I just did this upgrade on a v.1 unit I picked up a while ago, and it sounds WAY better than I expected. It tightened up the sound and added considerable clarity in the high mids and treble, as well as better instrument separation and greater sense of space in the music. It is still a quite laid back amp with a warm, muscular sound. I'm very, very pleased. I went with slightly different caps because of availability and personal taste (KZ over ES) and the OPA2134 since the OPA2604 is obsolete. I might try it with a mascot 24v smps I have. The one that comes with the unit is pretty flimsy.
Highly recommended if you have one of these kicking around!
Thanks Bigsky!
Highly recommended if you have one of these kicking around!
Thanks Bigsky!
Nichicon KZ are fine except use the Nichicon ES BP (non-polar) for C4, C104. The np electrolytic will sound a little better than a polarized one. Make sure to use Holco (old UK made) for R6/R106. The OPA2604 is worth finding as it will beat the OPA2134 in sound quality. Laid back is a characteristic of the 2134. Michael Percy Audio sells the OPA2604 but I do not know what the minimum dollar amount is for an order. If you can't find the Holco resistors, I probably have some left but I'm still unpacking from my out of state move 8 months ago!
Hi Bigskyaudio!
Missed your answer here, somehow... I changed the opamp to a OPA1656 and it really transformed the amp. I might try to score the Holco's and might change the KZ's to ES if they ever get restocked again. But I'm very happy with the sound now and it competes with my Burson Soloist mkII in imaging and tone. The Soloist is definitely more detailed and has snappier transient response and instrument separation, but an impressive transformation of the little creek, none the less. Hope you're starting to settle in from the move!
Missed your answer here, somehow... I changed the opamp to a OPA1656 and it really transformed the amp. I might try to score the Holco's and might change the KZ's to ES if they ever get restocked again. But I'm very happy with the sound now and it competes with my Burson Soloist mkII in imaging and tone. The Soloist is definitely more detailed and has snappier transient response and instrument separation, but an impressive transformation of the little creek, none the less. Hope you're starting to settle in from the move!
Hi, can you share more details about it, then will be able to share my views on it. Sometime it face some error but these are fixable things.
I'm not sure what you mean? The details of the mod is attached in the first post. I used opa1656, somewhat equivalent resistors and all Nichicon KZ-caps, but I'm considering changing them per the recommendations of the op and originator of the mod, Bigskyaudio. Or is it more of a review you want? /Vilding
All three of Muzammal45's posts are mystifyingly un-specific. Wait and see if he/she makes more sense with more posts.
Hi all and a big thanks to Bigskyaudio for sharing the mods list.
I'm newbie to mods and need some help here. I've managed to change out most of the components except the 1.0uf/63V Evox Rifa MMK5, I've replaced C11 with the 2200uf Panasonic FC, could anyone be kind to elaborate how to install the MMK5 "across" C11? Many thanks
I'm newbie to mods and need some help here. I've managed to change out most of the components except the 1.0uf/63V Evox Rifa MMK5, I've replaced C11 with the 2200uf Panasonic FC, could anyone be kind to elaborate how to install the MMK5 "across" C11? Many thanks
Greetings to you. A friend was moving, packing up, and unexpectedly gave me a Creek Audio OBH-11 SE with a big transformer power supply. Not sure what the differences are between the regular and SE versions, but wondering if I should try the mods here on the SE version? I listened with a good source using both AKG 701 (around 65 ohms) and HD 650 (around 300 ohms). In both cases, I had to turn the volume knob to 12 or 1 o'clock to get to a reasonable volume listening level. Is that normal and would the mods here improve that? Otherwise, I found the amp to be surprisingly good as is for a small little amp. Thank you.
I can add that both "SE" versions were Class A, the earlier one was MOSFET + BJT based, "zero feedback", the later version was JFET + BJT with a negative feedback, with the constant current supply arrangement. I still use the second version OBH-11SE here when I need a headphone amp.
Cheers
Alex
Cheers
Alex
Hi Alex,
Thanks for posting your design - it looks great to me. I have played with in the LTSpice and it has a beautiful-looking 2nd harmonic dominant profile. Would it be okay if I post my spice file, and build one for personal use?
jason
I have no objections, however today I would replace the output devices with a modern option (for example MJE253G) as currently made BD140s are quite horrible and have nothing in common with the original Philips devices used in OBH-11SE . Also don't forget to put output devices on a heatsink.
Cheers
Alex
Cheers
Alex
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Attached is my .asc file, where I just used generic devices and a 4.5V zener since my LTSpice library doesn't have a 3.9V. I will at least breadboard a version with lower gain (R2=100k or maybe even 68k) since I use low impedance phones and listen at low volumes. Time to add some jfets, zeners, and other stuff to my next order.
Thanks Alex!
jason
Thanks Alex!
jason
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