My own SSE and speakers are already packed up and going north next week, so I can't actually hear the sound on the video. There isn't enough volume on the headphones I am using to hear anything recognizable.
I have never seen an SSE oscillate, and every amp I have seen oscillate will cause some interference on a nearby TV set in the lower VHF channels or on a radio. The absence of "finger effect" also seems to rule this out.
I have seen a "frying eggs" sound caused by a bad power transformer in my own TSE, but that transformer had been very wet about a month prior to its slow death. It, and the whole amp got soaked due to a broken window during a hurricane. After drying everything out the amp played normally for about a month. Then the random static started, then the frying eggs sound, then the funny smell, then the smoke! Autopsy revealed severe rust inside the end bells and a carbon tracked burnt mark from the laminations to the primary. It was a Hammond built Allied power transformer. The Electra-Print OPT's still work fine 6 years later.
Another thing that came to mind.....Did you add any RF generating devices to the area near the SSE, the source, or the speaker wiring. A WiFi router can create random hissing, so can a 3G or 4G cell phone or other wireless device.
It is possible for a cathode cap in the output stage to cause strange sounds in the speakers. I had one start crying through the speakers right before it vented it's goo all over the board. I was tinkering with sweep tubes in my SSE and ran about 70 volts through a 50 volt cap. Removing the 12AT7 should reveal this, because the sound won't stop.
I don't think there is an issue with your chassis layout. The power transformer in the middle layout was standard issue on a lot of older amps (Dynaco, Stromberg Carlson, Scott and others) and I have build an SSE and two SPP's this way. If it doesn't hum it's OK, and it worked for several months, so the layout is good.
I have never seen an SSE oscillate, and every amp I have seen oscillate will cause some interference on a nearby TV set in the lower VHF channels or on a radio. The absence of "finger effect" also seems to rule this out.
I have seen a "frying eggs" sound caused by a bad power transformer in my own TSE, but that transformer had been very wet about a month prior to its slow death. It, and the whole amp got soaked due to a broken window during a hurricane. After drying everything out the amp played normally for about a month. Then the random static started, then the frying eggs sound, then the funny smell, then the smoke! Autopsy revealed severe rust inside the end bells and a carbon tracked burnt mark from the laminations to the primary. It was a Hammond built Allied power transformer. The Electra-Print OPT's still work fine 6 years later.
Another thing that came to mind.....Did you add any RF generating devices to the area near the SSE, the source, or the speaker wiring. A WiFi router can create random hissing, so can a 3G or 4G cell phone or other wireless device.
It is possible for a cathode cap in the output stage to cause strange sounds in the speakers. I had one start crying through the speakers right before it vented it's goo all over the board. I was tinkering with sweep tubes in my SSE and ran about 70 volts through a 50 volt cap. Removing the 12AT7 should reveal this, because the sound won't stop.
I don't think there is an issue with your chassis layout. The power transformer in the middle layout was standard issue on a lot of older amps (Dynaco, Stromberg Carlson, Scott and others) and I have build an SSE and two SPP's this way. If it doesn't hum it's OK, and it worked for several months, so the layout is good.
OK, I plugged the Sennheisers into my laptop and it's plenty loud. The slight pitched squeally sound buried in the hiss does sound like the sound I get from a 4G cell phone right next to the cheap computer speakers I had at work. A wireless router would emit the same type of signal. Remember that wood or sheetrock walls are virtually transparent to RF. What's in the next room could be suspect.
Another simple test I just thought of, measure your source's output with a DVM. Any residual DC can cause the swishing noise heard when the volume control is turned. Does the 12AT7's plate voltage change when the volume control is turned?
Another simple test I just thought of, measure your source's output with a DVM. Any residual DC can cause the swishing noise heard when the volume control is turned. Does the 12AT7's plate voltage change when the volume control is turned?
There is wifi enabled equipment near it atm but there wasn't originally when the noise started. I've also move house during this time reorientaring my equipment into different positions all of which made no difference. With all wifi stuff unplugged the noise was unchanged.
Removing the 12at7 stops the noise!
I'm using an xpwr059 pt. I've had concerns with it since day one as its a buzzer and gets jolly hot. Too much to touch bearably after an hour for more than a few seconds. I'll revisit that today.
I'll also dig out the meter and have a measure today as well.
