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Uh .....If you want to buy flexible wire, you probably need to ask for multistrand wire, right? Sure, 'strand' is the wrong term but it's in common use to mean an individual wire in a bundle.
Quote from a Wiki: The term wire is also used more loosely to refer to a bundle of such strands, as in "multistranded wire", which is more correctly termed a wire rope in mechanics, or a cable in electricity. Wire comes in solid core, stranded, or braided forms.
You can see its entrenched.
Quote from a Wiki: The term wire is also used more loosely to refer to a bundle of such strands, as in "multistranded wire", which is more correctly termed a wire rope in mechanics, or a cable in electricity. Wire comes in solid core, stranded, or braided forms.
You can see its entrenched.
There may be little problem with DC protection circuit in schematic from post #1.
If someone already figured this out, then forgot about the rest of this post - I didn't fully read this thread, and I realize, that I'm very too late.
In case of DC at output, TR11/TR12 may be turned off too slow. Then FET1 and FET2 may become too hot, and and then fail and become shorted, before TR11/12 will be fully turned off.
That problem can make all this protection useless. The same may happen, if You put strong input signal, just after turn on power, but before C18 will be charged to fully turn on both FETS.
A possible solution - put some kind of Shmidt trigger before OPTO.
If someone already figured this out, then forgot about the rest of this post - I didn't fully read this thread, and I realize, that I'm very too late.
In case of DC at output, TR11/TR12 may be turned off too slow. Then FET1 and FET2 may become too hot, and and then fail and become shorted, before TR11/12 will be fully turned off.
That problem can make all this protection useless. The same may happen, if You put strong input signal, just after turn on power, but before C18 will be charged to fully turn on both FETS.
A possible solution - put some kind of Shmidt trigger before OPTO.
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Hi Wojtek,
There is always going to be some delay before the dc will turn off because you need to avoid 'false trigger' from powerful low frequency music signals. Generally, the SS relay is still faster than the 'usual' approach of using mechanical relays. The time constant for my circuit is based on R27 charging C14, so 10kohm and 47uF which is a cut-off frequency around 0.34Hz. Do you think this is too low ?
There is always going to be some delay before the dc will turn off because you need to avoid 'false trigger' from powerful low frequency music signals. Generally, the SS relay is still faster than the 'usual' approach of using mechanical relays. The time constant for my circuit is based on R27 charging C14, so 10kohm and 47uF which is a cut-off frequency around 0.34Hz. Do you think this is too low ?
You don't understand. I'm not talking about delay, but about switching itself.
Mechanical relays have built-in hysteresis. They turn on fast when voltage cross over (lets say) 0.8U, ant turn off fast when voltage falls below (lets say) 0.1U. In both cases switching is fast (usually much less than 10ms), no matter how slowly voltage is changing. They can be only on or off, and anything between that can't stay longer than couple miliseconds.
In case of MOSFETS, they are on when Vgs>5V, and off when Vgs<2V, but what happen, when voltage is somewhere between? At some point Rds will be comparable to loading resistance, and MOSFETS will dissipate some serious power, especially at high output voltage or DC failure (about amplifier rated output power, lets say). Without some serious heatsink they surely fail, if stays in that condition long enough (100ms should be long enough).
You need some circuit, that rapidly (in less than 10ms) switches MOSFET on when voltage cross over ~6V, and turn off when falls below ~5V. Shmitt trigger is one of possible solutions.
Mechanical relays have built-in hysteresis. They turn on fast when voltage cross over (lets say) 0.8U, ant turn off fast when voltage falls below (lets say) 0.1U. In both cases switching is fast (usually much less than 10ms), no matter how slowly voltage is changing. They can be only on or off, and anything between that can't stay longer than couple miliseconds.
In case of MOSFETS, they are on when Vgs>5V, and off when Vgs<2V, but what happen, when voltage is somewhere between? At some point Rds will be comparable to loading resistance, and MOSFETS will dissipate some serious power, especially at high output voltage or DC failure (about amplifier rated output power, lets say). Without some serious heatsink they surely fail, if stays in that condition long enough (100ms should be long enough).
You need some circuit, that rapidly (in less than 10ms) switches MOSFET on when voltage cross over ~6V, and turn off when falls below ~5V. Shmitt trigger is one of possible solutions.
