Dead Phonoclone opamps
Richard and all Phonocloners,
First I would like to let you know that I successfully built a Phonoclone based on Richard's circuit design. I used Burr-Brown OPA27G opamps, Riken and AN Tantalum resistors, Silver Micas for the RIAA and Black Gate as C3. I used silver wire to pin-to-pin solder the The power supply is two Panasonic 12 V lead acid batteries with capacitors as Franz suggested. The sound of this phono preamp was so great that it exceedeed all my expectations. I used a Denon 103 so the values of the components were exactly those suggested by Richard.
First of all I would like to thank you, especially Richard, for your amasing efforts and invaluable help. This Phonoclone is really a great preamp.
Now, my problem is the following. Last week I took the preamp to a friend of mine to listen how it sounds in his sistem. He has a Linn Sondek with a Linn MC cartridge, the type of which I am not sure of. Anyway, we had a good listening session and the preamp sounded quite good (though not as well as in my system). I have to note that I did NOT change any resistors when I went to his place and, as I later realised, his cartride has only about 3 ohms of internal impedance vs. 40 of my Denon. So the gain of the first stage was more than 10 times more than with my cartridge. Still, the preamp worked quite well. However, when I got home I reconnected my system and there was no signal at all. It was strange. I was trying to figure out what was wrong. After a while I disconnected the phono cables and the output cables and started to measure offsets. And here comes the misterious thing. The input voltage (offset) of both channels was 0,7 volts !!!!
The output of the first stage was 1,8 volts and the output of the second stage is about 3 volts. (all DC). I tried later to disconnect the two stages and measured the offsets of the opamps and they all seem to be some volts! They all seem to be destroyed 
Now, could someone please help me in finding out what might have caused this trouble? BTW, the Denon seems also to be killed due to the 0,7 volts
I would greatly appreciate your help. Of ourse I am able to replace the ICs and I hope it will again be working nicely but it would be very good to know what caused this trouble.
Thanks in advance,
Szabolcs
Richard and all Phonocloners,
First I would like to let you know that I successfully built a Phonoclone based on Richard's circuit design. I used Burr-Brown OPA27G opamps, Riken and AN Tantalum resistors, Silver Micas for the RIAA and Black Gate as C3. I used silver wire to pin-to-pin solder the The power supply is two Panasonic 12 V lead acid batteries with capacitors as Franz suggested. The sound of this phono preamp was so great that it exceedeed all my expectations. I used a Denon 103 so the values of the components were exactly those suggested by Richard.
First of all I would like to thank you, especially Richard, for your amasing efforts and invaluable help. This Phonoclone is really a great preamp.
Now, my problem is the following. Last week I took the preamp to a friend of mine to listen how it sounds in his sistem. He has a Linn Sondek with a Linn MC cartridge, the type of which I am not sure of. Anyway, we had a good listening session and the preamp sounded quite good (though not as well as in my system). I have to note that I did NOT change any resistors when I went to his place and, as I later realised, his cartride has only about 3 ohms of internal impedance vs. 40 of my Denon. So the gain of the first stage was more than 10 times more than with my cartridge. Still, the preamp worked quite well. However, when I got home I reconnected my system and there was no signal at all. It was strange. I was trying to figure out what was wrong. After a while I disconnected the phono cables and the output cables and started to measure offsets. And here comes the misterious thing. The input voltage (offset) of both channels was 0,7 volts !!!!
The output of the first stage was 1,8 volts and the output of the second stage is about 3 volts. (all DC). I tried later to disconnect the two stages and measured the offsets of the opamps and they all seem to be some volts! They all seem to be destroyed Now, could someone please help me in finding out what might have caused this trouble? BTW, the Denon seems also to be killed due to the 0,7 volts
I would greatly appreciate your help. Of ourse I am able to replace the ICs and I hope it will again be working nicely but it would be very good to know what caused this trouble.
Thanks in advance,
Szabolcs
Uuups, a sad experience! Specially the burned DL103!
I regret very much!
Last november, I burned a DL160 with voltage at the input of a VSPS.
In my case, it was my mistake, as I connected the psu with the wrong polarization. After a short test, the chip was gone an produced DC at the input.
So, it is generally a risk of this amp, having no input cap. It is recommended, to measure the input DC before connecting a cartridge.
But in your case, in dont see any reason! The low imp and the resulting high gain of the cartridge from your friend can hardly be the reason.
BTW: the cartridge from your friend: still O.K.?
Regards
Franz
I regret very much!
