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Showing posts with label preamp. Show all posts
Showing posts with label preamp. Show all posts

February 21, 2014

Budgie Cinemag MC Step Up Transformer (SUT)

The Budgie Cinemag MC Phono Step up transformer (SUT), phew, that's a mouthful. If you haven't been initiated into the wonderful world of vinyl, or even if you have, you might not know what all that means, so I'll do a quick clarification.

The Budgie series is Shannon Park's series of audio circuits that are designed around offering both great sound and reasonable pricing, Budgies for audiophiles on a budget. These include phono pre-amps, single ended amplifiers, step up transformers, and more. Cinemag is an american maker of fine audio transformers for microphone, phono and other applications. MC stands for moving coil. Many record players include MM cartidges (moving magnet) which have a higher (louder) output than moving coil cartridges. Many of the most high-end cartridges, as well as the immensely popular Denon DL-103, are moving coil.

A step-up transformer, or SUT for short, is needed to bring the low output level of moving coil cartridges up to the level of moving magnet cartridges, so one can use a traditional phono pre-amp for pre-amplification purposes. The SUT is plugged in right between the turntable and the phono preamp. Granted, there are phono preamps with both MM and MC capability, but they're not as common as the standard MM phono pre, which many audio enthusiasts are likely to already have.

Enter the Parks Audio Budgie Cinemag SUT. If there is beauty in simplicity, this design is Kate Upton in a bikini. A pair of load switches (MC high at 141 ohm load for medium output MC cartridges and MC low with a 35 ohm load for cartridges with a low output [less than 0.2mv]) and a ground lift are the only controls adorning the unit. Other than that, you have the input RCAs, output RCAs and ground binding post and that is all she wrote.

The attractive Budgie SUT board

Internally simple as well, only 48 solder points are required for an operational unit, including eight for each MC transformer, eight for each switch, and two for each RCA. Only twenty or so parts are necessary, including the PCB, the RCAs, the transformers, the switches, the screws, the black aluminum box for shielding purposes, and the feet.

Hammond alumminum chassis painted black

Cute little isolation feet

The Budgie SUT will work with three different Cinemag transformers, depending largely on your budget. (The pricing listed is as of this writing, Feb 2014 and may be different by the time you order.) You'll need two transformers, the CMQEE-3440APC runs $50ea, the CMQEE-3440AHPC runs $75ea, and the CM-1254PC runs a whopping $175ea. For differences, see below statement from the Budgie manual:

“The CM-1254 was designed specifically for moving coil phono cartridges. The CMQEE-3440A was originally designed for Quad Eight for microphone and line input to their preamps. The CM-1254 is much more difficult to make than the CMQEE-3440A and, hence, the price difference. The CMQEE-3440AH uses laminations which have seen collected over many years for characteristics which are optimal for
moving coil applications. We use the same laminations for the CM-1254.”

For this particular build, I used the CMQEE-3440AH PCB version with the nicer lams.

Cinemag CMQEE-3440AH transformers - PCB versions

In addition to the nicer lams, I added a set of Vampire RCAs with Teflon dielectric (below) and a Vampire binding post for the ground connection (seen above next to the transformers).

Vampire chassis RCAs

Thanks to the simplicity of this design, one won't need the little isolator rings or the ground rings that come with the RCAs, although it's always wise to save spare parts like these for later use.

Ground and isolation rings not needed

The RCAs (and ground binding post) will simply be screwed in the existing holes on the PCB, which effectively grounds them to the board. You'll need a small wire to run between the RCA signal and the solder pads on the PCB. For this I chose to use some Cardas 5Ns silver. A little bit of fashioning is necessary with a pair of needle nosed pliers for the solid core silver to give it the right form.

Silver wire looking like a deformed paper clip

Before soldering in the Cinemags, I chose to lay down a piece of electrical tape on the board, then poke the pins through it. This would help ensure the solder would not leak through the PCB holes while hot and short to the transformer housing.

PCB with electrical tape in place

Each of the little switches is soldered in place, and I put a dab of solder on the ground post as I didn't want it to loosen over time. The board was then cleaned up with some isopropyl alcohol and a toothbrush, followed with a few dabs of a towel (do note the black coloring on the PCB may bleed a little bit).


Holding the board to the chassis are some size #8 machine screws. I went with brass to match the mostly gold look of the unit.



This is a great little build from Shannon Parks and a bit more straightforward than using vintage microphone transformers or the wired versions of the "can" transformers.


The Fine Print:
Please remember that building circuits and performing circuit modifications can be dangerous to you and/or your surroundings and should only be performed by a certified technician. The owner of this blog and all associated parties can not / will not be held responsible if you attempt a build or modification posted above and cause physical harm to yourself or your surroundings. Many electronics contain high voltages that can kill, and mods, if performed improperly, can be a fire hazard. Please keep this in mind. 





May 30, 2011

A new upgrade for the Bottlehead Seduction Phono Pre-amp

In the interest of a little tweak for the Bottlehead Seduction Phono Pre-amp, a pair of Hammond 155J chokes were added to the power supply in place of the two 1K resistors. On paper, they are 1026 ohms +/- 15%. In practice, they measured about 900 ohms each, which should be close enough for this purpose. Chokes allows better filtering in the power supply (less hum in the output of the amp and less voltage drop) which should translate to better sound. There's a nice quick lesson on the purpose of chokes here. Since the stock Bottlehead design lifts the transformer with a pair of standoffs for noise reduction, I decided to use a pair of standoffs for the chokes to physically move them away from the tubes. As typical with Bottlehead kits, once you start dropping in some fancy parts, the real estate tends to go pretty quickly. The most accommodating place to mount them in my case was right next to the C4S constant current upgrade board.