I also like the Nordost. Few years ago I had the chance to buy some 5m really cheap, because the guy was cleaning his old stock. I like how their speaker cables sound, and I like the idea behind the flat cables. As for Nordost interconnect I don't believe in cables without shielding, especially in the era of all-wireless and all-switching.
The Nordost speaker cable is the only cable that I've tried that sounds as good or better than NACA5. I sold my NACA5 in result, because I really hated the stiffness. Honestly, I would take something not so good that is more workable. Now, Nordost also claims some impossible parameters like velocity factor of 95, but the cable is definitely good for what it is.
Recently, I found on Mouser these ribbon cables, which very much resemble the newer Nordost series:
http://ca.mouser.com/Molex/Wire-Cab...Z1z0zlewZ1yzxo77&Keyword=ribbon+cable&FS=True
Same FEP (Teflon) insulation, silver plated, however VF~83-85
I bought a piece and I find it very nice as a speaker cable. Still in my system. You just need to use one half of the ribbon for +ve, the other for -ve. You can also leave one or two conductors in the middle not connected, if you are chasing even lower capacitance. Number of conductors, AWG etc. - up to your pocket (think Nordost product range upgrade). Actually, considering that not many places in the world are able to manufacture this type of cable and insulation, I'll put a bet that Nordost order their stuff from Molex. Just the Nordost package is prettier and impressive for the audiophile crowd.
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Wojtek - brilliant observation, thank you for persisting with this - you have saved me a potential failure mode ! As you say, if it takes 30ms for the circuit to shutdown the photovoltaic we have a chance to exceed the SOAR of the MOSFET assuming worse case full rail voltage across the speaker.
It is worse case, for smaller dc voltage errors there's no issue - I have tested the circuit out into an 8R load many times without issue. Let me think about this further.
Just to say again. 0.6mm x 10 metres = 0.06 ohms. That would make a 5 metre run. As said before NACA5 would take a 1000 amp transient and > 50 amps constant. We need about 5 amps constant at most with 20 amp transients. That's a reactive 1R transient load which the Naim might allow very briefly. 2R including the 0.22R + 0.06R is still a bit unlikely. What people seem not to realise is other than active speakers most have a series inductor or choke that also has DCR. No way the cable needs to be so large. In my opinion most active speakers sound a bit wrong. I suspect this is because they need the choke to balance the good and bad ( Qts, Qte ). Active with a series choke might be an idea to deliberately divorce the amplifier from speaker. If a speaker unit is designed to be active from the start it might be better. Paper might be best. Dynaco A25 has no choke ( HB1's ? ). They can have a bit of magic, they need big rooms to be giant killers. That bass unit is very special.
I use a PA unit called 12 Lta ( 15 inch bass and DT74/8 tweeter ). 12 Lta is better without a choke even when 200 uH looks on paper ideal. I use 5mH 0.05R DCR to the 15 inch. The tweeter at 6 kHz ( it really works as a semi super tweeter, no LF resonance when 6K ) ). One day it will go active as it is the one that can. I might keep the 5 mH choke. The 12 Lta might be SE valve driven. It would make for an ideal output transformer. Tweeter driven directly from a SE valve via a coupling cap. Bass might be Hypex. It could be cooled on the 15 inch magnet near the air vent. The hardest part and the part I hate is a simple active crossover. Simple active is not easy. Semi passive is. For example the input cap to an amplifier can be all it needs. The output transformer also. Quad ESL uses that trick to cut at 18 kHz. It also is cheaper to make. Some active EQ required.
If I build a NAP it would be for my Royd speakers.
0.2mm ideal for tweeters and interconnects. The latter in Sellotape to look like 300 ohm cable. Shield often is not a problem. Sounds more open and seems to shape the wave better. PrAT might be greater as rhythm with more timbre = more music.
0.6mm is an all rounder. NACA5 has strands of about that size so has some similarity. 19 mm spacing.
1.5 mm for subwoffer sized units. However 0.6 mm kept short can be best. If the unit is truely for no more than 250 Hz - 6 db then NACA5 is still first choice.
