[mekanoplastik]

Quote:

But that's just me .

not really..i also think a portable amp the size of a brick +18AA'a that "requieres" an stepped att. is not very apealing....the fact the amp is a ppl design is enaugh reason for me to build it but i also would rather a no-limits amp.


but that is just us

m.

 

[Nisbeth]

Quote:

Originally posted by eric343 Tangent - why not go with a transformer attenuator while you're at it? Seriously, though, pads for both the Alps Blue and DACT CT2 would be a nice compromise and offer lots of flexibility. The Alps Black Beauty is sort of an interim step that I'm not sure can be board-mountable.

The Black Beauty is board-moutable AFAIK, but it's bloody huge and where do you get them at a reasonable price

I think the Alps Blue would be a good, solid option for most people, but if you want to go all-out, by all means include the option of adding an attenuator. (just out of curiosity though, how much is a CT2 in the US ?)

BTW, tangent, have you checked volume pricing for the alps blue? I imagine that there will be quite a big interest in buying these so the price could come down to a very different level because of the quantity. If the only other feasible option is the DACT, and the alps is difficult to get via normal channels, my guess would be that a large percentage of buyers will buy the pot from you along wth the board. (but of course I realise it'll be a big outlay for you

)


Hmm, just writing random thoughts, mainly because I am a little overwhelmed at the thought of a brand new amp design to build (but also because it's 3 a.m. here

.) Good work Team PPA

/U.

 

[puppyslugg]

Quote:

Originally posted by Voodoochile We still have the META42 for portability. I think a META configured for battery operation is pretty hard to beat, and still be considered a truly portable amp. It's a lot of amp in a small package, with good battery life even from 1 or 2 9v batteries. I do think you loose a little something when you try to be all things to all people. Personally, I seem to know of more people interested in a major-league stationary amp than a little portable. We have LOTS of little portables to choose from, many of which sound very nice. I figure if you want something more than a META, go whole-hog, and make a nice, mains-powered amp, in a substantial case, with a substantial PS, possibly the DACT or TDK, beefy jacks, etc. We have lots of little amps, and many of them end up fastened to wall-wart anyway. If it's a portable, I like it to be not much bigger than a mint tin, or the small serpac cases. And no outboard battery packs, or 16-AA cells in a case the size of my grandmother's kodak. But that's just me .

Welcome to Team 'PPL's Not So Portable Amp'!!

 

[Squalish]

Quote:

Originally posted by Nisbeth The Black Beauty is board-moutable AFAIK, but it's bloody huge and where do you get them at a reasonable price I think the Alps Blue would be a good, solid option for most people, but if you want to go all-out, by all means include the option of adding an attenuator. (just out of curiosity though, how much is a CT2 in the US ?)

I believe that Partsconnexion has the black beauty, either the real black beauty or the same part as WKLeung's ebay "alps blue" stepped attenuator, for $50.

 

[mhamel]

I for one would much perfer a no-holds-barred AC powered amp to compliment the Meta and all of the other portable designs that are popular here and on Headwize.

I also see the Alps Blue as the "minimum" pot for this. And slightly off-topic, but don't count on Mr. Leung's attenuators. I purchased 12 of them from him in various values and none of them are built with resistors - he denied that they were any different until I told him I took a couple of them apart and sent him photos of the two different styles. He's still "looking into it," but I'm not sure how much chance we have of seeing more of those Alps-sized attentuators from him.

Whatever way the PPA design comes together as, I'm really looking forward to building one!

-Mike

 

[Squalish]

Quote:

Originally posted by mhamel I for one would much perfer a no-holds-barred AC powered amp to compliment the Meta and all of the other portable designs that are popular here and on Headwize. I also see the Alps Blue as the "minimum" pot for this. And slightly off-topic, but don't count on Mr. Leung's attenuators. I purchased 12 of them from him in various values and none of them are built with resistors - he denied that they were any different until I told him I took a couple of them apart and sent him photos of the two different styles. He's still "looking into it," but I'm not sure how much chance we have of seeing more of those Alps-sized attentuators from him. Whatever way the PPA design comes together as, I'm really looking forward to building one! -Mike

I need more empirical evidence, but based on what people have said, it appears that the RH2702's are stepped attenuators, and the RH2701's are crappy pots. Some of the auctions he has up now show pictures with RH2702 as the serial, some show RH2701. Also, based on pics from auctions, I think the RH2701 has 30 steps, and the RH2702 has 21(audiotronics advertises 22). I know all of yours are 2701, but do are your pots 30step or 21/22step? In that thread, ffish posted this, taken from the partsconnexion newsletter:

