I have a pair of original 8417 Quicksilvers (1985) and am going to upgrade the caps and resisters and apply some of Ned Carlson's mods.
http://www.triodeel.com/8417.htm
I noticed that his last mod is to put a 5watt 80v zener diode into the 2nd screen line from the output transformer to reduce IM distortion. Has anyone tried this? Any theories or ideas on this mod?
http://www.triodeel.com/8417.htm
I noticed that his last mod is to put a 5watt 80v zener diode into the 2nd screen line from the output transformer to reduce IM distortion. Has anyone tried this? Any theories or ideas on this mod?
Feedback circuit mods
That reminds me of another question. I noticed that the feedback circuit in the original 8417 Quicksilver schematic has a 562 ohm resister from the 8 ohm output connecting back to the cathode of the 12AX7 through an 820 ohm resister and with a 120 pf capacitor to the plate of one of the 8417s. In other circuits posted here this has been changed to a 5K resister connected to the 16 ohm output and a 100pf capacitor to the 8417 plate. Is this a change that should be made? What is the effect of leaving this like the original?
That reminds me of another question. I noticed that the feedback circuit in the original 8417 Quicksilver schematic has a 562 ohm resister from the 8 ohm output connecting back to the cathode of the 12AX7 through an 820 ohm resister and with a 120 pf capacitor to the plate of one of the 8417s. In other circuits posted here this has been changed to a 5K resister connected to the 16 ohm output and a 100pf capacitor to the 8417 plate. Is this a change that should be made? What is the effect of leaving this like the original?
There are two different versions of the 8417 amp depending on the year made.
My suggestion is to leave as is. Your amps don't have 16 ohm out would be my guess. A quick check of the terminal strip will answer the question. Your feedback is taken off the 8 ohm leg and this is the reason for the different values from what is in the schematic.
The 8 ohm leg has the 562 ohm resistor and different values on the 12AX7.
If you wanted to try something you could purchase 2) caddock resistors of say 300 ohms and replace the 562 ohm with these. One for each mono block amp. In addition, place a 500 ohm pot in series to allow the adjustment range from 300 ohms to 800 ohms.
Personally, the only modification I like and have kept is the bias mod to allow the usage of either 6550's or KT88's.
My suggestion is to leave as is. Your amps don't have 16 ohm out would be my guess. A quick check of the terminal strip will answer the question. Your feedback is taken off the 8 ohm leg and this is the reason for the different values from what is in the schematic.
The 8 ohm leg has the 562 ohm resistor and different values on the 12AX7.
If you wanted to try something you could purchase 2) caddock resistors of say 300 ohms and replace the 562 ohm with these. One for each mono block amp. In addition, place a 500 ohm pot in series to allow the adjustment range from 300 ohms to 800 ohms.
Personally, the only modification I like and have kept is the bias mod to allow the usage of either 6550's or KT88's.
Feedback loop
Ahhh.. thanks for the explanation. You are right, my amp does not have a 16 ohm output. I think I will stick to just the bias changes. I am however, planning on changing the power supply by doing the following:
1. Remove the 2 Mallory 320uF cans (mine are bulging at the seams anyway). Add a ASC 50uF 600v PIO cap as the first cap in the CLC network. Add a Unlytic 650uF 500v cap as the last cap in the CLC network. Bypass the caps with Film and Foil .22uF Rel Caps. Frank indicated using .1 uF ... not sure which I should use since .22uF is in the schematic.
2. Add the 8 1N4007 diodes rectifier in front of the 5AR4s per your Quicksilver mod and schematic on this forum some time back.
While I am making the bias mods, I am planning on using Auricaps for the coupling caps and Multicap polypropylene film and foil RelCaps for the other caps.
Do you think upgrading resisters is worthwhile too?
Ahhh.. thanks for the explanation. You are right, my amp does not have a 16 ohm output. I think I will stick to just the bias changes. I am however, planning on changing the power supply by doing the following:
1. Remove the 2 Mallory 320uF cans (mine are bulging at the seams anyway). Add a ASC 50uF 600v PIO cap as the first cap in the CLC network. Add a Unlytic 650uF 500v cap as the last cap in the CLC network. Bypass the caps with Film and Foil .22uF Rel Caps. Frank indicated using .1 uF ... not sure which I should use since .22uF is in the schematic.
