[ozshadow]

I guess buf634's sound more noticable with other cans. With Grado's, I do not notice them sounding bad at all. Maybe its because they already had a pretty bright sound ?

 

[luvdunhill]

pddjsteve

so, just choose either the v1+- or v2+- on the intersil DIP-8 and that translates to the V- V+ on the BUF634? Since there isn't an equivalent of the BW pin on the Intersil, is this just not used?

Thanks!

 

[pddjsteve]

Quote:

Originally Posted by luvdunhill pddjsteve so, just choose either the v1+- or v2+- on the intersil DIP-8 and that translates to the V- V+ on the BUF634? Since there isn't an equivalent of the BW pin on the Intersil, is this just not used? Thanks!

Well, I looked how the PPA had the HA5002 wired, and I just connected that to a buf634. V1+ and V2+ got connected to V+, V1- and V2- got connected to V-, and yeah nothing got connected to the BW. I haven't tested it yet, though.

 

[tomb]

Guys,
Please remember to include those output resistors on the headphone output of the amp. The reason you never hear much about the Intersil's is that they destroy so easily. It may be a $10 mistake every time you plug/unplug a set of headphones with the amp on.

Quote:

Originally Posted by pddjsteve so, just choose either the v1+- or v2+- on the intersil DIP-8 and that translates to the V- V+ on the BUF634? Since there isn't an equivalent of the BW pin on the Intersil, is this just not used?

Correct. There is no BandWidth resistor control on the Intersil.

Quote:

Originally Posted by ozshadow I guess buf634's sound more noticable with other cans. With Grado's, I do not notice them sounding bad at all. Maybe its because they already had a pretty bright sound ?

Not at all - BUF634's were the hottest thing going when they first came out. There is nothing wrong with them. There are a couple of things that may be better, though - if you want to go through the effort. DB's definitely, Intersil's - I think so if stacked.

Quote:

Originally Posted by pddjsteve My goal is to be able to swap between LMH6321, Buf634, and the HA5002 along with swapping opamps so I can find the combo I like the best.

Good goal. The Millett has been setup that way for quite awhile - BUF634 pads, Intersil pads, and then Amb promoted the jumper that made the BUF634 sockets compatible with OPA551 (as a buffer). The OPA551 cannot be stacked, and is competitive with a single BUF634. The Intersil is not competitive with either one until stacked (my opinion). Then there is the ultimate: Steinchen's DB's. That's a lot of options for a little tube amp.

I love the PIMETA, too - so if you guys figure out some of these options - woo-hoo!!

 

[pddjsteve]

Quote:

Originally Posted by tomb Good goal. The Millett has been setup that way for quite awhile - BUF634 pads, Intersil pads, and then Amb promoted the jumper that made the BUF634 sockets compatible with OPA551 (as a buffer). The OPA551 cannot be stacked, and is competitive with a single BUF634. The Intersil is not competitive with either one until stacked (my opinion). Then there is the ultimate: Steinchen's DB's. That's a lot of options for a little tube amp.

I really want to try a tube amp, either that or the SOHA, but I'm still trying to figure out a portable amp first.

Quote:

Originally Posted by tomb Guys, Please remember to include those output resistors on the headphone output of the amp. The reason you never hear much about the Intersil's is that they destroy so easily. It may be a $10 mistake every time you plug/unplug a set of headphones with the amp on.

Hmm. Good point. I'd been putting 75ohm resistors between the out pads on my amps and the actual jacks for my ER4P, and I figured that would probably suffice, but maybe I should put an output resistor on the adapter instead.

Edit: How does this look?

 

[rsabo]

I belive you also need an input resistor for the 5002s.

 

[setmenu]

I used resistors on the input of each 5002.
As for short circuit protection,I have had no problems.
But i guess it depends on the application.
Locking headphone sockets are used or recommended
with amps like the ppa.
But if the amp is likely to be used in a set up with
3.5mm plugs then extra precautions to prevent partial
engagement would be wise.
Resistors on the chip output are fine if your headphones
can cope with the extra source resistance without undue
effect on their frequency response.
But if the phones can't then short of making up a protection
circuit or implementing the one on 5002 data sheet, the
easiest solution would probably be some kind of mechanical
retainer for the plug.
With my unprotected 5002 based amp I simply wrap the
headphone cable around the amp so that the plug can't get
dislodged easily.



.

 

[pddjsteve]

Quote:

Originally Posted by rsabo I belive you also need an input resistor for the 5002s.

Well, I know the PPA v1 uses a 1k resistor before each HA5002, but from the wording of one of the posts in this thread it sounded like someone just stacked them, so I wasn't sure.

Edit: Here is one with both input and output resistors. Should drop right in. Size is about 16mmx16mm depending how close you trim it.

 

[luvdunhill]

Quote:

Originally Posted by pddjsteve Well, I know the PPA v1 uses a 1k resistor before each HA5002, but from the wording of one of the posts in this thread it sounded like someone just stacked them, so I wasn't sure.

pddjsteve

if you decide to get some of these guys made, count me in for a dozen or so!

 

[pddjsteve]

Quote:

Originally Posted by luvdunhill pddjsteve if you decide to get some of these guys made, count me in for a dozen or so!

If I wasn't such a camera noob and could get a non blurry shot, I've got a few etched already. I am not sure if I'd get them professionally done, but I can put the eagle files up if you want to either etch them or order them.

 

[tomb]

Quote:

Originally Posted by pddjsteve Well, I know the PPA v1 uses a 1k resistor before each HA5002, but from the wording of one of the posts in this thread it sounded like someone just stacked them, so I wasn't sure. ... snip ...

I said it. They sounded much better than BUF634's stacked, but it was on a Millett. So, the experience is probably not applicable.

 

[pddjsteve]

Quote:

Originally Posted by tomb I said it. They sounded much better than BUF634's stacked, but it was on a Millett. So, the experience is probably not applicable.

I guess my biggest question then is whether I'd need the input resistor in front of EACH buffer in a parallel set, or if it would work ok with a single input resistor and then stacking them. If the buffers themselves functioned fine in the millet just stacking them, then maybe I can do that here.

 

[applegd]

I had a close look at the 04' electronic module in my MOH, it looks like the signal goes into two HA5002s directly, no input resistor in front of EACH buffer at all.

 

[pddjsteve]

Quote:

Originally Posted by applegd I had a close look at the 04' electronic module in my MOH, it looks like the signal goes into two HA5002s directly, no input resistor in front of EACH buffer at all.

Ok, cool. I'm going to leave a single input resistor on the adapter, and not worry about having one per buffer (Tangent's writeup on the PPAv1 says R11-R14 are optional but reccomended).

Here is the one I'm going to etch. I removed the output resistor since I'm using one between the output jack and the amp out pads instead:

 

[rsabo]

Quote:

Originally Posted by pddjsteve Ok, cool. I'm going to leave a single input resistor on the adapter, and not worry about having one per buffer (Tangent's writeup on the PPAv1 says R11-R14 are optional but reccomended). Here is the one I'm going to etch. I removed the output resistor since I'm using one between the output jack and the amp out pads instead:

There's not a lot of spare room on the left side of the left buffer on the pimeta when using a RK27 'blue velvet' pot - are you sure this will fit? I used an SMD buffer and vertical resistor for my adapters and it's a snug fit.

Edit: Also, you might want to move those two topmost traces more apart. eyeballing it, it doesn't look nearly far enough apart.