Quote:

"Alps "Black Beauty" 21-step Dual/Stereo Series Attenuator $39.95 (US) For years, Alps was "the" name in conductive plastic potentiometers. Used by countless consumer and pro-audio companies, Alps was the market leader. However, they no longer make conductive plastic pots at all. The "Black Beauty" pot was so called due to its case color and size - differentiating it from their other, smaller, "Blue Velvet" potentiometer series. However, Alps also used this same case style to build a special order "series attenuator" as well, primarily for the pro audio market. pcX was lucky enough to find a large NOS quantity of these RARE controls. Substantially superior sonically to any pot, this series attenuator has 21-steps, a 60dB range and superior Channel-to-Channel tracking. This control should be compared to many other discrete series attenuators at well over $100 US, making our price of $39.95 US an absolute best buy! Anyone looking for a stereo volume control between 50K and 250K, should consider this part!"

The 100k version of this is still selling on their website for $50.

 

[puppyslugg]

Quote:

Originally posted by mhamel I for one would much perfer a no-holds-barred AC powered amp to compliment the Meta and all of the other portable designs that are popular here and on Headwize.

Welcome, Mike!

Yet another enlightened member of Team 'PPL's Not So Portable Amp'!

 

[ppl]

The Absence of a Dc Servo. The Inclusion of Bass Boost items are things that I my self insisted upon in addition to Power supply isolation To be considered a true Design of Mine.

Bass Boost is real useful with headphones more so than with loudspeakers. When the Amount of Boost and turnover points are chosen, The Low bass can be boosted while leaving the Critical midrange like voice intact. The action of the Boost would not be noticed on most recordings with the bass boost set this low. The availability of selecting several preferably ideal turnover points to accommodate different situations. for example if the bass was to be used to improve the almost no low bass output of small street style Phones or just correcting for lack of low bass in the recording like most 60's and 70's Rock. In these cases I find 90% of the time these recordings need Bass boost unless a quality Mined Artist like Pink Floyd, However these are rare and most Doors and Led Zeppelin sound Thin in the Bass. The Bass boost circuit employed in the PPA is of about the Simplest topology and IMHO the Least sonically intrusive Eq technique Available. Unlike other Tone Control Schemes no additional circuitry need be added eliminating one entire stage of Circuitry the Signal has to go through prior to the Input of the Amp. The PPA method simply adds a gentle first order Ring free Bass Boost with one capacitor and one Resistor added within the Existing feedback loop. This topology has many other performance enhancing properties like increasing the output impedance proportionally to Boost. good Idea. Lastly but not least if total accuracy is desired then with the bass boost bypassed or turned off there is no reactive components reaming in the feedback loop and all is as if bass boost was never an option. But for me it is a must have option.

the finest home High End Audio power Amplifiers employ some sort of separate power supply for the voltage gain stages and the Output stages. I Believe a headphone amp is nothing more than a low powered loudspeaker Amp. All the Performance qualities that separate the Common from the truly great stuff is real world Operating potential.

this implies High output current, A low and constant output impedance over the Audio range ( The PPA continues this well outside the audio range from DC-80,000 Hz.) A low noise output. headphone Are quite revealing of noise and distortion, thus the Amp must have as small amounts of these as possible. An Amp that is noise free with Loudspeakers can be very noisy over Headphones. this makes the low noise requirement real important on Headphone Amps and the PPA is Dead Quiet. The Preliminary Tests on the PPA's performance indicate more than Adequate for First Class Audio reproduction.

The Intent on Making the PPA portable was not to have an Amp you can carry around in your Shoulder bag Although you could if Desired. Anyway My pocket Amp serves me well while on the road. The Portability of the PPA comes into play if for example you like to use it camping or other places other than home where you want portable entertainment Just hook up the laptop and watch DVD's True you could use a small Pocket style amp for this Also But you also will not get the sound quality out of the Pocket style you get with the PPA.

The PPA can be a power Guzzler up to 200 mA if ICq is possible with the AD-843's and (4) Buffers per channel and we have not two but three channels in the PPA. A normal PPA configuring of an OPA-627, AD 825 and other 6 mA Op Amps with only (2) buffers per channel is about. 76 mA. not all that Battery friendly But still manageable.