I use a PA unit called 12 Lta ( 15 inch bass and DT74/8 tweeter ). 12 Lta is better without a choke even when 200 uH looks on paper ideal. I use 5mH 0.05R DCR to the 15 inch. The tweeter at 6 kHz ( it really works as a semi super tweeter, no LF resonance when 6K ) ). One day it will go active as it is the one that can. I might keep the 5 mH choke. The 12 Lta might be SE valve driven. It would make for an ideal output transformer. Tweeter driven directly from a SE valve via a coupling cap. Bass might be Hypex. It could be cooled on the 15 inch magnet near the air vent. The hardest part and the part I hate is a simple active crossover. Simple active is not easy. Semi passive is. For example the input cap to an amplifier can be all it needs. The output transformer also. Quad ESL uses that trick to cut at 18 kHz. It also is cheaper to make. Some active EQ required.
If I build a NAP it would be for my Royd speakers.
0.2mm ideal for tweeters and interconnects. The latter in Sellotape to look like 300 ohm cable. Shield often is not a problem. Sounds more open and seems to shape the wave better. PrAT might be greater as rhythm with more timbre = more music.
0.6mm is an all rounder. NACA5 has strands of about that size so has some similarity. 19 mm spacing.
1.5 mm for subwoffer sized units. However 0.6 mm kept short can be best. If the unit is truely for no more than 250 Hz - 6 db then NACA5 is still first choice.
https://en.wikipedia.org/wiki/American_wire_gauge
go down to ~ 22.5awg (~0.6mm diameter) and look across to column 8 and the table shows ~ 60milli-ohms/metre
Are USA ohms different from everyone else's ohms?
or using Rhocopper = 1.68 / 10^8 & 0.6mm diam = 0.283sqmm
Resistance = 1.68 /10^8 * 1m / .283 * 10^6 = 0.0594 ohms = ~60milli-ohms/metre
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I used a online calculator. Must have been wrong. Could be.
I see where I went wrong. 50 cm isn't 5 metres. Feet is my better thing. More than I thought.
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4 metres should be OK. One could use it to substiute the 0R22 output. 0R1 + 3.5 metre runs?
I see where I went wrong. 50 cm isn't 5 metres. Feet is my better thing. More than I thought.
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4 metres should be OK. One could use it to substiute the 0R22 output. 0R1 + 3.5 metre runs?
Wireless World had dampling factors as needing to be better than 3 in the past. Naim is about 16 when 4 ohms.
If we take 0R1 and 3.5 metres we are at circa 0R5. That is still close to 10 where it is debatable that it shouldn't be any different if it were 100. Into a more typical 6R it is well above 10. Many go for higher as it looks good on a tick list. It might be a mistake. Sid Smith of Marantz thought a small output resistor like the Naim would suit most designs. It is an electrical water-shed of sorts.
Give it a try and use the propper 0R22. Up to 3.5 metres I think the losses should favour other positive sound changes. Use 19 mm spacing. Tape is good to set the space.
One reviewer thought too high a damping factor was like too many develloped muscles. That's the weightlifter trying to be a runner.
If the damping is critical it allows the bass unit to slightly overshoot. Guitar amps thrive on this. It is very interesting to find your own taste in this. New speakers will demand a new solution to your taste.
If we take 0R1 and 3.5 metres we are at circa 0R5. That is still close to 10 where it is debatable that it shouldn't be any different if it were 100. Into a more typical 6R it is well above 10. Many go for higher as it looks good on a tick list. It might be a mistake. Sid Smith of Marantz thought a small output resistor like the Naim would suit most designs. It is an electrical water-shed of sorts.
Give it a try and use the propper 0R22. Up to 3.5 metres I think the losses should favour other positive sound changes. Use 19 mm spacing. Tape is good to set the space.
One reviewer thought too high a damping factor was like too many develloped muscles. That's the weightlifter trying to be a runner.
If the damping is critical it allows the bass unit to slightly overshoot. Guitar amps thrive on this. It is very interesting to find your own taste in this. New speakers will demand a new solution to your taste.
1.- I for one would definitely build it if it partners TGM10 nicely.
2.- I do recall reading your thread with regards to the pre-amp build and issues and
do realise time constraints is a major factor for you(but I have to add that I like your approach to all of your projects).
Enough off-track rambling for now.
