So I’ve been binging on amp repair vids on YT, etc and while watching a GZ 4K monoblock repair on BareVids (UK based dude who’s awesome) he mentioned “this amp runs 24n40f output mosfets which is a bit excessive on the voltage side, I could make this amp more stable at .5 ohm with 69n25’s but that would increase the cost blablabla ...”
After looking them up to see what the difference was the main spec difference I can see (I’m very layman lol) is the stock have a 400v 23a rating, the 69n25 he mentioned are 250v 69a rated. How do these specs effect output and how does changing them increase the stability of the amp when running a lower ohm load? And is that a common practice for increasing an amp’s stability at lower ohm loads? What else, if at all, would be needed for something like this?
I’d like to know the whats, how’s, why’s of it and really understand what’s happening here and why it would increase stability, that’s all he mentioned about it so I don’t know if there’s other small stuff needed as well (gate resistor change outs, etc) but I’m very interested, specifically for my 06ZX750.1 Power Supply repair I’m currently doing (which I’m writing up and plan on making a post about soon) and for my other personal amps.
I’m the type that likes to increase stats/specs if possible on any/all of my gear. One of the main goals when building&OC’n my gaming PCs for example 🙂 I realize this doesn’t inherently increase the output, which is not what I am after, just stability. Any and all types of info/insight would be much appreciated, thank you all!
🦾🤖🔊
After looking them up to see what the difference was the main spec difference I can see (I’m very layman lol) is the stock have a 400v 23a rating, the 69n25 he mentioned are 250v 69a rated. How do these specs effect output and how does changing them increase the stability of the amp when running a lower ohm load? And is that a common practice for increasing an amp’s stability at lower ohm loads? What else, if at all, would be needed for something like this?
I’d like to know the whats, how’s, why’s of it and really understand what’s happening here and why it would increase stability, that’s all he mentioned about it so I don’t know if there’s other small stuff needed as well (gate resistor change outs, etc) but I’m very interested, specifically for my 06ZX750.1 Power Supply repair I’m currently doing (which I’m writing up and plan on making a post about soon) and for my other personal amps.
I’m the type that likes to increase stats/specs if possible on any/all of my gear. One of the main goals when building&OC’n my gaming PCs for example 🙂 I realize this doesn’t inherently increase the output, which is not what I am after, just stability. Any and all types of info/insight would be much appreciated, thank you all!
🦾🤖🔊
Do you think a power supply that's marginal for the 1 ohm load will be able to supply 2x the previous current into 0.5 ohms?
This may be suitable for an amp that is to be used only intermittently but it's not likely to be viable for an amp that's going to be used for long periods.
What if you had a graphics card that was asking for 90% of the reserve capacity from the 12v out of your computer's power supply, then added a second identical graphics card?
This may be suitable for an amp that is to be used only intermittently but it's not likely to be viable for an amp that's going to be used for long periods.
What if you had a graphics card that was asking for 90% of the reserve capacity from the 12v out of your computer's power supply, then added a second identical graphics card?
Only one way to find out...
I sent Sam a cheap Chinese amp I got off eBay, just to see what it would do with some mods. Stock specs on it were 1250w@1 ohm, when I got it back it dyno’d as follows in the below screenshot. YMMV, but obviously there are things that can be done to increase the current handling.
Attachments
Wow bro, that’s amazing. From the looks of it to a layman it’s basically redesigning the amp but just the fact it can be done and you gained that much more output ...just wow. Thx for the post, really appreciate your reply with the pic, etc. still learning all this and obviously I have some far fetched and random questions, as all newbs do lol. If it weren’t meant to be done there wouldn’t be ppl who do it and get the job done right 😉
Edit: you mentioned a “Sam”? Care to share/expand on that?
