Here is what I have done so far:
2 Vishay Polypropylene Film Capacitors 200volts .15uF 5%
2 Panasonic Polypropylene Film Capacitors 0.015uF 800volts 3%
2 Panasonic Polypropylene Film Capacitors 0.018uF 800volts 3%
4 Panasonic Polypropylene Film Capacitors 0.027uF 800volts 3%
2 Nichicon 220uf 100v
All matched
2 Vishay Polypropylene Film Capacitors 200volts .15uF 5%
2 Panasonic Polypropylene Film Capacitors 0.015uF 800volts 3%
2 Panasonic Polypropylene Film Capacitors 0.018uF 800volts 3%
4 Panasonic Polypropylene Film Capacitors 0.027uF 800volts 3%
2 Nichicon 220uf 100v
All matched
The cx pins are for determining the high pass (6db) right? You must know the impedence of your amp for this cap. Going from memory on this and could be wrong, but this cap should have more impact on sound than anyting you do to the bottom end (18db) although worthwhile
When you determine the value one of the best caps this side of teflon is TRT "e" red signature caps. Very transparent and not overly expensive
Regards
David
When you determine the value one of the best caps this side of teflon is TRT "e" red signature caps. Very transparent and not overly expensive
Regards
David
Absolutely David, and luckily my modded Dyna ST-70 mains amp has an input Z of 475K, so a series 0.01uF cap with a trim resistor will give me most of the crossover points I'm likely to use. I'm likely to start with a generic polystyrene film cap and experiment from there. It will be a great way to evaluate the sound of caps! I have old TRT Infinicaps in the ST-70, so I'll probably give Peter's new ones a go.
The signal path resistors are 5 % carbon films - put in some 1% metal films (preferably non magnetic leads like Dale or PRP), some soft recovery power supply diodes, replace the signal path electrolytics with same value and power supply electrolytics with larger Elna Simic II - watch the Panasonic polypropelenes as some have steel leads and some have copper leads - you want the tinned copper ones. For $50 in parts you'll have it at the point where changing op amps is more audible - also you need jfet inputs on the opamps because they are filters.
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I realize that this an old thread but I'm hoping there is still some interest out there in the LP1.
I just bought one on ebay and am trying to get the parts together to upgrade it so I can be ready when it gets here.
I've been able to glean a lot of information about the upgrade path from old posts and help from Jim and Jeffrey - thanks guys, but the question about a suitable opamp still remains. The problem seems to be the transformers output is only 35ma and most modern opamps need more than that.
One that looks like it might work is the LME49723 which is is 6.7 or 33.5ma for the five. Is this too close? The other thing is that it is rated 17v and the transformer is 15v. Again, is this too close for comfort?
Finally, at least for this post, can someone tell me the difference between the LME49723MAX/NOPB and the LME49723MA/NOPB and if one would be preferable to the other.
thanks
Bryon
I just bought one on ebay and am trying to get the parts together to upgrade it so I can be ready when it gets here.
I've been able to glean a lot of information about the upgrade path from old posts and help from Jim and Jeffrey - thanks guys, but the question about a suitable opamp still remains. The problem seems to be the transformers output is only 35ma and most modern opamps need more than that.
One that looks like it might work is the LME49723 which is is 6.7 or 33.5ma for the five. Is this too close? The other thing is that it is rated 17v and the transformer is 15v. Again, is this too close for comfort?
Finally, at least for this post, can someone tell me the difference between the LME49723MAX/NOPB and the LME49723MA/NOPB and if one would be preferable to the other.
thanks
Bryon
Whoops - looks like I forgot that the LME49723 has two channels which would make it 67mA and totally unsuitable.
Would LME49725MA at 3mA, or LM833MM at 2.5mA per channel work?
Bryon
Hoping there is still a chance I can reach someone with a few questions on the DQ LP1
I rebuilt one several years ago - with guidance from this group ( thank you) -- but my system changed and I took it out. I now want to put it back in if I can confirm it will work form me.
