Showing posts with label Audio Sector The Phono Stage DIY preamplifier preamp moving coil. Show all posts
Showing posts with label Audio Sector The Phono Stage DIY preamplifier preamp moving coil. Show all posts
Monday, June 4, 2012
Using the Cinemag CMQEE-3440A step-up transformer
Ah, the moving-coil phono cartridge is famous for it's speed, detail, and audiophile street-cred. Ranging from the lowly Denon line, up to multi-kilobuck units, the low output moving-coil (LOMC) requires more gain than your average phono stage delivers. Since I recently bought a Quicksilver full-function preamplifier (review forthcoming), I needed a way to boost the lowly voltage of my Denon DL-103R before hitting the tubed phono section. I could continue to use my Audio Sector Phono Stage into a line input, but if you're going to run a tube preamp, what's the point of letting the phono section lay fallow?
Enter the Cinemag 3440A step-up transformers. Cinemag, once a division of the famed Altec-Lansing, has been making this inexpensive step-up transformer for some time. Word is, coupled to the Denon Cartridge, this step-up makes beautiful music. Since I already had an aluminum chassis, RCA jacks, switch, and ground post from a previous DIY project, this was an easy decision to make.
Here's a list of what you would need:
Solder
four RCA jacks
DPDT switch (optional)
ground post
wire cutter/stripper that can handle 26awg wire
a few nuts/bolts to hold down the transformers to the chassis
some sort of chassis, metal or plastic will work
a drill press
two Cinemag CMQEE-3440A transformers
Since I didn't want to wait the few weeks for Cinemag, I ordered at a slightly higher price from an Ebay seller. A few days later and I received a small package with two dinky transformers, two L brackets and two screws. With both transformers, I screwed on the L brackets, using the longest piece against the bottom of the transformer. The other end of the bracket was fastened to the chassis into some holes that I drilled with my press.
I put in new RCA jacks and a binding post. I was lucky enough to already have a DIY phono project that already had holes for these. If you're not steady with a drill, Front Panel Express or some other company can do the work with a professional fit and finish.
Now comes the wiring. I used Cinemag's wiring diagram:
Input: Brown and Yellow wire RCA input lug
To Position 1 of switch: Red and Green Wire
To Position 2 of switch: Orange and Blue Wire
From Switch, solder a single wire to the RCA ground lug
Output: Purple wire to RCA input lug
Black, White, and Great wire to RCA ground lug
Note: The switch is optional if you know you are going to just use one of the taps. With the the Denon DL-103R, the 37.5 ohm input seems to work the best. At least in my system. But having the switch does allow one to try both settings.
Another Note: This wire is thin and fragile. I use a GB-branded wire stripper from Home Depot. When stripping off the insulation, make sure not to pull hard on the wire. I use a needle-nose pliers to hold a section of wire downstream, giving some support. I would hate to yank a wire off from inside the transformer.
Okay, here comes the moment of truth: So how does the Cinemag/Quicksilver combination stack up against the Audio Sector Phono Stage? Well, I will save the nitty gritty for my review of the tubed Quicksliver, but for now I will say that I was pleasantly surprised by the Cinemag. My presumption was that running the small output of the Denon DL-103R through several lengths of wire would give less detail and dynamics. But the real world shows great performance: deep bass, good 'slam', extended treble and, as the transformer broke in, plenty of detail.
I may give the nod to the Audio Sector Phono Stage for hi-fi pyrotechnics - attributes like detail and speed. But the Cinemag/Quicksilver has a more relaxed presentation that makes it easier to enjoy music. Stay tuned!
Monday, June 21, 2010
Building the Audio Sector Phono Stage
I've had some turntable upgrades in mind, starting with a low output moving coil cartridge and a new tonearm. With my current setup I was worried about having enough gain for a .3mv MC, so I decided to build the Audio Sector Phono Stage. This is based on the 47 Labs Phono Cube, but utilizes better parts and a shunt regulated power supply. Audio Sector just provides the PCB board, while you provide the sweat, enclosure and passive parts selection. The board quality is excellent and is designed so the power supply transformer can even be mounted within the same enclosure. For my build, I mostly stuck with the recommended parts, but opted for RelCap Teflon and Polysterene film caps over the specified (and expensive) V-Caps. Instead of Blackgates, I chose Nichicon for power supply capacitor duties. Building was done over the course of a few days as I have a hard time soldering such small parts onto the PCB board.
The signal path is unique as there is no cartridge loading per se - the input impedance is zero, which is pretty much a straight current-to-voltage converter. Gain and frequency response are determined by the cartridge voltage and output impedance. There are also no signal capacitors in the signal path as RIAA equalization is done in the feedback loop. Feedback? Oh no! Did I mention the OPA627 op-amps that are used? Now things are getting weird for a discrete parts builder like myself.
Don't let the integrated circuits and feedback put you off as the end results were beyond my expectations. This the most transparent phono preamplifier I have ever heard. Hyper detailed, it shows every flaw in your turntable setup and the recording quality. It's not a kind, mellow sound at all - but is revealing, quick but still grain free. Bass is also oh-so fluid, deep and bouncily rhythmic which started my feet a-tappin'. With my Magnepan speakers, vocals are eerily real and float wonderfully between the two panels. This is a very forward sounding preamplifier and pulls the listener right into the soundstaging. In comparison, my Threshold FET-10/PC sounds a touch muffled and dark.
I can't stress patience enough as the upper-midrange energy is extreme until some time has been burned into the circuit. I don't think I've ever heard any audio component break-in like this. It literally takes hours for everything to settle down and start sounding good.
As I'm using a high output Dynavector 10X5 phono cartridge, I'm expecting some better results with a low output moving coil. Stay tuned!
System:
preamp: Threshold FET-10/HL
phono preamp: Threshold FET-10/PC
amplifier: Threshold S/500
analog: VPI HW19 MkIII - Rega RB300 with Incognito wiring - Dynavector 10x5
speakers: Magnepan 1.6/QR
speaker cable: Kimber 4PR/8PR Bi-wire with banana jacks
Interconnects: Cardas Cross and Cardas Quadlink 5C
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