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Ya no I understand all of that, way more then you might think Perry, my question tho was as to the what/why/how to get to understanding why lowering the voltage and upping the amperage had the effect of increasing stability at lower ohmage, and what else is usually also done when trying to increase the stability with this method. I don’t plan on running my amps at a lower then rated ohmage, I never have, but we all know companies usually do the bare minimum to get their products to perform as stated, and obviously increasing stability at a lower ohm load would have a positive effect at the lowest rated ohm load, and for my fav amps it’s def something I want to consider, who wouldn’t want to increase stability on their fav piece of equipment 🙂 I’d make a totally diff post on “mods for increasing output” if that was my question/goal, but this isn’t that, I know the 2 are related but that’s not what my intention is. I get why you’re apprehensive about it, and I appreciate it a lot, but you have no worries here brother, just trying to learn 🙂
Edit: I know I’m super uneducated in this field, and me separating changing output fets to increase stability vs all that was done in above pic/post to increase output might be more the same then I realize right now, just the way the repairer was in the vid gave off a vibe of that there’s diff levels to modding, like say changing out fets to increase stability, and then there’s doing what was done in the above pic to increase output crazy at a waaay lower ohm rating, I’m just wanting to look at methods to increase stability/robustness/over all health of my fav equipment. I’m a modded at heart, but I’m not stupid lol, I just like my stuff upgraded if possible, but I ain’t looking to run my ZX750.1 amp at.5ohm ...lol. So ya brother if you can help my understand after knowing that plz do 🙂
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There is so much wrong with this thread I don´t even know where to start.
I´ll try anyway.
They must always do that.
Do they stand more than bare minimum? ... GOOD!!!
2) "stable" is a nonsense catchword/"spec" way misused by car amp "designers" or at least marketers.
Stable means it does not oscillate with load applied, either continuously or in bursts at some point of the waveform, period.
Marketers state, say: "amp puts out 500W into 2 ohm, and is 1 ohm stable" , letting unsophisticated end users "think" : "oh! it can drive 1 ohm loads!!!"
No, it does not mean that (if they stated so clearly they could be proven wrong) , simply "it does not oscillate if loaded with 1 ohm", a completely different thing. And much easier to achieve.
As relevant as stating "cat safe into 1 ohm loads" meaning your cat won´t die if doing so ... so what?
IF it did, Youtuber would show amp oscillating into a 1 ohm load, then curing that problem by using different Mosfets.
He does none of that.
If so, please show it.
Specially scope screen captures,details on the load you use and amp schematic.
Could go on and on, but the above is more than enough to show the flaws in following an obscure YT video as the Revealed Truth ... it´s not.
I suggest IF you are repairing an amp, return it to Factory specs; you don´t have enough data available to "improve" it.
As of:
also there is so much wrong with it.
To begin with, all we have is the Modder´s word for it.
Did he increase MosFet specs?
Change some resistors and caps?
Probably.
Did he turn a 1250W amp (which is already suspect, being as described a "cheap chinese amp off EBay" , not my words but as described) into a 5kW fire breathing monster?
May I very very very much doubt it?
If anything: what was he feeding it with?
A super bank of 24 truck sized batteries in parallel?
Through arm thick wires?
As an extra note, I doubt the sanity of anybody who states:
I´ll try anyway.
First RED flag.
1) Who cares if power transistors stand more than than supply voltage?
They must always do that.
Do they stand more than bare minimum? ... GOOD!!!
2) "stable" is a nonsense catchword/"spec" way misused by car amp "designers" or at least marketers.
Stable means it does not oscillate with load applied, either continuously or in bursts at some point of the waveform, period.
Marketers state, say: "amp puts out 500W into 2 ohm, and is 1 ohm stable" , letting unsophisticated end users "think" : "oh! it can drive 1 ohm loads!!!"
No, it does not mean that (if they stated so clearly they could be proven wrong) , simply "it does not oscillate if loaded with 1 ohm", a completely different thing. And much easier to achieve.
As relevant as stating "cat safe into 1 ohm loads" meaning your cat won´t die if doing so ... so what?
As I said above, stability has no meaning here.
