I have been completely rebuilding a pair of dbx 234XL analog crossovers.
I swapped all the TL074 types for OPA1644, & LM353 for OPA1642 dual - all worked very well in that position.
The output opamp drivers were more hassle - replacing NE5532 using a mix of OPA828 for the high end/ upper mid, OPA627 for the bass and Burson v7 Vivid discrete for the sub - all these opamps are working at their peak in these frequency ranges.
I had to make up some custom boards (white/ gold) for the OPA828's with the heat transfer pads, and a transfer plate for the 1644 SMD taking it back down to fit the 14 pin DIL sockets.
Caps were changed to WIMA FKP, and the decouple caps to Nichicon UKZ. Bridging/ bypassing the UKZ decoupling caps are Mundorf EVO Silver/ Gold caps 0.47uF for the high frequency channel.
External dual R-core PSU replaces the standard onboard transformer - the R-core has 14,000uF capacitance per +15/-15v side and is dead silent.
The speed and pin sharp detail and clarity of the OPA 2828 's is on a completely different level from other opamps/ discretes.
Possibly because of its ultra-fast slew rate of 150v/uS & 45Mhz bandwidth gain, but its bass is almost non-existent, so can't be used full bandwidth.
Quite a story all told, but sounds a real WoW - at the end you couldn't believe its the same circuit.
The crossover drives 16Kw of Alcons amps and the speakers are a modified Alcons Pro-ribbons.
* if anyone wants to buy either of the 2 PCB types or mounted OPA2828 you can message me.
I swapped all the TL074 types for OPA1644, & LM353 for OPA1642 dual - all worked very well in that position.
The output opamp drivers were more hassle - replacing NE5532 using a mix of OPA828 for the high end/ upper mid, OPA627 for the bass and Burson v7 Vivid discrete for the sub - all these opamps are working at their peak in these frequency ranges.
I had to make up some custom boards (white/ gold) for the OPA828's with the heat transfer pads, and a transfer plate for the 1644 SMD taking it back down to fit the 14 pin DIL sockets.
Caps were changed to WIMA FKP, and the decouple caps to Nichicon UKZ. Bridging/ bypassing the UKZ decoupling caps are Mundorf EVO Silver/ Gold caps 0.47uF for the high frequency channel.
External dual R-core PSU replaces the standard onboard transformer - the R-core has 14,000uF capacitance per +15/-15v side and is dead silent.
The speed and pin sharp detail and clarity of the OPA 2828 's is on a completely different level from other opamps/ discretes.
Possibly because of its ultra-fast slew rate of 150v/uS & 45Mhz bandwidth gain, but its bass is almost non-existent, so can't be used full bandwidth.
Quite a story all told, but sounds a real WoW - at the end you couldn't believe its the same circuit.
The crossover drives 16Kw of Alcons amps and the speakers are a modified Alcons Pro-ribbons.
* if anyone wants to buy either of the 2 PCB types or mounted OPA2828 you can message me.
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Great question, YES is the answer - that's next on the list - any suggestions as to the best Pots to use here?
And one issue with the XL234 is that some pot pins are only connected to the top layer through the Via connection, and they can get cracked or dry jointed. So its always worth desoldering and resoldering them by hand anyway just in case.
And one issue with the XL234 is that some pot pins are only connected to the top layer through the Via connection, and they can get cracked or dry jointed. So its always worth desoldering and resoldering them by hand anyway just in case.