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Rob's Amp tests

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On 4/23/2020 at 10:37 PM, SME said:

Good points about live kick drums used in rock and metal.  When you talk about the 100-1000 Hz decade being attenuated are you talking about live music shows too?  Or just content mixed for release? 


If you look at the native frequency response of two extremely popular bass drum mics (mostly used for live events) that question will likely be answered:

Audix D6:
0567.png


Shure Beta52A:
0219.png


I like to have two high shelves on my mixing desk for the kick drum, one centered at 1-2khz and one around 4-6khz, which I can individually boost to colour the sound to my liking.
Sometimes a broad boost around 1.5-2khz can be very pleasant with extremely muffled kick drums aka Evans emad style. The Shure Beta91 has a dip switch, which basically is a cut around 400Hz (~two octaves effective range).

Studio mics generally tend to be more flat, to leave it neutral for the engineer to work with, but most of the midrange will be scooped to make room for other stuff in the mix. That'll be extremely busy if you add an orchestra to a band, or generally have a lot going on (Fallujah - Starlit Path as extreme example).

Neuman U47:
0710.png

Keep in mind that mics used for live settings are usually cardioid mics. These don't care much about room resonances. Most 'mud' you'll be fighting will be instruments competing for the same frequency range. Or for example sustained instruments leaving no room for transients in a certain frequency area. If the room is small enough to cause resonance problems in the low mid range, you'll be fighting much much bigger problems anyways (stage bleed).

 

@kipman725Are you sure about the Q of 4? I'd go as far as saying that a change like that will be inaudible to most. Maybe the guy in the PDF mixed up bandwidth with Q there.

  

On 4/23/2020 at 10:37 PM, SME said:

I don't put much stock in generic EQ recommendations.  Every situation is different, and it's good to be able to identify and fix the major problems at whatever frequency region they occur in.  That takes a lot of skill and experience though.

Agreed, it's most important to learn to interpret what you're hearing. Some people reading such a guide might not even be able to identify a certain problem as "muddy" and try to fix it by breaking something else. I know that from experience, done that long ago when I 'followed' a Yamaha sheet on how to mix. I'd boost all guitars at 2khz no matter what. Today I basically cut all guitars at 2khz because the presence region delivered by amps sounds good with a guitar cab, but not good when you mic said cab and amplify it through the PA. If you cut the presence region you can make the guitars louder without them being ear-piercing, which helps a lot in busy rock/metal mixes.

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Small update from my side: I was very eager on posting results here but the blown amp has demotivated me to the part that I went on to finish other projects first. So now I have a vacuum hold down on my CNC. And about the broken amp, the replacement power input board arrived and it blew up as well. Means the PSU is broken, which will run me about 300$ probably.

Good thing is that I've watched a movie with one of the spare amps I had in the store and the clip lights didn't even light up once. I didn't change the settings and volume matched everything properly. Means I can now run the quieter amp (fan noise) with much lower idle power draw without any performance penalties. The spare amp does like 2000W total, which is fine with the SKHorn as efficient bass maker and the BOSS platform as efficient TR maker.
Now that I think back about the times that I had the bridged clone amp on the SKHorn and this bridged amp on the TR I realize how overkill it was. I watch my movies at -10MV with the EQ at +15db at 20Hz. No dynamic EQ.

Will post the first test results some time next week I guess, I will add different frequency tests when I have the time to do those.

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Sanway FP-13000 (MKI)

X6KDTVO.jpg

Vmax(RMS): 134,9V

No frequency response since it blew up. It's +-1db from 3,5Hz to 44khz.

Idle power draw: 115W

Efficiency at 4KW output: 78%

Highest observed amperage readout: 48A (@231V)

Blew up after 90 seconds of 4KW output. PSU broken, power input board damaged, internal fuses on the amp stage damaged.
Soft limiter was non-functional. It just clips the waveform.
VPL kicks in at 188V, hence the lower ratings into 8 and 4 Ohm. I'll check if I can adjust that internally when I manage to bring the amp back to life.

