# Panda amp



## zoiberg

Anybody try or have an opinion on these?   http://cgi.ebay.co.uk/HiEnd-Headphone-AMP-KIT-Drive-AKG-and-Sennheiser-good-/180579438949?pt=LH_DefaultDomain_0&hash=item2a0b5f9165


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## yellowjeep

No idea about the circuit but the parts look to be of good quality even if the pot is mounted to the board all goofy. It looks like an interesting amp and its cheap enough that I am tempted to just go for it out of curiosity.


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## zoiberg

Circuit can be downloaded from here  http://www.mediafire.com/?coj09gxd57q3cyb


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## yellowjeep

I should have said I have no idea about any circuit. I have only built one amp and it is the Super Simple 6DJ8 and to be honest I don't know how it works, I just know how to put them together. I guess I am in the same boat as you now as this has piqued my interest. I hope somebody with more knowledge chimes in.


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## Claus-DK

It will blow your mind, it is a very nice little amp.
  It is quite easy to build also, almost like painting by numbers-
   
  here is a picture of mine
   

   
  one of the insides


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## Zigis

Nice build Claus-DK, maybe except... you really need to drill an other hole for power cord, in opposed corner (low on inside pic) and replace power cable
	

	
	
		
		

		
			




  PCB is very smart, with sensitivity input stage on one side and power supply on other side, heatsink work like shield between. In your box long power cable go close to pot, this is not good. You can run it short and in power supply side.
   
  What material you use for enclosure? Is it floor parquet or something els? I like wood.


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## yellowjeep

Very very nice build! What are your impressions? What other amps have you heard how would you say it compares? So many questions. I'm intrigued.


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## Claus-DK

Quote: 





zigis said:


> Nice build Claus-DK, maybe except... you really need to drill an other hole for power cord, in opposed corner (low on inside pic) and replace power cable
> 
> 
> 
> ...


 
   
   
  Thanks for the kind words, I will make the powercord on the opposite side in the next one or move the toroid and pcb around so that the toroid is close to the back of the box..
   
  This is a picture of the unfinished box

  
  Notice this one has feets..
   
  The material is indeed floor parquet, the only tools used are a drill, a saw, sandpaper and a truck load of glue..
   
  BTW are you Zigis from Zigis soundlab ??


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## Claus-DK

Quote: 





yellowjeep said:


> Very very nice build! What are your impressions? What other amps have you heard how would you say it compares? So many questions. I'm intrigued.


 


  Thanks, my former favorite amp was my Xcan V8 closely followed by the fully modded V2, so it is up there with some very nice amps, it crushes my portables D10, Headsix, ALO recept, so it is a real bargin of an amp..
   
  It has lots of power I use one for driving my Ergo AMT and the pot seldom travels past 12, the dark one is for "normal"  headphones and has an ouput resistor mounted..
   
  Ask away..


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## Zigis

Quote: 





claus-dk said:


> BTW are you Zigis from Zigis soundlab ??


 


  Yes, it's me
	

	
	
		
		

		
		
	


	



   
  Do you use output resistor, because too much gain? If so, amps output impedance raises too, it is not too good for sound.
  You can decrease gain in better way, install resistors between input socket and pot with resistance x3 or x4 of pot resistance (105-200K with 50K pot).This way you increase input resistance too, this is good for source and interconnect more easy loading.


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## Claus-DK

Wow, you make very nice amps..
   
  To be honest I do not know why they are there, I just read on another site that it was better for the SQ also, but I am not so sure I think it is better.....It also prevents me from blowing up my cans...
  I will try it without and see if I can reach any conclusion..
   
  At the moment I mainly use one without resistors feeding my Ergos (the new toy)..
   
