[radrd]

Quote:

I believe a Member of the Trade is allowed to answer direct questions about products they sell.

Not if it is advertising or customer service related.

 

[Budgie]

I think your understanding is correct on the issue of commercial use of Head Fi. The point was to stop the forums from being bombarded with sales pitches from commercial manufacturers, not to limit the free trade of ideas, knowledge, parts, etc. between hobbiests. (Even if those hobbiest happen to work professionally in electronics.)

The biggest problem I see with moving such threads to Headwise, is Chu's need to keep his bandwidth down, to control costs. The more of us who frequent his site, the more likely he will need to shut it down again. Maybe some people wern't around for the dark days when Headwise was off line due to money issues caused by traffic at the site. That is what eventually resulted in Jude's decision to create Head Fi.

There was alot of threads about this but for those of you not around at that time here is one-
http://www4.head-fi.org/forums/showt...y&pagenumber=1

 

[jamont]

Before the PPA boards hit the streets, I hope that the developers will specify a "reference configuration", which at least:

1. specifies a single choice for every part
2. sounds good to them
3. provides RMAA benchmark measurements made with the reference configuration[/list=1]
   I am disappointed that the new material on tangent's website does not include this information, but I hope that it will appear before the boards go on sale.

 

[guzzler]

correct me if i'm wrong, but i don't think Team PPA have got the final prototype board yet so there can't be a list for it or measurements!

g

 

[jamont]

Quote:

Originally posted by morsel Thanks for the feedback. The final prototype has been ordered.

They are clearly getting close, it seems like a reasonable time to discuss such things.

 

[morsel]

Guzzler has it right as far as RMAA tests of v1.0 goes. Suggested component values are specified on the schematic. Tangent suggests specific parts on his website:

http://tangentsoft.net/audio/ppa/amp/plists.html
http://tangentsoft.net/audio/ppa/amp/pguide.html

For what it's worth, here are my suggestions:

Elpac WM080 wall wart
tulip style DIP sockets
4 HA5002 buffers per channel
AD8610 or OPA627 opamps depending on your taste
generic 1% metal film resistors or Vishay Dale if you insist
C1 just 2 Panasonic FC 35WV 1000uF in positions 3 and 6
C2, C5 BC or Wima 1-2uF PE film
C3 BC or Wima .1-.01uF PE film
C4 Panasonic FC 35WV 100-220uF
C6 10pF ceramic NPO, COG, or silver mica
C7 BC PP film .082uF
Q3 1 pair 2N5486 per channel or 2 pair if you want to minimize voltage drop
D1 1N4001
all other parts per the schematic

 

[puppyslugg]

I noticed tangent listed the ad843 as an 'optional' opamp. I thought there was a problem with the ad843 'latching-up'

 

[sneared]

With the suggested parts, how much current does the amp draw?

power supply voltage and battery vs. wall wart?

 

[tangent]

Quote:

But it's not like the oracle has spoken and we need to make sense of it - just ask Jude...

We have. It's great to see the support I have here, but the fact of the matter is that some people believe I'm violating the rules. Some of them are just concerned about this, and they complain to Jude. Others have been slapped by the moderators themselves, and they bring me up as an example of someone who they perceive to be getting away with something they aren't allowed to do. I think I'm in a gray area, but my belief doesn't really matter. The point is, Jude's catching a lot of flack over my presence here, so I have to do something to make peace.

Those who want threads like this to be here, ask yourselves: what would you do to silence the outside critics and stop people from using me as an example to justify their actions? If you can't do that, Jude's headaches will continue. I don't want to make problems for him, so my path seems clear.

Quote:

The biggest problem I see with moving such threads to Headwise, is Chu's need to keep his bandwidth down, to control costs.

You're welcome to suggest an alternative.

Quote:

Only thing is the PPA schemactic...

I don't understand what you're getting at.

Quote:

I am disappointed that the new material on tangent's website does not include this information,

It will be included as part of the new benchmarks, simply as a matter of disclosure of what was tested.

Quote:

C4 Panasonic FC 35WV 100-150uF

I'm in a bit of a quandary about that, actually. The 100-150uF FCs are 8mm in diameter at 35V. You don't get 10mm caps until 180uF, so my site recommends 220uF at the moment, because it's a more common value. I wonder, though, would it be better to recommend 100uF/50V just to keep the capacitance there low but sufficient?

Quote:

I thought there was a problem with the ad843 'latching-up'

That was in the first prototype. We made some changes that seem to have fixed this in the second prototype.

 

[tangent]

Quote:

With the suggested parts, how much current does the amp draw?

It's dominated by the quiescent currents of the devices you use. Each buffer draws 8.3mA, and there are 3-12 of them. Add that to the draws of your op-amps (3) class A current sources (3) and power LED and you'll be really close to the real draw of your amp. A typical range is 45 to 150mA, depending on the configuration.

Quote:

power supply voltage

The minimum depends on the op-amp and how much voltage your headphones need. I go into all that in detail in this article. Whatever you want to use between that minimum and the maximum your op-amps will tolerate depends on the op-amps as well. Some chips sound better with more voltage, others don't.

Quote:

battery vs. wall wart?

I don't understand what you're asking.

 

[morsel]

I overlooked the 220uF 8mm caps. Those are good, too.

 

[sneared]

My questions about current draw were directed at what Morsel measured with her prototype and suggested configuration. I assume such measurements were made. It also helps to know under what conditions the measurements were made under (battery power or wall wart, size of battery pack or voltage of wall wart, etc etc). I know Tanget has posted some performance specs. But I was seeking information specifically about the recommended configuration.

I'd also like to know other measurements if they were made like THD, etc.

Thanx

 

[morsel]

I haven't measured current draw in quite a while, but I think it was about 115mA. 100mA for 12 buffers, 9mA for the opamps, 6mA for the current sources and TLEs adds up just about right.

 

[jasonhanjk]

Quote:

-------------------------------------------------------------------------------- Only thing is the PPA schemactic... -------------------------------------------------------------------------------- I don't understand what you're getting at.

The ground channel input is connected to the volume pot, whereas the one at Morsel site shows differently (connects directly to ground).

I found out this when I built one according to your site.

 

[PeterR]

Well, no offense, but that one isn't really that hard to catch, given at least a rudimentary understanding of the circuit. Don't blame tangent, it should've been very clear that this is a work in progress you shouldn't follow blindly...