 

Single Channel

1x8Ω - 2075W @1khz
1x4Ω - 3964W @1khz
1x2Ω - 7197W @1khz

iB9LhPR.jpg

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Will post the results of the other amps I have soon and add other frequency tests when I have the time to do those. All test durations will now be ~12s so I have enough material for my 10 second window. The Sanway delivers solid power and I think it blowing up and tripping my 230/16 breaker constantly wouldn't have happened with actual music content. The 10KW spikes will thou. I'm not a generator expert, but I've been told it's not good for them.

Anyways, next amp on the list is super famous in Germany and that for a reason as I found out.

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these are very solid numbers, if it could avoid blowing up it would probably be OK with 2ohm load.  What kind of instrumentation are you using on the supply side?

 

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9 minutes ago, kipman725 said:

these are very solid numbers, if it could avoid blowing up it would probably be OK with 2ohm load.  What kind of instrumentation are you using on the supply side?

 

I'm using a Stairville PD-332 Power Distributor, which provides me with basic voltage and current readouts. It's probably not the most accurate but it works well enough to approximate the data I'm after (idle power draw and efficiency under heavy load). Being able to check on the voltage sag is also useful. And the fact that I have the breaker right where I can reset it quickly is nice with bigger amps.

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t.amp TSA-1400

zLWKu37.jpg

Frequency response:

lStCCzv.jpg

Vmax(RMS): 68,9V

Idle power draw: 25W

Efficiency into 8R and 4R: 80-85%

Efficiency into 2R: 70-75%

Highest observed amperage readout: 14,8A (@232V)
Mains connection is a C14, which is rated at 10A. There should be an S10 fuse inside.

Started smoking 20 seconds into the 2x2 test. Test aborted, no damage. Amp is fan modded, but the part where the smoke came from is isolated from the air flow.
Fans are temperature controlled and have 3 speeds. Fan speed lowers when amp is under heavy load (Voltage sag from PSU).
Soft limiter is quick and reliable. Can't be bypassed. I couldn't get the amp to hard-clip, except for a few ms at the beginning of a test.

C47Usqw.jpg

 

Single Channel

1x8Ω - 502W @1khz
1x4Ω - 904W @1khz
1x2Ω - 1460W @1khz

5vJ5Wor.jpg

 

Dual Channel

2x8Ω - 2x463W @1khz
2x4Ω - 2x799W @1khz
2x2Ω - 2x1231W @1khz

weXy8my.jpg

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t.amp TSA4-300

6SOd9AP.jpg

Frequency response:

e96lBba.jpg

Vmax(RMS): 66,9V

Idle power draw: 95W

Efficiency: 80% at around 500W output, gradually drops to 60% at 4KW output.

Highest observed amperage readout: 17A (@230V)
Mains connection is a C14, which is rated at 10A. Resettable fuse triggered during 4x8 and 4x4 tests.

Long term power output tapers down to about half the numbers seen here. Amp goes into protect after about 90s during any 4 Ohm test. 4x4 triggers the fuse after 15 seconds.
Fans are temperature controlled and have 2 speeds.
Soft limiter is quick and reliable. Can't be bypassed. I couldn't get the amp to hard-clip, except for a few ms at the beginning of a test.

 

Single Channel

1x8Ω - 475W @1khz
1x4Ω - 682W @1khz
1x2Ω - 278W @1khz

 

Dual Channel

2x8Ω - 2x450W @1khz
2x4Ω - 2x698W @1khz
2x2Ω - 2x237W @1khz

 

Quad Channel

4x8Ω - 4x392W @1khz
4x4Ω - 4x594W @1khz

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Gotta say I'm impressed that these amps sustain more power than what they're rated for. Especially the naming scheme threw me off.
Being used to other manufacturer namings I'd expect the 4-300 to burst 4x300W into 4R, but instead it does 4x400W into 8 and 4x600W into 4.
The soft limiter is a nice feature for a non-dsp amp, as I think it's better than hard clipping. Gonna sell it for 250 bucks, as I have no use for it anymore. Very nice amp for the money.

