Phono Preamplifier Scrapbook - Schematics and Snippets
I have this problem with phono preamplifiers. The problem is that I spend hours and hours poring over different designs, building them, and comparing them. It seems like a pretty obscure thing to spend so much time on, but for some reason, I find it fascinating. This page contains the results of such late-night meanderings.
PAiA RIAA Compensated Stereo Phono Preamp Model 9802K
PAiA has a long history of creating great kits for analog music tinkerers. And their FracRack enclosures offer a great way to box up modular gear. One of their fine kits is the Model 9802K phono preamplifier. This simple design uses a dual opamp along with a split power supply. The offered kit is designed to be used in a modular system, almost as an afterthought. As such, the simple passive design does not offer a huge amount of hi-fi-, more like convenient-fi.
Modified Analog Addicts El Cheapo
This basic design is a perenial favorite amongst DIY builders. Shown here is a slightly modified/simplified version of the Analog Addicts 'El Cheapo' phono preamp circuit. As with many designs of this type, it is a pretty standard dual opamp design with fairly standard RIAA curve values. Compare this one with the PAiA design above and you'll see lots of similarities.
RJM Audio - Very Simple Phono Stage
For simple passive opamp-based designs, this design from RJM Audio is one of my favorites. As with the designs above, the topology should be very familiar. However, the Very Simple Phono Stage (VSPS) has a very nice RIAA curve to it. For a basic passive design, it sounds very good. The following schematic shows one channel. The original VSPS schematic shows a range of values for R2 to set the gain. Check out the original RJM page for more information.
The Beavis HiFi Kitchen Sink Phono Preamplifier
This one is a combination of all the things I like in a phone preamp: great audio performance, a good power supply, and lots of tweakable options.
TCC TC-750 Phono Preamplifier
This is a low-cost unit available commercially from phonopreamps.com. I've used this unit for a while and am pretty happy with the sound quality. It is a discrete design using 2SC1518 transistors and runs off a 12 volt DC wall wart. I spent a few evenings poring over the PCB, check part values and tracing the routes. Here is the resulting schematic. I haven't verified this yet by building one, but I'm pretty sure it is accurate. If you want to take a look at the PCB with parts notations, check it here.
The Grado PH-1 is a compact phono preamplifier offered commercially by Grado. There has been a lot of speculation on the web as to its innards, but unfortunately Grado chose to goop the PCB, thereby making reverse engineering a bit of a pain. One enterprising fellow on the web claimed to have de-gooped one and provided a schematic. I can't vouch for the veracity or accuracy of this schematic, but it appears to be the only one available on the interwebs. Here is a great thread full of details (as long as you speak French).
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