Regards
phunk
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Have you tried bypassing the FETs to see if that makes a difference?
There are other suspects, of course.
Vivid, energetic sound does not require irritation.
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I have not tried bypassing the FETs, but I've used FETs before like this in amplifiers that are certainly not irritating. These FETs have some nicely linear Rds-on conductive channels through their silicon bodies.
It's not clear that this is all down to the amplifier. It varies with recording quality. The speakers will also have some impact. The source is a many-year old Sony blue-ray player pressed into service temporarily. I don't have a trusted source right now - my best source was a YBA CD player that I sold off over a year ago with the aim of moving to a music server. Still haven't bought one (or made one out of a raspberry).
But I have read many different comments about the Naim amplifier all over the internet. There is a consistent note from some listeners that they find the sound to be as I believe it sounds to me. It gives me the sense that the amp is not 'broken' at all and there are set-ups and people who will find it too vivid at times. The comments I've read cover a wide range of Naim amps, certainly included those from the era that inspires this TGM10 project.
I would like to do some more experiments with it though. Some really simple things don't need a lot of effort: output inductor, additional output resistor, speaker cable swap, speaker swap (I've had some fatigue from these speakers in the past using a Bryston amp with large speaker cables), go back to tuner as a source etc.
Last night I was going to do some more listening but my son was on the piano drowning it out - no objections from me. I did get some time later. I started with a CD soundtrack to The Full Monty - sounded crap. Not just that it was irritating, the recording quality of the opening sound track gave me the perception that it was poor. This set-up I have now appears to punish, without mercy, any kind of marginal recording.
I swapped that out for a Jaz compilation CD. It's not a disc I'm familiar with, it's been hiding in my car for a long time. It's light Jaz. The sound was beguiling to say the least. Every instrument was vivid, in front of me, every movement of a finger, every breath, it was all just in front of me 'alive' like you wouldn't believe. Strings, brass, piano and voices all so 'present' in the room. Boy I liked it.
It's not clear that this is all down to the amplifier. It varies with recording quality. The speakers will also have some impact. The source is a many-year old Sony blue-ray player pressed into service temporarily. I don't have a trusted source right now - my best source was a YBA CD player that I sold off over a year ago with the aim of moving to a music server. Still haven't bought one (or made one out of a raspberry).
But I have read many different comments about the Naim amplifier all over the internet. There is a consistent note from some listeners that they find the sound to be as I believe it sounds to me. It gives me the sense that the amp is not 'broken' at all and there are set-ups and people who will find it too vivid at times. The comments I've read cover a wide range of Naim amps, certainly included those from the era that inspires this TGM10 project.
I would like to do some more experiments with it though. Some really simple things don't need a lot of effort: output inductor, additional output resistor, speaker cable swap, speaker swap (I've had some fatigue from these speakers in the past using a Bryston amp with large speaker cables), go back to tuner as a source etc.
Last night I was going to do some more listening but my son was on the piano drowning it out - no objections from me. I did get some time later. I started with a CD soundtrack to The Full Monty - sounded crap. Not just that it was irritating, the recording quality of the opening sound track gave me the perception that it was poor. This set-up I have now appears to punish, without mercy, any kind of marginal recording.
I swapped that out for a Jaz compilation CD. It's not a disc I'm familiar with, it's been hiding in my car for a long time. It's light Jaz. The sound was beguiling to say the least. Every instrument was vivid, in front of me, every movement of a finger, every breath, it was all just in front of me 'alive' like you wouldn't believe. Strings, brass, piano and voices all so 'present' in the room. Boy I liked it.
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How do you propose we "bypass" the three lead FETs?
Surely that will take the transistor out of circuit and break the amplifier.
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Andrew, The FETs are there only to isolate the speaker during power-up and power-down and with the hope of mitigating risk of damage should the amplifier put out dc onto the speaker output. Bypassing the signal path through the FETs (this was the suggestion) wouldn't stop the amplifier from working.
That's not the Naim sound IMO. Naim adds a bit of MSG to recordngs which tends to mildly exaggerate tonal colour and rythym. Great recordings are slightly subdued and poor recordings are slightly enhanced - the end result is very appealing for long term listening. The downside is a slight homogenisation of all tyes of music. Overall a decent compromise, but not the only game in town!
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