[Cloud]

 
Finished up my EHHA Rev A along with some modifications which yields great results. 

 

1) If you prefer punchier, deeper bass and a more full bodied sound, consider swapping the 2200uF caps in the power supply to 4700uF. I uses a pair of Rifa 4700uF 63V on each power supply to excellent results. Terrific sound on my LCD-2

 

2)I use AMRG(Amtrans) 300ohms resistor for R2(plate loading resistor) as advised by a DIY shop dealing with tubes. More transparent, wider soundstage and silkier highs! 

 

These are the 2 mods i tired and really like the effect, especially the caps mod. Try it folks!

 

I will post up some pictures this weekend.

 

 

[iamthecheese]

Quote:

Okay. With a diagram like that, you really must be busy.  

 
 
So, are you using the glassware A3?
 
The goal of the exercise is to ensure the ground is correctly routed through the attenuator circuit. You should be able to buzz out the continuity from the jacks into the inputs of the amp boards for both the signal as well as the ground wires. Be sure nothing is plugged into the rca jacks when you make this measurement.
 
Are the switches isolated from the chassis front panel? In this case, you do not want them to be isolated. They should be directly attached to the chassis front panel (attached to chassis ground).
 
Additionally, measure to be sure the front panel and bottom panel are electrically connected (you should be able to measure a direct short between the front panel and bottom panel). Sometimes, due to paint or anodizing, the front panel can float from the rest of the chassis. This happened with my panel (too much paint) and I had to wire my pot body directly to a chassis ground point on the bottom plate.

It is the A3, the metal housing of the switches is right against the front panel. I'll check resistances over the weekend, my weeks have become consumed by school work.
 

 

[capernicus]

can anyone tell me the dimensions of the Rev A PWBs?  I'm getting ready to make my order and am starting to think about enclosure options...
 
Any case recommendations?

 

[funch]

The Par-Metal case with a 12 x 12 footprint, 3 or 4 inches tall is popular. I used a 3" tall one myself and was very pleased.

 

[wdahm519]

Any hope that I could crap the EHHA Rev A into a case sized 11.928 x 7.93 x 2.93.  It'll be about 4 inches shorter in the back than a 12 x 12.  I just really want to use this enclosure, badly:
 
http://www.mouser.com/ProductDetail/Hammond-Manufacturing/1441-24BK3CWW/?qs=sGAEpiMZZMsrGrAVj6eTvQj%2fOYSSS1QrYDN8rBC3RLk%3d
 
 
 

 

[sachu]

Might be possible. YOu will probably have to mount the transformers on the outside/ on top of the case however.

 

[wdahm519]

Hmm, that might kind of kill the look.  I may have to go with the 16.8" x 9.5" or however large that one is.  Eh, maybe its just worth going with a Par-Metal case in the end.  I guess I can figure out minimum dimensions after I build the boards.
 
Thanks for your input.

 

[cfcubed]

>  will probably have to mount the transformers on the outside/ on top of the case however.
 
Or in a separate enclosure where they belong    How's that for opinion  
I've come around to trying to make all my builds 2-case builds now, having experimented w/transformers - input stage distances WRT hum.  No ground-loop breaker to fit in either.
 
Going that route w/my budgety compact EHHA I:
 

 

[wdahm519]

I don't know. Everpne always whines about hum but my big hammond transformer is inside my Bijou case and its dead silent...

 

[cfcubed]

So now I'm whining about you whining about others whining about hum 
Anyway there a lot of variables WRT hum & its my opinion that its nice to eliminate one of them.  Builders choice.

 

[capernicus]

As I start to embark down the EHHA build path I am interested if anyone has listened to the EHHA with some Denon D2000s?  I'm considering them as an upgrade to my SR60s / SOHAII Rig.  Any thoughts on this one? or can anyone possibly suggest a better pairing in the price range? I have a broad taste in music - everything from Reggae artists to Dave Matthews and Sarah Mclachlin to heavy hitting rock like Breaking Benjamin type stuff...  Not much classical or Jazz to be honest.  Looking to keep the price down in the sub $300 range... (found Denons for $250!)  Thanks!

 

[hahihuheho]

Guys..i've searched the thread and couldnt find it.. could anyone clarify what's the power output of this amp at 50ohms??

 

[glenda]

I couldn't find the info on the site.  What is the gain?   What is the Vrms out before clipping?

 

[jdkJake]

The default gain is ~9, but, can be changed. Either at initial build time or by socking a few resistors, changed with minimal effort as desired.
 
Power output is dependent upon the chosen output devices (MOSFET or BJT).

 

[glenda]

Quote:

The default gain is ~9, but, can be changed. Either at initial build time or by socking a few resistors, changed with minimal effort as desired.
 
Power output is dependent upon the chosen output devices (MOSFET or BJT).

 
Power is not a concern only need 200 mW,   but voltage swing is a challenge for most headphone amps with inefficient 600 ohm phones.  
 
The Betta 22 would definately get the job done (specs are well documented) and a 2 channel build from GJA isn't much more than the EHHA kit,  read thru this thread and there wasn't much technical info on the design capability).  How close can the output swing to the rails before clipping ?