Replacing ne5534's with doa's

[plumsolly]

So I have an auditronics 110 console and I would like to experiment with replacing some of the ne5534's in the mic pre setion (and maybe later in the eq) with doa's. I have some daughter boards that have the 2520 footprint on them and I was planning on attaching an 8-pin ic soket to them - so bassically 8-pin ic to 2520-style opamp adaptors . I was going to buy a couple of burdij's smd2520 semi kits for starters. but I also wanted to try purple opamps, 990's, and maybe some others. what should i be thinking about in order to make this work? Here is the schematic:
http://www.mediafire.com/?6ymbzyi2txv
ic 1 is the one im talking about. any suggestions would be appreciated. Thanks, Ben

 

[clintrubber]

[quote author="plumsolly"]So I have an auditronics 110 console and I would like to experiment with replacing some of the ne5534's in the mic pre setion (and maybe later in the eq) with doa's. I have some daughter boards that have the 2520 footprint on them and I was planning on attaching an 8-pin ic soket to them - so bassically 8-pin ic to 2520-style opamp adaptors . I was going to buy a couple of burdij's smd2520 semi kits for starters. but I also wanted to try purple opamps, 990's, and maybe some others. what should i be thinking about in order to make this work? Here is the schematic:
http://www.mediafire.com/?6ymbzyi2txv
ic 1 is the one im talking about. any suggestions would be appreciated. Thanks, Ben[/quote]
Note the presence of Q1, Q2, they're in the feedback-loop of IC1 and give that IC1 a more beefy output-stage (and pull the IC into A a bit). So if you want to start spending there (990 etc) you might want to skip Q1,2.

Or looking at it from the other side, the present task for IC1 can be all kinds of things but delivering muscle isn't one of them. I don't have a clear view where the little remaining vices of the 5534 are, but you might want to take this into account.

Regards,

Peter

 

[plumsolly]

Thanks for the insight Peter. So what you are saying is that with the presence of Q1 and Q2, IC1 is doing less work(gain) and contributing less to the sound?

 

[Baltimore]

i have an auditronics 501 console, it is very similar. I replaced the 5534s in the summing/output stage with 2520s, and it sounds amazing! all i did was use little cards like you've described. i did remove the two extra output transistors on the final amp that drives the output transformer, as they weren't needed. i didn't do anything else to ensure stability or anything...it works great, is stable, and sounds incredible.

i've been wanting to do some of the mic pres and EQs as well. i might try the purple kdj3, the one without the beefy output section. then it can utilized the extra transistors on the channel cards.

if you ditched the 5534 and its output stage and stuck a 2520 in there, you'd essentially have a 312 without the output transformer. i think it will work fine.

kevin

 

[clintrubber]

[quote author="plumsolly"]Thanks for the insight Peter. So what you are saying is that with the presence of Q1 and Q2, IC1 is doing less work(gain) and contributing less to the sound?[/quote]
Q1 & Q2 are doing no voltage gain (they form an unity gain buffer), so all that kind of gain still done by the IC.

But the IC has an easier job with Q1,2 present since it doesn't need to deliver as much 'muscle' (current); that's done by these transistors.

So the same amount of gain compared with a setup without those external transistors, but less current to be delivered by the IC....
I don't know which is the main thing that can make a 5534 sound 'bad' (this is all very relative here since we know the 553X is far from being a bad IC), but the circuit you posted gives no definitive answer to which loads could show up (what's the fader impedance ?), so under not unlikely circumstances Q1,2 avoid that IC1 would other wise had come into trouble (heavy load)). Still with me ? :wink: Sorry, no time to come up with a compact answer.

 

[plumsolly]

Thanks for the encouragement Baltimore. The person i bought these daughter cards from was using them on the output amps of his 110 to replace the 5534's with doa's. I'm interested in doing that to a few of my output cards, but i was even more interested in replacing the some of the 5534's in the channel strips. I'll post my findings after I experiment some. I wanted to revamp the summing amp as well - its interesting that you just plugged in some doa's and it worked! I was thinking i would kind of have to rebuild it. That interesting also about the two different purple opamps - I had seen them on their website, but didn't really understand the intended applications. Maybe the kdj3 would be perfect for the mic pre because it has the discrete transistors in conjunction with the opamp.

Thanks again Peter

Sorry, no time to come up with a compact answer.

Not at all - any response is appreciated and yours even made sense to me sort of :grin: I'll have to post the fader impedance when i get home. It sounds like i have some experimenting to do...
-Ben

 

[peranders]

plumsolly, why don't you settle for just changing opamps? You have a couple that can compete with NE5534. AD8610 is one of my favorites. I have adapter for sale if you are interested since AD8610 only comes in SOIC08.

http://www.svalander.se/shoppen/smdadapter.htm I sell those outside Sweden (I'm the designer of all those)

 

[plumsolly]

[quote author="JohnRoberts"]there are many drop in replacements that will give superior performance to the "long in the tooth" 5534, so unless you have a desire to make things harder than they need to be, there are easier ways to make a difference.
JR[/quote]

I thought about that. Im certainly not against the idea and id welcome some ic recomendations, but when I was researching that topic before it seemed that not everyone could agree that the alternatives to the 5534 were that much better. Id like to try both doa's and different ics - see what i like and maybe have some different flavors in different channels.

Peter: the faders are 5k..

