# need suggestion in upgrade of a Creek OBH-11



## yzriver

Hi all:

 I wonder whether you could give me suggestio on the upgrade of this Creek OBH-11. I know there are a lot of arguement on this AMP.Most of the guys say it is a crap. However it is compact and with a nice case. I want to dig its limit and place it in my office.

 From the picture, you can see the problems:
 1. OBH-11's dirty DC supply is a non regulated DC source OBH-1, and a "SANWA" power filtering capacitor;

 2. There are input and output capacitors. if they are bad, they will effect the sound qulity.

 3. NE5532 is so so?

 I trace the left and right channels from in to out by orange and green line. (sorry both channel starts with orange line. but after OPAMP, they are in different color for yor convience).

 what is the capacitance of the input capacitor, the blue one wht sth like u22k63. the output cap is 220uF, 25V. The transitors are BD139.

 Any suggestion? what OPAMP is better than NE5532?


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## tangent

Quote:


  Originally Posted by *yzriver* /img/forum/go_quote.gif 
_Most of the guys say it is a crap._

 

I wouldn't say so. There's a lot worse available commercially. At least they've bothered to buffer the output.

  Quote:


 OBH-11's dirty DC supply is a non regulated DC source OBH-1, and a "SANWA" power filtering capacitor; 
 

A very good place to start. I wouldn't worry much about the filtering inside the amp. Just replace the wall wart with a good regulated linear. Both my STEPS and TREAD designs test a lot better than Creek's OBH-2, and I don't claim that either is special. There's better to be had beyond that level, if you want to go to extremes.

  Quote:


 There are input and output capacitors. 
 

I guess they're those 0.22uF box caps just behind the pot? If the circuit doesn't require them and you know you don't have a DC offset problem, you can just jumper them. Otherwise, you can replace them with some audiophile caps. Big ol' Orange Drop 715Ps will fit in there, with creative lead bending, for instance.

  Quote:


 NE5532 is so so? 
 

It's serviceable, but not special. I'd put a socket here and roll some op-amps. You don't have to worry about any of my commentary on supply voltages or output current limits. The buffering and the 24V supply keep you from hitting any of these. (Caveat: you might get more than 24V with the unregulated OBH-1. I'm assuming that whatever you replace it with is regulated to 24V.)

  Quote:


 the output cap is 220uF, 25V 
 

Uck. This may really be needed, depending on the design of this amp. It's single-supply, and they may not be using a virtual ground. They may be counting on an AC coupled output. If so, there's not much you can do here other than replace these caps with better electrolytics.


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## majkel

Replace the NE5532 for the AD8599, and those blue electrolytic for something of truly audio grade, like Elna Silmic, Rubycon Black Gate STD... just try and listen. Regarding op-amps, I tried almost all well-known, and some other, and thus far the only worth attention, depending on application are:
 single:
 AD825, LT1028, AD797, AD8021, OPA604
 dual:
 AD8599, AD8022, OPA2604
 All the rest is a waste of time and money IMHO. These can play music, others just (re)produce sounds. We're not talking about high-current op-amps here, of course.


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## yzriver

Majkel, tangent, thanks a lot.

 How to read the capacitance of those blue box caps? 22k63=? 1J63=?
 Can I use other type of caps to replace the blue box caps, such as Nichicon, or black gate? They are easy to find.
 Tangent: where can I buy the PCB of your design?

 Thanks again.


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## Pars

Quote:


  Originally Posted by *yzriver* /img/forum/go_quote.gif 
_Majkel, tangent, thanks a lot.

 How to read the capacitance of those blue box caps? 22k63=? 1J63=?
 Can I use other type of caps to replace the blue box caps, such as Nichicon, or black gate? They are easy to find.
 Tangent: where can I buy the PCB of your design?

 Thanks again._

 

The blue box caps would be read as u22k63 = 0.22uf 63V and u1j63 = 0.1uf 63V I believe. I would not replace these with electrolytics. The 0.1uf appear to be used as power supply decoupling caps, so what is here appears to be adequate. Hard to say, but I would guess the stock ones are polyester or more likely metalized polyester. Replacing these with polypropylene, particularly the input capacitors (0.22uf) or with orange drops, etc. since you have the room would be beneficial (as Tangent noted). The output caps should be as Tangent suggested.

