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EHHA Rev A - Interest Thread

Jul 15, 2013 at 8:09 AM Post #1,501 of 1,752
Yes, the transformers are identical (at least they should be. :) )
If they are not exactly identical, could that cause a substantial problem?

Unfortunaly the secondaries on both are just two black wires - so I would have
to find out which is which first.

So, if understand correctly since the green line is 180 Deg out of phase with the blue one
(which creates the required + - supply) then the green and blue connected together
cancel each other out - thus creating a ground?

Just to make sure: you suggest that I connect the secondaries in series and the
DMM between green and blue should read 60v.

If I make the mistake and connect them parallel DMM should read 30v.

The primaries should however be connected in parallel.

I maybe saying very stupid things right now, but my knowledge of AC current is close to 0.
 
Jul 15, 2013 at 9:38 AM Post #1,502 of 1,752
Where can I find a EHHA Rev A builder? Also, how much would it cost for a builder to build it and ship it to me? Can you help me find a builder or point me to somebody who could help me further?

Aakshey
 
Jul 15, 2013 at 11:13 AM Post #1,503 of 1,752
Quote:
newbienewbie said:
Yes, the transformers are identical (at least they should be.
smily_headphones1.gif
)
If they are not exactly identical, could that cause a substantial problem?
Click to expand...

 
I don't believe so, but I've never done it.  You'll be restricted in current limits to the lower of the two, but the voltages should stack...at least between secondaries on the same transformer.
 
Quote:
Originally Posted by newbienewbie /img/forum/go_quote.gif

So, if understand correctly since the green line is 180 Deg out of phase with the blue one
(which creates the required + - supply) then the green and blue connected together
cancel each other out - thus creating a ground?

Just to make sure: you suggest that I connect the secondaries in series and the
DMM between green and blue should read 60v.

If I make the mistake and connect them parallel DMM should read 30v.

The primaries should however be connected in parallel.

I maybe saying very stupid things right now, but my knowledge of AC current is close to 0.
Click to expand...

 
It's like connecting batteries, although there is phase, for the example you can ignore it.  You can't connect them in parallel, as the configuration is for series.  Parallel would be green+green and blue+blue.  If you connect them wrong, you would get 0V.  Before you connect, you should check the phase with a DMM.
 
Transformers float.  Ground is just a reference point, whatever you want to make ground.
 
If you have problems, you could just make 2 PSUs and connect them on the DC side.  Honestly, if you're tackling this you should be able to read a schematic and know how to debug a circuit and be self reliant.  These forums are pretty much dead, and getting support is going to be spotty.
 
Jul 15, 2013 at 11:32 AM Post #1,504 of 1,752
Thanks for the support holland,

I know that I am biting of more than I can chew right now, but I wanted this to be a bit of a challenge
so that I can learn some things along the line. I can take it easy and one step at a time. :)
Again, thanks a lot!
 
Jul 15, 2013 at 11:37 AM Post #1,505 of 1,752
Quote:
newbienewbie said:
Thanks for the support holland,

I know that I am biting of more than I can chew right now, but I wanted this to be a bit of a challenge
so that I can learn some things along the line. I can take it easy and one step at a time.
smily_headphones1.gif

Again, thanks a lot!
Click to expand...

 
No worries.  Just be aware that there might not be anyone here to help you much.  If you can work out voltages and current via pen and paper (i.e., EE student), you should be fine.  Also, make sure, that if you check the secondaries (not connected), that you do get 0V at some point.  If you get some small voltage, you may have some phase issues and noise.
 
Quote:
holland said:
 
I don't believe so, but I've never done it.  You'll be restricted in current limits to the lower of the two, but the voltages should stack...at least between secondaries on the same transformer.
Click to expand...

 
I think I might be wrong, after mulling it over.  Off the same transformer, connecting secondaries is OK (say a 10V secondary and a 20V secondary).  There may be a problem connecting 2 separate transformers, say a 15V transformer and a 100V transformer.
 
Jul 29, 2013 at 5:38 PM Post #1,508 of 1,752
Hi All;
 
Finally finished casing my amp.  Moving from the plywood base to it's final enclosure some how caused the amp to hum a bit.  Nothing major.  Problem was fixed by using a ground loop breaker on the input grounds.  Dead quiet again.  Settled on the Amprex 6GM8's as sounding the best.  Still looking for the Telefunkens.  As was my M3, casing was inspired by a design of Stixx's
 
Some pictures:

 

 
A few inside shots:
 

 

 

 

 

 
Next up is The Christensen Damn Good 300B.
 