IF it did, Youtuber would show amp oscillating into a 1 ohm load, then curing that problem by using different Mosfets.
He does none of that.
Congratulations on your thirst for knowledge 👍 , sadly here we can´t explain what is NOT happening.
Do you have a real stability problem?
If so, please show it.
Specially scope screen captures,details on the load you use and amp schematic.
Could go on and on, but the above is more than enough to show the flaws in following an obscure YT video as the Revealed Truth ... it´s not.
I suggest IF you are repairing an amp, return it to Factory specs; you don´t have enough data available to "improve" it.
As of:
also there is so much wrong with it.
To begin with, all we have is the Modder´s word for it.
Did he increase MosFet specs?
Change some resistors and caps?
Probably.
Did he turn a 1250W amp (which is already suspect, being as described a "cheap chinese amp off EBay" , not my words but as described) into a 5kW fire breathing monster?
May I very very very much doubt it?
If anything: what was he feeding it with?
A super bank of 24 truck sized batteries in parallel?
Through arm thick wires?
As an extra note, I doubt the sanity of anybody who states:
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I THINK, higher voltage fets would have higher gate capacitance, so the gate resistor and who knows hoe many places ne needs to reccover the stability and it matters which methods are being used. Dominant pole? Miller? 2-pole Miller? Output Miller?
.5 Ohm load? WHAT?
.5 Ohm load? WHAT?
I have not been shown any instability, so ..... why try to solve a non existing problem?
Image claims 0.35 ohm load 😵
😉
Image claims 0.35 ohm load 😵
😉
Some people want to run their amps into lower ohm loads than the manufacturer recommends. I still don't understand that except possibly for competition where the amp will be driven to full power for a few seconds at a time. I quit taking in one brand of amps because someone had spread the word that they had to be run well below the lowest rated impedance to make any real power and nothing I could say would change their minds.
Thank you for the statement on 'stability'. Purely marketing.
Modification of a class D amp (which are often designed right on the edge of functioning properly) is not an easy thing. If you don't really know what you're doing, success could be a matter of luck.
I typically don't help with modifications unless it's to solve a problem with reliability for normal operation.
Thank you for the statement on 'stability'. Purely marketing.
Modification of a class D amp (which are often designed right on the edge of functioning properly) is not an easy thing. If you don't really know what you're doing, success could be a matter of luck.
I typically don't help with modifications unless it's to solve a problem with reliability for normal operation.
This type of detailed explanation is what I’m after, although it seems to have gotten you in your feelz some, but hey if we can’t be parionate about what we love why bother right lol, I’m just trying to learn myself cuz I got that fire starting up 🤓 I appreciate the in depth analysis, and I’ve said many times I’m def a layman just starting out asking questions. But BareVids on YT knows his stuff, I trust him and his abilities, so he’s not just a fly by the seat of your pants repair hack and even so I still don’t take his words as gospel truth, but like I said he just mentioned it in passing and didn’t even go into detail at all and I’m sure it was specific to the amp he was working on, it was just something I picked up on during a repair and wanted to know more about wondering if it as easy as replacing output fets to increase stability or does it take more then that and how much, etc. Wanting to improve upon a design is not bad thing, we all know most companies usually go with bare minimum to get something going, and I’m not asking “where’s the protect circuit so I can disable it and run.5 loads” and then go burn up my amp lol, I’m not even after a lower ohm load/more power at all, I’m trying to learn the proper way, if there is one, of upgrading an amp to improve its stability, which is all theory atm to me right now. Maybe you’re a “stock only” guy and if so cool man, that’s awesome, there’s a reason it’s built the way it is right. But you almost seem negative about the whole thing, maybe try not to be homie, you yourself said “stable/spec” is just BS and it was insinuated that it can not be trusted, so why not do something to improve upon an amp the proper way? That’s what I was asking, Im wanting to learn how to do it correctly if/when I ever do get to that point where I think the amp would benefit from it, and since “spec & stable” is just a catchphrase and can’t be trusted wouldn’t that stability mod trickle up to all other ohm loads as well? I don’t know that’s why I’m asking, I know I need to learn the basics and should prolly repair a bunch to stock before I go modding, hell I still don’t even know how to take proper readings in the right areas to know if something is properly working or not lol, but I got ideas and I’m reading & hearing stuff and I’m wanting to know is all. But I get what you’re saying, I’m sure you pro’s see/hear a lot of these types of questions and it must get old watching ppl burn up their **** lol, hence your approach, but hopefully you get what I’m saying too, all positivity here man, just wana learn 🤓 and you’re right, I ain’t got enough data to even repair something to working stock yet let alone mod it, but I’m a modder at heart so there’s always that question for me “can I improve it” 🤠 lolThere is so much wrong with this thread I don´t even know where to start.
