New SE 6P15P project

[chrish]

just completed this 6P15P amp. It is a variation of this amp http://www.geocities.com/dmitrynizh/6p14p-twzsh-pio.htm

Changes are that I am running 6P15P (EL83) instead of 6P14P. Gain was a little low, so I added a 1500uF cathode bypass cap on the 6P15P cathode resistor. Also wired switcheable cathode feedback and since the output transformer has an ultralinear tap, I made that selectable on/off as well. Power supply is 5U4G, 47uF-5H choke - 47uF - 22R - 68uF - 22R - 80uF motor run cap.

Chassis is something I picked up in Singapore last week for $40 Singapore dollars, about $28 US dollars. Back panel was pre cut for IEC power socket, fuse holder and two sets of input sockets.

This is my third valve amp project. First was a SimpleSE from TubeLab. Second project was a push pull 6BM8 point-to-point wired project that did not work out very well. It did kind of work, but the hum was awful. Forced me to get in to the books and look a little more closely to how I was doing things. I have dis-mantled it and will now attempt a re-build. This project is a little simpler, and I gave myself a little more room with the chassis. Hum is almost non-existent (have to put ear inside of speaker cone to hear any hum).

Overall it sounds pretty good. Not quite as good as my SimpleSE, but as a "learner" project, I feel pretty that I have met my goal of a hum free amp. This project will be used to power a set of mini-fonken speakers using Fostex FE 127E drivers. Speakers are just about finished, just waiting for the paint to dry. The whole package will be a Christmas gift for my girlfriend to be used as computer sound system in her office to accompany her new iMac computer.

Now if only I could get the internal wiring looking as neat as some of the people posting here!

Cheers,

Chris

[chrish]

Still not sure how to post multiple photos...

[chrish]

Another shot...

[chrish]

And another...

[chrish]

Here she is next to my TubeLab SimpleSE...

Think I forgot to mention before that output transformers are Edcor XSE 15-8-5K. Input valve is 6N1P. All valves (5U4G, 6N1P, 6P15P) are Soviet sourced cheap on Ebay. Motor run cap is $12 Ebay. Power transformer was $40 Singapore 150 mA 270-0-270, 5H 150 mA Hammond open frame choke. No other fancy components inside, just stock resistors from the local electronics shop. Figured it was not worth spending mega-dollars on a learning project that was going to be playing MP3s from a computer.

Cheers,

Chris

[Sal Brisindi]

I am impressed, very nice job on both of your tube amps. How many watts per channel is your new amp putting out. I was curious about the Edcor transformers, did you solder wires to the tabs or did you order them with leads already attached?

BTW, nice chassis too!

Sal Brisindi

[chrish]

Thanks for the compliment Sal.

Both the amps use the Edcor transformers. For the SimpleSE I used spade connectors to attach to the solder lugs, then covered with heat shrink. For the new amp, I simply soldered to the tags and covered with heat shrink. The 6BM8 failed project (not a real failure, it taught me a lot) used the slightly smaller 10 watt push pull transformers. I will re-use them for the re-build on a chassis the same size as this project. The amp is playing at the moment, so cannot connect to the scope to see the total output power. As the topology (in triode mode) is very similar to the Decware Zen, and it uses the same valves, I am guessing around 2 watts per channel.

Chris

[arnoldc]

Hi Chris, may I know where in Singapore you got the chassis from?

[chrish]

Chassis was purchased from Well Audio Labs,

Ground floor, Burlington Square (behind Fatty's Restaurant). Burlington Square is next to Sim Lim Square.

This is the smaller chassis. 11" x 8" x 2.25". Top, bottom, front , back, sides are all screwed to each other and you can remove all individually - very convenient when building. Steel construction with aluminium front plate. The recesses part of the front plate detaches for easy drilling of switch/knob holes. Not bad for the price. Picked up two of these, one for this project and one to re-build 6BM8 that I will use to go in my office to play iTunes from Mac.

Larger version available for $60 Singapore dollars, 14" x 10.25" x 2.25". I got one of these too to build a push pull EL84 ("Baby Huey").

Chris

[tubelab.com]

Here she is next to my TubeLab SimpleSE...

Two pretty amps in a row. If you are not careful, you may come down with a full blown case of Single Ended Fever. The only cure is to build a push pull amp. The recovery process is not foolproof though. I have started down the path twice only to have a relapse. My P-P amp has been pushed aside and there are two unfinished SE amps on my workbench.

Just kidding, your second amp looks better than the first, whats next?