I have a home theatre pre-amp -- as well as a music only pre-amp (with a home theatre bypass) ----- I have a pair of subs - with two inputs each -- and I want to have one input from my home theatre preamp (xlr) -- and one input from the DQ LP1 (rca) -- before the pre-amp - yet instructions indicate it should go after. That way there is no chance that the subs will ever receive two inputs at the same time -- and the DQ LP1 is completely out of the loop when I'm using the home theatre pre-amp ( FL & FR outputs of the HT pre-amp -- go to the HT Bypass Inputs on my music pre-amp -- and flow directly through to my amps when the music pre-amp is either off - or switched to the HT bypass input -- but I always turn it off when using the HT pre-amp )
I'm looking for guidance on whether this will work or not --
Also the input impedance on my music pre-amp is 50kOhm -- and the input impedance on my amps is 25kOhm -- so would I change the Cx resistor in the unit to accommodate 50kOhm for the pre-amp -- or 75kOhm for both together ?
thanks a lot
Bart
I rebuilt one several years ago - with guidance from this group ( thank you) -- but my system changed and I took it out. I now want to put it back in if I can confirm it will work form me.
I have a home theatre pre-amp -- as well as a music only pre-amp (with a home theatre bypass) ----- I have a pair of subs - with two inputs each -- and I want to have one input from my home theatre preamp (xlr) -- and one input from the DQ LP1 (rca) -- before the pre-amp - yet instructions indicate it should go after. That way there is no chance that the subs will ever receive two inputs at the same time -- and the DQ LP1 is completely out of the loop when I'm using the home theatre pre-amp ( FL & FR outputs of the HT pre-amp -- go to the HT Bypass Inputs on my music pre-amp -- and flow directly through to my amps when the music pre-amp is either off - or switched to the HT bypass input -- but I always turn it off when using the HT pre-amp )
I'm looking for guidance on whether this will work or not --
Also the input impedance on my music pre-amp is 50kOhm -- and the input impedance on my amps is 25kOhm -- so would I change the Cx resistor in the unit to accommodate 50kOhm for the pre-amp -- or 75kOhm for both together ?
thanks a lot
Bart
You can use the DQ-LP1 with the Tympani IV or IVa, just dial in the crossover frequency and you have the 18 db/octave low pass roll-off on the basses. You will need to tailor the high pass section to suit the Tympani. I find the Dahlquist DQ-LP1 overpriced, you can build a similar crossover for a lot less.
Hey I just picked up an LP1 in great shape and being a total novice I was hoping the group could give me any " must do" vs "nice to do" upgrades on this unit and the best parts to use for maximum benefit for my system. Did any previous posters regret or try other solutions later? I really want to keep a clean signal on the HP signals to my main speakers and my SVS SB 1000 and REL Storm subs.
I will be likely keeping my cross set for less than 60Hz. I listen low level most of time and use Parasound A21 with amp input impedance of 33k oHms. My mains are high sensitivity full range Zu Omens and Tekton Lores. I even may attempt using this to biamp an old set of DQ Prelude towers which have dual binding posts on their W2 woofer basses. All input appreciated before I start! Thx
I will be likely keeping my cross set for less than 60Hz. I listen low level most of time and use Parasound A21 with amp input impedance of 33k oHms. My mains are high sensitivity full range Zu Omens and Tekton Lores. I even may attempt using this to biamp an old set of DQ Prelude towers which have dual binding posts on their W2 woofer basses. All input appreciated before I start! Thx
Gentlemen:
Being home-bound until Coronavirus passes, I have a DQ-LP1 whose left channel low-pass section is not working. I'd like to fix it.
From what I've read in this thread, the most likely culprit is the shoddy RCA-jack on the thing. I've noticed that the originals were directly soldered to the PC-board.
I'd prefer to mount some better jacks on the chassis and connect them to the board with wiring. Ideally, the jack washers would precisely fit the chassis holes so that I wouldn't have to do any modification to the chassis itself. Can you recommend any such jacks?
Should the jack turn out not to be the problem, the next most likely culprit is the IC chips. If I have to replace them, I'm seeing a LOT of different recommendations in this thread, but without any follow-up to say which worked and which didn't. Again, I'd prefer an IC that draws no more current than the originals and that I can pop in using sockets. Chips mentioned in this thread included:
OPA2107
NE5532
AD712JN
AD8066
AD8599
OP270
So which work and which don't? Enquiring minds want to know...
Finally, I read somewhere that the original passive high-pass capacitor was intended for an amplifier input impedance of 22K Ohms, and that the crossover frequency was in the 80 Hz. range. Are these claims so? I could change the passive cap if y'all think it would be an audible improvement, but I'm not eager to fix things that aren't broken.
Recommendations?
Thanks! Boomzilla (moniker not indicative of listening preferences)
Being home-bound until Coronavirus passes, I have a DQ-LP1 whose left channel low-pass section is not working. I'd like to fix it.