Removing the 12at7 stops the noise!
I'm using an xpwr059 pt. I've had concerns with it since day one as its a buzzer and gets jolly hot. Too much to touch bearably after an hour for more than a few seconds. I'll revisit that today.
I'll also dig out the meter and have a measure today as well.
You could always install an X2 cap across your live and neutral at your IEC socket. I always install one on any gear I build or fix. The X2 cap is used as a mains filter and will get rid of any line noise coming into your amp there. Looks like you have plenty of internal shielding but that doesn't keep line noise out. Maybe one of your neighbors or you have computer case open or sometimes even fluorescent light ballast or dimmable lighting can introduce some noise on the line coming into your gear. Try it can't hurt and may even work... I think an
X2 cap cost .10 cents maybe.
Cheers,
Bob
X2 cap cost .10 cents maybe.
Cheers,
Bob
Good, so we have isolated it to the front end then.
Since tube rolling doesnt seem to do anything I would concentrate on the CCS and first validate values and then start playing with maybe dropping the current a little...maybe down to between 5 or 8mA and see if running cooler helps.
Also, does it make a difference between sources? As in plug an mp3 player in directly to the amp, then try whatever preamp you normally use and see if that makes a difference.
You said you had replaced every component but the coupling caps...does that include the CCS IC's? Are you using the 10M45's?
Good piece of information. Sounds like insulation breakdown within the power Transformer is causing all the Noise within your amplifier.
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Yeah it is a concern.
Just to confuse things a bit more I've been reaaly scrutinising the sound todat. There's some abnormal crackling coming through the right channel as well. I've noticed the occasional noise from that side before but the left channel and main culprit has always taken my attention more.
Just to confuse things a bit more I've been reaaly scrutinising the sound todat. There's some abnormal crackling coming through the right channel as well. I've noticed the occasional noise from that side before but the left channel and main culprit has always taken my attention more.
Transformer too hot to touch for longer than 5 secs is a problem. If it was me I'd start at the beginning and take voltage readings per the checkout procedure and see if there's something amiss. Also check ALL the wire nuts and be sure everything is tight. Why you are going thru all the wires to be sure they are tightened down properly (power off of course) check wire location against the schematic to be sure you have it right. Check the center taps and be SURE 100% they are in the proper location. Where is that extra center tap located that you're not using?
For a X2 cap across the line ~.1uF is fine they will be rated to 275v get the polypro version. That will take care of any RFI on the mains or near by your power chord in the room. I install them right across the line/neutral on the IEC - yes they are hot 100% but they will last a VERY long time and when they let go you won't even know it; well you may hear noise it was filtering out 20 years from now maybe longer.
For your problem - I think the TEMP of the PT is your clue.
You will find something probably wont want to tell us what it is... simple things are the hardest to find sometimes, don't give up, this amp sounds fantastic working properly.
Cheers,
Bob
For a X2 cap across the line ~.1uF is fine they will be rated to 275v get the polypro version. That will take care of any RFI on the mains or near by your power chord in the room. I install them right across the line/neutral on the IEC - yes they are hot 100% but they will last a VERY long time and when they let go you won't even know it; well you may hear noise it was filtering out 20 years from now maybe longer.
For your problem - I think the TEMP of the PT is your clue.
You will find something probably wont want to tell us what it is... simple things are the hardest to find sometimes, don't give up, this amp sounds fantastic working properly.
Cheers,
Bob
I've just double checked the wiring, all is well. The 375v ct goes 4th terminal up one the left in my picture which corresponds to georges wiring diagrams.
All terminals are tight (I've checked them multiple times since starting this) but the ends of the wires are soldered so contact might not be as good as possible.
I'll do a checkout in a bit.
Re sound quality, its superb just with a hissy crackly background (or sometimes foreground)
All terminals are tight (I've checked them multiple times since starting this) but the ends of the wires are soldered so contact might not be as good as possible.
I'll do a checkout in a bit.
Re sound quality, its superb just with a hissy crackly background (or sometimes foreground)
I've had another pop at a checkout.