  Anyhow it is a very good amp. which I can only recommend, one has to be able to solder and have a multimeter.. (I know you solder quite nicely)..
  There is a thread here http://rockgrotto.proboards.com/index.cgi?action=display&board=m&thread=5700&page=1 , your inputs will be valued


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## mrarroyo

There are also two other threads, such as: 
   
  http://rockgrotto.proboards.com/index.cgi?board=m&action=display&thread=5931
   
  http://rockgrotto.proboards.com/index.cgi?board=m&action=display&thread=6047


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## yellowjeep

The more I read about this amp the more it seems like it will be my next project.


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## francisdemarte

Using hardwood flooring is genius!  Great job!


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## JoetheArachnid

That's a beautiful-looking circuit (aesthetically, no idea about how well it works).
  A few questions: what's the stock gain? How does it sound?
  This is suddenly looking like a very viable project, oh dear...
  £50 for amp parts+shipping, ~£30 for transformer and shipping, ~£10 for wires and connectors. Also a box. Gonna be around £100+ then, which isn't bad if it's a quality product.


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## 00940

It's like a big opamp... jfet input ltp, followed by a bjt ltp for high gain, followed by a quite basic double emitter output stage.
   
  I'm a bit puzzled because the gain stage is very good: good fast transistors, nice design, extra regulation. But the output stage is crude: it uses old, slow transistors and simply a zener for the output stage biasing. The slow output transistors probably don't help to compensate the whole thing. At the power required by headphones, they could have used the same small signal bjt and bd139-bd140 (or the like) for the output. In cfp fashion, it would have helped both linearity and thermal stability (see the ckIII).
   
  Gain is 6 btw.


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## Claus-DK

You can probably find info on the gain part in the link I posted earlier, what I can say is that without the outputresistors it cranks out about 3 watt, which will be able to drive anything headphone related..
  The gain can be adjusted to be more or less..
   
  I use one for powering my Ergo AMT and they are supposed to be driven by a small speaker amp.
   
  In short it sounds awesome, I wont say that it is the best I ever heard, but you have to go pretty far up the foodchain to something on par (talking well above the 500-1000 £ mark) so in terms of value for money it is a clear winner.
   
  Yellowjeep: plug in the soldering-iron and get to work, you will not regret building it


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## Claus-DK

Quote: 





francisdemarte said:


> Using hardwood flooring is genius!  Great job!


 

 Thanks, I have been using it for years, my table has it my windowbenches got it, my diningroom table got it, so a lot of my home is covered with oakfloor, it is fun to work with, easy and it is very entertaining to come up with new patterns and variations, it is almost as addictive as Tetris............
  It is in building the box, I find my pleasure, the soldering part is OK, but not that funny..
   
  here are some of my other boxes


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## Avro_Arrow

The spiral patten cube is just too cool...


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## jcx

I would have to spend more time  but on a quick look the basic circuit topology is basically OK
   
  but any designer is going to have differing concerns - to me some of the parts choices seem odd - TIP41/2 are slooow, 3.9 V zeners are poor shunt regulators


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## MrSlim

Quote: 





jcx said:


> I would have to spend more time  but on a quick look the basic circuit topology is basically OK
> 
> but any designer is going to have differing concerns - to me some of the parts choices seem odd - TIP41/2 are slooow, 3.9 V zeners are poor shunt regulators


 

 Looking forward to your ideas..


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## 00940

@mr slim: Just for kicks (it's all sims, so take it with a grain of salt), with similarly biased amps (100ma):
   
THD @10Khz, 2Vrms into 30r : 
   
  Original:
   
  Harmonic    Frequency     Fourier     Normalized     Phase      Normalized
  Number       [Hz]       Component     Component    [degree]    Phase [deg]
     1       1.000e+04    8.982e-02    1.000e+00      179.71°        0.00°
     2       2.000e+04    1.266e-06    1.410e-05      -20.56°     -200.27°
     3       3.000e+04    3.220e-07    3.585e-06      -86.45°     -266.16°
     4       4.000e+04    1.914e-08    2.131e-07      111.41°      -68.29°
     5       5.000e+04    2.963e-08    3.298e-07      102.45°      -77.26°

