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    Building, troubleshooting and testing of these amplifiers should only be
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New Valve Project Completed

smittola

Member
2015-01-13 4:21 am
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I’m a newbie, but have been enjoying following the forums for quite a while. This is actually my third valve amp project. I build this one for myself so I wanted an original looking system. I made the chassis made it from scratch using a 1/8” copper stock and 1” copper pipe for the corner legs. I do a little gold-plating for a hobby, so many of parts are gold plated. The gold-plated copper parts initially had to be plated with nickel prior to the gold. Copper tends bleed through the gold if this step isn’t taken.

The power-amp circuit is based on the wonderful Dynaco-70 stereo amp (rated 35 watts per channel). I purchased a VTA70 modified PCB driver board and a PA- 060 power transformer (5 vs 3 amps as the original) from Bob Latino at tubes 4 hifi (http://www.tubes4hifi.com/ST70.htm). This allowed the use of four KT88 output tubes. Three 12UA7 triode tubes are used for the driver board in place of the original two 7199 tubes. Four Russian K42Y-2 (paper in oil) .22uF capacitors were used on the driver board. The two A-470 output transformers are original from an old Dynaco unit. There are four pots for bias adjustment on each of the output tubes.


I also incorporated a solid-state tone control / pre-amp circuit using a Philips TDA1524A tone chip. I’ve used this chip in the past and have been pleased with it. Two output headphone jacks were also added on the top panel. Currently I’m using my trusty MacBook Air as my music source, with the signal first passing through a BSR EQ 110X graphic equalizer. All labels were made on my mac. Simply for added looks, I installed five blue LED light strips on the outside of the bottom cover.

For speakers on this unit I’m using a pair of great old JBL PAT-40T studio speakers & a JBL PB-10 (10”) sub-woofer. I can honestly say, this is one of the best sounding systems I’ve heard. I really love that "warmth" the tubes provide! It’s amazing how music I’ve been listening to for years sounds so much better with the power and engineering of a really good valve amplifier!

A few photos of the project can be seen at: https://newvalveproject.shutterfly.com/

smittola
 
Wow, certainly a striking amp, not really my cup of T but I can see you put a lot of work into it. I tried gold plating myself and it's not easy. What method did you use for printing the legends of the controls etc?


Tried to look for pics via the link but couldn't find them and didn't want to join, can you post them here?


Andy.
 

smittola

Member
2015-01-13 4:21 am
Wow, certainly a striking amp, not really my cup of T but I can see you put a lot of work into it. I tried gold plating myself and it's not easy. What method did you use for printing the legends of the controls etc?


Tried to look for pics via the link but couldn't find them and didn't want to join, can you post them here?


Hmm...You shouldn't have join Shutterfly to see the pics, I made them available for public viewing? Regarding the labels: For the round control dials, I actually just used a combination of Avery's free 'P-Touch Editor' software, Apple's 'Preview' program and MS 'Excel'. I printed out on photo paper and then punched out with large hole punch. Sprayed them with a clear coat and then glued in place. All other labels were made using my Brother label maker with gold on black tape self-adhesive stock label tape. Really nothing too difficult.



Andy.