12at7 voltage checks:
Pin 4 = 7.1v
Pin 5 = 7.1v
12at7 resistance checks:
Pin 2 = 67.3k
Pin 7 = 67.4k (both done with the volume wide open)
Pin 3 = 220ohm (this took a while to settle down)
Pin 8 = 220ohm
Viewed from the front - Left driver socket:
Pin 2 = 7.1v
Pin 5 resistance: 220k
Pin 3 - 4 resistance = 100ohm
Right driver socket -
Pin 2 = 7.1v
Pin5 resistance: 220k
Pin 3 - 4 resistance = 100ohm
Rectifier Socket:
Pin 2 = 5.96v
Pin 4 = 215v
Pin 6 = 214v
I think the B+ was due to my meter as I measured it later and got 6v...
12at7 voltage checks:
Pin 4 = 7.1v
Pin 5 = 7.1v
12at7 resistance checks:
Pin 2 = 67.3k
Pin 7 = 67.4k (both done with the volume wide open)
Pin 3 = 220ohm (this took a while to settle down)
Pin 8 = 220ohm
Viewed from the front - Left driver socket:
Pin 2 = 7.1v
Pin 5 resistance: 220k
Pin 3 - 4 resistance = 100ohm
Right driver socket -
Pin 2 = 7.1v
Pin5 resistance: 220k
Pin 3 - 4 resistance = 100ohm
Rectifier Socket:
Pin 2 = 5.96v
Pin 4 = 215v
Pin 6 = 214v
I think the B+ was due to my meter as I measured it later and got 6v...
Your heater voltages are high on the driver tube - that will cause noise. What 12AT7 are you using? Pin4 & 5 should be closer to 6.3v. The 12AT7 is being pushed pretty hard in this application, if you're using new stock 12AT7 suggest going to old stock.
Rectifier pin4 and 6 should be pint4 to ground and pin6 to ground - add together that's your raw B+ - you can measure pin to pin but depending on your meter sometimes that can blow your meter fuse.
Are you measuring with tubes in place?? If not that would be the reason for the high heater voltages. If tubes in place your supply voltage to your power transformer is too high or your PT is not hooked up properly for the mains voltage you have.
Your rectifier heater pins should be 5v there as well not almost 6v.
If mains voltage is what it should be then check to see how your power transformer is connected - be sure you're set up for the mains voltage you have there - looks like you're getting too much voltage on the heaters. Just taking cursory look and that stands out to me. Maybe George will have more comment.
Measure these with all tubes in place:
12AT7
Heaters
pin4 to gnd
pin5 to gnd
Plate voltages
pin1 to gnd
pin6 to gnd
Cathode voltages
pin3 to gnd
pin8 to gnd
output tube 6L6/KT88 whatever you are using here (tube in place)
heater pin 2 to gnd
heater pin 7 to gnd
plate - pin 3 to gnd
grid pin - 4 to gnd
cathode - pin8 to gnd
cheers,
Bob
12AT7
Heaters
pin4 to gnd
pin5 to gnd
Plate voltages
pin1 to gnd
pin6 to gnd
Cathode voltages
pin3 to gnd
pin8 to gnd
output tube 6L6/KT88 whatever you are using here (tube in place)
heater pin 2 to gnd
heater pin 7 to gnd
plate - pin 3 to gnd
grid pin - 4 to gnd
cathode - pin8 to gnd
cheers,
Bob
Sorry for the late reply, I've been working non stop lately and haven;t had a chance to do any further tests.
Another clue that may add to the problem solving. When watching films I'll have the amp, ps4 and tv on. They all run from a power strip which has some mains noise isolating features built in (no snake oil here, the tv and sound quality and improved noticably).
Once things are fully up to temp I get the occasional blip through the tv picture. The picture distorts heavily for a split second and is accompanied by a lloud pop/crack through the sound. This happened with the ps3 I used previously thus ruling that out and this doesn't happen with the amp off. Its infrequent but makes you say "whoa! wtf..." when it does.
Another clue that may add to the problem solving. When watching films I'll have the amp, ps4 and tv on. They all run from a power strip which has some mains noise isolating features built in (no snake oil here, the tv and sound quality and improved noticably).
Once things are fully up to temp I get the occasional blip through the tv picture. The picture distorts heavily for a split second and is accompanied by a lloud pop/crack through the sound. This happened with the ps3 I used previously thus ruling that out and this doesn't happen with the amp off. Its infrequent but makes you say "whoa! wtf..." when it does.
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