[JBThazard]

To cut to the chase, I use the Maverick Audio Tube Magic D1 Plus Headphone Amp + DAC and just today got three of Sparkos Lab's Discrete SS3602 op-amps, but there's a problem. One of my three opamp slots is causing an issue. If I plug in one of the discrete op-amps into this slot, there is a faint static noise in the left-channel of my headphones. This noise becomes louder and more "squeakier" when adjusting the volume knob. However, for the other two op-amps slots, the discrete opamps work fine. I am currently using two of the discrete Sparkos Labs op-amps and one Burr Brown OPA267 opamp in this third slot just fine, but whenever any of the discrete op-amps goes in this third slot, I get the squeaky static noise issue. Can anyone tell me what is going on?

In case it is helpful, this issue happens with all three of my headphones: Beyerdynamic DT 1350 (80 ohms), Sennheiser HD650 (300 ohms) and Monolith M1060 (50 ohms)

 

[tomb]

For one reason or another, your Sparkos Labs opamp is oscillating in that third slot.

 

[JBThazard]

For one reason or another, your Sparkos Labs opamp is oscillating in that third slot.

Any tips on I what can do? 2 of them sounds great but I'd really like to use all 3 for maximum impact

 

[tomb]

Any tips on I what can do? 2 of them sounds great but I'd really like to use all 3 for maximum impact

Maybe … or not. Best case is that it's something in the socket, perhaps. I sort of doubt that if the static is variable with the volume. That usually implies the noise is caused by the circuit itself, not some physical factor such as pin connections, etc.

If it's worst case oscillation - it depends on the circuit, the gain involved, voltages, etc. You're probably talking about an extensive DIY effort with tons of testing - and no guaranteed resolution of the problem.

Many amps are built for opamp swapping, but that doesn't mean all opamps are compatible. The Sparkos are probably more tame than most, but that doesn't mean they're compatible in all circuits. I can't find a schematic for the TubeMagic anywhere, but things to look for are proper decoupling capacitors that could be too small, too slow, or not there at all. Other things can be the gain ratio. Most opamps are not stable in certain gain regimes. Some are extremely sensitive to low gains, others at high gains.

I built a phono stage a while back using the AD797. It was a Pete Millett design, so it's not like it was a shot-in-the-dark design. However, AD797s from the very same batch would not work in some positions, but other AD797s would. The implication was that the sensitivity of the phono preamp circuit was greater than the actual manufacturing tolerance in the AD797 chip. Other builders had the same experience and the advice was to order about twice as many opamps as you needed (the design needed 4), then keep the ones that worked.