Tangent&rsquo;s Parts Shop

 Lots of goodies here, so poke around.


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## yzriver

If I build TREAD, can I use OBH1 as the DC supply, which V+ goes to TREAD's C5's positive, ground to TREAD's C5's ground?


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## tangent

Quote:


  Originally Posted by *yzriver* /img/forum/go_quote.gif 
_If I build TREAD, can I use OBH1 as the DC supply, which V+ goes to TREAD's C5's positive, ground to TREAD's C5's ground?_

 

Certainly. The OBH-1 is just an off-the-shelf unregulated AC-DC wall wart.

 You'll end up with a lower supply voltage to the amp, but I seriously doubt that anything in the circuit cares.


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## yzriver

I have a plan:
 Using a TREAD regulate circuit to provide +24V to transistors' buffer;
 Using the +/-12V regulate circuit such as SOHA's power supply(BR2, 78L12, 79L12) to drive the OPAMP(2134 or 8599), of course I will only disconnect the OPAMP VCC and GND from the creek's board.
 My question is whether I can use one 110/30V 500mA transformer for these two circuits?
 How is the idea?


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## yzriver

As the circuit in pic, does it work?


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## synaesthetic

I'd replace those generic 220uF electrolytics on the output with some beefier Nichicon Muse or other audio-grade electrolytics. With creative placement you can fit some massive caps in there.


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## yzriver

I replace the input cap with the orange drop 715P 0.33pF, and the output cap with 470uF Nichincon KZ series. The orange drop caps look ridiciously huge!
	

	
	
		
		

		
		
	


	




. Also I change the NE5532 with OPA2134 with a plugin socket.
 I increase the cap value because I hope I can get more bass to my K501. Now I can feel the sound from the amp is warmer and more vivid.

 Next step is to make a new PSU. The OBH-2 is only 24V, 150mA, which limits the dynamic performance of the headphone amp.

 thank you for your suggestion.


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## rds

Very nice!


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## pabbi1

Making me have good old day syndrome for my OBH-11 / OBH-2 - the gateway amp for the sickest among us.


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## yzriver

How do you compare these capacitors? Mundorf br63 470uF, blackgate NX 470uF 35V, blackgate FK 220uF 25V, and ELNA silmic ARS 330uF 35V, and MUSE KZ that I have used?
 The circuit of this amp is pretty straitfoward, so that I am interested in the sound of the capacitors in coupling. Pairs of above won't make me bankrupt.


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## pabbi1

Having used the Blackgates and Silmics in other builds, you will wait for a while to really notice the Blackgates, and love the Silmics from day one. No experience with Muse or Mundorf. I just can't imagine this circuit will benefit from anything more than the Silmic ot Muse - if from that.

 I do wonder if any resistor positions would benefit from tantalum resistors?

 Tread definitely recommended, as I really noticed the difference when I got the OBH-2 over the default wall wart.

 Still, the OBH-11 is a loud snotty beast - I miss mine sometimes. It was a simpler time.


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## yzriver

Hi all:
 I need more eduacation from you.
 I just measured the Vin Vout of this headphone amp. I don't like the performance of it. I have a 300Ohm resistor as a load at the output. I captured the curve of voltage drop on this resistor. Please look at the curve. Input is 1KHz sin wave.
 The output voltage saturates at +-5V, as the red line indicates. What cuases this problem? Is it from the OPA saturation? I have a powerful DC source, 24V 3A, so I don't think it is the problem of DC supply.







 The other problem is that it is pretty slow. It takes 10 nS swich from -5V to 5V. Is it the slew rate 1V/1uS? This number dispoints me. The C2kIII have 70V/us.






 Look at the circuit. Is it a hopeless circuit? Is it the negative feedback cause this problem? How can I tune it to swing higher than +-5V, like +-10V. 




 Thank you for you reading. I appreciate your reply.