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KMT LC1300

QgAxewU.jpg

Frequency response:

PYUmoMe.jpg

Vmax(RMS): 70,4V

Idle power draw: 0W (current readout was 0,0A)

Efficiency into 8R: 83%

Efficiency into 4R: 78%

Efficiency into 2R: 69%

Highest observed amperage readout: 13,5A (@232V)

DC protection relais kicks in below 20Hz (only above a certain volume threshold about 10db near max output). It mutes the output for half a second.
Fans only spin up when both channels are under load, amp started smelling 2 minutes into the 2R test.

 

Single Channel

1x8Ω - 507W @1khz
1x4Ω - 842W @1khz
1x2Ω - 1304W @1khz

 

Dual Channel

2x8Ω - 2x451W @1khz
2x4Ω - 2x723W @1khz
2x2Ω - 2x1069W @1khz

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8 hours ago, maxmercy said:

Are the t.amp amplifiers readily available in the US?

JSS

More or less. You can order them via Thomann, but you‘ll pay 45$ shipping.

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Update on the Sanway: I fixed the PSU but dropped a fuse into the open case just 2 minutes after I tested it without the amp modules connected. It shorted out one module and broke it. Big boom. Thought I just discharged the caps a little violently and didn't think much about it, but apparently there is something else amiss.

The amp "boots up" again and one channel is operational. The "Mute" light on channel B won't go away. The fuses are good, since the Temp light will light up when those are not installed/blown.

One good thing: I measured the rails and they are 185VDC+-. When I measured the amp's maximum unclipped output voltage I got 131,4V RMS, which is 185,3V peak. Looks like that measurement seems to be reliable. The amp should make 190V peak according to its spec.

When unplugging the amp from the wall, rail voltage drops to 5V+- after 5 minutes. I wore rubber gloves and use non conductive tools when working on the amp, but waiting for a little longer would've prevented the "fuse incident".

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That's a real bummer.

So if the voltage decayed exponentially (i.e. as a series RC circuit), then the rail voltage after 2 minutes powered off was probably like 45 V.   Of course the amount of energy involved in the discharge depends on how much capacitance there is, and I imagine 45 V with a lot of capacitance can do quite a bit of damage if it's released all at once.

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I also touched a heatsink in the power supply to feel how hot it gets. There was some high voltage which made my hand spasm (not high enough to make my arm hurt). I whipped out my voltage meter, which measues up to 1000V DC/AC. It showed "over" on the 1000V setting. I'm not sure what to think of this.

I don't know what part of the amp stage got damaged, since I basically only shorted the PSU output. I am quite confused. I will trace the tracks on the PCB to see what the first components in line are and check those. I will also check with Sanway show much the board costs. The PSU is 185$ and this amp board is quite a lot smaller. Well for now I have an amp which does 7KW bursts and sustains 4KW. Better than a completely broken amp.

Another odd thing I noticed is that one of the amp boards gets unusually hot. I will investigate this, but it might also just be normal and the broken board doesn't heat up anymore since the circuitry in the amp switched it off. I will double check without the internal input/logic connectors in place.

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Large caps should have bleed resistors on them, even when stored.  In some cases large film caps can charge to lethal voltage sat on a bench due to dielectric absorption effects or polymer relaxation effects.  I have been 'thrown' across a room but 3 kM of HV armored cable that self charged itself beyond 1kV and had a large self capacitance.  I'm not saying these long term effects are the case here but to me the bus should discharge itself on power off.

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6 hours ago, kipman725 said:

Large caps should have bleed resistors on them, even when stored.  In some cases large film caps can charge to lethal voltage sat on a bench due to dielectric absorption effects or polymer relaxation effects.  I have been 'thrown' across a room but 3 kM of HV armored cable that self charged itself beyond 1kV and had a large self capacitance.  I'm not saying these long term effects are the case here but to me the bus should discharge itself on power off.

I was not aware of electric absorption effects, but wouldn't a bleed resistor discharge that lingering voltage as well?

