Hi Guys and Girls,
I recently bought this preamplifier as not working and with a little effort I had it back up and running. After putting it in rotation, I have to say I'm pretty impressed by this little preamp when I compared it with my Pass P1.7 and Decware Zen CSP. It does a whole lot right. However it does have one issue that I am hoping you could help me with. It has much more hum/noise than I would like or expect looking at the schematic. If I had very insensitive speakers I am sure this wouldn't be much of an issue, but my speakers are 98db/watt/meter and even a little noise can be very apparent.
I've attached the schematic, I don't see that this is copyrighted and considering it's no longer sold I hope it's ok to post. If not mods, please let me know and I can remove it.
Looking at this schematic can anyone tell me what might be able to be done to reduce the noise on this preamp? It looks like the first triode is setup for gain and the second as a buffer. Beyond that the powersupply looks pretty reasonable to me as a CRLC with a bypass film cap.
As an amateur, what are the thoughts on the following
1. snubbers on the rectifiers (with fast recovery I would think this isn't needed)
1b. There is a kind of digitalish noise as well as a very slight hum, could the problem be the regulator / DC filaments. The hum is louder but with my ear near the speaker I can hear the additional noise.
2. Something about the layout of the build is causing an issue
3. The upgraded caps take a up a lot of room, could they be a source of noise
4. The gain is set too high on the first triode
5. I am asking too much for a tube preamp to be dead silent. My Pass P1.7 is pretty much dead silent but that is SS.
What isn't shown on the schematic is that the rectifiers have been upgraded to fast recovery, the caps have been upgraded to hovland musicap (5uf I believe, which is higher than stock) and the original volume pot has been upgraded.
At this point I'm just looking for some directional information and possible things to try, any help would be greatly appreciated.
I recently bought this preamplifier as not working and with a little effort I had it back up and running. After putting it in rotation, I have to say I'm pretty impressed by this little preamp when I compared it with my Pass P1.7 and Decware Zen CSP. It does a whole lot right. However it does have one issue that I am hoping you could help me with. It has much more hum/noise than I would like or expect looking at the schematic. If I had very insensitive speakers I am sure this wouldn't be much of an issue, but my speakers are 98db/watt/meter and even a little noise can be very apparent.
I've attached the schematic, I don't see that this is copyrighted and considering it's no longer sold I hope it's ok to post. If not mods, please let me know and I can remove it.
Looking at this schematic can anyone tell me what might be able to be done to reduce the noise on this preamp? It looks like the first triode is setup for gain and the second as a buffer. Beyond that the powersupply looks pretty reasonable to me as a CRLC with a bypass film cap.
As an amateur, what are the thoughts on the following
1. snubbers on the rectifiers (with fast recovery I would think this isn't needed)
1b. There is a kind of digitalish noise as well as a very slight hum, could the problem be the regulator / DC filaments. The hum is louder but with my ear near the speaker I can hear the additional noise.
2. Something about the layout of the build is causing an issue
3. The upgraded caps take a up a lot of room, could they be a source of noise
4. The gain is set too high on the first triode
5. I am asking too much for a tube preamp to be dead silent. My Pass P1.7 is pretty much dead silent but that is SS.
What isn't shown on the schematic is that the rectifiers have been upgraded to fast recovery, the caps have been upgraded to hovland musicap (5uf I believe, which is higher than stock) and the original volume pot has been upgraded.
At this point I'm just looking for some directional information and possible things to try, any help would be greatly appreciated.
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These were made by Cary Audio in my town of Cary, NC. I'm good friends with a tech who worked there for many years. Another friend had AE3, got his upgraded by the other friend. I will ask him what he recommends for upgrading it.
I know the output caps are cheap, like Solen or worse, that's a very good opportunity for upgrade. Don't judge the digititis until you upgrade the signal path caps. I like Jantzen "Superior Z" caps for good sounding, good value coupling caps. The interstage coupling caps (.22uF) are also ripe for upgrade for the same reason, they are cheap and are in the signal path.
The heaters are regulated, so that should be quiet enough.
Get some decent tubes in there. If you have worn out original Sovteks then it will sound edgy and thin. New Sovtek is just OK, intended for student guitar amps. New issue TungSol 6SN7 is good. I can't see what the input/gain tube is on the schematic, but typical for Had's designs was 6922 type gain tube. New issue Gold Lion 6922 is good for that. The combination of 6922>6SN7 is an awesome tone monster.
Avoid the temptation to over improve it,
and enjoy your little jewel!
Rich
I know the output caps are cheap, like Solen or worse, that's a very good opportunity for upgrade. Don't judge the digititis until you upgrade the signal path caps. I like Jantzen "Superior Z" caps for good sounding, good value coupling caps. The interstage coupling caps (.22uF) are also ripe for upgrade for the same reason, they are cheap and are in the signal path.
The heaters are regulated, so that should be quiet enough.