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## tangent

Quote:


  Originally Posted by *yzriver* /img/forum/go_quote.gif 
_The output voltage saturates at +-5V, as the red line indicates. What cuases this problem?_

 

What do you get with no load on the output? I don't see that the peaks can be any higher than 9 V from ground, due to the +/-3 V output-to-rail limit of the OPA2134.

  Quote:


 Is it from the OPA saturation? 
 

No, it's buffered.

  Quote:


 I have a powerful DC source, 24V 3A, so I don't think it is the problem of DC supply. 
 

Indeed. You're only asking for about 40 mA with what you show.

 That's a very curious number: the op-amp itself is capable of this, so if the circuit isn't capable of more with the buffer, why have the buffer?

  Quote:


 The other problem is that it is pretty slow. It takes 10 nS swich from -5V to 5V. Is it the slew rate 1V/1uS? This number dispoints me. 
 

It's probably the huge capacitive loading from having that electrolytic on the output. You can only charge and discharge the thing so fast. Microfarads require microamps to charge quickly.

 This might get back to the clipping problem, too.


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## amb

The low-pass RC filter at the input and the compensation cap in the feedback loop might be excessively large, causing the slow square wave response. You don't show any parts values so I don't know what their effects are. Since you have a scope, you can try smaller cap values to speed things up.


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## yzriver

I really your experienced guys' time on my questions. Sooner or later I will make a CKK or tube hybrid headphome amp, before that I would like to get more understand on the audio circuit. 

 If the Vout limited by the output swing of OPA2134, which is about +-2.5V, I can replace it with NE5532 that is capable of +-13V. The following curve is measured from the amp with NE5532. I also put the Vout of open and Vout on 300Ohm. The Vout on 300Ohm is about half of the Vout on open because there is a about 220Ohm resistor on the output. Is the clip from the input of the OPA, since the clipping starts at Vin about 0.6V, or from the negative feedback?




 the rising speed is nearly the same as with OPA2134.

 Following is the circuit with components’ value. I measured the resistors on board. The 63pF caps are those with F530 labeled. Is it correct? I don’t know the type of the diodes, so I just pick up any one I know. 





 I also attached the Orcad project. I am new to Orcad, there are several problems. For example I don’t know how to link the BD139.lib to *.olb. Could any Orcad expert please fixed it? The load resistor should be 1M/300Ohm.

 Thanks a lot.


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## amb

Are you sure that C6 is 47uF? That could be the problem right there...


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## yzriver

sorry, C6 is 0.1uF,63V.


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## Uncle Bob

I've been following this thread with interest because I've got an OBH-11 as well and have been thinking about doing some mods.

 I've a question though. There are three components on the board, labelled LK1/2/3, which I assume are inductors? I wonder what they're intended to do in the circuit? I notice that you've ignored them on your circuit diagram so far (good work btw, gives me a headache trying to figure these things out from the pcb)


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## yzriver

LK1/2/3 are small resistors, 1 or 2 Ohm. They are used for jumpping over the thrace.


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## tangent

The OBH-11 board is single-sided, so these are used as jumpers, where a dual-sided board would just take a via to the other side. They're nominally 0 ohms. The prefix might stand for "LinK".


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## Uncle Bob

Ok, thanks guys 
	

	
	
		
		

		
		
	


	




 live and learn....


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## Uncle Bob

I decided I'd try an op-amp upgrade to my OBH-11 - I happened to have an AD8397arz on a browndog adaptor which I could try. I wasn't sure whether it would work but it certainly seems to...

 I say '_seems to_' because although I've been using it for over a week and it sounds a lot better than the NE5532 it's replaced, it does seem to run very hot.

 Does this indicate that it might be oscillating or that there's too much voltage being supplied? Or is this normal for this class of op-amp?


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## Pars

The AD8397 will run a bit warm. It is also a cranky part, so I would measure the current draw of the part or the amp and see if it looks like it is in line with datasheet values. If not, I'd suspect its oscillating...


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## yzriver

if you heard of a good sound, the opa is working well. However, the AD8397 is not suit in this amplifier well. The rating power supply of it is 24V, and the voltage at V+ is a little higher than 24V in my Creek OBH-11. So your AD8397 is working under over bias, although the AD8397 can suvive under 26V. 
 The AD8397 has a high current capability, which could heat it up.


