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Cavalli EHHA Embedded Hybrid Headphone Amp - Page 112

post #1666 of 1816

I prefer to go with a separate transformer.

 

This way I can use a tube delay circuit to bring up the heaters first and then the HV supply.

post #1667 of 1816

I have been considering building this for a long time now, sold my x-can and have an excuse now biggrin.gif. I like the idea of this because it can also power efficient speakers if properly setup. I am a bit new to DIY however, have previously built a cmoy and a cth. Have a few questions about the build; If setup for speaker use, I assume the headphone out would also be setup for high gain use. Is it possible to have a switch for the gain on this amp? Allot of the headphones in my inventory at the moment are low impedance. Or do you just have to socket resistors and switch them? 

post #1668 of 1816

a switch for the gain will definitely be the way to go. Perhaps John can pitch in with his observations/comments as he is the only person thus far to have built one for dual duty.

post #1669 of 1816

As Sachu pointed out a gain switch in your case will be necessary.

 

My amp has no gain switch, in my scenario I’m using it with efficient horn speakers and various high impedance phones.

post #1670 of 1816

Finished my first DIY build - EHHA.

Its a BJT build with Toshiba 2SC2238 / 2SA968.Here are a few pics:up1f.jpgup2u.jpgup3o.jpg


Edited by gurubhai - 10/28/10 at 8:20am
post #1671 of 1816

Thanks for the replies sachu and john, I will have to do some research on how to make a gain switch. Nice build gurubhai!

post #1672 of 1816

Nice build indeed gurubhai..love the use of the adapter for the heaters lol 

 

Need better shots of the amp fully cased up buddy. smily_headphones1.gif

post #1673 of 1816

Nice Job!

 

One quick suggestion about the Adapter.  De-nude it and mount on stand-offs.

 

Don't be offended --

 

A few suggestions about the Nude adapter:

 

1) Would look More professional

2) Would look less "SinglePower Inspired"

3) Probably would run Cooler

 

Sweet Work!

 

What are the Specs on the adapter?

 

 

Quote:
Originally Posted by gurubhai View Post

Finished my first DIY build - EHHA.

Its a BJT build with Toshiba 2SC2238 / 2SA968.Here are a few pics:up1f.jpg


Edited by les_garten - 10/28/10 at 10:39am
post #1674 of 1816

Thanks Sachi : your encouragement & support has been invaluable.

 

Thanks arteom.

 

@ les : Not offended at all, all suggestion are welcome. Considering I didn't even know how to solder 4 months back I am just happy that the amp is running even if the workmanship looks 'SinglePoweresque'.

I have a custom stand-off plate on order for the adapter & will shift it once its ready.

The adapter doesn't generate much though.

 

Edit : Its a 12V, 1A SMPS


Edited by gurubhai - 10/28/10 at 10:59am
post #1675 of 1816

guru...you need to up the size of the heatinks for the output devices on the amp and also on the S22 power supply..only just noticed them now. Monitor the temperature on the heatsinks and it might be a good idea to either run the amp off of a un-interrupted power supply to avoid risking blowing the output devices when you get those power cuts wink.gif. And I highly recommend it in your case as you have the locking headphone jack (hate those)

 


You will need to use these ones

 

One other tweak would be to shunt the potentiometer using some takman or riken resistors depending on the value of your potentiometer. Use anywhere from 40-47k resistors for shunt modding it if its a plain ALPS blue velvet 50k pot.


Edited by sachu - 10/28/10 at 11:23am
post #1676 of 1816
Quote:
Originally Posted by arteom View Post

Thanks for the replies sachu and john, I will have to do some research on how to make a gain switch. Nice build gurubhai!



Just use a simple miniature SPDT ON-ON switch..One resistor value (depending on gain setting) for each switch position and you are done.

post #1677 of 1816

Ya, I have been keeping an eye on the heatsink temperatures & they have been fine even after 6 hours of continuous running. Anyway it shouldn't be issue during the winters, I shall look into it later.

 

Can you point me to some detailed info on 'shunt' mod. I have alps 'blue velvet' 100k pot.


Originally Posted by sachu View Post

guru...you need to up the size of the heatinks for the output devices on the amp and also on the S22 power supply..only just noticed them now. Monitor the temperature on the heatsinks and it might be a good idea to either run the amp off of a un-interrupted power supply to avoid risking blowing the output devices when you get those power cuts wink.gif. And I highly recommend it in your case as you have the locking headphone jack (hate those)

 


You will need to use these ones

 

One other tweak would be to shunt the potentiometer using some takman or riken resistors depending on the value of your potentiometer. Use anywhere from 40-47k resistors for shunt modding it if its a plain ALPS blue velvet 50k pot.

post #1678 of 1816

You've come a LONG way then.  Congratulations!

 

Shoot a PIC back at us when you strip the PS, that would be sharp!
 

Quote:
Originally Posted by gurubhai View Post

@ les : Not offended at all, all suggestion are welcome. Considering I didn't even know how to solder 4 months back I am just happy that the amp is running even if the workmanship looks 'SinglePoweresque'.

I have a custom stand-off plate on order for the adapter & will shift it once its ready.

The adapter doesn't generate much though.

 

Edit : Its a 12V, 1A SMPS

post #1679 of 1816

out of curiosity, which transistors are you using to replace 2SC2705/2SA1145 in your EHHA? Also, is it just me or are those 6GM8s are awfully bright?

post #1680 of 1816
Quote:
Originally Posted by gurubhai View Post

Ya, I have been keeping an eye on the heatsink temperatures & they have been fine even after 6 hours of continuous running. Anyway it shouldn't be issue during the winters, I shall look into it later.

 

 


 


i forget what the quiescent current of the EHHA is, but the o22 is rated for 1A continuous with the recommend heatsinks per AMB's BOM. .  i used the recommended 1.5" Avid Therm. for a +/-30V o22 powering a 3-board B22, with each board drawing 200mA.  my o22 heatsinks barely get warm.     

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