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need suggestion in upgrade of a Creek OBH-11

post #1 of 63
Thread Starter 
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?

post #2 of 63
Quote:
Originally Posted by yzriver View Post
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.
post #3 of 63
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.
post #4 of 63
Thread Starter 
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.
post #5 of 63
Quote:
Originally Posted by yzriver View Post
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’s Parts Shop

Lots of goodies here, so poke around.
post #6 of 63
Thread Starter 
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?
post #7 of 63
Quote:
Originally Posted by yzriver View Post
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.
post #8 of 63
Thread Starter 
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?
post #9 of 63
Thread Starter 
As the circuit in pic, does it work?
LL
post #10 of 63
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.
post #11 of 63
Thread Starter 
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.

post #12 of 63
Very nice!
post #13 of 63
Making me have good old day syndrome for my OBH-11 / OBH-2 - the gateway amp for the sickest among us.
post #14 of 63
Thread Starter 
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.
post #15 of 63
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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