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## Uncle Bob

Well I finally got round to measuring the current draw of the amp with the following results;

 no chip installed - 6.4mA
 standard NE5532 installed - 34.9mA rising to 35.4mA after about 5min
 AD8397 installed - 47.4mA rising to 48mA after about 5 mins

 both tests ran with nothing connected to either the inputs or output, Vcc measured at Pin 8 is 23.5V

 From the spec sheet, the Icc of the NE5532 @Vcc=15V is 8mA typical / 11mA Max while the AD8397 @Vs=24V is 22mA typical / 30mA max

 So an extra 13mA of current draw would appear to be in line with the specs of the chips, indicating normal operations - correct?


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## tangent

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_So an extra 13mA of current draw would appear to be in line with the specs of the chips, indicating normal operations - correct?_

 

Half correct. The fact that it isn't drawing lots of extra power means it probably isn't oscillating wildly. It could still be misbehaving. The fact that it sounds good mitigates against that possibility; I'm just being picky.

 Most likely, that extra heat is just due to the higher Iq of this chip.


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## Uncle Bob

Quote:


  Originally Posted by *tangent* /img/forum/go_quote.gif 
_Half correct. The fact that it isn't drawing lots of extra power means it probably isn't oscillating wildly. It could still be misbehaving. The fact that it sounds good mitigates against that possibility; I'm just being picky.

 Most likely, that extra heat is just due to the higher Iq of this chip._

 

thanks for that feedback, the ad8397 was bought from you recently (just as an impulse purchase when ordering some other parts 
	

	
	
		
		

		
			





) and the amp is currently being powered by a TREAD based supply and both 'upgrades' have improved the performance of the amp substantially. 
	

	
	
		
		

		
		
	


	





 (now I've just got to get round to building that PPA v2)


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## SmellyGas

Quote:


  Originally Posted by *Pars* /img/forum/go_quote.gif 
_The blue box caps would be read as u22k63 = 0.22uf 63V and u1j63 = 0.1uf 63V I believe. I would not replace these with electrolytics. The 0.1uf appear to be used as power supply decoupling caps, so what is here appears to be adequate. Hard to say, but I would guess the stock ones are polyester or more likely metalized polyester. Replacing these with polypropylene, particularly the input capacitors (0.22uf) or with orange drops, etc. since you have the room would be beneficial (as Tangent noted). The output caps should be as Tangent suggested.

Tangent&rsquo;s Parts Shop

 Lots of goodies here, so poke around._

 

I tried straight jumpering these u22k62 caps like Tangent suggested = BAD NEWS. There was no output until you cranked up the potentiometer, and then all I got was horribly distorted sound. I cut the jumpers, and thankfully, the sound returned to normal. Any idea why these caps are apparently necessary? (I'm using AD843 x2 via Brown Dog adapter, if it makes a difference.) I initially thought this may have been due to major DC offset introduced from the input, but I measured 0mv offset at the headphone out.


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## tubes

I have some .22uf 450v auricaps that I can use in place of the input caps in my OBH-11. Is the 450v rating going to affect the sound adversly, the original caps are 63v.

 Phill


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## yzriver

Quote:


  Originally Posted by *SmellyGas* /img/forum/go_quote.gif 
_I tried straight jumpering these u22k62 caps like Tangent suggested = BAD NEWS. There was no output until you cranked up the potentiometer, and then all I got was horribly distorted sound. I cut the jumpers, and thankfully, the sound returned to normal. Any idea why these caps are apparently necessary? (I'm using AD843 x2 via Brown Dog adapter, if it makes a difference.) I initially thought this may have been due to major DC offset introduced from the input, but I measured 0mv offset at the headphone out._

 

I measured about 12V at the NE5532 input. i didn't track where it is from, but whatever, there is it. If you short the cap, you change the bias.
 There is a cap before the headphone out. It blocks the DC, so the DC offset is 0.


