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 Post subject: Another smaller 5902 iPod amp
PostPosted: Jan Mon 02, 2012 6:25 am 
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Location: Haledon, NJ, usa
Hi All:
Some of you may remember the first mini-tube iPod amp I built and posted here a year or more ago.
( viewtopic.php?t=121453 )
Image

It was a fun and learning experience and a lot of you members here were most helpful to me in getting it done properly. (Thanks again!)

Well THAT amp has been working beautifully ever since.. and so this year I decided to build another one as a slightly-belated Christmas gift for my brother down in Florida.

So this time I decided to build the identical circuit but I decided this time, to re-arrange the layout a bit and try to fit everything into an even smaller wood box than the first amp ( which was in a small square, wooden tissue-box cover)

I chose wood again this time but I also decided to put the output transformers inside the box along with the entire power supply.

The box itself came from Michael's Craft stores for about $3.00.

I stained it with Minwax English-Chestnut stain and gave it about 6 coats of satin-lacquer and hand rubbed that out.

I used brass finishing washers on the top for the tubes to project up through and to dress the hole openings. However when I drilled the 3/8" side vent ports I used brass grommets. These were an excellent choice because each has a center sleeve that fit into the holes nicely.... then glued.
The end result seems to have a bit of a nautical feel to it. Perhaps in part due to the port-holes and the brass hardware... almost a tiny pirate's "treasure chest" look... no?

I used a 30va transformer which runs at only about 80% rating .. so it doesn't get too hot.

I ended up using two 6VA dual-wound "6.3v" filament transformers as output transformers 230v/6v = a ratio of 31:1.
(Actual unloaded output is 7.4v which accounts for the 31:1 ratio)
http://www.tamuracorp.com/clientuploads ... FD-4XX.pdf
Only $8.80 each at Digi-key as compared to about $32.00 each for Hammond 125A PP output transformers. I have both and have not been able to discern any significant audible difference ....although I am sure there are.

These transformers are providing an impedance of about 7.5k @ 8 ohms and 3.8k@ 4ohms.
Amazingly this sounds absolutely wonderful especially with the 4 ohm speaker load!

I'm bench testing this week before shipping:
here's the schematics:
Image

Image

And here's the finished amp:
Image

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To be a man, Be a non-conformist, Nothing's sacred as the integrity of your own mind.
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Last edited by Pbpix on Feb Sun 24, 2013 7:57 am, edited 7 times in total.

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 Post subject: Re: Another smaller 5902 iPod amp
PostPosted: Jan Mon 02, 2012 7:42 am 
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Location: Aurora Colorado
Very nice, Peter! Your best effort yet.Thanks for sharing. :D

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 Post subject: Re: Another smaller 5902 iPod amp
PostPosted: Jan Mon 02, 2012 1:49 pm 
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Location: Howell, Mi
Very nice work, Peter!

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 Post subject: Re: Another smaller 5902 iPod amp
PostPosted: Jan Mon 02, 2012 9:59 pm 
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Posts: 1974
Location: Hinsdale, IL, USA
Peter,

Very cool! Nice job looks great.

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 Post subject: Re: Another smaller 5902 iPod amp
PostPosted: Mar Thu 08, 2012 5:11 am 
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Location: Mission Viejo, southern California
Wow, that is very nice!

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many of my radios http://s269.photobucket.com/user/FSteph ... t=3&page=1


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 Post subject: Re: Another smaller 5902 iPod amp
PostPosted: Mar Thu 08, 2012 5:54 am 
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Location: Haledon, NJ, usa
FStephenMasek wrote:
Wow, that is very nice!

Thanks Stephen.. but not only was it fun to build and nice to look at...
this amp sounds exquisite!

It may only be 3watts.. but it fills my LR and most of the house with beautiful sound.

I also have an ASL AQ1003dt 30 watt el-34 PP amp... which is dynamite sounding.
But THIS little 5902 amp is just as beautiful-sounding .... though less power.

I recommend you build one.. it's a quick build and really worth it.. as the fidelity is unbelievable.

I thought it was good with 8 ohm speakers reflecting about 8k impedance.. but I added another pair of speakers in parallel equaling 4 ohm... and then the reflected impedance is about 4k and WOW that made a great improvement even though I thought it was great with 8 ohms.. it got even better with 4.

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