I´ll try anyway.
First RED flag.
1) Who cares if power transistors stand more than than supply voltage?
They must always do that.
Do they stand more than bare minimum? ... GOOD!!!
2) "stable" is a nonsense catchword/"spec" way misused by car amp "designers" or at least marketers.
Stable means it does not oscillate with load applied, either continuously or in bursts at some point of the waveform, period.
Marketers state, say: "amp puts out 500W into 2 ohm, and is 1 ohm stable" , letting unsophisticated end users "think" : "oh! it can drive 1 ohm loads!!!"
No, it does not mean that (if they stated so clearly they could be proven wrong) , simply "it does not oscillate if loaded with 1 ohm", a completely different thing. And much easier to achieve.
As relevant as stating "cat safe into 1 ohm loads" meaning your cat won´t die if doing so ... so what?
As I said above, stability has no meaning here.
IF it did, Youtuber would show amp oscillating into a 1 ohm load, then curing that problem by using different Mosfets.
He does none of that.
Congratulations on your thirst for knowledge 👍 , sadly here we can´t explain what is NOT happening.
Do you have a real stability problem?
If so, please show it.
Specially scope screen captures,details on the load you use and amp schematic.
Could go on and on, but the above is more than enough to show the flaws in following an obscure YT video as the Revealed Truth ... it´s not.
I suggest IF you are repairing an amp, return it to Factory specs; you don´t have enough data available to "improve" it.
As of:
also there is so much wrong with it.
To begin with, all we have is the Modder´s word for it.
Did he increase MosFet specs?
Change some resistors and caps?
Probably.
Did he turn a 1250W amp (which is already suspect, being as described a "cheap chinese amp off EBay" , not my words but as described) into a 5kW fire breathing monster?
May I very very very much doubt it?
If anything: what was he feeding it with?
A super bank of 24 truck sized batteries in parallel?
Through arm thick wires?
As an extra note, I doubt the sanity of anybody who states:
This is exactly why I was wondering if it could be done the way stated above, and if it was as “easy” as it seemed to a layman of just replacing some fets. I was never trying to run an amp at lower ohm loads, I’m just wanting to improve upon a design where I can since I am willing to spend a few extra bucks on parts the company isn’t, that’s all, since all their numbers, etc are just marketing I assumed that the “stability mod” I overheard would be as easy as it sounded, and thinking it would have a trickle effect throughout the entire amp making it run “better” ...but I have no idea that’s why I asked 🤠
As you stated, companies go with the bare minimum. This means that all parts of the amp are designed to produce full power and no more.
You stated that you're not looking for more power or driving a load below the rated impedance. You have to realize that the people who are at the top of the design/development of these amps aren't laymen. They are well educated and likely have a lot of experience. There is VERY little chance that you can improve on their choices, especially in the output selection. When I was new to repair work, I attempted to out-think the design engineers. I was wrong virtually 100% of the time.
The voltage and current parameters of an output is only the beginning. Some people may be able to chose a substitute looking at the specs alone but I've never been able to do that more than about 25% of the time (maybe not that often).
