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March 30, 2012

DIYTube Get*Set*Go Single Ended Amplifier

Shannon Parks, head-honcho of DIYTube, has made plenty of projects available since 2003 when the DIYTube ST35 clone was made available. Since then, a handful of projects have been released, from the 60 watt Eiclone amplifier to driver boards for Dynacos to stand-alone single-ended amplifiers like the Clementine and Get Set Go. The projects are all well documented, feature circuit boards for easy building and if a builder runs into trouble, DIYTube features a forum with a very friendly user-base that is happy to help with problems.

This post is dedicated to the building of the Get*Set*Go. Get "Set" Go is a cute play on words for SET (Single Ended Triode). The tube compliment features an on-board 6SL7 driver and 6AX5GT rectifier, which feed two 6B4G power tubes running in single-ended Class A with no feedback. Power output is approximately 3 watts, so it's important to pair this amplifier with some very efficient speakers.

Get Set Go Schematic from DIYTube

Get Set Go Power Schematic from DIYTube

A variety of transformers can be used, including James, Triode Electronics, Edcor, etc. James 6113HS outputs were the initial recommendation on the BoM (bill of materials), however it seems there are no local suppliers at them moment, and having them shipped overseas is an expensive proposition due to the weight. Transcendar TT-312-OT 5K were settled on for the outputs for this build, they're a very highly recommended value and made in the U.S.

A pair of  Transcendar 312-OT output transformers

The power transformer is the Triode Electronics PA-774, which is a well-made clone of the Dynaco ST-35 PA-774 transformer. The laminations of this transformer are a natural metal finish, and since the 312-OT outputs are wrapped with adhesive black cloth tape, I wanted the PA-774 to match a little better. The particular cloth tape that Gery at Transcendar uses runs $50+ a roll, which wouldn't really be worth the cost for a single application, so black engine enamel was settled on to darken the lams on the PA-774 for its high heat properties.

Black Engine Enamel used to darken transformer laminations

Also from Triode Electronics is a pair of reproduction C-354 chokes. These little guys will help reduce ripple in the power supply. The chokes arrived with a bit of excess transformer lacquer that had solidified roughly on the edges, which is perfectly fine but not the most attractive thing to look at. A little bit of sanding and a black oil-based Sharpie touch-up worked wonders.

Triode Electronics C-354 Chokes

I had the aluminum chassis made for this build from my friend Keith (po1019 on Ebay) with beautiful walnut side panels.

Custom chassis with walnut side panels

The build begins with the silk-screened bright red PCB made of FR4 fiberglass. Beginning with the smallest parts (resistors and diodes) and working up to the larger parts (capacitors), the board is carefully populated.  This begins with Kiwame carbon film resistors, along with Vishay and Mills wirewound power resistors.

Board with Kiwame, Mills and Vishay resistors in place

Some fun boutique parts that will be dropped in are a set of four Nichicon Fine Gold and two Elna Cerafine electrolytics. Generally the "audiophile" marketed electrolytics (think Black Gate, Elna Silmic / Cerafine, Nichicon Muse / Fine Gold) are much larger than their similarly rated counterparts, but in some rare cases, they'll fit on a circuit board without issue. Also to be included are a set of matched Jupiter Beeswax HT 0.22uF caps. Below you'll note the populated board with above items. Also, the power supply electrolytics (Panasonic 150uF 450V) are being bypassed with a pair of Solen 1.0uF 630V film caps. This is probably not necessary as the two chokes should minimize the power ripple, but they were sitting in the parts bin and it couldn't hurt ;)

Bottom of the populated Get*Set*Go Board

Top of the populated Get*Set*Go Board

Next came creating all the necessary holes in the chassis using a combination of the drill press, Greenlee die punches for the tube holes and a Dremel cutting disc for the IEC inlet. Below is the chassis ready for a fresh coat of paint at the powdercoater.

Chassis top plate with all necessary holes
Chassis bottom plate with ventilation holes

The chassis was then powdercoated a warm cream color.

Powdercoated GSG Chassis

The components can now be added. Cardas copper binding posts, Cardas RCAs, Teflon 8-pin tube sockets, and VT4C aluminum tube surrounds were installed. The chokes and transformers were installed using a combination of rubber washers, brass washers, locking washers and brass nuts. The rubber washers are used to help dampen vibration from the transformers to the chassis. A heavy duty toggle switch was added to the front of the chassis for the sake of convenience. The usual vintage-style pilot light was also added to the front panel.

Initial parts installation

Once the parts were in place, the PCB could be fitted on top of the standoffs. This is when you find out how accurate your drill-work is ;) Thankfully all the holes lined up and a few screws were placed to keep the board secured.  

The GSG PCB in place

The Get Set Go makes use of convenient barrier terminal blocks so that the board can easily be removed without an iron if the situation calls for it. Each wire is trimmed to size and a small binding post is attached at the wire termination, the binding post is then screwed to the board with a standard Philips head screwdriver. 

Most of the wiring up complete

I did take note of Shannon's suggestion that a few of the power resistors should be mounted on the other side of the board to maximize heat dissipation, so R15B, R16B, R19 and R20 were relocated. Two pieces of shielded Cardas 2x21.5 were trimmed to size and used to run the low level signal to the board. Finally the Bayonet light featuring a 6.3V LED was wired to the board, completing the project. The bottom was screwed on and some nice tubes were dropped in place.