From what I've read in this thread, the most likely culprit is the shoddy RCA-jack on the thing. I've noticed that the originals were directly soldered to the PC-board.
I'd prefer to mount some better jacks on the chassis and connect them to the board with wiring. Ideally, the jack washers would precisely fit the chassis holes so that I wouldn't have to do any modification to the chassis itself. Can you recommend any such jacks?
Should the jack turn out not to be the problem, the next most likely culprit is the IC chips. If I have to replace them, I'm seeing a LOT of different recommendations in this thread, but without any follow-up to say which worked and which didn't. Again, I'd prefer an IC that draws no more current than the originals and that I can pop in using sockets. Chips mentioned in this thread included:
OPA2107
NE5532
AD712JN
AD8066
AD8599
OP270
So which work and which don't? Enquiring minds want to know...
Finally, I read somewhere that the original passive high-pass capacitor was intended for an amplifier input impedance of 22K Ohms, and that the crossover frequency was in the 80 Hz. range. Are these claims so? I could change the passive cap if y'all think it would be an audible improvement, but I'm not eager to fix things that aren't broken.
Recommendations?
Thanks! Boomzilla (moniker not indicative of listening preferences)
I used "Tiffany" style inside mount RCA jacks on my LP1. They fit fine. I can't remember where I picked them up, it was years ago. There is no other alternative for the IC that doesn't use more current, I stuck with the NE5532. It's in the LP section anyway, so the fact that they're not a "fast" ic is rather moot. If you change nothing else on in the unit, upgrade the high-pass filter caps. I used teflon films in mine, but I'm using an old tube amp with a high input impedance for the mid/highs, so that meant the cap value was small. I also replaced all the electrolytic caps in the unit, and used larger values on the first section. Good luck with it, it'll be worth it. Cheers Phil
I've ordered a brace of replacement NE5532 chips and sockets plus some Sprague Orange Drop replacement caps for the high pass section. Will desolder stuff tomorrow so the board will be ready for the fresh parts.
I've tried polypropylene and Teflon caps before, and have found them excessively "smooth sounding." For my tastes, the Sprague caps hit the right spot.
I've tried polypropylene and Teflon caps before, and have found them excessively "smooth sounding." For my tastes, the Sprague caps hit the right spot.
I had a similar problem with the DQ-LP1 (single bass channel out). turns out it was one of the opamps.
since they're soldered to the PCB, you'll have to trace that channel back to the suspect opamp.
I had decided at that time to re-cap, re-do the RCA back panel, and socket the opamps.
do note that the best way to re-do the RCA is to make a replacement back panel.
Replacing the jacks may cause the jacks to move around.
also, the power supply does not supply enough current to drive any other opamps
other than the original. and replacement transformers don't fit.
good luck
CaliforniaBob
since they're soldered to the PCB, you'll have to trace that channel back to the suspect opamp.
I had decided at that time to re-cap, re-do the RCA back panel, and socket the opamps.
do note that the best way to re-do the RCA is to make a replacement back panel.
Replacing the jacks may cause the jacks to move around.
also, the power supply does not supply enough current to drive any other opamps
other than the original. and replacement transformers don't fit.
good luck
CaliforniaBob
Thanks @CaliforniaBob -
Yeah - I'd already been informed of all that (but I appreciate your reminder). My game plan is to:
1. Shim the RCA jack holes with rubber grommets and use Tiffany replacements
2. Use replace ALL op-amps with sockets and NE-5532p replacement chips
3. Use an external wall-wart power supply with more wattage
4. Remove the internal transformer, diodes, and caps
5. Replace the original high-pass caps with Polyethylene film ones
Not everyone might select these options, but I think that they'll work for me.
Thank you again for the reply - I appreciate your input!
Glenn (aka Boomzilla)
Yeah - I'd already been informed of all that (but I appreciate your reminder). My game plan is to:
1. Shim the RCA jack holes with rubber grommets and use Tiffany replacements
2. Use replace ALL op-amps with sockets and NE-5532p replacement chips
3. Use an external wall-wart power supply with more wattage
4. Remove the internal transformer, diodes, and caps
5. Replace the original high-pass caps with Polyethylene film ones
Not everyone might select these options, but I think that they'll work for me.
Thank you again for the reply - I appreciate your input!
Glenn (aka Boomzilla)
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