2. Add the 8 1N4007 diodes rectifier in front of the 5AR4s per your Quicksilver mod and schematic on this forum some time back.
While I am making the bias mods, I am planning on using Auricaps for the coupling caps and Multicap polypropylene film and foil RelCaps for the other caps.
Do you think upgrading resisters is worthwhile too?
Hi,
If you replace the electrolytics with ASC (polypropylene in oil) and Unlytic (polypropylene?), bypassing with filmcaps isn't really necessary.
In fact I doubt it would bring any advantage at all.
Can't quite remember what's in there as standard but the Caddocks and Vishays are both fine sounding resistors.
Start with the gridstoppers first if you like, later you can tackle the plate and cathode Rs.
Personally, I'd rather spash out on solid core high purity (4N+) silver wire to redo the P2P internal wiring rather than spending dollars on the resistor upgrade but YMMV.
Joe,
Thanks for the thumbs up. Glad to see you like the QSs as much as I do.
Cheers,
If you replace the electrolytics with ASC (polypropylene in oil) and Unlytic (polypropylene?), bypassing with filmcaps isn't really necessary.
In fact I doubt it would bring any advantage at all.
Can't quite remember what's in there as standard but the Caddocks and Vishays are both fine sounding resistors.
Start with the gridstoppers first if you like, later you can tackle the plate and cathode Rs.
Personally, I'd rather spash out on solid core high purity (4N+) silver wire to redo the P2P internal wiring rather than spending dollars on the resistor upgrade but YMMV.
Joe,
Thanks for the thumbs up. Glad to see you like the QSs as much as I do.
Cheers,
Quicksilver mods
Frank,
The previous post was prior to my seeing your reply. Thanks that is exactly what I was getting at. With a somewhat limited budget I think I agree that rewiring the signal path with silver core wire and replacing the connectors (speaker terminal strip and RCA inputs will have more impact than the resistor upgrades.
Joe,
Thanks for all the help too.
Cheers,
Doug
Frank,
The previous post was prior to my seeing your reply. Thanks that is exactly what I was getting at. With a somewhat limited budget I think I agree that rewiring the signal path with silver core wire and replacing the connectors (speaker terminal strip and RCA inputs will have more impact than the resistor upgrades.
Joe,
Thanks for all the help too.
Cheers,
Doug
Quicksilver mods
Joe,
Great. This is my Christmas present, and I plan to do the work over my Christmas holiday. I will let you know how it sounds when it's done. The Quicksilvers are great, and I am amazed that they sound as good as they do after so many years without having done any upgrades... I think it is due to the fact they were in storage for about 10 years and that I religiously turn them on softly with a variac and never a sudden surge of voltage.
Merry Christmas
Doug
Joe,
Great. This is my Christmas present, and I plan to do the work over my Christmas holiday. I will let you know how it sounds when it's done. The Quicksilvers are great, and I am amazed that they sound as good as they do after so many years without having done any upgrades... I think it is due to the fact they were in storage for about 10 years and that I religiously turn them on softly with a variac and never a sudden surge of voltage.
Merry Christmas
Doug
Quicksilver grounding
I am beginning work on the upgrade, and I notice that the Quicksilvers are wired without using the chassis as ground. I was thinking of upgrading the power cord to a shielded cord, and grounding the shield to the chassis, but this careful isolation of the chassis has me concerned. What is the recommendation for grounding power cords in this case?
In the cap replacement and other upgrades, I am going to be careful to continue this philosophy of physically wiring the ground side of the circuit and isolating it from the chassis, but I am curious about it. What are the advantages of this?
I am beginning work on the upgrade, and I notice that the Quicksilvers are wired without using the chassis as ground. I was thinking of upgrading the power cord to a shielded cord, and grounding the shield to the chassis, but this careful isolation of the chassis has me concerned. What is the recommendation for grounding power cords in this case?