Ben

 

[nielsk]

Just re polarize the generator, reverse the leads on the coil and battery, and make it be negative ground, we do it all the time to old Jags....
ANYWAY, more on point, I am modding a 501 right now, and one thing you may want to try is to move the feedback point from the junction of the transistors back to where it belongs at the output point on the op amp. This means do it to ALL of the output drivers.
Changing the mic pre to a "312" is a great idea, and will sound way better than the current circuit. Don't listen to the nay sayers, go for it

I am curious about the experience of changing out the mix amps, this is a part that I am working on. Did you change out all 24 op amps in the QSM?

 

[plumsolly]

I ordered my 2520s from burdij! Are the power connections ok to be left the same for the 2520 as they were for the 5534? meaning can the value of the caps between the power rails and ps common can stay the same?
Thanks, Ben

 

[keefaz]

Tell us what the caps values are...
I used with success 220uF with 100nf in parallel as psu filter caps with JE990 doa
(the 100nf being very close to the IC power pins)

 

[plumsolly]

Hey Keefaz, thanks for the reply. I posted a link to a schematic on page one that shows the values and location of the caps better than i could explain it. ps: I forgot to mention that on the 2520 daughter boards I have there are places for diodes coming off the power pins. I figued these would be 1N4007 as those are the ones listed on the diy312 bom.
Thanks, Ben

 

[keefaz]

Ok, I was able to read the schematic after a little battle :wink:
Try http://www.twin-x.com for hosting schematic next time :thumb:

So you want to replace IC1 or IC3 ?
In both case, the caps values seem ok to me
C6 & C7 = 100nF for IC1
C12 & C13 = 100nF for IC3
Try to put them very close to the power pins

 

[plumsolly]

Thanks Keefaz- I'll use http://www.twin-x.com next time. I was thinking of replacing both ic1 and ic3 eventually, but Im focusing on ic1 for now. ic2 is just of buffer for the fader right? - it shouldn't contribute a lot to the sound?

 

[keefaz]

Looking at the schematic, I would not know how to start
(if I was considering like you, to replace the 5534s)
Frankly it seems like there will be big mooves in the circuit, lot of parts removing (transistors, diodes, resistors)
Why not just change the mixer summing stage as suggested by Baltimore in a first step ? It is surelly worth it imo, there will be a big change in sound
[edit]
I wanted to add, do not consider doa as simple opamps, they are complete preamps or maybe amps

 

[plumsolly]

Im planning on replacing the summing amps as well :green: I have not really put much though into (or started asking questions about) replacing ic3. It seems like changing ic1 shouldn't involve too much more than removing the ic and the transistor follower section, after that it should look a lot like a 312 sans output transformer. Im looking forward to learning from trying to make it work and eventually enjoying the (hopefully improved) sound.
-Ben

 

[Baltimore]

[quote author="nielsk"]Just re polarize the generator, reverse the leads on the coil and battery, and make it be negative ground, we do it all the time to old Jags....
ANYWAY, more on point, I am modding a 501 right now, and one thing you may want to try is to move the feedback point from the junction of the transistors back to where it belongs at the output point on the op amp. This means do it to ALL of the output drivers.
Changing the mic pre to a "312" is a great idea, and will sound way better than the current circuit. Don't listen to the nay sayers, go for it

I am curious about the experience of changing out the mix amps, this is a part that I am working on. Did you change out all 24 op amps in the QSM?[/quote]

my board has a QMM, no QSM. it WAS a big nasty VCA based job, with a single fader to control the quad bus outputs via the VCAs. i ripped all that crap out and reworked it a bit. now i have stereo summing and a nice P&G stereo fader. from summing to output transformers there are 8 2520s in total, 4 of fabios and 4 vintage ones. sounds sweet.

what affect did moving the feedback resistor to exclude the output drivers have on the sound? i'm interested in trying this.

kevin

 

[PRR]

Most car-talk moved to CD player in my old Studebaker.

 

[plumsolly]

I've been looking over the auditronics 110 circuit and the 312 circuit in anticipation of receiving my 2520's. One difference(among many) that I noticed is the presence of C4, a 470 microfarad electrolytic cap in the signal path coming out of the junction of the transisitor pair that follows the 5534, right before the fader. I was hoping to find out what the purpose of this cap is and if it is still neccessary after I remove the transistor pair and install the 2520. I didn't see a similar cap in the 312 circuit, but obviously it has an output trasformer and the output of my 2520 will go right to a fader.
As always, any insight is appreciated.

I am modding a 501 right now, and one thing you may want to try is to move the feedback point from the junction of the transistors back to where it belongs at the output point on the op amp. This means do it to ALL of the output drivers.

When you say output drivers, you are talking about all of the transistor pairs that follow 5534's?

what affect did moving the feedback resistor to exclude the output drivers have on the sound? i'm interested in trying this.

Me too! How did it sound Niels?

Thanks, Ben

 

[axisdreamer]

Hey Ben!

Stace here, I just did more of my output cards the other day with the same 2520 daughter cards that I sold you. I took off the two transistors and 6 resistors and the ic socket.I just solder long legs from the daughter card to some of the socket holes and use the same two diod's that are already on your output card and mount them on the daughter board and add legs to the diod's long enough to reach the output card. I'll try to do one of my smaller output cards like yours and see how it turns out and send you a picture if you want to see the mod.I've only modded the long cards so far!

Did you try doing any of yours yet?

Stace