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## yzriver

Quote:


  Originally Posted by *tubes* /img/forum/go_quote.gif 
_I have some .22uf 450v auricaps that I can use in place of the input caps in my OBH-11. Is the 450v rating going to affect the sound adversly, the original caps are 63v.

 Phill_

 

I use orange drop 715P 0.33pF, 600V rating. They are working well.


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## Girlsound

This is a crappy sketch of a more complete schematic. You missed the power supply section. You can now see why the input cap is needed.

 The first thing I did was to use a proper regulated supply and remove that awful zener. The 5532 went next. I swapped in an AD8620. I got a bit warm, but sounded great. 

 Input and output caps need to be upgraded. But you've already got that covered.

 The output buffer is kinda wimpy, but it's not a job for the meek to find a way to heatsink the BD139/140 transistors. I replaced the 30ohm output resistors with nice RN60 25ohm ones.

 I was even thinking of a way to convert it to a bipolar power supply in order to DC couple the amp. It was about that time that I realized it would be a lot easier to go with something else. I was actually quite happy with my DC output coupled Szekeres.


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## millwood

it looks like a fairly good amp. the use of a discrete buffer (to225 transistors) is a good sign - many of the amps built here don't even have that.

 I would try to figure out how the output buffer is configured and if it is underbiased - it looks like a class AB buffer biased with 3 diodes per channel. if true, the output is underbiased.

 I would leave the ne5532 alone: it was a pretty good opamp then and it is a still a good opamp today. it may not have as impressive spec as other newer opamps do but it is better than what most people can tell with their ears.


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## millwood

well, having a schematic helps a lot.

 it does seem that the output stage is properly biased: the to92 transistors form a constant current sink to drive the diodes.

 the design is a single rail type and you have to have the input / output caps.

 a few things to do:

 1) you can bypass C8/C10/C4 (if electrolytic) with a small cap (.01u - .1u).
 2) you can turn the output into a class A buffer, by cutting the pnp transistor's emitter out, and then taking one of the diodes out. now, R11 and the supply voltage determines the Class A amp's idle current: I=(Vc/2)/R11 so you will need to reset R11.

 you may also wish to put a small resistor (around 110ohm on the npn transistor's base).


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## SmellyGas

After my little fiasco jumpering the input caps, I decided to do an all-out upgrade. 

 NOW the amp sounds fantastic! Pre-modification, the headphone out jack on my $200 cheapo Sony receiver sounded BETTER than the Creek. Adding a regulated power supply only seemed to improve the SNR. The Sony receiver still sounded better. I then tried various opamps - LM4562, OPA2132, and finally dual AD843's. The AD843's sounded the best of the 3. I then tried a pair of OPA627BP's (normally $27/each) that I got cheap off ebay, but they turned out to be COUNTERFEIT - ironically, they sounded better than the AD843's! 

 My last step was to replace the input caps with AudioCap polypropylenes and all of the electrolytics with Elna Silmic II's, except the big power supply cap, which I replaced with a Nichicon FG. I also replaced the counterfeit OPA627BP's with real OPA627AP's from digikey. The only problem was that the caps were too big to fit in neatly, so they're bent into funky directions.

 The headphone amplifier sounds way better now. Before the Creek's bass was weak, and the upper highs were muted compared to my cheap receiver. After the upgrade, the receiver now sounds considerably worse - "dry" and less pleasant. Bass is improved, and vocals sound buttery smooth. There is much more detail and separation in the upper highs. I'm very happy with the way it sounds now with my HD650's.

 Total Cost of mods:
 Elpac WM080-1950-760 regulated PS - $19 
 OPA627AP x 2 = $38
 Brown Dog adapter = $10
 Elna Silmic II and Nichicon caps = $20

 I hope this additional information will help someone. The OBH-11's were selling new for <$100 on ebay a while ago, so this might be a worthwhile project.


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## rogerlike

Nice. Does it still fit into the case?


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## SmellyGas

Quote:


  Originally Posted by *rogerlike* /img/forum/go_quote.gif 
_Nice. Does it still fit into the case?_

 

Yes, with the creative capacitor bending. I guess I could have also used smaller caps (with lower voltage rating). Oh well.