In the cap replacement and other upgrades, I am going to be careful to continue this philosophy of physically wiring the ground side of the circuit and isolating it from the chassis, but I am curious about it. What are the advantages of this?
I would be a bad one to ask about grounding the chassis of an amp. In my opinion I do not like the grounded equipment because I can/usually does contribute to unwanted noise in a system. This is especially true of very large commercial systems. Ever wonder why there is a switch on the back of most good commercial pieces to use the ground or float it? I do however use a grounded cord on one set of my "Quicksilver" amplifiers and I do this for proper polarity and I also use a cheater plug also.
It is IMPERATIVE that the chassis be firmly connected to earth ground for safety reasons! Your soundstage and signal-to-noise will not be improved when you're laying in the morgue- or, worse yet, identifying one of your family members. Cheater plugs are used to make firm ground connections in two pin sockets, NOT for floating three-pin power cords!
If you run into a hum problem, it is OK to float the signal grounds above the chassis. See, for example, Morgan Jones's "Building Valve Amplifiers" for details on this.
Geeezz. Take it easy Sy!
I didn't tell him not to put a three prong on it. I said I don't like grounded cords. My personal opinion because I don't like ground loops. That is what you have when you use a 3 prong plug because the neutral and ground are at the same point in the fuse panel.
Yes, I understand that Morgan Jones Valve Amplifier Book states the need for proper earthing. Maybe it should have stated that people should not touch amplifiers while standing in a pool of water. In other words use common sense.
In large industrial or commercial systems there is an audio ground that goes to earth that is NOT shared with other circuits. Audio equipment racks are insulated above the floor on non conductive material and the electrical conduit carrying the electric wires to power the circuits is insulated from the rack by means of a nonconductive element AKA plastic pvc pipe in the last few inches going to the rack. This is a true ground situation that does not lead to problems in most cases.
newears
Do not forget to ground the darn amp! I will use mine with my cheater plug.
I didn't tell him not to put a three prong on it. I said I don't like grounded cords. My personal opinion because I don't like ground loops. That is what you have when you use a 3 prong plug because the neutral and ground are at the same point in the fuse panel.
Yes, I understand that Morgan Jones Valve Amplifier Book states the need for proper earthing. Maybe it should have stated that people should not touch amplifiers while standing in a pool of water. In other words use common sense.
In large industrial or commercial systems there is an audio ground that goes to earth that is NOT shared with other circuits. Audio equipment racks are insulated above the floor on non conductive material and the electrical conduit carrying the electric wires to power the circuits is insulated from the rack by means of a nonconductive element AKA plastic pvc pipe in the last few inches going to the rack. This is a true ground situation that does not lead to problems in most cases.
newears
Do not forget to ground the darn amp! I will use mine with my cheater plug.
This goes well beyond things like standing in a puddle of water. Doing something simple like plugging in a cable from another piece of equipment could be deadly. DO NOT post recommendations for highly unsafe practices. It's not just the stuff that you don't know that can hurt people, it's the stuff you don't know that you don't know. Ground loops are easily taken care of by lifting signal grounds from chassis grounds.SY/ got a nasty shock this way from a cable TV output cable
Hi,
What I don't quite understand is why anyone would say the QS amp isn't grounded...
All I've seen (admittedly those are for export) were, invariably so.
Looking at the circuit diagram you already notice the grounding points.
On top of that the powerxformer also uses an electrostatic shield which is utterly useless unless it is grounded....
As for the shielding of powercords....Just don't get me started.
Cheers,
What I don't quite understand is why anyone would say the QS amp isn't grounded...
All I've seen (admittedly those are for export) were, invariably so.
Looking at the circuit diagram you already notice the grounding points.
On top of that the powerxformer also uses an electrostatic shield which is utterly useless unless it is grounded....
As for the shielding of powercords....Just don't get me started.
Cheers,
Quote:
DO NOT post recommendations for highly unsafe practices.
Don't see where I did. Personally, I will not add a three prong to any piece of equipment I own. My opinion here not a recommendation for unsafe practices.