Last november, I burned a DL160 with voltage at the input of a VSPS.
In my case, it was my mistake, as I connected the psu with the wrong polarization. After a short test, the chip was gone an produced DC at the input.
So, it is generally a risk of this amp, having no input cap. It is recommended, to measure the input DC before connecting a cartridge.
But in your case, in dont see any reason! The low imp and the resulting high gain of the cartridge from your friend can hardly be the reason.
BTW: the cartridge from your friend: still O.K.?
Regards
Franz
Hello Franz,
Thanks a lot for your reply. Yes, his cartridge is fine, fortunately. Actually, the phonoclone was playing properly when we listened to it, showing no sign of trouble.
Now I believe I have some problem here at home. I started to measure the DC and AC voltages between the signal and ground terminals of the phono lead cable. Strange results, sometimes even 1 V AC, but of course, now the resistance is infinity. I suspect these are due to voltages inducated in the wires by the 50 Hz field.
What I recall now is that ever since I finished building the Phonoclone I was using it so that the phono cables were plugged in and I only switched off and on the PSU. However, in this case when I got home, as I remember, I first switched on the power supply and only after that did I connect the phono RCAs. Can it cause such big trouble? I know there is huge and terrible sound if you accidentally touch the signal wire of a preamp, the earth being disconnected. Maybe. Also, my tonearm has a separate earthing wire which I connected to the grounding terminal of the Phonoclone after the phono RCAs were plugged in. The PSU of my turntable was also off, so there were different earth potentials? Should I connect the grounds of the preamp and the turntable also? I have never had any problem with noise.
Still a mistery ... Thanks a lot again for the help.
Szabolcs
Thanks a lot for your reply. Yes, his cartridge is fine, fortunately. Actually, the phonoclone was playing properly when we listened to it, showing no sign of trouble.
Now I believe I have some problem here at home. I started to measure the DC and AC voltages between the signal and ground terminals of the phono lead cable. Strange results, sometimes even 1 V AC, but of course, now the resistance is infinity. I suspect these are due to voltages inducated in the wires by the 50 Hz field.
What I recall now is that ever since I finished building the Phonoclone I was using it so that the phono cables were plugged in and I only switched off and on the PSU. However, in this case when I got home, as I remember, I first switched on the power supply and only after that did I connect the phono RCAs. Can it cause such big trouble? I know there is huge and terrible sound if you accidentally touch the signal wire of a preamp, the earth being disconnected. Maybe. Also, my tonearm has a separate earthing wire which I connected to the grounding terminal of the Phonoclone after the phono RCAs were plugged in. The PSU of my turntable was also off, so there were different earth potentials? Should I connect the grounds of the preamp and the turntable also? I have never had any problem with noise.
Still a mistery ... Thanks a lot again for the help.
Szabolcs
I have been thinking ... 
The solution must be some common cause failure since all 4 opamps are gone. Common is only the PSU and thus the ground if I am not mistaken.
Now, what did I do differently than previously? I think I know the solution. The battery PSU and the Phonoclone are connected using an XLR connector. Whenever I wanted to switch on or off the PSU, I disconnected the +12 V and -12 V from the batteries but the earth always remained in place and the XLR connected to the preamp. Now, this time, when I assembled the system, the XLR was disconnected, I first connected the ground, + and -12 V to the batteries and only AFTER THAT did I connect the XLR to the Phonoclone. I suppose that what could happen was that for a short period the preamp had +12 V and -12 V but NO GROUND. Now this is my suspition.
Can someone please tell me whether this could cause the death of all the opamps? I believe yes but am not sure. If so this can be a trick to be avoided for those who want a long life for their Phonoclone and cartridge 
Greetings,
Szabolcs
The solution must be some common cause failure since all 4 opamps are gone. Common is only the PSU and thus the ground if I am not mistaken. Now, what did I do differently than previously? I think I know the solution. The battery PSU and the Phonoclone are connected using an XLR connector. Whenever I wanted to switch on or off the PSU, I disconnected the +12 V and -12 V from the batteries but the earth always remained in place and the XLR connected to the preamp. Now, this time, when I assembled the system, the XLR was disconnected, I first connected the ground, + and -12 V to the batteries and only AFTER THAT did I connect the XLR to the Phonoclone. I suppose that what could happen was that for a short period the preamp had +12 V and -12 V but NO GROUND. Now this is my suspition.
Can someone please tell me whether this could cause the death of all the opamps? I believe yes but am not sure. If so this can be a trick to be avoided
for those who want a long life for their Phonoclone and cartridge Greetings,
Szabolcs
Very unfortunate.