Jim
 
 
Jul 29, 2013 at 11:19 PM Post #1,509 of 1,752
Outstanding, muskyhuntr.  First class build.
 
I have a couple NIB pairs of telfunken if you're interested.
 
DG300B = diy has its grip on you.  What cans you using?  Would like to try that one myself.
 
BK
 
Jul 30, 2013 at 3:15 AM Post #1,510 of 1,752
Very nice build, Huntr! And thank you for the credits... :) That's a very clean execution... I especially like the top cover with the tubes popping through and the use of the TDK pot. When I may add a tiny bit of critizism I would tidy up the wiring some... or wrap the wires in braided sleeves now that you have established all the connections. I have yet to case my EHHA Rev A up... it is playing music on the breadboard (doing great with my freshly aquired HE-500's) but I am still struggling with a theme for the case. Maybe its gonna be in the Stealth direction... matte black with a few accents :)
 
Jul 30, 2013 at 6:46 AM Post #1,511 of 1,752
Hi All;
 
 
Quote:BK_856er
DG300B = diy has its grip on you.  What cans you using?  Would like to try that one myself.
Click to expand...

For the most part, I use Senn 600 hds.  However, I was at a meet a few weeks ago and brought the amp before it was 100% complete.  I was able to try it with a number of different cans, though all sounded good, a set of Grados and a pair of Beyer 880s (250 ohm) stood out.  My DG300B is being built to drive speakers in a small room but there is a thread on this board where the builder is using it for head phones.  He is having a few problems, but I think they are mostly from the builders choices and not the designers.  As for the DIY bug, your right!   I should probably seek medical help!  Not only am I working on the DG300B but I'm also at various stages with an Aikido pre amp (dual chassis, fully dual mono) and a B24 by AMB.  Would like to do a set of speakers and if AMB ever finishes his high end DAC, I would do that in a second.  Being retired helps.
 
Stixx:
 
Your right about the wiring.  Looks almost like a point to point!  I do plan on cleaning it up though.  Haven't used braid before, should be interesting!  I used all the wrap I had on a pair of the AC secondaries. But this does lead to my one complain about this amp.  There is a ton of wiring external to the boards. If the pc boards are left in one piece, the wiring can be a bit neater.  But even then, you have to run wires that could have been better implemented as traces (the filament wires for example).  When you break the boards, the problem becomes worse.  I was rigid on the case design as I wanted it to match my M3, so had no choice but to break them helping to increase the wiring's complexity.   Also, because of all this, hum was my biggest fear during construction.  As I pointed out, the amp was dead quiet on a piece of plywood, but had a bit when installed in the case.  Easy fix though.  There is a plus to this design as it allows for flexibility in a final lay out, which I took advantage of. This is a minor criticism and in no way detracts this from being a great amp.  It has a super reputation and in my opinion, well deserved.  By the way, I plan on using the housing design one more time on the DG300B,  my other projects will be more traditional. 
 
Thanks all,
Jim
 
PS; Looking forward to seeing your project completed!
 
Sep 9, 2013 at 8:54 AM Post #1,514 of 1,752
I am finally close to finishing my EHHA
 
Now I have a problem early in the initial check:
 
I connected and powered one heater supply without any problems.
(LED light, voltage is correct, tube lights, voltage stable at 6.3V)
 
Now when I power up the second heater, the LED ist not as bright
as the the other one and slowly get's dark then. I also don't get the
right voltage on the output.
 
I did already check the diodes (All ok) and compared the resistors
values (all the same).
 
Where might my problem be?
 
Sep 9, 2013 at 9:40 AM Post #1,515 of 1,752
Just measured the input voltage and found only 7.xx Volts on the non-working heater.
 
Strange, have to check the wiring again.
 
The secondary windings of the torroid are 
 
black+red: 9V @ 1.67A
orange+yellow: 9V @ 1.67A
 
I get about 9V from orange+yellow, but only 7.2 from black+red.
 
 
Very strange!!
 
Might the transformer be damaged?
 
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