Does anyone try this amp with output Mosfet k1058/j162?
I have some problems.
1. DC offset about +-100mV when I use Fet input opamp(opa2134, opa2604). but when i use the bipolar opamp such as 4558 or 5532, the offset goes down to +-1.5mV. Sound is great with both type of opamps
I have some problems.
1. DC offset about +-100mV when I use Fet input opamp(opa2134, opa2604). but when i use the bipolar opamp such as 4558 or 5532, the offset goes down to +-1.5mV. Sound is great with both type of opamps
Thanks for the effort, Wayne! I appreciate your putting this design out here for us.
Populated the PCB yesterday on the dining room table while my wife was preparing Christmas lunch. Tested the PSU and all seems to be fine. Now waiting for my Alps pot to come so that I can test the rest of the project.
Used Toshiba 2SJ313/2SK2013 outputs. LME49720NA as Op-Amp. Also have OPA2134PA that I can use for comparison.
😎
Used Toshiba 2SJ313/2SK2013 outputs. LME49720NA as Op-Amp. Also have OPA2134PA that I can use for comparison.
😎
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Decided not to wait for pot (Bored and not in the mood for World of Tanks today 
). I just shorted the inputs to GND at the pot pads.
Importantly, no magic smoke!
Offsets with LME49720NA: -0.8mV and 2.0mV.
Offsets with OPA2134PA: -1.2mV and -0.2mV.
Now I just wait for pot to test with actual music on inputs.
). I just shorted the inputs to GND at the pot pads.Importantly, no magic smoke!
Offsets with LME49720NA: -0.8mV and 2.0mV.
Offsets with OPA2134PA: -1.2mV and -0.2mV.
Now I just wait for pot to test with actual music on inputs.
C2 C7 were put on the PCB in case the circuit needed it due to oscillation or if there need to be some external compensation in the loop. It's easier to have them already on the PCB during the original layout. They have not yet been needed with quite a variety of opamps, leave empty.
The Alps is a darn nice pot. A good stepped attenuator might be better. I like both. there are some very good sounding ones at tubecad.com that use 2 switches in series/parallel that give a coarse/fine control, it seems weird when reading about it but in practice I rather like it. Quality is wonderful and they sound great. Also inexpensive. Win win.
The Alps is a darn nice pot. A good stepped attenuator might be better. I like both. there are some very good sounding ones at tubecad.com that use 2 switches in series/parallel that give a coarse/fine control, it seems weird when reading about it but in practice I rather like it. Quality is wonderful and they sound great. Also inexpensive. Win win.
'Just looking at the WHAMMY "PCB Details" at the DIYaudio store.
> 70oz Copper
Now that is a serious PCB! What are people using for soldering implements? 💩
> 70oz Copper
Now that is a serious PCB! What are people using for soldering implements? 💩
Hi,
The diyaudiostore page mentions that there is an enclosure being developed for this kit. Anybody knows the status on that? When can we expect it, and at what approximate cost?
The diyaudiostore page mentions that there is an enclosure being developed for this kit. Anybody knows the status on that? When can we expect it, and at what approximate cost?
One small step away from completion or so I thought. Start up with Variact set at 30V and 0.125A slo-blow fuse. Instant fuse blow.
Previous start up with temporary wiring to check power supply was successful. Wiring of input socket is correct and nothing appears to be grounded so assume fuse value is too low.
Is there a recommended minimum?
Previous start up with temporary wiring to check power supply was successful. Wiring of input socket is correct and nothing appears to be grounded so assume fuse value is too low.
Is there a recommended minimum?
The kit came with 1A slow blow fuses, and that is what worked for me. I have some 0.5A as well, but I have not yet tried them.
Still, I'd check A LOT of places with the multimeter to know that there is nothing shorting to ground or chassis, that cabling is all correct with no shorts, etc, before attempting another turning on with a higher valued fuse.
But that's just me, best regards,
Rafa.
Edit: I missed the part about 0.125... then yes, surely higher than that! Still I'd double check, but seems too small a fuse.
Still, I'd check A LOT of places with the multimeter to know that there is nothing shorting to ground or chassis, that cabling is all correct with no shorts, etc, before attempting another turning on with a higher valued fuse.
But that's just me, best regards,
Rafa.
Edit: I missed the part about 0.125... then yes, surely higher than that! Still I'd double check, but seems too small a fuse.
Thanks for input.
At this stage I have checked all the logical points including putting insulating sheet between underside of PCB and bottom of chassis. Multimeter shows no obvious path to ground. Since the only change from working condition is wiring an input socket any problem should be limited to that area.
As a next step I will get some 0.5A and 1A and hope (never a good strategy) that will solve the problem.
At this stage I have checked all the logical points including putting insulating sheet between underside of PCB and bottom of chassis. Multimeter shows no obvious path to ground. Since the only change from working condition is wiring an input socket any problem should be limited to that area.
As a next step I will get some 0.5A and 1A and hope (never a good strategy) that will solve the problem.
I finally finished my WHAMMY. Big thanks to Wayne for the wonderful
design and for supplying the PCB. Thank you Jim for the build guide.
The build is pretty standard. I'm using a 2x18VAC transformer,
100K Alps pot, Fairchild mosfets and LM4562 opamp. The passives
are mostly Panasonic and Dale. Bias is about 60mA.
I measured about 0.8mV and 3.8mV offsets on the two channels.
(I'm assuming 3.8mV isn't too high?)
I'm now using AKG K701 through the WHAMMY. So far so good.
Cheers,
Dennis
design and for supplying the PCB. Thank you Jim for the build guide.
The build is pretty standard. I'm using a 2x18VAC transformer,
100K Alps pot, Fairchild mosfets and LM4562 opamp. The passives
are mostly Panasonic and Dale. Bias is about 60mA.
I measured about 0.8mV and 3.8mV offsets on the two channels.
(I'm assuming 3.8mV isn't too high?)
I'm now using AKG K701 through the WHAMMY. So far so good.
Cheers,
Dennis
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I'm curious about the case that will be available in the future. Has there been any thought to additional optional holes for the hardware needed to run it as a preamp? 😀
I have been running my Whammy without the C1 & C5 coupling capacitors for the last six months during which its been regularly used for headphone (Sennheiser hd800) and preamp duty.
You will need to check your dc offsets are low enough. (running Burson V6 Classic opamp) and use wire jumpers in their place.
Sounds fantastic without them 🙂
The offsets of the source component?
I've always heard, the best capacitor is no capacitor!