jel ima neko ovde da se razume u step atenuatore?
naime ne zanimam se ali cu morati, dosao mi u ruke odlican preamp koji ima samo jednu manu, a to je da mu je kriva atenuacije apsolutno jezivo glupa, prvi klik od nule vec otvara dosta veliko pojacanje. svi ostali klikovi su vrlo blago pojacanje i to je uradjeno OK ali ovaj prvi klik jebe nanu koliko je glasan.
da li je jedina opcija zamena celog ili moze neka svajserska budzevina bez sonicnih ustupaka da se izvede?
inace nije pitanje celog gaina preampa, to je blago, 6-7db (cefka je 6n6p)....samo atenuator
predmetni atenuator je ovaj (SM verzija):
Stepped Shunt Attenuator
Those of us who are using differential tube preamp circuits like the Raleigh Audio active output stages or Lynn Olson Raven-style preamps have had to use conventional audio potentiometers or their discrete resistor analogues, like the DACT or Goldpoint controls to provide control of volume. You can review the choices for volume control implementation in these types of preamp circuits below.
We prefer the implementation with one variable element per channel, the so-called "U" or balanced shunt attenuator. It is simpler and cheaper and has the significant virtue of causing no change in common mode rejection as different volume settings are used.
So what is special about our implementation of the "U" attenuator control? A standard audio potentiometer or discrete resistor analogue has a resistance profile (called a "law") that is configured for standard series attenuator use, not shunt attenuator use. You will probably have to trust us on this, but the math is not the same. Hence, when you use a smallish value of series resistance and a large value audio pot to make a shunt attenuator that won't cost you very much lost gain in the maximum volume position, you will get a control where most of the volume attenuation capability is in the first third of the rotation from zero volume to maximum volume. That's not really what you want, obviously. To fix this situation you can use a series resistor value that is approximately the same value as the pot and now the shunt attenuator performs more reasonably, so that attenuation is spread more evenly over the rotation of the pot, but you lose a fair amount of gain at maximum volume setting. (approximately 10dB in the case where the pot is the same value as the series resistors). Compromises, compromises.....
To avoid these compromises, we have designed the resistor values used for the stepped control to provide equal dB volume intervals (1.5dB) with 5K series resistors, which result in a reasonable 10K input impedance at minimum volume setting. Of course, any kind of volume profile can be implemented with discrete shunt resistors, however this one has proven to be useful for me for the 2 years I've lived with such a control (implemented in my case with a much bulkier (and slightly inferior sounding) array of Holco resistors). To be fair, there is a compromise inherent in these controls, too; that is price. Using Seiden 32NEG switches specially imported by us for this purpose, these are not inexpensive, but are reliable, sound excellent, and have a wonderful "feel". In my experience, no audio potentiometer provides the sound quality that these stepped attenuators do.
Note that you can also utilize these attenuators in single ended circuits with a single 10K series resistor per channel without any other changes.
We auditioned several candidate resistors for these attenuators and selected Vishay parts for their sonic properties. Surface mount resistors have the advantage of making a compact 23 step attenuator possible. The finished attenuator is little bigger than the Seiden switch that it is based on. The SM attenuator is not a kit; it is supplied with all of the SM resistors already soldered in place. Each attenuator is also supplied with 4 (2 for each channel) 4K99 Mills MRA-5 resistors for the series resistors, unless you have purchased the Combo Input Stage Kit, which already comes equipped with the appropriate series resistors..
We are also offering a kit of parts including the Seiden switch and PC boards that will accommodate standard through-hole leaded resistors (like Holco H4, Caddock MK-132, naked Vishay or Kiwame 1w resistors; Rikenohm or Allen Bradley 2w resistors are too large) so that you can use your favorite resistors and concoct your own shunt attenuation profile. Obviously these are considerably larger than the SM resistor-based attenuators.
23 step custom assembled SM attenuator and series resistors $189 23 step attenuator parts kit for your favorite standard through-hole resistors (includes switch, PC boards, and instructions, but no resistors)$129