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SOHA II Builders Thread - Page 108

post #1606 of 1665

Not sure if we are on the same page. I have no hum with headphones, I just have hum when I am using my floorstanders as headphones :D, I have no hum too when I use the floorstanders as speakers. :D It's also not exactly a hum, more like white noise that has low frequency element, that varies with volume setting, so it has to occur before the input stage. I am guessing it is RFI related, and I haven't covered it up. My Beta 22 is similar (but better, though it is cased), although it used to be silent, I supposed I made some changes that I am not aware of.

 

I don't recall paying a lot for the clear tops, but I got them used, I paid less than a pair of new production tubes for 3 of them. They may be a bit on the bright side, but I prefer to call it sparkly. :D That only happens after a week, after I fed music at max volume for a couple of days. And only a few days ago I hear some really low bass coming out of this thing. I think my coupling capacitors aren't settled yet.

 

I also ordered some Sylvania 12BH7 and Philips JAN 6922, let's see.

post #1607 of 1665

So, how exactly do you have your speakers connected? I think I can presume you have an amp between your SOHA II and speakers?

Can you lift the ground between your amp and SOHA II? Are your input wires well shielded? Do you have a ferrite bead you could try?

 

The input design itself has a small-ish grid resistor. Increasing that would probably filter out some RFI. I don't know about any negative effects, tho. Probably less gain etc.

 

Tubes always hiss a bit and that alone could be noticeable after extra amplification.

But as long as your phones are silent, I wouldn't touch anything :D

post #1608 of 1665
Yes, the headphone amp serves as a pre amp, driving a power amp. The power amp is not grounded btw, it comes with a fixed 2 wires power cable.

In the past I managed to make it dead silent by installing a power filter at the source and pre amp (I still have it). Just that for some reason, I no longer have it, even if I don't use the SOHA II.

Yes I would not touch it. biggrin.gif And the SOHA II is most likely going to the bedroom anyway. Another tube headphone amp for the living room is already half build. biggrin.gif This SOHA II is making the Beta 22 sound clinical (although it is much cleaner sounding and more transparent). As far as home headphone amp goes, I think I am sold on tubes.
post #1609 of 1665

I bet the noise is just from the unfiltered AC.

I have got to buy a power filter myself as soon as I can afford one. Some Furman units are quite cheap actually.

 

Nice man! Good luck with your new build. I think I have no need for another headphone amp in the near future thanks to my excellent SOHA II biggrin.gif

post #1610 of 1665
I'm trying to get some information on the differences between the SOHA II and the EHHA.  What's the pro's and con's of each?  Which one pushes more current / voltage?  I would like one of these build in a balanced design.  4 boards for the EHHA and I think 2 boards for the SOHA II (not sure).  
 
Any information is greatly appreciated. 
post #1611 of 1665
Quote:
Originally Posted by preproman View Post

I'm trying to get some information on the differences between the SOHA II and the EHHA.  What's the pro's and con's of each?  Which one pushes more current / voltage?  I would like one of these build in a balanced design.  4 boards for the EHHA and I think 2 boards for the SOHA II (not sure).  
 
Any information is greatly appreciated. 

 

SOHAII is a low power design, the EHHA is a power house. See the designers webpage.
post #1612 of 1665

I've got a build going but as I was scanning things over I noticed that I had opted for the M Cap's which are quite a bit bigger then the space reserved on the board for the C1's.

 

Does anyone have any tips or suggestions on how to place/solder those points in? I'm not a electronics guru yet so I don't want to just jump in and McGyver it without getting a second opinion. I'm doing all top mount for my board so I'm wondering if I should extend the wires out from the caps and place them far from the board or what you guys would suggest.

post #1613 of 1665
You will want to keep the wire as short as possible, while keeping the cap body away from the tube and the heat sink.

FWIW, mine is a bottom mount build. I have one lead attached to one hole and connected the other end with wire. You can then place the cap body in front of the heat sink or at either side of the board.

P5132960.jpg
post #1614 of 1665

Oh ok good, I'm glad that a slight extension to the wires won't cause any issues.

 

Very much appreciate that =)

post #1615 of 1665

Hi, just curious about popping sound when turning off SOHA II, does everybody have the same problem or is it just me?

Or maybe is it because epsilon 12 on my SOHA II have a problem?

 

thanks,

Nicko

post #1616 of 1665
Mine does that too, and I wonder if it is a design flaw.
post #1617 of 1665

The fact that SOHA II's (& CTH's)  epsilon 12 derivative circuit(s) can allow a pop or click at power-off has been discussed, perhaps search will find the discussions.

This is not considered a design fault nor damaging to connected headphones, just an issue with timing/release of relay at power-off.  Note amb's epsilon 12 design has progressed since these derivative implementations & may not exhibit this issue.

 

BTW I've used DPDT on/off switches on a couple CTHs, cutting e12 relay coil voltage off at same instant as power-off.  A brute-force hack that works quite well.


Edited by cfcubed - 7/12/12 at 12:27pm
post #1618 of 1665
Quote:
Originally Posted by cfcubed View Post

just an issue with timing/release of relay at power-off.


That is exactly what I meant by design fault. biggrin.gif Most (if not all) modern equipments have relay that can cut off output at the event of power failure/cut-off.

But you can argue that it was never designed for that purpose in the first place. smily_headphones1.gif
post #1619 of 1665
Quote:
Originally Posted by cfcubed View Post

BTW I've used DPDT on/off switches on a couple CTHs, cutting e12 relay coil voltage off at same instant as power-off.  A brute-force hack that works quite well.

 

Would you be so kind to share how to do that?
thanks

post #1620 of 1665

Here is my write-up of this for CTH:  http://www.head-fi.org/t/542279/the-cth-compact-tube-hybrid-rev-a-thread/360#post_8100335

 

The equivalent PCB trace for SOHA II:

SOHAII_relay_trace.JPG

 

But I only did this in a couple CTHs because I could (the builds used toggle switches), prior to that & in other builds with this exact issue I just take the cans off my head @ power-off.

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