Is your DL103 really gone? 0.7 V into 40 ohms is only 12 mW. I'm surprised that was enough to kill it.
Likewise, I've been trying without success to work out how floating the power supply (i.e. disconnecting its ground from the phonoclone's COM signal) could completely wipe out the four op-amps. It would scream like a banshee, yes, but I doubt it would self destruct...
I'm not about to use my own phonoclone to verify this one way or the other, however. There are limits as to how far I'm willing to go for you guys.
Are you sure you never reversed the + and - connections? Four dead op-amps and a dead cartridge would suggest that this happened at some point. Right Franz?
With voltage regulators on the board you you get an insurance policy against improper connections of the power supply, as the positive Vreg will withstand -20V or so on the input pin. When you use batteries with no voltage regulation you lose that protection, so I suggest installing diodes on the V+ and V-.
On the PCB, just solder the diode between the input and output pads where the Vreg normally goes.
-Richard
Is your DL103 really gone? 0.7 V into 40 ohms is only 12 mW. I'm surprised that was enough to kill it.
Likewise, I've been trying without success to work out how floating the power supply (i.e. disconnecting its ground from the phonoclone's COM signal) could completely wipe out the four op-amps. It would scream like a banshee, yes, but I doubt it would self destruct...
I'm not about to use my own phonoclone to verify this one way or the other, however. There are limits as to how far I'm willing to go for you guys.
Are you sure you never reversed the + and - connections? Four dead op-amps and a dead cartridge would suggest that this happened at some point. Right Franz?
With voltage regulators on the board you you get an insurance policy against improper connections of the power supply, as the positive Vreg will withstand -20V or so on the input pin. When you use batteries with no voltage regulation you lose that protection, so I suggest installing diodes on the V+ and V-.
On the PCB, just solder the diode between the input and output pads where the Vreg normally goes.
-Richard
Richard,
Thanks a lot for the suggestions. I will use diodes. I am very grateful for your help.
It is very kind of you that you started to experiment but I would in no case want anyone to try to simulate what had happened in my case . Again, I have to say that without your suggestions and lot of thinking and careful design I would not have been able to create a phono pre of such high quality. I had heard the original Phonocube and for my ears there is not much difference. The transparency, rhythm, timing, and especially musicality far far exceed those of the tubed preamps I heard and used so far.
I am still also a bit dubious about the real cause of the death of the opamps. Something drastic had to happen and it had to be common cause type failure.
Actually, I use two 1000 uF BG standard capacitors at the batteries and 22 uF BGs in the Phonoclone box so if I had reversed polarity I believe they would have exploded or at least gone wrong. On the other hand, I made the connections so that it physically be quite impossible to reverse the polarity. I know what happened to Franz so I thought about this possibility. Since nothing is impossible ... Can ax XLR connector be plugged in with reversed connections?
As for the cartridge, I measured the resistance between the hot and ground pins of both channels and they always show infinity. However, there is a resistance of about 7 ohms between the two grounds.
One more idea came to my mind. What if there is some short circuit in my turntable? I tried to measure voltages but have not found anything. Or: can some problem in the power amp - in my case a Gainclode a la Peter Daniel - cause trouble in the pre? In the Phonoclone I use 4,7 uF non polar BG caps so no DC can be coupled from the power to the pre.
I will finish replacing the opamps and have another cartridge so I will probably be able to listen to music soon. Nevertheless, I am a little afraid that such a strange phenomenon may happen again. I will be very very careful.
Thanks again very much for your help,
best regards,
Szabolcs
PS. I think that I have learnt a lot since this happened. Though I lost a cartridge, I gained a lot of knowledge. For me it is in fact like scientific investigation
Thanks a lot for the suggestions. I will use diodes. I am very grateful for your help.
It is very kind of you that you started to experiment but I would in no case want anyone to try to simulate what had happened in my case
. Again, I have to say that without your suggestions and lot of thinking and careful design I would not have been able to create a phono pre of such high quality. I had heard the original Phonocube and for my ears there is not much difference. The transparency, rhythm, timing, and especially musicality far far exceed those of the tubed preamps I heard and used so far. I am still also a bit dubious about the real cause of the death of the opamps. Something drastic had to happen and it had to be common cause type failure.