The Get Set Go from the front

I was able to source a nice pair of matched Raytheon 6B4G tubes, a coin-base GE 6SL7 driver and a Sylvania 6AX5GT.

The Get Set Go from the rear

I designed the nice little engraved plate in Illustrator. Anyone who wants to use it is welcome (for non-commercial applications).

The amplifier started up right away with no issues thanks to Shannon's great online documentation. The response was crisp and clear, and the bottom-end was more plentiful than I was expecting from such a low wattage output. I'd imagine with the 5K output transformers the output is likely around 2.5 watts. It still needs a little help from a subwoofer in my humble opinion, but the sound is quite nice.

Want more? Read about another DIYTube SET build: the Clementine.

Need some high quality audio cables to take your music to the next level? Contact Zynsonix Audio for a great sounding solution.

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. 

March 13, 2012

Glassware Audio LV-Regulator Power Supply

Wallwarts... you know them as the little black plastic boxes that take up precious real-estate on your wall outlet or your surge protector. These little devices are generally mass produced overseas as a cheap method of converting your house's AC (alternating current) to usable DC (direct current) for whatever device they'll be powering. This process requires transformation, rectification and filtering in order to make the power worthwhile for your device. Transformation is the process of converting the voltage from 120v (in the U.S.) to whatever the device is calling for, whether it be 9V, 12V, etc. Rectification periodically reverses the direction of AC to convert it to DC, usually using diodes or vacuum tubes in some circumstances. Filtering is reducing the power ripple to produce stable power and reduce EMI (electromagnetic interference), often times making use of capacitors.

Not all power supplies are created equally. Many high-end electronics shrug off the little wallwarts and have a dedicated power supply built-in, or even in a separate chassis. Using higher quality transformers and better filtering circuits improves the quality of power entering your equipment, which will hopefully improve the listening experience if all goes according to plan. As many forum members agree, there are a number of devices that can benefit from a dedicated power supply, such as the Squeezebox, Cambridge Audio DACMagic, Wadia 170 and 171 iTransport and the Musical Fidelity X-Series and V-Series components. 

This brings us to the Glassware LV-Regulator (LV standing for Low Voltage) which can be configured for 5v, 9v or 12v DC output and makes use of a 3A low-dropout regulator (LD1085). As stated by John Broskie on the Glassware website: "The LV-Regulator uses a simple RC filter (1 ohm & 10kµF) as a pre-filter before the LDO regulator and holds bypass capacitors for all the electrolytic capacitors and a 4.7µF/400V polypropylene shunting capacitor at the output. The 1-ohm resistor is a 4W device, so the maximum current output is 2A. The RC filter before the voltage regulator unburdens the regulator from having to deal with sharp transients."

The Glassware LV-Regulator board (copyright Glassware)

This board, when combined with a suitable transformer, will make a nice power supply for low voltage devices like many mentioned above. The one being assembled in this particular post will be 9v and making use of a center-tapped Hammond transformer. Below is the initial board assembly and the Hammond 166M10 3A transformer. Because the transformer is center tapped, the board would be configured as full-wave center-tapped. 

Transformer and LV-Regulator Board

Aside from the transformer and board, a few other things will be necessary, including a chassis, IEC inlet, power outlet, umbilical power cable, pilot light, and on-off switch. The IEC inlet will be a EMI/RFI filtering type that should help further clean up the power. For the power outlet, a Neutrik Powercon connector will be used. For the chassis, I'll be using a custom 8" x 5.5" chassis from Keith (Ebay member po1019). Below is a quick initial chassis layout for the build.  

Custom 8" x 5.5" chassis with mahogany panels

Initial chassis layout

Below is a photo of the chassis after the holes were drilled and it was powdercoated a cream color. I have a nice Greenlee punch for handling the Neutrik Powercon connector (it handles the Powercon, the locking 1/4" jack and other similarly shaped panel mounted jacks). The IEC inlet has to be cut with a Dremel cutting disc which requires a bit more time and effort. I typically drill four holes in the corners, then cut between them with the cutting disc, then finally use a hand file to smooth out the cuts. All the other holes on the chassis were created with a drill press. 

The LV Regulator Chassis

Next comes the process of adding the parts and the populated circuit board to the chassis. Thankfully everything fit without issue. 

Parts added to chassis

With everything in place, the circuit could be wired up. 16 gauge silver-plated copper in PTFE was used for all wiring, aside from the pilot light which was 18 gauge. The wood side panels were then slipped in place and screwed in. 

The LV Regulator all wired up

With the wiring complete inside the unit, there will be a need to get the amps to the transport it will be powering via a cable. The cable from a power supply to the unit it is powering is typically called a "umbilical" cable. The center of this cable is a twisted pair of 18 gauge silver plated wire, one for power and one for return. This was carefully wired to a small 3 pin power connector that closely matches the Wadia 171i input. Multiple layers of heatshrink were used to ensure to possibility of a short within the plug. 

Creating an umbilical cable for the power supply

I decided to shield this cable, so some additional steps are necessary. The twisted pair was covered with Teflon tape, then a bus wire wrapped around it. This bus wire will conduct to the foil shield that will be wrapped around it. 

The foil tape is made by 3M and is a basic way to reduce EMI (electro magnetic interference). I used it rather than copper mesh to keep the cable from getting too bulky. 

3M foil tape wrap

The cable then gets another layer of teflon tape on top.

More to come...

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.