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post #1486 of 1671

Thanks funch, I'll check that out.
 

post #1487 of 1671

I'm a pretty novice DIY (I've only built small and simple devices like a CMOY and a mini^3) but I'm also thinking about picking up an EHHA kit from glassjaraudio to scratch the itch for new gear and avoid buying something else.  Reviewing the pcb on the EHHA rev A, it seems like a step up in difficulty that I think I could work my way through if I take it slow.  Am I delusional for thinking about trying this out with my limited experience?  

post #1488 of 1671

Sounds like me:  cmoy --> mini3 --> EHHA revA.  Take your time, lean on the helpful folks here if required, and you'll have no problem.  Set aside some time for chassis work and wiring (that'll be new compared to your prior projects).  Go for it - great amp!

 

BK

post #1489 of 1671

I have started much bigger many years ago and didn't run into major problems... when you take your time, ask before you proceed with something unknown and employ your best soldering skills it definitely can be done. Layout is quite tight on the EHHA board so always check parts values and designations /orientation before soldering... put it in a nice case (Hifi 2000/Parmetal as mentioned recently) and you'll have a great amp!

post #1490 of 1671

Hi All;

 

For some reason, this sight won't let me post pictures so a written dialog will have to do. Plugged my in EHHA  about  2 weeks ago for the first time.  In its present shape, its a tangle of wires on a 12x12 plywood board.  Minimal thought to EMI and grounding. Gave it a few hours break in with some 1K Hz square waves  and a final bias adjustment  to 220 mV before the first listen.  To be honest, it sounded cruddy.  Bass had a little promise but every thin else stunk!.  The more complicated the music, the worse it sounded. Decided to give it another 5 or 6 hours before the next listen and still blah!  Scope traces for both square and sine waves were not good to say the least.  I decided to let it burn for another 8 or 9 hours while I made plans for my favorite pass time...trouble shooting.  Returning to my shop, I noticed the traces on the scope looked really good.  Reset the bias to 220 mV and gave it another listen.  In one word "AWESOME".  This thing sounds better than great!  Even with the sloppy temporary wiring, the amp was dead quiet.  For those interested this is a stock build from Glass Jar using Mosfet's and 6GM8's for tubes.  Right now I am deciding on how I want to case it up.  Final version will have a TKD pot,  SUMR transformer, and Vampire connectors.  I've been looking around Ebay for some tubes to roll it with.

 

Hopefully I can figure out the picture problems before I finish casing it up.

 

Jim

post #1491 of 1671

Hi All;

 

Did a little work on my enclosure with with the new 4.2 version of Front Panel Designer.  (This new version is not as stable as the previous release.  Crashed a number of times.  Will not save files created in previous versions. Other problems! Beware!)  Also, still waiting on the SUMR transformer before finalizing any design decisions.

 

Whats a person to do.  Tube roll!  I received 4 6N27Ps in the mail a few days ago.  Vintage 1969's.  I randomly selected 2 and placed them into the amp for some break in time.  After about 10 hours, I gave them their first listen.  Much worse than the 6GM8's sounded!  Indeed, would have sounded better if I had threw them on the floor just to hear them pop!  Any who,  came back for subsequent listens until after about 25 hours, they gave up their stubbornness  and sounded really good.  Their tonal quality is a bit different than the 6GM8s, but they sound really really good.  Score: Good tubes 2....Bad tubes 0.    

 

I have a pair of 6DJ8's coming soon to try out.  Also looking for the elusive Telefunken 6GM8's.  Will keep you all informed.  Still can't post a picture, but...maybe someday.

 

Jim

post #1492 of 1671

Hi Again;

 

Finally letting me upload some pictures!

 

 

 

 

 

Getting there!

 

Jim

post #1493 of 1671

Hi there,

 

i bought a mosfet EHHA rev a.

As i was not satisfied about the components layout, especially the power transistors, i made a pcb.

I also reviewed some components sizes, psu capacitors, and the J511 constant current diode.

i also used an R-core transformer.

It is only for my personnal use to satisfy myself.

here are some pics, it is actually not finished , because i burned my opamp during my tests :

 

 

http://hpics.li/3fb3dd4

 

http://hpics.li/3f0e9c7

post #1494 of 1671
Klechty,

A most interesting take on the build.

How high are you planning to bias the MOSFETs such that you went with the external heatsinks? Or was it more of an aesthetic reason?
post #1495 of 1671

Hi,

 

there are some trimmers on the pcb.

Also i can set up my + -30V.

I made a new pcb to use with ECC88 .

 

Thanks for the interest.

post #1496 of 1671

Hi guys, 

I'll be doing the classic newbie thing and introduce myself with a silly question. :)

I just started getting together the parts necessary for the build and I messed up something in the communication

with my supplier about the transformers, so instead of getting a center tapped 30-0-30 toroid,

I got two regular 30V (10 VA). Can I make them work somehow as a + - supply or do I have to

order a new transformer? Unfortunately I made the mistake, so I can't claim a refund.

 

Any ideas?

 

One more thing the 1N5313 diode no longer seems available.

Can I replace it with 1N5314? They are quite close in specs.


Edited by newbienewbie - 7/11/13 at 7:48am
post #1497 of 1671
An answer to either question would be great. wink.gif
post #1498 of 1671
Quote:
Originally Posted by newbienewbie View Post

Hi guys, 

I'll be doing the classic newbie thing and introduce myself with a silly question. :)

I just started getting together the parts necessary for the build and I messed up something in the communication

with my supplier about the transformers, so instead of getting a center tapped 30-0-30 toroid,

I got two regular 30V (10 VA). Can I make them work somehow as a + - supply or do I have to

order a new transformer? Unfortunately I made the mistake, so I can't claim a refund.

 

Any ideas?

 

One more thing the 1N5313 diode no longer seems available.

Can I replace it with 1N5314? They are quite close in specs.

 

Yes, you can use 2 transformers to make a split rail.  It just uses more space.  What PSU are you using?  You can connect them from the secondaries or connect them after the rectifier.  I think people prefer connecting after the rectifier.

 

1N5314 is fine, though the E452 might work better.

post #1499 of 1671
Hi, thanks for the answer - I assume that by e452 you mean this: http://cpc.farnell.com/1/1/29753-diode-current-regulator-4-5ma-e-452-atc-semitec.html ?

I planned to use PSU that is part of the PCB. Sorry, but I am not sure that I understand how could I connect them after the rectifier? The toroids are AC.
post #1500 of 1671

If using the stock PSU, connect the secondaries.  I presume the transformers are identical.  Let's say they have 2 leads each, blue and green.  Connect them like this.  Blue, then Green+Blue, and Green.  Green+Blue would be connected to ground on the PSU board.  Double check with a DMM.

 

Yes, on the e452.

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