hello head-fi
here is a small accumulation of projects:
a bottlehead seduction MM phono stage. i sanded the case for about an hour gradually working to finer and finer sandpaper and then finished it with tung oil. the wood has a silky smooth look and feel. the luster of the finish is just right for the amp. not shiny and glaringly bright, but not dead and flat either it looks like the amp sounds. to the rear in the ugly black tin are a pair of cinemag MC stepup transformers. they are switchable for 37, 150, and 600 ohm use. there is a 4'th setting, but im not sure exactly what impedance it is. nothing fancy here, cardas input/output rca's, a nice binding post, and some 4pdt switches. i have plans to move the transformers into the seduction chassis in an effort to remove a cable but no time to do the work.
my DIY pseudo-passive single ended to balanced transformer setup.
i call it pseudo-passive because it has a buffer between the input and the transformer but all conversion from SE to balanced is done by the transformer. none of my sources can drive 600 ohms directly, so this is how it had to go. the transformers are cinemag's and the buffer is a buf-634. the output half of the transformer has a floating ground - what is a ground loop? the power supply for the buffers is a hopped up Ra-1 type system (2X9V, centere tapped for ground) with lots of elna cerafine caps.
this was today's project.
a balanced mahogany cmoy
some small liberties taken with all sorts of stuff, but it uses a jrc4556 dual opamp.
the PSU is more along the lines of the classic cmoy than the traditional mahogany cmoy. it uses a resistor pair to split the rails, since this is a balanced amp and will never be run single ended there is no need for an active ground channel. there is a nichon fine-gold 1000uf/35V cap from rail to rail, and 2 elna cerafine 220uf/25V from rail to ground. there are also a couple tantalum and ceramic caps closer to the opamps.
i deviated slightly on the resistors to get slightly lower gain for each half of the balanced pair but care was taken to minimize input offset currents. the overall gain of the circuit is about 8, but when you take the transformer into account i find it QUITE nice.
the input caps are some craptastic 1.5uf/100v caps that came out of a melos headphone amp. they will be gone soon, but this amp was built on a whim with parts on hand. i will replace with auricap's the next time i need to put an order in with partsconexion.
the pots are dual noble 10K units - one for each channel. i dont have good knobs for them at the moment, but they are QUITE smooth and easy to turn with just the shafts. im sure that with a proper knob they will be a joy to use.
Millett MAX
Linear Mode
