Dahlquist DQ LP1

[soundalot]

What op amp can replace the "ancient" 4558 in the Dahlquist LP 1 crossover?

[bobrown14]

Originally Posted by soundalot

What op amp can replace the "ancient" 4558 in the Dahlquist LP 1 crossover?

Try OP2134 or TL072 or OPA2227/8 do you have a schematic you can post here? That would help to see if a more modern chip would be a good replacement. The 4558 is a pretty slow chip by modern standards. Are you using the LP-1 with DQ-10s by chance?

Cheers,
Bob

[soundalot]

I am using this crossover with Martin Logan CLS ll's to crossover to a subwoofer. Several people have recommended the OP 2106. I have the instructions but no schematic.

[bobrown14]

Originally Posted by soundalot

I am using this crossover with Martin Logan CLS ll's to crossover to a subwoofer. Several people have recommended the OP 2106. I have the instructions but no schematic.

The OP2106 is a bass expander. The 4558 is a dual opamp. They are not compatible. The 2106 that I found a datasheet for is 16 pin. The 4558 is a 8 pin chip. So as I suggested you should try the OP2134, looks like you need 5 of em. Also I'd be re-capping and replacing resistors with 1% MF and install sockets for the new OP2134 chips in case you want to experiment with other different sounding op amps. I'm not saying the 2134 sounds bad, it will be a huge improvement but there are other chips out there with a different taste in sound. With those speakers I'd be putting in the sockets and trying out some different chips to get the sound YOU like. I found a schematic but it's more like a block diagram with no parts specified. Here's a pic of a properly rebuild LP-1. If you need any help with rebuilding your LP-1, let me know. I can help you.

BTW those are some nice speakers. What amp(s) are you driving them with? Also what sub are you using?

Cheers,
Bob

[stratus46]

Originally Posted by soundalot

What op amp can replace the "ancient" 4558 in the Dahlquist LP 1 crossover?

The 4558 is a bipolar input dual 741 (essentially) and while many opamps will work, I personally would go to the venerable 5532. It's faster, a little quieter and has similar input bias currents and they're pretty easy to get. I've used lots of 5532s in the past and was never disappointed.

G²

[soundalot]

I am using a Spectral DMA 50 and DMC 10 . I would like to find another DMA 50 to run each amp in mono. I was using a Kef B139 in a vented enclosure but looking for a more modern driver to use in either a sealed or dipole configuration. As you probably know the high pass on the DQ LP1 is a 6 db passive requiring a top quality cap. I do not use for HT, just music. So ear-shattering output is not necessary.

[InfernoSTi]

You may want to contact the factory as they offer an upgrade service for the op amps.

Dahlquist Speaker Service DQ-LP1

The main page is here (look under "services" then "DQ LP1" and also under "Online Store" and "DQ LP1"):

Dahlquist Speaker Parts & Service index Page

Thanks,
John

[soundalot]

The factory upgrade kit consists of either a capacitor or resistor upgrade kit. No op amp upgrade. Judging from feedback from Benchmark's Siu the NE 5532 should do the job, remember it is used under 200hz.

[InfernoSTi]

Originally Posted by soundalot

The factory upgrade kit consists of either a capacitor or resistor upgrade kit. No op amp upgrade. Judging from feedback from Benchmark's Siu the NE 5532 should do the job, remember it is used under 200hz.

Really? That is funny. I wonder why their web site says they do opamp chips in the upgrade:

Dahlquist DQ-LP1 Upgrade Service

Dahlquist provides standard service (repair of problem) & the upgrade service for the customer willing to ship their DQ-LP1 to our facility.
This upgrade service consists of:

Full bench diagnostic test
capacitor upgrade kit
upgraded op amp chips
Push button defeat switches
Match input impedance of customers amp*

*Customer must provide the input impedance value of the amplifier, if not provided, unit will remain at factory setting.

[soundalot]

I missed clicking on DQ LP1 image. I prefer to do the upgrade myself. I do not need them to upgrade other parts e.g. loading resistors.When I purchased the DQ LP1 from Larry Smith many parts were upgraded.