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## rogerlike

You should send the pic in to Creek, see what he says!


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## tubes

I have some 220uf Rubycon ZL low impedance caps that I can use to replace the existing output caps. Are low impedance caps the wrong choice for the output caps, I have heard that low impedance caps can cause oscilation? Thanks for your help.

 Phill


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## yzriver

Quote:


  Originally Posted by *tubes* /img/forum/go_quote.gif 
_I have some 220uf Rubycon ZL low impedance caps that I can use to replace the existing output caps. Are low impedance caps the wrong choice for the output caps, I have heard that low impedance caps can cause oscilation? Thanks for your help.

 Phill_

 

the Rubycon ZL is low ESR caps, which is good for power decoupling. For audio application, the caps with low tan d value are prefered. Usually, the power caps have higher tan(d) then audio caps, for Electrolytic caps, but you can try. You still can hear the sound.


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## tomano58

Hi all, I'm new to this forum but have read it for a while. I know the thread is old but I recently got my self a Creek OBH-11 v1 for coffee money and decided to upgrade it a bit. I contacted Creek and asked nicely if they could provide me with a schematic diagram and they did (thank you). So for those of you who might still want it, here it is. This is the v2 version, which most of you seem to refer to and I have the v1 version but my guess is all that differ is that in v1 it's a TL071 and only one set of RCA sockets. *If publish it like this is not ok, please let me know.*
   
  I noticed the zener diode, ZD1, is a 22V one. Do you think I can skip it and use the 24V/1A supply I have (switched and stabilized) without compromising anything? Or do I need to keep the zener?
   
  My plan is to do as most of you have, upgrade the in/out capacitors, better power supply, probably a better pair of RCA sockets (wire connected) and the opamp. I'll start with a OPA2134 (I was actually going for a LM4562 but it was currently out of stock at my supplier)


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## Avro_Arrow

The OPA2134 is a waste of time.
  I'd try an LME49720 as a drop in replacement or
  a pair of LME49990 on an adapter.
   
  If you find you can't turn the volume up very much I would lower the gain.
  If you lower the gain you can also reduce the value of the output resistor (R11, R111).
  I would use a value of 120 ohms and add a switch to bypass it all together.
   
  Replace C4/C104 with ELNA SILMIC II, 25v, as big a uF as will fit.
  Replace C11 with something like a Nichicon VR , 35v, also as big as will fit.
   
  Keep the Zener. You can still use the power supply you have.


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## tomano58

Quote: 





avro_arrow said:


> The OPA2134 is a waste of time.
> I'd try an LME49720 as a drop in replacement or
> a pair of LME49990 on an adapter.
> 
> ...


 


  Thanks for your input! The OPA2134 is just a starter but still considered good by many. Regardless it should be an improvement relative TL071 to begin with. Actually LM4562 which I was aiming for is the same as LME49720 and I'll order one as soon as they're back in stock again.
   
  Yes, volume is high already at 10 to 10 and should benefit by decreasing the gain, I'll look into that. Haven't done this for over 20 years... Gain I assume is determined as (1 + R6/R5) so which one to change, R6? Gain now is ~23, what might be suitable, 15?
   
  C4/C104 will be replaced by ELNA SIMLIC II, already ordered but I kept the original value. Why increase it?
   
  C11 I haven't looked at at all so far. But I assume like in most power supply decoupling, the bigger the better.
   
  C1/C101 will be replaced for audio graded ones.


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## Avro_Arrow

I would drop the gain down to 5 or no more than 10.
  Change R6/R106.
   
  C4/C104 form a high pass filter with the impedance of your headphones.
  For buds that average down around 16 ohms, 1000uF gets you down to
  just a few Hz. You want your corner frequency to be an octave lower than
  the lowest frequency you want to reproduce. The short answer...Better Bass.
   
  Again, C1/C101 would benefit from an increase in value to as much as 1uF.
  Same reason...better bass. A good quality film is best here.


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## Avro_Arrow

Footnote:
   
  The "standard" output impedance is supposed to be 120 ohms.
  I don't think that is followed much any more in headphone design.
  Multi driver IEM in particular seem to expect as close to zero
  output impedance as possible.
   