 Total Harmonic Distortion: 0.001456%
   
  "Improved":
   
  Harmonic    Frequency     Fourier     Normalized     Phase      Normalized
  Number       [Hz]       Component     Component    [degree]    Phase [deg]
     1       1.000e+04    8.984e-02    1.000e+00      179.87°        0.00°
     2       2.000e+04    8.903e-07    9.910e-06      -33.48°     -213.35°
     3       3.000e+04    2.808e-08    3.125e-07     -135.43°     -315.31°
     4       4.000e+04    1.746e-08    1.944e-07      111.29°      -68.58°
     5       5.000e+04    1.628e-08    1.813e-07      107.32°      -72.56°

 Total Harmonic Distortion: 0.000993%
   
Bandwith @-3db
   
  Original: 3.5Mhz
  "Improved": 11.5Mhz
   
   
  Would it translate into any audible difference ? Who knows...
   
   
  The circuit, with classical vbe and cfp outputs.


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## 00940

Quote: 





			
				Avro_Arrow said:
			
		

> The spiral patten cube is just too cool...


 
   
  It sure is.... Lovely woodwork.


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## bada bing

Quote: 





00940 said:


> @mr slim: Just for kicks (it's all sims, so take it with a grain of salt), with similarly biased amps (100ma):
> 
> THD @10Khz, 2Vrms into 30r :
> 
> ...


 


 I like the looks of your improved version much better. I think there probably would be an audible improvement and it looks more "right".
  The power rails design on the original is pretty funky looking and I agree the output stage transistor choices are odd.
  On the original, what is the unregulated +- voltage on the rails for the output stage ?
  The original power rail arrangement looks more like it's intended for a speaker amp than a headphone design.


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## Claus-DK

Quote: 





avro_arrow said:


> The spiral patten cube is just too cool...


 


  It was a terrible job to do, there is more than one pattern in it, hard to see on the pictures, but it drove to the edge of insanity, I had to stow it away for a month and then, try again, there is two faults in it, nothing anybody would notice, but having build it it is the only things I see...


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## Claus-DK

How can you judge an amp. you have not heard ??
   
  I think it is sad to sit in ones chair listening to nothing and telling others how it sounds...
   
  Build the thing listen to it, then you can comment on the sound....


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## JoetheArachnid

Wow, from reading the first fifteen pages of the Rock Grotto thread this seems like the real deal. I think I'll bite, I've got £250 in scholarship funds that I'm meant to be spending on practical projects anyway. This almost seems _too _perfect...
  I'd love to see what two of these rigged for balance could do.
  Hurm, anybody know an easy DIY DAC for under £100 (assuming I'm left with about that much)? Or I could just lie and buy a uDac2...


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## 00940

I don't think either jcx or I meant to say anything about how it sounds. It's just that there are some "technical oddities" about that design.
   
  Now, I would caution anyone about jumping to conclusions too fast. At normal listening levels the theoretical discrepancies in thd (as in sims) in between the stock amp and the "improved" one are nothing to go crazy about. While the slow output require more compensation and restrict the achieved bandwith, I'm not certain it matters that much for the reproduction of audio frequencies. And, finally, an unregulated output stage, while uncommon for headphones amplifiers, isn't  big concern in such a design: the amp has plenty of feedback, which offers it plenty of power supply ripple rejection.
   
  Honnestly, I'm not certain that chasing the last % of performances will always and automatically translate into a better subjective sound (but it sure is an amusing intellectual exercise). Considering the input stage and the compensation scheme, the designer apparently knows what he's doing. If he had considered that a better output stage was necessary, he had the skills to put one onboard. Why didn't he ? No idea. Could be cost cutting but it could also be that he thought that it sounded better that way.


