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EHHA Rev A - Interest Thread - Page 109

post #1621 of 1657
Quote:
Originally Posted by Mullet View Post
 
Quote:
Originally Posted by FOXY View Post
 

Anyone using ehha with HD800?

 

I've been curious about this as well. Don't have them, but I could see getting them in the future.

 

Anyone know if Jeff Rossel at Glass Jar Audio is away on vacation or still selling kits? I've emailed twice and haven't gotten a response. Maybe, I'm just being a little impatient.


Yes, maybe you are.;)   He must be super-busy, as usual.  I've just completed a small deal with him over the weekend.  So, I know for a fact he is alive, well, and pursuing business as usual.

post #1622 of 1657
Quote:
 Anyone using ehha with HD800?

Though my EHHA RevA is still on the breadboard (... and will remain there for a while because of too many other projects...) I have tried it with my HD800's.

Works very well with a balanced sound, quite tight bass and, most important, natural highs! The EHHA doesn't have the upper midrange glare of some solid state amps so does very well with the sonic character of the HD800.

 

Btw. anybody wanting to tame the slight treble peak of the HD800 try the so called *Anax mod*... there is a very nice write up with extensive measurements on Innerfidelity.com!

post #1623 of 1657

Hi guys,

 

does anyone know what is the input impedance of EHHA rev A?

 

I've tried searching this thread, but found nothing.

 

Thanks,

Fedor

post #1624 of 1657
Quote:
Originally Posted by Fred_com View Post
 

Hi guys,

 

does anyone know what is the input impedance of EHHA rev A?

 

I've tried searching this thread, but found nothing.

 

Thanks,

Fedor


Not my thread, but for any amp that has the volume pot at the input (everything ever designed except the O2) - it's the impedance of the volume pot.

post #1625 of 1657

Hi tomb,

 

thank you for the answer.

 

What if there is no volume pot? Could we say that input impedance will be equal to resistor which is connected to ground at the input (grid leak resistor?, which is 1M in EHHA), if such resistor exists?

post #1626 of 1657

Today I finally managed to put in the e12.

 

Wired OG seperately from each board to the e12 and from there

to the headphonejack - tying them together there.

 

Now again, there's a slight hum ... (where the amp was quiet before.)

 

At the moment I'm experimenting with the wire routing, we'll see :-)

post #1627 of 1657

I read a post over on DIYAUDIO that suggested a 5751 tube as a possible substitute for the 6GM8. Any thoughts on this?

post #1628 of 1657
Quote:
 I read a post over on DIYAUDIO that suggested a 5751 tube as a possible substitute for the 6GM8. Any thoughts on this?

 

Looking at the data of the 5751 tube it appears to be a replacement for 12AX7/ECC83 but not 6GM8... plate voltage is much higher and so is gain (70 vs 14).

I haven't bothered to check the pin-out. A real substitute would be ECC86...

post #1629 of 1657

hi there, I'm back - and still having noise problems.

 

Good news is that I finally found out where (at least a part of) the hum came from.

 

 

Here's a picture of the now final interior of the case:

 

I shifted the AC wires from the 30-0-30 torroid a bit and the hum was much less - crazy.

 

 

Now there's still some kind of buzzing noise, higher pitched than the usual 50Hz hum.

Apart from that, there's no hum or noise even with open inputs and fully open pot.

 

I'm doing some testing at the moment since the noise is extremely sensitive

to how the wires from the torroid are routed...

 

______________________________________

 

Tried several variants now, gave some more twist to the already braided wires...

Tried alternate and normal grounding scheme again, also asymetrical.

 

No change, except that hum and buzz are changing a bit depending on how

I arrange them at their origin at the torroid.

 

Now I found that I can actually "feel" the torroid, I clearly feel it's vibrations.

 

Maybe I have to get another torroid?

 

 

This amp is driving me crazy.


Edited by Sathimas - 3/19/14 at 3:11pm
post #1630 of 1657

I am afraid I can't help much except for saying you should have gotten the toroids from Rondo... no vibration issues whatsoever ;)

Have you mounted them on rubber discs (or cut some from 5-8mm Moosgummi)?

post #1631 of 1657

Hi! I have one of these, but it's killed the right driver of two of my headphones. Does anyone know what could potentially be the problem?

post #1632 of 1657

I just took the avel lindberg torroids because they came with the kit and never made problems before in my other builds.

Think I'll get some new ones from rondo now.

 

What size are your's stixx?

 

 

Quote:
 Hi! I have one of these, but it's killed the right driver of two of my headphones. Does anyone know what could potentially be the problem?

 

High DC-offset at amp startup - have you ever measured that?

post #1633 of 1657
Quote:
 What size are your's stixx?

They are 40VA... in my case 2x27V /0.65A and 1x7V for the heaters...

Good luck... you are almost there!

post #1634 of 1657
I meant physical size, since I dont habe much room.
post #1635 of 1657

Sorry, of course.

 

They are 87mm dia. and 42mm high.

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