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A Very Compact Hybrid Amp - Page 6

post #76 of 2213
There is actually a small guitar amp called the Champ made by fender.

I hope my board is in my mailbox when I get home.
post #77 of 2213
Made a lot of progress this weekend:



All went very well w/the build... Note in the pic I placed heatsink paddles on the BC3X7s that should be unnecessary, I just had them around. Also, the coupling caps (C4R, C4L) where temporarily removed.

But it appears that through my pinching of too many pennies (mixing some BC components I had in my parts bin), I've compromised the ability of my OB to zero offset. IOW, choosing random BC5X0s & BC3X7s you have laying around and mixing in some new ones from a different vendor is NOT a good way to save a few $s
You never know what a builder might do... They may even ignore BoM notes like "BC devices should be in the same class. ā€œCā€ class for the 550/560 and ā€œ25ā€ class for the 327/337"...

Doing some work soon that should correct that dumb move & hope to have more info in the next couple days...
post #78 of 2213

We have a nice amp folks!

Installing the correct BC5X0 devices has completely solved my offset issues.. I'd mixed in a couple class "A" BC5X0s (hFE = 200) with the spec'd class "C" ones (hFE about 500). That was not ideal. Correcting this tonight has resulting in a good sounding, well behaved headamp.



Need to box her up & listen a while more for meaningful impressions, but liking very much what I'm hearing so far Certainly drives my D2000s & DT-880s with authority and has no noise issues that I can detect...

Good stuff.
post #79 of 2213
excellent work - looks fantastic ..dB
post #80 of 2213
Cool, how easy would be to debug something like that, i can spot only like 3 test points.
post #81 of 2213
I thought that this build was going to use "pencil" tubes. Isn't that the same sized tube from the SOHA? Hard to put it all in perspective....
post #82 of 2213
Quote:
Originally Posted by m0b1liz3 View Post
I thought that this build was going to use "pencil" tubes. Isn't that the same sized tube from the SOHA? Hard to put it all in perspective....
See my post here WRT pencil tubes Is says it all. Take a 3" x 5" (or 120mm X 75mm) index card and look at it. Now imagine this whole headamp on that card. And look at its features, flexibility, design & likely cost.


Thanks dB! How'd you like to build one

> Cool, how easy would be to debug something like that, i can spot only like 3 test points.

Heh, I think there may only be one labelled TP... The rest are used spots (SG, etc.). Dude, its a small board... And crammed. Runeight may add a few more TPs in 1st production run PCBs, that's up to him.

There's an easy answer here: Make no mistakes & assure all your parts are functional (and proper values) prior to installing But seriously, getting voltage readings for runeight to diagnose my wrong OB parts was not hard.. Just had a zoomed image of PCB w/traces & schematic & a steady hand for test probes.

BTW, listened some more.. My build has ZERO noise. Only thing is a little (expected) hiss when vol turned wwwaaayyy up (about 3X louder than I could bear - starting near full volume). The hiss is far less than the hiss from the LINEOUT of an IPOD when it is powered on (ipod lineout hiss is several times "louder"). This is expected & again has no affect on music at any sane listening level.

I'm really liking this thing... Chilled to some Norah Jones last night & with eyes closed she was in the room. Need to box it up & spend some time with it, but hard to imagine someone listening to it and not being impressed. And its sooo small for a tube headamp
I could be slightly biased tho, so again builders/listeners all have their own tastes. BUT you can roll a bunch of popular low & high priced tubes in this amp. My EH has range in it for example... Plenty of bass & treble extension. My Raytheon CK5814A, a fav @ 40V in my SOHA, may not be my fav @ 80V in this, but does lend an interesting texture to the sound. My gut feeling is this amp will sound like its tube... Which is what you want out of an amp.
post #83 of 2213
Ooh, this looks very awesome.

Now, for a complete kit group buy
post #84 of 2213
Thread Starter 
You guys can maybe see why I've been getting pretty excited about this amp.

I have 10 boards available from the first order. These are what cfcubed and forsakenrider are building.

Once forsakenrider verifies a second build without problems (cfcubed problems were, as he noted, due to using wrong class transistors and once the right transistors were used the amp came right up) then I will make these boards available.

We will provide the builders with the BoM as revised from the build process (a few small changes). Then you guys will have to start building.

So, if you want a proto board you'll have to get on forsakenrider's case. But wait until he gets his board in the mail.
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
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post #85 of 2213
Has there been any further developments/thoughts on making a pre-drilled enclosure available?
post #86 of 2213
Thread Starter 
Yes, we are thinking on this. First we have to determine where cfcubed and forsakenrider place the pots, jacks, and switches. Then I can cook up the FPE panels.
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
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post #87 of 2213
cool

I'll keep an eye on developments

UB
post #88 of 2213
Looking great guys. Two boards = Super compact balanced tube amp anyone?
post #89 of 2213
Looks very impressive, never seen such a tight layout...

Quote:
Originally Posted by cfcubed View Post
BUT you can roll a bunch of popular low & high priced tubes in this amp.
What tube types can be used in this amp?
post #90 of 2213
Quote:
Originally Posted by cfcubed View Post
I'm really liking this thing... Chilled to some Norah Jones last night & with eyes closed she was in the room.
Oh yea.
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