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## BobSaysHi

Quote: 





joethearachnid said:


> Hurm, anybody know an easy DIY DAC for under £100 (assuming I'm left with about that much)? Or I could just lie and buy a uDac2...


 

 Gamma 1
   
  I really want to build one of these. If anyone wants one I might be tempted to build one for you. With that said it looks ridiculously easy to build.


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## Claus-DK

I understand the nerdfactor very well, after all I am one, and the amp, could prabably be even better with some tweaks here and there, but the thing is, it is already very very good, so why bother ??
  If you end up "only" getting an amp that is better on paper and sonicly inferior, then what has been gained ??
   
  By all means I love improvements, but I just think it is the wrong way to do things, build it and then start tweaking it..If we just tweak it before we build it we cannot know if it is better..


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## jcx

Quote: 





claus-dk said:


> I understand the nerdfactor very well, after all I am one, and the amp, could prabably be even better with some tweaks here and there, but the thing is, it is already very very good, so why bother ??
> If you end up "only" getting an amp that is better on paper and sonicly inferior, then what has been gained ??
> 
> By all means I love improvements, but I just think it is the wrong way to do things, build it and then start tweaking it..If we just tweak it before we build it we cannot know if it is better..


 


  
  the converse is that engineers are trained to use their knowledge of the state of the art to be able to reliably design circuits and choose parts to achieve some performance goal - did the original designer do any more than select the cheapest output Q that can handle the power - or do yau have evidence that they are carefully "voiced" by some audiophile "guru"?
   
  taking measurable accuracy of signal amplification as a goal, and available parts suitable for the circuit topology - changing to 10x faster, flat hfe output Q and even faster, smaller driver Q would enable >10x less audio frequency distortion in the given circuit with "safe" adjustment of the compensation
   
  there is little point in claiming you must listen to everything 1st before trying what engineering principles suggest gives better measurable performance - unless you propose to go through the 100's of transistor model # that would "work" in the circuit topology with careful subjective listening evaluation between all pairings?


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## Avro_Arrow

From what I have seen of the products from HiFiDIY (where this amp is from), they have
  some good ideas and engineering blunders in most of their designs. I have one of
  their DACs and while most of it seems designed well, the ground driver is designed
  really badly. In the end, it sounds OK but how much better would it have sounded
  done right?
  
  Quote: 





jcx said:


> Quote:
> 
> 
> 
> ...


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## Claus-DK

JCX:
  I know perfectly well what you are talking about, I have the same problem when eating icecream, I study them long and hard before eating them, as you might guess I have been producing icecream in my working life..
   
  But I also do suspect that we do not know everything and I do not know if things can have synergi when paired up, which is better than using the "right" parts ??
   
  Next time you are at Macdonalds try ordering a strawberry milkshake and use it to dip your french fries in, you will be surpriced with the result, which is very hard to believe before you try it...
   
  Anyway I was in no way out to get or offend you, just wanted to provoke a bit and get a little more life into the thread, hope you can forgive me


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## jcx

I actually attended a "Ice Cream Seminar"  in college - an excuse to explore off campus - I have had Lowenbrau beer ice cream, and Fritos as mix-ins are among the more memorable


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## jigsawPB

How this amp work with high-resistance phones (300-600ohms)?


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## Claus-DK

Very well, I have bulidt one with different output resitors one for low ohmic an done for high ohmic phones, it drives almost everything quite well.


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## oldson

got my shovel out and dug up this old thread.
  anyone try this with lcd-2 or other orthos ?


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## oldson

will take that as a "no" then?
  will be ordering my lcd-2 tomorrow, so will find out soon enough


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## Claus-DK

If I remember correct it can pump out 3,75 Watts, so it should have enough power for the orthos


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## oldson

Quote: 





claus-dk said:


> If I remember correct it can pump out 3,75 Watts, so it should have enough power for the orthos


 
  just to round off this thread, the Panda/lcd-2 combo kicks the arse out of my d7000


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