Op Amp upgrade
The boards come with x5 OPA2134 fitted to each.
The boards require dual channel unity gain stable devices, I tried the following in all kinds of combinations (Adaptors needed for SMD and/or single channel chips).
Burson Supreme Sound V5 Discrete
I got some major improvements with *AD825 for Bass and AD8066 for Treble* (Also worked for Bass), with LME49720HA and LM4562 doing well for Mid Range Band Pass and Input Buffer. OPA1612 worked well for Mid Range, as did LT1358, which could also do well in the Bass filter.
Burson Discrete Op AmpsThe whole thing moved to a different level when I tried the new Burson SS V5 discrete modules (Launched 22 Sep 15). The more of these I fitted, the better it sounded, especially when used for the buffer and band pass filter for the Mid Range (+ op amps at *). With this arrangement it produced a Blacker background and deeper well defined Bass. I got a smooth top end and a very detailed and natural tone to voices and instruments. These new V5 modules are very compact and when soldered direct to my PCB’s, which have 6mm mounting pillars, will fit in a 1U case with a few mm’s head room. Using the Burson modules has produced a seriously good sound with this circuit, which is now considerably better than the stock passive crossover, they gave a significant improvement over the other Op Amps tried.