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EHHA Rev A - Interest Thread - Page 103

post #1531 of 1636

I run dual E12s on my EHHA RevA and have no issues using the AMB default values with LCD-2s.

 

I had some early annoying quirkiness on one channel, but after I redid all the molex crimping that went away.

 

If I recall correctly, the E12 will trip if I sweep the volume knob really fast with the headphones unplugged, but that's not normal usage.

 

Nothing against glassjar, but can you still get just the EHHA RevA boards and spec your own parts?

 

BK

post #1532 of 1636

Laziness? I know it's fun to spec your own parts -- I've done it plenty with some of my projects as of late. Sometimes expediency is your best friend. No fuss no muss. I think going thru Glass Jar should be overall cheaper. Although with some of the extra parts ie resistors sockets, e12 parts, etc. then the cost will jump up a little more. I'm not sure I'm going to go the par-metal case just yet, but it surely will be the standard 12x12x3 size everyone seems to like. I'm thinking of going with my source of custom aluminum/wood chassis in Oregon, if he's still making them.

post #1533 of 1636

I also run dual E12's.  I found that until my amp stabilizes (about 5-6 minuets) they are very touchy, sometimes tripping with volume adjustments (fast or slow), moving the volume past 12 o'clock, or even on it's own.  After that the E12's are very stable.

 

Jim

post #1534 of 1636
I have no issues with the e12 using the standard values. That said, there are multiple versions of the e12 out there. I am using the v1.2 boards without any issue. I did have to recalibrate them after the first week or two, but they have been fine since.

You might want to consider building the standard gain first and then backing your way down. Or at least build the standard gain first and then swap out to a gain of 5. The sound does change a bit as you fiddle with the gain resistors. I would have a number of values on hand until you find the combination you like best with the gain that fits your system.
post #1535 of 1636

@jdkJake I'll most likely do the default gain or at least have the parts on hand for it. Don't want to shoot myself in the foot -- hence sockets for everything. I read your earlier posts and took some notes on what to do in terms of gain settings. I'm thinking at the start going for 3 different combinations and seeing what works best. I like to have some ride on my volume knob -- ideally, but if I like a certain sound vs. ride on the pot I'll go for sound.

 

@muskyhuntr It's good to know that they stabilize. After things settle, do the e12s still trip with high impact transients like drum beats, etc?

post #1536 of 1636

Once the amp stabilizes, I have never had a problem with the E12's tripping.  I listen to a wide variety of music including Japanese drum music-Kodo, and have never had a problem.  This is a nice amp!

 

Jim

post #1537 of 1636
Someone make a long comparison between Mofset ans BJT version ?

I start thinking to building a balanced EHHA rev A...
post #1538 of 1636

People have been asking for a comparison for quite a long time. I'm sure there are at least one or two DIYers that have built both. I know Sachu had built an EHHA I with BJTs and an EHHA Rev A with mosfets. Reading in the EHHA thread, I thought I read that the BJT version would allow you to modify the amp to be able to drive small speakers. With the BJT it looks like you can use a few different varieties from different manufacturers. Toshiba seem to be the most popular. On Semi are the ones in the BOM. I'm not sure why the BJT would be better than a Mosfet other than the ability to have a higher powered amp for speakers.

post #1539 of 1636
Careful and judicious use of sockets would allow you to build a unit that would support either set of output devices.

In that manner, you would be able to decide for yourself which set of devices suits your tastes best.
post #1540 of 1636
Quote:
Originally Posted by runeight View Post
 

MHO is that device matching is not needed. The Toshiba transistors should be selected in the same hfe class though.

 

If I were matching I would match two things.

 

1. The O/P mosfets,

2. The mu of the two triode sections or even all four sections in both channels.

 

 But if I were building the amp I would not make the effort to do this. I do understand that others have different diy preferences.

 

 


I know this post is from way back in 2009. But I'm a little curious about tube matching, even if it's not utmost necessary.

 

I have a local guy that sells tubes out of what I deem to be a large garage. Place is a veritable rats nest, but this guys knows where everything is. He says he has 6GM8s. Not sure what brand, etc. but he was asking what % I want them matched to. This is what he asked...

 

"By matched pair do you mean with matched electrical characteristics? If yes, how closely matched, in percent and which parameter(s)?"

 

If I chose to go this route, what should I tell him? So the mu is the only thing that should match? Would I get a weird look if I asked for this?

post #1541 of 1636
Quote:
Originally Posted by jdkJake View Post

Careful and judicious use of sockets would allow you to build a unit that would support either set of output devices.

In that manner, you would be able to decide for yourself which set of devices suits your tastes best.


Wouldn't that increase the overall height of the heat sinks on the mosfets, hence a 4" height for chassis?


Edited by Mullet - 12/3/13 at 12:01pm
post #1542 of 1636

Thanks guys for the answer, I will come back on the EHHA when I will finish my Monolith and my Wire Bal-Bal & Se-Se :)

post #1543 of 1636
Quote:
Originally Posted by Mullet View Post


I know this post is from way back in 2009. But I'm a little curious about tube matching, even if it's not utmost necessary.

I have a local guy that sells tubes out of what I deem to be a large garage. Place is a veritable rats nest, but this guys knows where everything is. He says he has 6GM8s. Not sure what brand, etc. but he was asking what % I want them matched to. This is what he asked...

"By matched pair do you mean with matched electrical characteristics? If yes, how closely matched, in percent and which parameter(s)?"

If I chose to go this route, what should I tell him? So the mu is the only thing that should match? Would I get a weird look if I asked for this?

Does he have a tube tester? If so, what parameter(s) does it test?

Since you are most likely not testing the tubes at the operational parameters in which they will be used, the best you can do is approximate their relative performance against a known reference; hence the tube tester.
post #1544 of 1636
Quote:
Originally Posted by Mullet View Post


Wouldn't that increase the overall height of the heat sinks on the mosfets, hence a 4" height for chassis?

The use of sockets should not have any bearing on the chassis height. The legs of the output devices would be trimmed appropriately to fit the heatsinks while retaining a tight fit within the sockets.

Ideally, or at least how I would do it, the heatsinks themselves would not be soldered down, rather they would float or use a screw to hold them in place. The output devices would be mounted to the sinks and would be trimmed to firmly seat into the socket. In this manner, the output device and heatsink would form a replaceable combination. This would require two sets of sockets. One for the BJT side and one for the MOSFET side. Overall height should remain the same as the heatsink is the same regardless of device, they just mount of different sides of the heatsink.
post #1545 of 1636

My EHHA is slowly coming to life now...

 

After checking all the parts together with a friend of mine

(and finding nothing wrong) I just re-wired everything, double-checked

proper isolation and so on.

 

Now the offset still rises up to 25V on the right channel but

drops down to ~1mV after three or four secounds - and stays there.

 

But the high offset in the beginning still troubles me.

The other channel only rises to ~200mV.

 

I am also in contact with Mr. Cavalli himself, let's see if I can find the error.

( I have to, since there's no space for e12s inside ;-)  )

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