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
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
Attachments
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
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.
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
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
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.
Doing it yourself equals twice the satisfaction. Please post your results as I am very interested. I just bought a stock DQ LQ1 last week and have been trying to figure out the upgrade path myself.
I have an acquaintance, Doak, who first told me about the unit (he uses one) and I've been looking for one for about a year. Just now found one at a good price (#754, actually). It needs some care and attention, though.
Anyway, if you have good luck with the opamps, please post!
John
P.S. I know I'm new here...I hope I add some value over time!
Beware IC replacements
I upgraded my DQ-LP1 last year, replacing the RCAs, as well as all Rs and Cs. I tried replacing the ICs with OPA2604s, but the power supply voltages dropped to approx +/-11 volts (way out of +/-15V regulation). Turns out that the OPA2604 draws 10.5mA each for a total of 52.5mA for 5 ICs, versus the stock draw of 5mA for the stock 4558 ICs, which have a total draw for all 5 ICs of only 25mA. Note that the stock transformer is only a 35mA capacity unit. The lesson: Without changes to the transformer, look for low current draw ICs as replacements. Looks like the OPA2107 might be one good choice at 4.5mA.
Mike
I upgraded my DQ-LP1 last year, replacing the RCAs, as well as all Rs and Cs. I tried replacing the ICs with OPA2604s, but the power supply voltages dropped to approx +/-11 volts (way out of +/-15V regulation). Turns out that the OPA2604 draws 10.5mA each for a total of 52.5mA for 5 ICs, versus the stock draw of 5mA for the stock 4558 ICs, which have a total draw for all 5 ICs of only 25mA. Note that the stock transformer is only a 35mA capacity unit. The lesson: Without changes to the transformer, look for low current draw ICs as replacements. Looks like the OPA2107 might be one good choice at 4.5mA.
Mike
Re: Dalquist DQ-LP1
I got one today.
No schematics.
No manual.
Can you send me anything that would help me.
I would really appreciate it.
Michael A. Marks, MD
539 Briarwood Drive
Clarksville, TN 37040
(931) 561-1668
E-Mail: MichaelAlanMarks@aol.com
Please
I got one today.
No schematics.
No manual.
Can you send me anything that would help me.
I would really appreciate it.
Michael A. Marks, MD
539 Briarwood Drive
Clarksville, TN 37040
(931) 561-1668
E-Mail: MichaelAlanMarks@aol.com
Please
There's a Dahlquist user group over at Yahoo. They've got a files section with schematic and user manual in PDF for this unit.
Cheers,
Bob
DQ-LP1 reference materials
I put together a webpage with the reference materials I have for the DQ-LP1, including schematic, instruction manual, and a couple reviews.
https://sites.google.com/site/mpbarney/home/dahlquist-dq-lp1
Mike
I put together a webpage with the reference materials I have for the DQ-LP1, including schematic, instruction manual, and a couple reviews.
https://sites.google.com/site/mpbarney/home/dahlquist-dq-lp1
Mike
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