Pair of Hammond 155J Chokes next to the C4S
 The upgrade required about a half hour of time to mount the chokes and solder them in place, along with about $30 plus shipping for the chokes themselves. I'm listening away to the new Radiohead The King of Limbs vinyl as I write this, the sound is warm and smooth, just as a record should sound.


Please read the full story here: http://www.diyaudioblog.com/2011/02/bottlehead-seduction-phono-pre-amp.html 



The Fine Print:
Please remember that building circuits and performing circuit modifications can be dangerous to you and/or your surroundings and should only be performed by a certified technician. The owner of this blog and all associated parties can not / will not be held responsible if you attempt a build or modification posted above and cause physical harm to yourself or your surroundings. Many electronics contain high voltages that can kill, and mods, if performed improperly, can be a fire hazard. Please keep this in mind. 


February 26, 2011

Complete Restoration of a Dynaco PAS Pre Amp

This is a story of rags to riches; turning an abused Dynaco PAS 2 into a very modern PAS 3.

The Dynaco PAS 2, for those who are unaware, is a pre amp kit introduced by Dynaco in 1960 to compliment the Stereo 70 (ST70) that came the year before (1959) and other various other power amplifiers in the company's lineup. The Dynaco PAS has developed a cult following, and there are an immense amount of boards being produced for those interested in restoring such archaic technology :) CurcioAudio, Tubes4HiFi, AudioRegenesis, ClassicValve and others have created drop-in boards to restore the PAS, whether you want to maintain the same circuit or drop in something completely different.

I chose to use reproductions of the original PAS 3 boards and rather than recreate the rudimentary selenium rectifier with standard capacitors, I chose to make use of the high-tech ClassicValve PAS Regulated Power Supply.

ClassicValve Regulated Power Supply
The PAS is a design that was built to fit a budget, so a number of other things are recommended to be replaced. The 2 pole, 6 position switch is rather archaic compared to what is being produced today. A $10 switch would likely be an improvement. I opted to go with an Elma 2 pole, 6 position switch 04-1264 ($60 SRP) so that I wouldn't have to replace it down the line.

A Stock PAS Switch
The rear input and output board also leaves something to be desired. Many consider this to be one of the most drastic areas that Dynaco cut costs on the kit. Cheap Nickel plated RCAs on an old PCB board don't really inspire confidence.
Stock PAS IO Board

So... let's have a look at the splendid PAS 2 example that I was able to source:
Original PAS Back
Original PAS Back Detail
Original PAS Insides
Original PAS Outside and Bottom

The previous user left me with a lot more work that I would have had if I had a pristine PAS 2 / 3. There were a number of unusual mods, including plexiglass mounted RCAs, a 9 pin tube mounted in the middle, a non-descript transformer that was halfway mounted, some additional holes cut out of the back, and a powdercoated front panel that was rubbed with armor-all. No worries, one has to rise to the challenge.

The PAS was completely taken apart, a few parts were set aside, most were disposed of as they had been pillaged by mods. The chassis was sanded down and prepped for powder-coating.

Chassis Prep

The new boards were sourced and populated with my favorite parts, Kiwame and Takman resistors and Sonicraft caps. 

Old boards versus new boards
Curcio Audio has a number of nice tutorials on the PAS, including one to make the Phono board a bit more accurate. I performed those mods, along with bypassing the tone controls. I sourced a new input output board from Tubes4Hifi to connect to the Elma switch. I also picked up an Alps volume control (100K) and balance control, along with PCBs to make soldering a little easier.

Mostly done
The wiring was completed using Neotech PCOCC in teflon wiring, Kimber wiring and SPC in teflon. Russian teflon bypass caps were added to the main board (mounted to the front), and Russian PIO were used on the phono board. A power LED board was sourced from ClassicValve, and a new transformer was sourced from TriodeElectronics. After all was said and done, I sent off the PAS to Sal at Dynaco-ST70.com to look over all my wiring and fire it up. I wanted to have an expert give it the final eye and do the final wiring.

Here's the final build:

PAS guts from the right

PAS guts from the left

Inside Detail

Inside Detail

Bottom wiring

Outside with new gold front panel from ebay

Outside Photo 2

Rear, notice rear vent and Cardas output RCAs
Some final details were the Cardas RCAs added to use the holes made by the initial owner, a power supply vent to eliminate the ugly holes in the chassis, the bottom slots were covered using slightly larger than stock power receptacles from Radio Daze, and the front panel was replaced with a gold anodized version from Michael Nipomo on eBay (he typically only sells black and silver, but had this gold one as a one-off).

This little baby was an amazing amount of work, but it came out well and I'm really happy with it. Good luck to everyone out there restoring their PASs :)

Wondering where I got all my parts for this build? Check out a list of my favorite online vendors here.


The Fine Print:
Please remember that building circuits and performing circuit modifications can be dangerous to you and/or your surroundings and should only be performed by a certified technician. The owner of this blog and all associated parties can not / will not be held responsible if you attempt a build or modification posted above and cause physical harm to yourself or your surroundings. Many electronics contain high voltages that can kill, and mods, if performed improperly, can be a fire hazard. Please keep this in mind.