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5th Calgary meeting: January 2012 - Page 5

post #61 of 67
Thread Starter 

Nice work 2000impreza! I have a similar cmoy amp and have tried it with my LCD-2's.  It actually runs them pretty well.  You are not going to get the best clarity or definition but it definitely is still musical.  Bring it to the next meet and you can try them out on my pair.

 

Cheers.

post #62 of 67
Quote:
Originally Posted by 2000impreza View Post

Here is one of my recent projects since the meet. This amp really is nothing special. Just a DIY 18v Cmoy amp built using JDS labs PCB with a few component spec changes I made.

 


The 'component spec changes' you mentioned - were they just in the op-amps used? If so, would you mind telling us what you used and why? While I'm still reluctant to make any changes to my new E9 right now, I'm definitely curious as to what you chose and why.

 

PS: the build looks great!


Edited by AgentXXL - 2/4/12 at 3:05pm
post #63 of 67


 

Quote:
Originally Posted by AgentXXL View Post


The 'component spec changes' you mentioned - were they just in the op-amps used? If so, would you mind telling us what you used and why? While I'm still reluctant to make any changes to my new E9 right now, I'm definitely curious as to what you chose and why.

 

PS: the build looks great!

 

For op-amp choices, I would suggest looking at some of the op-amp rolling guides on head-fi and diyaudio. You won't be short of choices depending on the sound signature you are looking for. Also keep in mind op-amp sound signature may differ between amps as well.

 

For my build, I stuck with the JDS labs recommended op-amp (TI OPA2227) at the time of the build. Planning to roll the op-amp in the near future.

 

Just going based on memory, I made the following changes.

1. R3 resistor: 1.65k ohm 1/8w

2. R4 resistor: 11k ohm 1/8w

Combination of R3 and R4 resistor would get 7.67 gain. I wanted a gain between 7 and 8.5 and decided to settle in between. This is enough to keep most op-amps stable and drive my beyerdynamic DT770-250.

3. RB-L/RB-R: 20k ohm 1/8w

RB resister value is lower to reduce the bass boost effect when the bass boost switch is activated.

4. Ceramic capacitors : Switched a few of the capacitors to ceramic in attempt to lower noise. Can't remember which ones I switched.

 

Future plans

1. NJM 4556 Op-amp - Higher current op-amp

2. Add second TLE2426 splitter with 0.1uf capacitor

3. AC/DC adaptor 18v to 24v, 500 to 750ma

Hoping the above changes will increase current enough to drive low sensitivity headphones.

 

The Cmoy in the current state definitely sounds better in comparision to the Fiio E11. Compared to the JDS labs pre production C421 amp (AD8620 op-amp), the Cmoy falls behind in reproduction of details and not as smooth through the entire frequency range. I am still very impressed with the Cmoy based on value. lol.  

 


Edited by 2000impreza - 2/5/12 at 4:25pm
post #64 of 67

Awesome! Thanks for the reply.

 

I'm assuming that you and/or others have done some reverse-engineering of the PCB since JDS Labs hasn't published the schematics for the BB? Of course it's not too difficult to figure out which resistors are used for gain with a given op amp configuration, but I still applaud you for taking the time to give it a try and hopefully make the BB match your DT770/250s even better!

 

I have been doing some reading on both head-fi and diyaudio re: op amp rolling. Heck, I even read a few articles about the current state (no pun intended) of tube rolling, even though it's unlikely I'll get myself a tube amp any time soon. 

 

As mentioned earlier, the only place I'm finding my E17 + E9 combo lacking is with the mid range when using the E17 as a DAC, docked to the E9. Using the E17 built-in bass/treble controls, I've been able to reproduce a pleasing signature, but I think I'm like most - I would prefer being able to run flat eq in the long run. Definitely more to read and eventually put to use!

 

Thanks again!

post #65 of 67

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Edited by SixthFall - 3/2/12 at 6:11pm
post #66 of 67
Thread Starter 

Hey everyone,

 

new meet in the works.  We're thinking the third week in April.  We will keep you posted so stay tuned.

 

Cheers,

Alphones

post #67 of 67

22nd april  sunday is the next meet>>

 

come join us if you can.

 

http://www.head-fi.org/t/599774/6th-calgary-meeting-april-2012

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