Quote:
What I don't quite understand is why anyone would say the QS amp isn't grounded...
All I've seen (admittedly those are for export) were, invariably so.
I have had three pair, none of which could be considered as properly grounded. All considered safe by U.L. standards at the time of manufacture. I take that back... one pair have had 3 prong cables added that provided a proper ground. The other two pair are not grounded properly.
Quote:
Ground loops are easily taken care of by lifting signal grounds from chassis grounds.
In some cases yes, others no. Jensen and other transformer manufacturers have made a fortune selling transformers for this purpose.
newears,
Please do not forget to ground the darn amp! There, posted recommendations for safe practices.
DO NOT post recommendations for highly unsafe practices.
Don't see where I did. Personally, I will not add a three prong to any piece of equipment I own. My opinion here not a recommendation for unsafe practices.
Quote:
What I don't quite understand is why anyone would say the QS amp isn't grounded...
All I've seen (admittedly those are for export) were, invariably so.
I have had three pair, none of which could be considered as properly grounded. All considered safe by U.L. standards at the time of manufacture. I take that back... one pair have had 3 prong cables added that provided a proper ground. The other two pair are not grounded properly.
Quote:
Ground loops are easily taken care of by lifting signal grounds from chassis grounds.
In some cases yes, others no. Jensen and other transformer manufacturers have made a fortune selling transformers for this purpose.
newears,
Please do not forget to ground the darn amp! There, posted recommendations for safe practices.
Grounding racks
I probably am guilty of a number of questionable practices... and actually am keen to learn from everyone's experience, but I started as a ham radio operator building power supplies and transmitters in my teens and had the dubious experience of getting bounced across the room by a ps capacitor on a 800v power supply I built but had disconnected the bleeder resistor while working on it.... ouch. I woke up a few minutes later but the lesson has stayed with me...
As far as grounding is concerned.. I do have a hum problem. I have tried to manage it by running a separate dedicated large gauge ground wire directly from the rack to a nearby cold water pipe(tested for true ground). I have religously grounded each piece of equipment by dedicated ground wire or rack mounting to this separate ground. However, some of my equipment does have 3 pronged plugs and although the grounding has greatly reduced the hum issue, there still is a bit of hum on my phono input... The preamp (LS-3) and Quicksilvers are pretty quiet without inputs... the problems come from some inputs. Anyway, now after reading the posts I am sure that I have numerous ground loops and am not sure that my separate grounding is the best way to deal with this ... so would still appreciate any advice on this.
I do however, believe that the grounding should be done for safety... Since I have physically grounded the equipment, should I not use shielded power cords? What should I do about ground loops created by 3 prong plugs on some of the equipment?
I probably am guilty of a number of questionable practices... and actually am keen to learn from everyone's experience, but I started as a ham radio operator building power supplies and transmitters in my teens and had the dubious experience of getting bounced across the room by a ps capacitor on a 800v power supply I built but had disconnected the bleeder resistor while working on it.... ouch. I woke up a few minutes later but the lesson has stayed with me...
As far as grounding is concerned.. I do have a hum problem. I have tried to manage it by running a separate dedicated large gauge ground wire directly from the rack to a nearby cold water pipe(tested for true ground). I have religously grounded each piece of equipment by dedicated ground wire or rack mounting to this separate ground. However, some of my equipment does have 3 pronged plugs and although the grounding has greatly reduced the hum issue, there still is a bit of hum on my phono input... The preamp (LS-3) and Quicksilvers are pretty quiet without inputs... the problems come from some inputs. Anyway, now after reading the posts I am sure that I have numerous ground loops and am not sure that my separate grounding is the best way to deal with this ... so would still appreciate any advice on this.
I do however, believe that the grounding should be done for safety... Since I have physically grounded the equipment, should I not use shielded power cords? What should I do about ground loops created by 3 prong plugs on some of the equipment?
There are some great papers about this on the Jensen Transformer site. It's quite straightforward to eliminate ground loops while retaining the safety earth ground. Input transformers are one way. Lifting the signal grounds from the chassis and having them all connect at one point in one piece of equipment is another.
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