While some might object to the compromises required to maintain portability the PPA in the tradition of my other Portable offerings include an isolated Supply Voltage for the Op Amp stages. thus not allowing contamination of the output rails to enter the Supply feeding the sensitive voltage gain circuits. this IMHO provides a blacker Background and more detailed Micro dynamics similar to what is obtained in High End Home Loudspeaker power amps. The PPA uses separate isolation circuits on each channel including that elusive third channel, Kind of reminds me of the third Eye. This provides Virtual dual mono for the Voltage gain stages and improve imaging and 3D Ability a lot vs just one isolated supply supplying all three channels. However even just one isolated power supply is an order of magnitude improvement over the conventional method of jut connecting the rails from the power output stage directly to the Gain stages.


This is all I can write at the moment

 

[tangent]

Quote:

I do think you loose a little something when you try to be all things to all people.

I know where you're coming from, but this amp is only compromised relative to The Absolute. Again, we can talk about building the greatest amp in the world sometime later. Meanwhile, we have a middle ground that needs filling.

All of you who are worried that this amp won't be extreme enough need to be a little patient. I've listened to it, and I'm telling you that it will be a very worthwhile upgrade from a META42. Comparing a META42 with components as similar as possible to a test PPA -- which was deliberately crippled for the purposes of the test -- showed the PPA to be the clear winner. The test results that I'll have soon will bear this out, as will listening tests if some of you people out there want to take the schematic on Morsel's web page and build your own version of this amp.

Will the PPA be the best possible amp in the world? Well, no. But I do think there's a place in the world for a pretty damn good amp that whomps the META42 yet can still be taken with you if you choose. I do realize that this is the very limit of "portability" for most people, but that's no excuse to just forget portability and go positively insane.

I'm willing to cede the ultimate high end. For now.

I don't know if it's clear from what you've seen yet, but this amp's minimum parts cost will already be something like 3x higher than the META42's. Once you do a few upgrades ton the main amp board, add the custom power supply, maybe add crossfeed and perhaps add the battery board, it'll be more like 5-6x the cost of a minimal META42 and probably take you 2x as long to put it all together. This is not a timid upgrade to the META42.

Quote:

i also think a portable amp the size of a brick +18AA'a that "requieres" an stepped att. is not very apealing

I don't know if it's been made clear yet or not, but the battery configuration for this amp is only for rechargeables. Partly because they sound better, but also for economics. That's why we're talking about a charging circuit -- not just because it's a neat idea, but because it's essential to the usefulness of the amp as a portable. Oh, and it's AAA's we're talking about, not AA's. It shouldn't add much to the weight of the amp, and they are expected to last 7 to 15 hours. The battery board, circuitry and batteries won't be all that costly, either -- about the price of a high-end linear power supply. Emminently workable.

Quote:

i also would rather a no-limits amp.

Some day, perhaps. Let's get this one rolling first, okay?

Quote:

how much is a CT2 in the US

diycable.com offers them for $151, but I got mine for about US$112 from THLAudio in Hong Kong.

We might also think about the TKD's, as those are considerably cheaper -- more like $90 through THLAudio.

Quote:

have you checked volume pricing for the alps blue?

The price of the individual pots in volume isn't the biggest problem. It's that it takes so long to get them, and they're so big and heavy that shipping costs aren't inconsiderable. See, if I started offering them, I'd have the people making META42s, PPAs, and other amps all draining the stock. In order to keep the frequency of orders low, I'd have to order something like 1000 at a time. Now, just how low do you think I could get them? Even at $5 apiece (1/5 to 1/6 what most people are charging onesy-twosy!) you're talking about a $5000 outlay.

If it has to be done, it has to be done. But for now, I'd rather fob the responsibility of supplying pots off on someone else. They're really not all that hard to get. I list something like 6 different suppliers in the META42 docs.

 

[ppl]

Yes this amp requires a quality Pot for sure a Alps Blue as the Min. stepped attuators are nice also as maby is possibly that counterfit switched attuator that is similar to the Alps Blue case and pinout.

This amps is alot more articulate that similarly confogured Amps nou using our differential Output Drive technique. This has showen in listening test to drmaticaly improve transients and Imaging over conventionaly configured Virtual ground supplys. the Mids and highs are well represented and the Bass is alot faster sounding than Conventional Virtual ground Configuations. The HA-5002 provide more quality than the BUF-634 in Hi Bias mode. with a real potent high end that the Differential drive just inhances. the BUF-634 provides a warmer Fuller low end with loss of microdynamics but still an extended High end. This Amp High lights the qualties of the IC's used in the Signal path and thus is sonicaly more sensitive to op amp and buffer changes than most amps

 

[mekanoplastik]

PPL

thank you for such a detailed explanation of the bass boost

m.