  As a result, I would use a 120 ohm output resistor and have
  a way to bypass it with either a second jack or a switch.
  That way you can see which sound best with whatever headphones
  you wish to use.


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## tomano58

Quote: 





avro_arrow said:


> I would drop the gain down to 5 or no more than 10.
> Change R6/R106.
> 
> C4/C104 form a high pass filter with the impedance of your headphones.
> ...


 

 Excellent explanation. Thanks! The amp will drive a pair of HD650 (300 ohm). Regarding cap values I'm about to order larger ones for C4/C104 but I don't have too much space to play with here. Will see what I can do with C1/C101. Again, thanks a lot.


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## tomano58

Ok, last question. There are three more electrolytic caps, C3, C10, C103. Would any of them benefit to be changed to better ones and/or higher value? Or should I simply have them decoupled with 47nF for example?


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## Avro_Arrow

C3/C103 isolate the feedback loop from the negative rail.
  An audio grade cap here would help, but to a lesser extent
  than directly in the signal path. Maybe a bit larger but I wouldn't
  go nuts. Maybe up to 100uF or so.
   
  C10 is a power supply cap and a low ESR cap (like the main power supply cap)
  would be best here. An organic polymer like this would be great.


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## tomano58

Ok, I'm all done and here's the final result. Sounds great and will drive my HD650 without issues. This was a well worth effort as I got it really cheap. Tanks Avro_Arrow for your help. Caps in signal path are switched to audio graded ones, 1uF MKP (in) and 330uF ELNA SIMLIC II (out). Larger power supply caps (low ESR), decreased gain (from 23 to 10). Opamp was switched from TL072(!) to LM4562 (same as LME49720).
   
*Update*: LM4562 has been switched out for a dual BB OPA627 with good result. I can't say it was a distinct upgrade but it was for sure not worse so it's a keeper.


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## Avro_Arrow

I'm glad to have helped out


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## aneker

any chance of posting the circuit diagram of this headphone amplifier?


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## tomano58

If it is the original schematic you are talking about it's posted already some page back.


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## aneker

and the design of the printed circuit board will be possible?


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## tomano58

Sorry, I don't have the pcb layout.


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## Avro_Arrow

aneker said:


> and the design of the printed circuit board will be possible?


 

 Why do you need the layout?
 Are you planning on making a copy?


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## tomano58

avro_arrow said:


> Why do you need the layout?
> Are you planning on making a copy?


 

 One can wonder.... Btw Avro, I've been trying out a few different opamps now and currently I'm using a LME49720HA Metal TO-99 which fits so well it's a keeper.


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## nikongod

wut is funnay es that a pcb is copirited and akordengli seeeng the uregineal 2 kopi is of know uses since copirite protekshun is very strongly.
 if u weir to seempli draw ur pwn pee sea bee from the schematek knowbodi cud sai boo! 
  
 Not actual legal advice. Just general advice.


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## aneker

This was not what I wanted. Enjoyed doing the OBH 21 SE

 Maybe if the cost of  components compensating can entertain me for experienced home ...

 Could do through the circuit posted above, but there may be errors in the connection of the transistors.


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## tomano58

Well, you can check directly with Creek, that's how I got the schematic.


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## linesplice

Sorry to revive an old thread, but it seems like a good place to post after lurking for a long time since it's related.
  
 I finally upgraded my old Creek OBH-11 (rev 2.).  Caps are mostly Elna Silmic II, with a Nichicon for the power, some WIMA's and two orange drop's until I can figure out how to put my big film cans in the chassis.
  
 Here's the problem:  After the upgrade, I don't have any bass.  Absolutely none.  What could have gone wrong?  Where do I look first?  I can put any of the old parts back in, one by one, if I have to, but I'd rather not go that route.  Suggestions?
  
https://postimg.org/image/ixczy5clv/
  
https://postimg.org/image/lfyoytyc3/
  
https://postimg.org/image/bjxlz6sk3/
  
https://postimg.org/image/8r4ef5s7n/


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## tangent

linesplice said:


> After the upgrade, I don't have any bass.  Absolutely none.


