"WHAMMY" Pass DIY headphone amp guide

[wayne]

Sounds like a short on the + supply line or maybe a backwards cap. Ohmmeter readings to ground on the + supply into the regulator would be useful.

 

[HRDSTL]

I have a whammy pcb coming this week, and after reading the whole thread I'm wondering what I'm going to fit it with. The following candidates are in play for the U1 position

1. OPA1612 with soic/dip adapter (7€)
2. OPA2107AP available at Digikey in dip8 (24€)
3. BURSON audio V6 Vivid, Dual - through ELTIM (80€)

But for now, I'm leaning towards choosing the BURSON audio V6 Vivid, which is the best so far. This year I would like to finish both WHAMMY and CFA preamp/Headamp GainWire MK3 and I am already looking forward to a direct comparison of these two rivals WHAMMY with Burson Vivid vs CFA GainWire MK3 (from dadod)

 

[ericoto]

Thank you Wayne for your response, caps all in correctly, I will check resistance readings when I get home tonight. Thank you again for your help.

 

[ericoto]

OK, so between ground and all 3pins on 7815 regulator resistance over limit. I think I have a ground issue, is the board to be grounded? Only ground connection is from input to ground via capacitor. I didnt see any other connections. Thanks

 

[ericoto]

here is a photo of build so far.

 

[Zen Mod]

have proper regs in proper positions?

 

[ericoto]

Yes, just confirmed regulators in correct position. What I get is it tested fine before board was stuffed. +/- 17 V

 

[Zen Mod]

parts pins cut from bottom side, not touching case ?

anyhow, check all components, both for proper placement and, if applicable, orientation

 

[HRDSTL]

R9, R13 shorted
R10, R14 missing

 

[ericoto]

Well, from the LED regulator configuration description those resistors are not used. Is that correct? Again the PSU worked fine prior to stuffing the board. Thanks

 

[Chris Jones KS]

The regulators are set to reference the LEDs, so those resistors should remain open. Looks okay. Since the voltage tested okay with only the PS components installed, I figured the problem may be downstream. Did you check Wayne’s comments?

 

[ericoto]

OK, figured it out had two of the MOSFET's reversed, corrected and working still has some hum but need to work on ground, Thanks for suggestions.

 

[mikorist]

The Burson V6 Vivid was provided unsolicited by John Garcia of Burson who wanted my to post pictures of their opamp in my builds. Both units are using Sparkos voltage regulators and one of them are using the Sparkos Pro opamp. The Burson appear to have tighter bass, but the Sparkos a more opened midrange. The Sparkos require about an hour to stabilize for DC offset adjustments. Since they are stacked, it took me a few days to get the Sparkos adjusted. The Sparkos are also sensitive to variations in ambient temps. DC offset in the Burson are not possible, but the opamp appear to be more stable in terms of DC offset.

The input capacitor 1UF_PP is not needed for OPA1612, Sparkos SS3602, Muses02 etc. because there is no DC offset at the input, or there is hardly any up to 1mV.

It won't interfere with the potentiometer. It colors the sound unnecessarily. You just need to put a jumper wire on it. Watch the video above where Wayne says it.

It's a waste of money to put Duelund there...

The two 100pF against oscillations are more important / of course nobody has them.

Has anyone read the Sparkos manual? "placing a 22pF capacitor across the feedback resistor (Rf) will cure any instability that may result. See the section called "Feedback Resistor Selection" for more info."

 

[timothyshields]

Has anyone had issues with the Schurter filtered power entry module included in the parts kit? When I tested the PSU the LEDS didn't lite. Testing AC from the module, I discovered no current. I pulled the fuse that was inserted it into a non-switched version. All was well and the PSU specs were fine.

 

[birdbox]

[Edited] I think I missunderstand your photo. Are you plugged into AC mains and using your voltmeter on VAC measure, and it shows zero VAC with a good fuse? The meter shows VDC on the screen. So something inside the entry module is broke. That's pretty crazy being those sell for 20-30 bucks each without the fuse drawer (another $5 additional fee).

 

[timothyshields]

Yes, it was plugged in, but my hand obscured the cord. Also, after some time of inactivity, the select function (allowing switching between AC and DC) on my meter switches back to the default DC (took too long to hold leads and take a picture). I used another module with the same fuse and all is well; trying to get a replacement as this module was included in the WHAMMY parts kit at the store.

 

[birdbox]

@timothyshields

The DD12.1121.111 needs two fuses (see datasheet attached). You did use two correct as it seemed like you specified singular in your post? One is needed on each hot and neutral, and you also need the associated dual fuse "drawer".

 

[timothyshields]

@birdbox you’re correct, I only used one fuse. The kit only came with one metal fuse holder, so I assumed the ‘complete kit’ was, well… complete? Thanks for the insight and posting the datasheet. Much appreciated.

 

[birdbox]

Sounds like you got a dual fuse power entry module, but only the single fuse drawer and a single slow blow fuse. I'm sure the store will make it right if that's the case. Glad you figured out the issue. Those 1amp DD12 Schurter PEM are really nice and sell for $28.50 plus shipping without the fuse drawer, which is another $5. Just a little tricky to be sure that you get the right drawer that works with the PEM. Don't ask me how I know that....errr...I may have "learned through trial and error" on that front.

Who knew there were so many options for Power Entry Modules from just a single brand. It's overwhelming to try and figure it out, so thank goodness the diyaudio store does it for ya. Occasionally they might make a mistake too, but not very often. If they do, they have always made it right in my experience.

 

[birdbox]

Well, @timothyshields isn't the only one to get a dual fuse PEM with a single fuse drawer. I just opened my kit I got last week and same issue for me.

I suspect others who have made recent purchases are going to run into the same issue.