Actually, I use two 1000 uF BG standard capacitors at the batteries and 22 uF BGs in the Phonoclone box so if I had reversed polarity I believe they would have exploded or at least gone wrong. On the other hand, I made the connections so that it physically be quite impossible to reverse the polarity. I know what happened to Franz so I thought about this possibility. Since nothing is impossible ...
Can ax XLR connector be plugged in with reversed connections? As for the cartridge, I measured the resistance between the hot and ground pins of both channels and they always show infinity. However, there is a resistance of about 7 ohms between the two grounds.
One more idea came to my mind. What if there is some short circuit in my turntable? I tried to measure voltages but have not found anything. Or: can some problem in the power amp - in my case a Gainclode a la Peter Daniel - cause trouble in the pre? In the Phonoclone I use 4,7 uF non polar BG caps so no DC can be coupled from the power to the pre.
I will finish replacing the opamps and have another cartridge so I will probably be able to listen to music soon. Nevertheless, I am a little afraid that such a strange phenomenon may happen again. I will be very very careful.
Thanks again very much for your help,
best regards,
Szabolcs
PS. I think that I have learnt a lot since this happened. Though I lost a cartridge, I gained a lot of knowledge. For me it is in fact like scientific investigation
I admire your stoicism, but in my opinion you haven't learnt anything worthwhile until such time as you discover what actually happened.
To answer a little more your earlier post, plugging in the XLR to the phonoclone with the power already applied to the supply shouldnt have caused the problem. I hot swap my Gainclone and Phonoclone this way frequently, with no ill effects so far.
I dont think any subset of -12, +12 and 0 applied in any order to the correct pins would have damaged anything.
Nor is it likely that any components in the audio chain (turntable, amp etc.) were at fault.
/R
To answer a little more your earlier post, plugging in the XLR to the phonoclone with the power already applied to the supply shouldnt have caused the problem. I hot swap my Gainclone and Phonoclone this way frequently, with no ill effects so far.
I dont think any subset of -12, +12 and 0 applied in any order to the correct pins would have damaged anything.
Nor is it likely that any components in the audio chain (turntable, amp etc.) were at fault.
/R
So still a mistery ... What I meant by learning is that when this thing happened I started to read all sorts of electronics litreture concerning how opamps operate and what may damage them. I also consulted colleagues of mine who are electrical engineers and they explained quite a few interesting ideas to me.
I'll keep on investigating ... and thanks for all the help again
Szabolcs
I'll keep on investigating ... and thanks for all the help again
Szabolcs
How bad is the phonoclone using the op637? I would like to try the phonoclone but right now all I have is opa637 and 627.
I can get op27 for $1 apiece but there is a minimum of $20,so I have to plan for future projects to spend the addition $16. Right now I like the try one the opas.
Anyone try it with the NE5534?
btw the opa637 vsps sounds very nice. It makes Si Zentner's Swing Fever sound good,this is the first time I could actually sit a listen to the record.
So cheers RJM
I can get op27 for $1 apiece but there is a minimum of $20,so I have to plan for future projects to spend the addition $16. Right now I like the try one the opas.
Anyone try it with the NE5534?
btw the opa637 vsps sounds very nice. It makes Si Zentner's Swing Fever sound good,this is the first time I could actually sit a listen to the record.
So cheers RJM
Hey, the new stylus pitched today, and right now I'm listening to Hammond a gogo. Bass is just a little light, can I remove the big output cap if my amp has an imput cap of 1uf...??????
As for detail, well its the first time I heard a phonoamp that wasn't part of a cheapish integrated amp, and was a little blown by all the detail.... kinda like when someone shines a bright light at you thats just a little bright... it takes a few seconds and then you adjust.
Sounds vely nice...
As for detail, well its the first time I heard a phonoamp that wasn't part of a cheapish integrated amp, and was a little blown by all the detail.... kinda like when someone shines a bright light at you thats just a little bright... it takes a few seconds and then you adjust.
Sounds vely nice...
Hi,
build a version today of the phonoclone on veroboard (one channel so far), tested with batteries, no regs so far.
I'm pleased! Punch/freshness and energy are nearly very good, resolution ok so far.
I think, the 'current input' thingie is worth further investigations, gaining high quality from that approach should be doable.
Thanks a lot for sharing, rjm!
Rüdiger
build a version today of the phonoclone on veroboard (one channel so far), tested with batteries, no regs so far.
I'm pleased! Punch/freshness and energy are nearly very good, resolution ok so far.
I think, the 'current input' thingie is worth further investigations, gaining high quality from that approach should be doable.
Thanks a lot for sharing, rjm!
Rüdiger