 
  
 Those input caps you've got there don't look any bigger than 0.1 µF. The originals are 0.22 µF, and that's on the small side, IMHO. I'd like to see 0.47 to 1.0 µF here.
  
 If you have more of those caps, you can simply solder-tack another one or two in parallel with the ones you already have. If that improves things, you've got your culprit.
  
 Otherwise, much of my troubleshooting guide is just as relevant to this amp as it is for the amps discussed elsewhere on my site. Post all the relevant measurements if following the guide doesn't lead you right to the problem.


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## linesplice

Thank you for the response!
  
 Believe it or not, those are .233 caps, so similar to the original ones, but I changed one out for a Cornell Dubilier 940C (1uf) I had,and sure enough, the bass is back (on that side).  I suppose I should find a better cap, but I'm not sure what is better and still on the value spectrum when compared to diminishing returns for performance?  i.e. I'm not likely to buy $25/ea caps unless there is substantial improvement compared to $10/ea. capacitors.
  
  
 Question:
 - Is there any point to replacing all five of the small caps?  If so, any recommendations make/model?  I believe they are all 1000pf.  
  
  
 The guide is great, by the way.  Thanks for posting.


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## Avro_Arrow

I would just go with something like this:
 http://www.digikey.ca/product-detail/en/panasonic-electronic-components/ECQ-E1225KF/EF1225-ND/56392


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## tangent

linesplice said:


> Believe it or not, those are .233 caps


 
  
 .233 _what_? Picofarads? Megafarads? Always give units.
  
 .233 is also probably the wrong value, since that is not one of the common capacitor values. You could have one custom-made, but off the shelf? No.
  
 It's also not likely to be a capacitance value code, since that would mean "23" for the significant digits and "3" encoding the decimal position, but again, "23" is not a typical 2-significant-digit capacitor value. "22" is, which means the code might be "223", which in typical capacitor numbering systems means 0.022µF, in which case no wonder your bass is totally rolled off, since your caps are 10x too small for the intended purpose.
  
 Furthermore, when we say "orange drop" here, we mean Vishay Sprague model 715P or 716p capacitors (or their CDE variants), which are about an inch and a quarter long for 0.22µF at 200V tolerance, so either those aren't what we call "orange drops" or they're not 0.22µF. It's a bit hard to tell scale from the pics, but it's much more plausible that those are 0.022µF 200V caps, which would be ¾" long.
  


> Is there any point to replacing all five of the small caps?


 
  
 Probably not. They all look like film types to me, which means Creek has already avoided most of the mines in the capacitor field, even if they're only so-so quality.  They're still miles ahead of ceramics or electrolytics for audio signal path applications.


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## linesplice

Tangent, I think you nailed it.  Maybe they are 2200pf!
 https://s16.postimg.org/xw9twy6v9/scaled_image_1.jpg


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## tangent

Yes, that appears to be the case. So, 100× too small.


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## linesplice

Well, here is the finished product (for now).  It was an interesting experiment.  30 hours of break-in and the sound is _slightly_ better than where it started prior to replacing the capacitors, and in some cases I still have a preference for what is coming out of my computer headphone jack to the little Creek amp.  I'll have to try some more demanding headphones to see if it matters, since the AKG K712 pro's I generally gravitate to are fairly easy to drive.
  
 What else could be done to really have a chance at improving the sound?  Should I have used a larger cap on C12 (100uf 35v)?  Replace the four little clear caps (C106, etc.) with something else?  Try to go larger on the power supply cap (c11)?  Replacement of resistors?  
  
https://s10.postimg.org/605xv13yh/IMG_20161003_240052008.jpg
https://s10.postimg.org/49ri7abt5/IMG_20161010_195319031_HDR.jpg
https://s10.postimg.org/k9a5qu7ux/IMG_20161010_195339519.jpg


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## linesplice

Also, are there any suggestions on how I would increase the output power while retaining the same design?  For it's size, there are plenty of modern portable units which can push a dozen times more power in a smaller form factor.  Any thoughts?


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