Get some decent tubes in there. If you have worn out original Sovteks then it will sound edgy and thin. New Sovtek is just OK, intended for student guitar amps. New issue TungSol 6SN7 is good. I can't see what the input/gain tube is on the schematic, but typical for Had's designs was 6922 type gain tube. New issue Gold Lion 6922 is good for that. The combination of 6922>6SN7 is an awesome tone monster.
Avoid the temptation to over improve it,
and enjoy your little jewel!Rich
Upgrading the O/P coupling caps. was necessary, if the unit is to drive the 10 Kohm IHF "standard" I/P impedance.
Dried out electrolytic caps. can easily be a source of hum. Replace the cheap OEM parts with quality 105o C. rated parts made by either Panasonic or Nichicon.
That's a no NFB circuit and the gain is what it is. Approx. 10X/20 dB. seems correct. "Hair trigger" volume controls are a common issue with line stages that exhibit substantial gain. Use "cut and try" to find padding resistor values, specific to each of your sources. Insert those "padders" between the I/P jack and source selector switch. For instance, a 100 Kohm part will introduce 6 dB. of attenuation, before the pot.'s wiper "does its thing".
New Sensor's "reissue" TungSol 6SN7 is definitely the best current production variant. Purchase specimens culled for superior noise performance from a reliable tube dealer. Don't get "EBoned".
Dried out electrolytic caps. can easily be a source of hum. Replace the cheap OEM parts with quality 105o C. rated parts made by either Panasonic or Nichicon.
That's a no NFB circuit and the gain is what it is. Approx. 10X/20 dB. seems correct. "Hair trigger" volume controls are a common issue with line stages that exhibit substantial gain. Use "cut and try" to find padding resistor values, specific to each of your sources. Insert those "padders" between the I/P jack and source selector switch. For instance, a 100 Kohm part will introduce 6 dB. of attenuation, before the pot.'s wiper "does its thing".
New Sensor's "reissue" TungSol 6SN7 is definitely the best current production variant. Purchase specimens culled for superior noise performance from a reliable tube dealer. Don't get "EBoned".
If a new tube doesn't reduce the noise, try a new/better 1W metal film 47k plate resistor for the input stage.
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Jim McShane is one of the best sources for New Sensor tubes in USA. No relation, just a happy repeat customer.
I agree with Eli that the PS storage/smoothing caps are probably the cause of the hum. Electrolytic caps can deteriorate with age, and Cary used the cheapest parts with the AES line. As they lose capacity they also lose the ability to smooth out the ripple from the rectifier.
I took some time to open up the preamp again and take two more pictures. One of the things I see right off the bat is that coupling caps are 5uF, which is obviously much larger than the 1uF on the schematic. Besides a possible improvement on lowend performance, are there any downsides to having this cap in there?
I also took my fluke DMM to measure AC on the output and ended up with 1.3-1.4mV of hum. I would love to get this down to a much lower level, would .1 -.5mV. From reading the recommendations on here it sounds like I should start with replacing the power supply caps. While I am replacing them, I would think it would be worthwhile increasing their size as well, as I am using SS rectification. Are there any potential downsides to me upgrading the caps from 100uF/350V to 150uF or possible 200uF, outside of having room to fit them?
I measured about 1mV of AC on the filaments. Looking at the schematic, would it be worthwhile for me to add another RC to the filter? Would I see an improvement with another regulator in there or is that reaching a point of very diminishing returns here?
Eli, what about of instead of putting a pad on the inputs I put a pad on the output? Would that cut down the hum leaving the preamp? I have plenty of gain and love the sound of this preamp so am I wrong in thinking that that could be a possible path here?
BTW thanks for all the input guys, it's been helpful.
I also took my fluke DMM to measure AC on the output and ended up with 1.3-1.4mV of hum. I would love to get this down to a much lower level, would .1 -.5mV. From reading the recommendations on here it sounds like I should start with replacing the power supply caps. While I am replacing them, I would think it would be worthwhile increasing their size as well, as I am using SS rectification. Are there any potential downsides to me upgrading the caps from 100uF/350V to 150uF or possible 200uF, outside of having room to fit them?
I measured about 1mV of AC on the filaments. Looking at the schematic, would it be worthwhile for me to add another RC to the filter? Would I see an improvement with another regulator in there or is that reaching a point of very diminishing returns here?
Eli, what about of instead of putting a pad on the inputs I put a pad on the output? Would that cut down the hum leaving the preamp? I have plenty of gain and love the sound of this preamp so am I wrong in thinking that that could be a possible path here?
BTW thanks for all the input guys, it's been helpful.
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The power supply without the Zeners sims as 2mV-3mV ripple to the buffer stage, much less to the gain stage. If you have 1.3mV on the output, then the supply ripple must be much greater than the design implies.
I'd replace the main caps. They are maybe "only middle-aged", but some of us get wobbly about that time. The stock values should be ample; I predict the old ones give much less uFd than they did when new.
