[jdkJake]

Quote:

Thanks for the help jdkJake.
 
Okay, how would I align this thing (J511)? There is no indication of poles or direction and Google doesn't directly assist me.
No idea what the led's are rated, my multi doesn't have that option. I can tell you they are blue (at least 3 are - 1 doesn't light up when using diode check). :<

 


 

I am assuming you have the linear systems part. Can you verify this is indeed true?
 
   http://www.linearsystems.com/datasheets/J500.pdf
 
As for the LED's, it would be nice to know the voltage and operating current in order to determine the correct resistors to use at R32, R33, R5R, R6R and R3H. What did you install at those locations?

 

[foet]

Yes, looks like thats it. So, when facing the round side to me, the right pin should be near the marking (litle arrow)?
 
For the resistors, I followed the BOM. I've quickly checked the coloring on R32 and R33 to be sure :
R32 / R33 : 2.94K
R5 / R6 : 47
R3 : 1K
 
Just ordered Q7 and Q6, 1.5 euro for 50 of each.. I'll have some spares .

 

[jdkJake]

So pin 1 is the anode and pin 2 is the cathode. 
 
Using the nicely placed diode reference on the silkscreen of the board, make it match the diagram.
 

 

 
 
As for your resistors. The value for R32 and R33 is completely dependent upon the LED's you are using. We really need to know the characteristics of the LED's you have to know if those are the correct values to use.
 
For R5 and R6, what value was originally shipped to use with the J511? The values of R5 and R6 are used to correctly set the bias of the tube. The maximum forward current for the J511 is greater than the maximum forward current of the 1N5313. So, while probably close enough, you might want to finesse this value to get it to match what Alex intended with the original CRC design.
 
 
R3 should match R4 and be the value as specified in the BOM (1k)

 

[Vaughn]

Hey guys,
 
I've been poking around trying to find a nice amp that plays well with vintage orthos as well as HD650's. The EHHA has caught my interest but I'm concerned that I might need to have different gains for these two types of headphones.
 
Any input? Also, is it fairly easy to switch gain (I.E. could I do it with a switch mounted on the front panel)?

 

[WyldRage]

Quote:

Hey guys,
 
I've been poking around trying to find a nice amp that plays well with vintage orthos as well as HD650's. The EHHA has caught my interest but I'm concerned that I might need to have different gains for these two types of headphones.
 
Any input? Also, is it fairly easy to switch gain (I.E. could I do it with a switch mounted on the front panel)?

The EHHA plays well with my both my orthos and Grado.
 
As for switching gain, that's what the volume control is there for.

Seriously, I have had not trouble setting the right volume.
 

 

[jdkJake]

Hey guys,
 
I've been poking around trying to find a nice amp that plays well with vintage orthos as well as HD650's. The EHHA has caught my interest but I'm concerned that I might need to have different gains for these two types of headphones.
 
Any input? Also, is it fairly easy to switch gain (I.E. could I do it with a switch mounted on the front panel)?

The default gain as recommended in the BOM is 9. That is more than plenty for most sources including the HD650s. I am currently running a gain of ~6.4 and have more than enough headroom for my HD605's and LCD2 orthos. What are the electrical and response characteristics of your orthos?

You could make switchable gain a number of ways. I socketed the four resistors involved in the setting of the gain (2 per channel). You could make those values switchable on demand, but, I am not sure the wiring challenge in doing so (along with the potential for inducing noise) would be worth it. Hard to say.

Willing to break new ground?

 

[Vaughn]

Right now I'm using an Audio GD-NFB 12 and it sounds best on the high gain setting with both the HD650's and the Fostex T20 V2's as well as modified T50rp's. I guess I am worrying too much about it...
 
I don't really want to break new ground, btw

 I'd rather leave that to someone else... 
 
I'm just trying to find something that will work will with both types that will be a definite upgrade from the amp in the NFB-12, which actually sounds pretty decent.

 

[jdkJake]

I think you will find the EHHA has more than enough gain for those phones. Some might even say too much with the default build of 9, however, that is highly dependent upon source and preferred listening level. If you build it and socket R11, R13 and R14 on each of the amp boards, you can always tweak until your hearts content.
 
Not sure how it compares to an NFB-12 as I have never heard one. But, I know the EHHA sounds mighty fine to these ears. Trying out a set of 6N27P tubes as I write this.

 

[Vaughn]

Thanks for the advice...I would be using the DAC in the Audio GD if I went in this direction.

 

[stringgz301]

Quote:

I think you will find the EHHA has more than enough gain for those phones. Some might even say too much with the default build of 9, however, that is highly dependent upon source and preferred listening level. If you build it and socket R11, R13 and R14 on each of the amp boards, you can always tweak until your hearts content.
 
Not sure how it compares to an NFB-12 as I have never heard one. But, I know the EHHA sounds mighty fine to these ears. Trying out a set of 6N27P tubes as I write this.

So what's your review of the 6N27P?

 

[jdkJake]

So what's your review of the 6N27P?

Well, I have only had a couple of weeks with them, the first few days of which were mostly letting them wake up from their extended slumber, so my impressions are still pretty preliminary. So far, I like them a lot. They have a very clean, detailed and extended sound. The highs are crisp, the bass is deep, tight and very much in control. The mids are smooth and full, but leaning away from lush.

I like the sound a lot with the HF-2, as I expected after your comments. The HD650 surprised me a bit. I really like what they did with these phones, particularly the low end which really focused up more than I expected. A very nice sound. With the LCD2, things get a bit different. The LCD2 sound is still new to me, so, I really should not be rolling tubes through it right now, but, life is short.  I am somewhat on the fence with these on the LCD2. I love the low end control and high end extension, but, the Telefunkens really bring out the lush creamy mids the LCD2 is capable of reproducing. The trade-off then becomes a bit less extension and slightly looser bass. The Tele's also have the edge in soundstage and presence as well.

So, at this point in time, I really like the 6N27P. Price and availability is also a big plus. In the end, I suspect the mu (amplification factor) of the 6N27P is higher than the Telefunken, which results in higher OL gain and a corresponding higher NFB. Back during my CL/OL/NFB experiments, I was able to take an individual set of tubes through a similar set of sound profiles by manipulating the NFB. I wonder if the NFB was brought down on the 6N27P by a few db and up on the Telefunkens by a few db, how close they would start to become. I suspect the Tele would still retain a more refined sound with the 6N27P being the more analytical of the two, but, it might be an interesting experiment.

 

[iamthecheese]

What size standoffs does everyone recommend? I have a 3" tall par metal enclosure, and the glassjar kit. I was thinking 1/2 in for better airflow than 1/4 inchers, but will that fit in a 3" tall case with the heatsinks and tubes?

 

[minez]

Hi,

Do I need to unplug the headphone before powering up?
I always unplug the can before turn on the amp, but last time I turn the amp on without unplugging the can and my can blown up.

Thank you

 

[sachu]

yes, if you have no DC protection circuitry in your amp, you ALWAYS NEED to unplug your headphones during power up and power down.
 
Also you need to make sure you turn the volume all the way down before changing headphones. 
 
Sucks about your headphones getting fried.

 

[minez]

Thanks sachu