Class D amps can be very finicky in the way they function. A slight difference in any component can make a huge difference in the way a class D amp functions.
If this is your amp, you can do with it what you wish but you should understand that if you get it right, especially on the first try, it was likely pure luck. Even if it initially appears to work, you may find that the change in the output may load the driver stage, cause too much cross conduction or other things that can make the amp unreliable, long term.
Please break up your text. Trying to read as one large block of text makes it hard to read.
You stated that you're not looking for more power or driving a load below the rated impedance. You have to realize that the people who are at the top of the design/development of these amps aren't laymen. They are well educated and likely have a lot of experience. There is VERY little chance that you can improve on their choices, especially in the output selection. When I was new to repair work, I attempted to out-think the design engineers. I was wrong virtually 100% of the time.
The voltage and current parameters of an output is only the beginning. Some people may be able to chose a substitute looking at the specs alone but I've never been able to do that more than about 25% of the time (maybe not that often).
Class D amps can be very finicky in the way they function. A slight difference in any component can make a huge difference in the way a class D amp functions.
If this is your amp, you can do with it what you wish but you should understand that if you get it right, especially on the first try, it was likely pure luck. Even if it initially appears to work, you may find that the change in the output may load the driver stage, cause too much cross conduction or other things that can make the amp unreliable, long term.
Please break up your text. Trying to read as one large block of text makes it hard to read.
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Sam Vennard=barevids
His business contact info is available on social media, most here know who he is so I assumed you did as well.
Agreed, I don’t like the slang/ambiguous terms used these days any more than you do. Might as well add the often quoted ‘Max power’ figure to that list, which is always a garbage number not achievable in the real world.
These terms are nebulous, and mean nothing. They mention making a ‘stable’ amplifier, as if a reputable company would produce and market an unstable amplifier. It’s laughable really.
OP if you really want to know what’s going on, do a deep dive on ohms law as it relates to power generation, transfer, and amplification. Only by understanding the formulae which underpin the practical application can you hope to grasp the full concept of what’s happening in a complicated circuit like an amplifier, but it does help to break things down into sections.
Maybe you could start by getting Perry’s amp course?
Did he increase MosFet specs?
Change some resistors and caps?
Probably.
Did he turn a 1250W amp (which is already suspect, being as described a "cheap chinese amp off EBay" , not my words but as described) into a 5kW fire breathing monster?
May I very very very much doubt it?
Words you can doubt, SMD’s amp dyno results not so much. I trust those numbers, to see one in action you only need to watch a few of Williston (Derek’s) videos on YouTube, which again I assumed was common knowledge- maybe it isn’t.
I believe he has a pair of mega ampere computer power supplies, probably something out of a mainframe. Doesn’t matter where you get the power from, the amp doesn’t care what’s feeding it so long as it’s well fed. It literally doesn’t know the difference between a battery bank or an engine driven alternator(s), as long as the input voltage doesn’t drop appreciably under heavy load all will be well.
Crazy was sort of the point with this project, and no I wouldn’t recommend people doing this in general. The point was to see what the average cheap Chinese half bridge can do when given a true chance on some good parts along with some common sense circuit changes.
It turns out you can get quite a lot, if you know what you’re doing.
Side note- I’m actually inclined to trust the numbers in the manual, given the parts originally used and the general layout of the board. Even though it did say ‘4000w’ on the box, there’s no reason I can think of that it wouldn’t do 1200w to a 1 ohm load in stock form.
Disabling OC protection is a requirement here, since it’s being asked to drive loads less than half the original impedance. Recalibrating it to work at the ‘new’ minimum impedance could have been done, but in the context of what I was going for it wasn’t necessary.
Same thing with bypassing the built in fuses- when you ask an amplifier to deal with more than twice it’s original current carrying capability, the original protection devices will no longer be adequate. Therefore you jump them out and use an outboard fuse instead.
That "guy on yt" aka Sam Vennard aka barevids is definitely a reliable source of information. Just saying.