap ones used in computers that people don't want them even for class D amps (that are SMPS) and designers do what sells.

Preamps need some oversizing perhaps 2x-3x to cover losses related to operation with rectifier and losses in voltage regulators that have to work in 90-132V mains range. Filtering here is done mostly by the regulators and current is pretty much constant (class A) with transitional current supplied from local caps.

Benchmark DAC1 supply is not an overkill - it takes from mains "16W peak" of average power but because of mentioned much higher RMS value of current spikes it needs to be about 32W and it looks like 30W toroidal transformer to me. It is toroidal because outside field of evenly woven toroidal transformer is zero and Benchmark achieves measured 140dB S/N.

You are right about power supply caps being in series with the speaker. People don't realize how important supply caps are. Cheap caps not only have high ESR "eating out" dynamics that amp could provide but also have high inductance filtering out fast transitions. Placing film caps in parallel is a band-aid and often a bad one since pure capacitance in parallel to main caps inductance creates parallel resonant circuit that rings (cap is in series with the speaker). There are low inductance caps (like slit foil caps) but very expensive. I would rather go with fast responding SMPS and that's what Jeff Rowland did (AFAIK) in latest high power class AB amps.

There is another thread talking about a custom made tube preamp that sports an oversized power supply so much so that the unit weighs 75 lbs (34 kg). The owners of these particular devices have only accolades for the sound that this special preamp creates. Of course their descriptions oft include the size of the power supply as though any preamp worth of hifi should have a power supply capable of driving speakers. I have seen that there is some science to putting an oversized power supply into a preamp for improved noise performance and voltage stability. Beyond that, I do not see the point. Unless I am mistaken, the power output (audio power) of a preamp is, at most, about 50 milliwatts. That is assuming a 20k ohm impedance looking into the amplifier. I have seen some preamps boasting 250 VA power supplies. All that to deliver 50 milliwatts? Sure, there are the tube heater circuits to power and other ancillary circuits, but that is not the case with SS preamps. It this just a case where we as audiophiles expect our preamps to be big heavy boxes with gobs of reserve power and so the hifi builders deliver to those expectations? Preamps have had oversized power supplies for decades now. It just seems like a type of arms race that each generation of preamps must have even bigger power supplies to show some type of advancement in technology. I remember when very expensive SS preamps could be left on all of the time because they consumed little more power than a night light.