I'd replace the main caps. They are maybe "only middle-aged", but some of us get wobbly about that time. The stock values should be ample; I predict the old ones give much less uFd than they did when new.
I agree, replace the filter caps. They tend to be a weak point even in the higher priced Cary gear.
You can also make an improvement in sound quality by removing the 0.22ufd caps and the grid resistor on the cathode follower and direct couple the cathode follower to the first tube. You could also reduce some noise by moving the cathode follower's power feed to after the resistor that feeds the input tube.
One more thing, the 5ufd cap is probably too large.
You can also make an improvement in sound quality by removing the 0.22ufd caps and the grid resistor on the cathode follower and direct couple the cathode follower to the first tube. You could also reduce some noise by moving the cathode follower's power feed to after the resistor that feeds the input tube.
One more thing, the 5ufd cap is probably too large.
ok I am about to order some new caps. I didn't quite find what I wanted from Nichicon so I am going to try Jenson (I was also considering F&T). I still have to double check the dimensions but I think they should fit in the same place as the old caps.
While I am at it, is the 5uF cap really that big of an issue? Wouldn't such a large cap just lower the f3 of the response curve, or could the circuit be negatively affected in some other way? I am happy with the sound of the preamp at this point so I would really only want to change them if I had to.
While I am at it, is the 5uF cap really that big of an issue? Wouldn't such a large cap just lower the f3 of the response curve, or could the circuit be negatively affected in some other way? I am happy with the sound of the preamp at this point so I would really only want to change them if I had to.
Ok so I have replaced the filter caps and there is an improvement but I am still getting a slight hum and noise when my ear is by the speaker.
Measuring hum at the end of some RCAs initially I am getting 1.1mV for both channels, an improvement but I was hoping for something a little better.
Before I start digging into some of the suggest mods by audiopro, is there more that can be done here? Could the residual hum be at all caused by the filament PS and if so is the solution a better regulator or possibly another filter?
Measuring hum at the end of some RCAs initially I am getting 1.1mV for both channels, an improvement but I was hoping for something a little better.
Before I start digging into some of the suggest mods by audiopro, is there more that can be done here? Could the residual hum be at all caused by the filament PS and if so is the solution a better regulator or possibly another filter?
You could try increasing the filament supply caps, but it will likely be a minimal improvement.
Looking at the build layout, I'm thinking you have induced hum problems. The filter choke is right next to the input wiring, there is a signal lead from a cap right on top of the rectifiers, and that's only a quick look. Are any of the signal wires shielded?
Looking at the build layout, I'm thinking you have induced hum problems. The filter choke is right next to the input wiring, there is a signal lead from a cap right on top of the rectifiers, and that's only a quick look. Are any of the signal wires shielded?
No the cables aren't shielded and they do run close to the choke. The idea did cross my mind that replacing those wires may be of value. I guess what I am looking for is if there might be some deficiency design wise and it sounds like there isn't. Maybe everything is down to layout and the limits of what is possible here.
Would a bypass cap on the filament supply cap be of value?
Would a bypass cap on the filament supply cap be of value?
AES AE-3 hum zombie thread lives again!
I also have a AES AE-3 that has low level hum. This one is a factory built remote version with the oil cap upgrade (Audio 1 2 uf caps that are huge). Renewing this thread from 2018. I replaced all of the electrolytics with German F&T's (except 2200 / 25v used is same as original Nichicon). Some small improvement, but I also own a DJH Signature version of the AE-3 that does not have this hum in the same system. T
The hum is just noticeable on my low efficiency Thiel PCS monitors, but more noticeable on high efficiency horn speakers. Currently playing on Cary CAD50 monoblocs, but also used on my Golden Tube SE-40SE Special edition amp. One thing I noticed on the schematic is that the filament supply is not center tapped, but is regulated. I contacted Cary today and am hoping they have some input or suggestions. Will update if I hear from them.
This is frustrating since the sonics of this piece are amazing. It even has a bigger soundstage and more deep bass extension than my DJH AE-3. The DJH wins in absolute resolution.
Wondering if the OP ever solved this?
I also have a AES AE-3 that has low level hum. This one is a factory built remote version with the oil cap upgrade (Audio 1 2 uf caps that are huge). Renewing this thread from 2018. I replaced all of the electrolytics with German F&T's (except 2200 / 25v used is same as original Nichicon). Some small improvement, but I also own a DJH Signature version of the AE-3 that does not have this hum in the same system. T
The hum is just noticeable on my low efficiency Thiel PCS monitors, but more noticeable on high efficiency horn speakers. Currently playing on Cary CAD50 monoblocs, but also used on my Golden Tube SE-40SE Special edition amp. One thing I noticed on the schematic is that the filament supply is not center tapped, but is regulated. I contacted Cary today and am hoping they have some input or suggestions. Will update if I hear from them.
This is frustrating since the sonics of this piece are amazing. It even has a bigger soundstage and more deep bass extension than my DJH AE-3. The DJH wins in absolute resolution.
Wondering if the OP ever solved this?