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Cavalli EHHA Embedded Hybrid Headphone Amp - Page 6

post #76 of 1813
5/3/09 at 12:57pm
Quote:
Originally Posted by runeight View Post
Does anyone have a schematic for that delay circuit? Or the specs on the relay contacts?
The relay was suggested on the OTHER forums, let me see what comments were posted....

It probably would not be too difficult to design (or swipe one) a simple heater delay circuit.
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post #77 of 1813
5/3/09 at 1:03pm
Sachu,

Looking good. I was puzzling over a case last night. Looks like you are air wiring your mosfets for chassis heat sink mounting?
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post #78 of 1813
5/3/09 at 1:12pm
Quote:
Originally Posted by runeight View Post
Does anyone have a schematic for that delay circuit? Or the specs on the relay contacts?
Apparently it's an AC rated Relay. No specs though, but Spritzer has one so perhaps we could contact him offlne.

Off course there is the time honored approach of Two Switches...
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post #79 of 1813
5/3/09 at 1:18pm
Quote:
Originally Posted by runeight View Post
Does anyone have a schematic for that delay circuit? Or the specs on the relay contacts?
Check out my post #32 on the thread, I posted a link for some 555timer circuits that I think would do a good job. A relay with the appropriate contact rating would have to be chosen to drive the Sigma 22.


You mentioned that the EHHA is capable of putting out about 18 watts into speakers. Are there any other changes besides the 2 watt rating on the resistor in question? It's making me think it might be a very sweet amp for a pair of efficient Single driver speakers like the Zigmahornets that I've been thinking about, when I don't want to listen to headphones.

*sigh* that would mean I would have 3 amp projects capable of driving speakers..
good thing we have understanding wives.. (or at least I do, for now..)
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post #80 of 1813
5/3/09 at 1:30pm
Quote:
Originally Posted by runeight View Post
Does anyone have a schematic for that delay circuit? Or the specs on the relay contacts?
Sophia Electric's Home Page
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post #81 of 1813
5/3/09 at 2:02pm
Thread Starter 
Quote:
Originally Posted by MrSlim View Post
Check out my post #32 on the thread, I posted a link for some 555timer circuits that I think would do a good job. A relay with the appropriate contact rating would have to be chosen to drive the Sigma 22.


You mentioned that the EHHA is capable of putting out about 18 watts into speakers. Are there any other changes besides the 2 watt rating on the resistor in question? It's making me think it might be a very sweet amp for a pair of efficient Single driver speakers like the Zigmahornets that I've been thinking about, when I don't want to listen to headphones.

*sigh* that would mean I would have 3 amp projects capable of driving speakers..
good thing we have understanding wives.. (or at least I do, for now..)
Yeah, you and me both, this Beta and another on the horizon all capable of driving speakers.

Anyway, that switch does look ideal to my simple mind
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post #82 of 1813
5/3/09 at 2:13pm

Another amp to build...

So I read through the design section yesterday - very creative Alex.

I'm still working my way through the details of the schematic, and I'm sure I'll have a few questions down the road, but once again thanks for putting together so much info on the website. This is a unique design for sure, and it'll take awhile for it all to sink in. I really love the symmetry of the design...

I did notice one typo on the schematic I believe. The signal path between the second triode and the lower VAS (Q6) passes through a unity gain mirror. The transistor pair in the mirror is labeled Q2-Q3, but I think it is supposed to be Q2-Q4, based on the parts list. Correct?
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post #83 of 1813
5/3/09 at 3:33pm
Quote:
Originally Posted by wiatrob View Post
Apparently it's an AC rated Relay. No specs though, but Spritzer has one so perhaps we could contact him offlne.
The relay is rated at 240VAC but I'm sure some other relay could be soldered in its place. I'm currently running it in my Egmont with 280VAC on each side of it and no arcy sparky yet.
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post #84 of 1813
5/3/09 at 4:16pm
We have a working S22 and heater supply.

Unloaded the S22 outputs +/-41 volts DC.

Unloaded the heater supply outputs about 8.3 volts DC.

Do I need to adjust the heater supply down to 6.4 , 6.5 volts unloaded?

Off to get some chassis work done while I await a reply.
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post #85 of 1813
5/3/09 at 5:08pm
What voltage is your σ22 PSU intended to be? I assume ±30V as recommended for the EHHA?
Even unloaded, the σ22 should give approximately ±30V (if it was cofigured for ±30V). ±41V seems to be an odd value.
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post #86 of 1813
5/3/09 at 5:15pm
Thread Starter 
sachu is an odd builder
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post #87 of 1813
5/3/09 at 5:22pm
Ferrari, yes, it is configured for +/-30 volts...There must be something wrong with the mosfets or gotten a resistor value wrong perhaps..
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post #88 of 1813
5/3/09 at 6:29pm
Yea a22 should give the same no matter what, loaded or unloaded. What's your R10 value? Should be 6.81k or thereabouts for +/-30V.
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post #89 of 1813
5/3/09 at 7:09pm
My R10 is 6.81k

It looks like there is a problem with Q13 and Q14 mosfets...

The voltages are off..I think on the drain of both are reading less than 100mV DC.
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post #90 of 1813
5/3/09 at 7:25pm
R8, R10 and D5 will determine the output voltage.
I was gonna give you some measurements but this should be all you need.
Lemme know if there is something you want measured as I have the hood up on mine.
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