 

[JMS]

Hi. I'm one of the masses here to give my opinion. I'm also in favor of an all-out non-portable amp, but mainly I want to say that I would love to use board-mounted parts and a custom case, for the following reasons:

a) the amp can look more professional

b) there would be less effort in building the amp - with the META42 the effort required to drill the Hammond case was at least as much as to populate the board (for me), and it was rather frustrating work. Also there's the danger of ruining the case, etc.

c) less equipment required for the builder - no drill/bit set/file/rasp/etc.

d) more flexibility - a "board-mount" board can still be used with panel-mount components with more effort, but not the other way around.

I understand that panel-mounted components allow for more flexibility, but I think it would be better to optimize for the common case, which I assume to be people (like me) who just follow what the designers have chosen. Those who want to customize probably know what they're doing and can work around any peculiarities of the board anyway.

 

[Whit]

Why is a capacitance multiplier being considered instead of a full out regulated one? Also, if the board is populated with the 2200uf Panasonics this would create 26,400uf of filter capacitance. Wouldn't this create a potential huge drain on the batteries upon turning the amp on? Also I think that the 4 C1 caps should be sacrificed for 2 16mm caps per channel. The 2200uf FC caps that do fit the 12.5mm spacing are only rated for 25V. 18 AAA batteries voltage is 27V. Also the 25V is very close to the 24V that I assume most people will use with this amp. Bumping up the spacing would allow for the use of a 16mm 2700uf FC cap at 35V as well as the larger BG and Elnas.

Whit

 

[eric343]

Quote:

Originally posted by JMS I understand that panel-mounted components allow for more flexibility, but I think it would be better to optimize for the common case, which I assume to be people (like me) who just follow what the designers have chosen. Those who want to customize probably know what they're doing and can work around any peculiarities of the board anyway.

That's a good point - if you put the pads in a form that accomodates a certain board-mount component, but label them, then people who want boardmount can do that and people who want panel-mount will be able to panel-mount.

 

[tangent]

Quote:

I would love to use board-mounted parts and a custom case

We've had this very argument within Team PPA, and you've pretty well covered all the positive-side arguments. Here are the downsides:

1. Board-mounting everything requires snakng traces across the board when many times that is highly inconvenient from a layout perspective. You'd end up having to go 4-layer or damaging the current optimized layout. For examples, take a look at the output holes and the bass boost switch pads. Realize that the big power rails coming down from the capacitor bank run on both sides of the board: V+ and V- on top of each other, to maximize the ability of the op-amps' CMRR. You can't cross those barriers without jumpers or without separating the rails and then using vias. Bleh.

2. Custom panels aren't cheap. This is not a fatal argument, just realize that it isn't free to do this.

3. Before we can even think of board mounting everything, we have to get everyone to agree on a single set of components. Once again for the slow of brain: you have to get a bunch of audiophiles to agree on a common set of components. I realize that those who disagree with the choices we come up with can just make their own panels, but it's still a problem we'll have to at least try to address.

4. One of the panels must be limited to components that either don't mount to the panel (i.e. that just poke through), or can be unbolted from the front. This is because the Hammond and Lansing cases we're looking at have a top/bottom panel that can only be removed when you remove one of the end panels. You have to remove the top/bottom panel for amp tweaking and maintenance, like changing the rechargeables every few years, or rolling op-amps. I really don't like the idea of using outside-mount RCAs and switches -- they're ugly -- so it has to be the front panel that you remove first. The LED and bass boost switch aren't a problem -- they can just poke through the panel. The pot isn't a problem -- it has a mounting nut, but it's hidden under the volume knob. The output jack will either have to be a poke-through type or panel-mounted, since a board-mount-with-nut type is ugly. Poke-through for 1/4" jacks requires a very strong mountng setup where the board takes the strain. Crossfeed there's no help for -- its switch will have to be panel-mounted, since the circuit won't be going on the board anyway.

5. Not everyone wants crossfeed, so do I have to make two kinds of front panels, one with a crossfeed switch hole and labelling, and one without? What about bass boost? This multiplies the combinations to 4 front panel types, all of which I have to prototype and stock. What about those who want 1/8" jacks? You can see how the combinations start to explode here.