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It will be safe to work with from a humanoid standpoint after two minutes, but that still might damage electronics when working on the amp. I'd leave it disconnected for at least 10 minutes before working on it again or using a ~400R bleed resistor to shorten the PSU, which would result in a 1A current flow at 400V, which might be useful to be connected with a switch if you plan on working on the amp a lot. I think I have a 50W 32R resistor somewhere, which would already quicken the process from 50V down to zero. But oh boy if I leave it connected and then switch the amp on...

Heres a fun vid about capacitors. He has a shorting wire for storage on that thing or it would probably kill you if you touched it. This thing does over 80000A at 4000V.

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Kinda off topic, but I once hooked up some "jumper" cables between 12V car batteries, and I didn't know that the other car had an electrical short.  The  insulation started melting off and smoking within a few seconds.  Even if the electricity didn't have lethal potential, somebody could have been burned pretty bad.

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https://en.wikipedia.org/wiki/Dielectric_absorption

From my tests the absorption of electrolytics can approach 50% (much more than Wikipedia claims).  Solved via bleed resistors.  I had a college who liked to leave 5kV film capacitors the size of a thermos flask without bleed resistors attached on his desk and around the lab when I worked at the University.

On the subject of amps I see that people who have experience with the Lab clones are reporting better reliability with CVR amplifiers:

https://www.cvr-audio.com/product/101.html

 

 

 

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@SME And luckily we have breakers in our homes to prevent that from happening inside a wall. I hope..!

@kipman725 If the cap has been discharged, a simple shorting wire will do the trick even. Leaving them open is very dangerous.

I'm not sure what to think about that video. I have seen it before, but he almost seems to "fanboy" over those amps and I'm not convinced if what he is saying is genuine. At times he almost sounds like a salesperson. Minor detail, but he uses the term slew rate incorrectly. Slew rate is not the time it takes for the caps to charge back up.

Either way I'd of course be very interested to test the CVR amps. Looks don't tell the whole story. The Sanway also looks very well made internally, as do the Sinbosen amps, but they lack protection. Of course you won't care much about that in your HT but if your system goes silent on a gig you're in for trouble and I'd surely not want to risk that.
I know Sanway have changed their PSU and it might be better now. They added a fan where my blown transitors sat.

There are very few reviews or even general info about CVR.

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5 hours ago, kipman725 said:

https://en.wikipedia.org/wiki/Dielectric_absorptionFrom my tests the absorption of electrolytics can approach 50% (much more than Wikipedia claims).  Solved via bleed resistors.  I had a college who liked to leave 5kV film capacitors the size of a thermos flask without bleed resistors attached on his desk and around the lab when I worked at the University.

That 50% figure sounds impressive, but one question I'd have is how much charge does the capacitor effectively store at that voltage?  I assume it's probably a lot less than it stores when fully charged, but the Wiki article doesn't clarify this point.

I mean, I fairly routinely discharge tens of thousands of volts by simply touching things around the house, but this static electricity carries so little charge that it's essentially harmless to me (but not necessarily my equipment).

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11 hours ago, SME said:

That 50% figure sounds impressive, but one question I'd have is how much charge does the capacitor effectively store at that voltage?  I assume it's probably a lot less than it stores when fully charged, but the Wiki article doesn't clarify this point.

I mean, I fairly routinely discharge tens of thousands of volts by simply touching things around the house, but this static electricity carries so little charge that it's essentially harmless to me (but not necessarily my equipment).

The stored energy is the capacitance times voltage squared, so at 50% voltage the cap will be 25% charged. Double the voltage and you quadruple the ‚power‘, seems familiar, doesn‘t it! ;)

Static electricity doesn‘t kill you because your capacitance is very low, so you only store a minuscule amount of energy. 

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Is it really that simple?  My first instinct is that it's different because the energy storage mechanism is a bit different.

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1 hour ago, SME said:

Is it really that simple?  My first instinct is that it's different because the energy storage mechanism is a bit different.

https://en.wikipedia.org/wiki/Capacitor#Energy_stored_in_a_capacitor

You can see that the charge is proportional to C*V while the stored energy is proportional to C*V². If it wasn't "that simple", these formulas would not be that simple either ;)

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