Ok to run IPR-1600 without speakers connected?

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check12
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Ok to run IPR-1600 without speakers connected?

Post by check12 » Sun Jul 17, 2022 12:47 pm

Hi, I can't find a definitive answer to this.

Some Class D designs require permanent connection to a speaker load.

Can the IPR-1600 and other Peavey Class D amplifiers be run safely without any load connected and with just 1x channel being used and the other unconnected?

check12
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Re: Ok to run IPR-1600 without speakers connected?

Post by check12 » Wed Jul 20, 2022 7:49 pm

I've emailed Peavey .... no answer.

Some say it can damage the amp to switch on without speakers (load) connected.

Some say they can be treated like most other solid state amplifiers.

Nothing in the manual but it does seem to give spec. for 1x speaker attached which would suggest that it would be ok to turn on with no load attached.

Anybody know for sure?

jim h
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Re: Ok to run IPR-1600 without speakers connected?

Post by jim h » Thu Jul 21, 2022 8:42 am

Under normal conditions it is safe to run class d amplifiers with no load.

However, there is one situation where it can be dangerous to the amplifier. If there is no load and the signal is over-driven to the point of square waves, there can be damage done to part of the output filter.

check12
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Re: Ok to run IPR-1600 without speakers connected?

Post by check12 » Thu Jul 21, 2022 4:15 pm

jim h wrote:
Thu Jul 21, 2022 8:42 am
Under normal conditions it is safe to run class d amplifiers with no load.
Do you mean pro-audio power amps with that comment or ALL Class D amps?

There are definitely Class D amplifiers that NEED a load attached or the amplifier IC's can be damaged e.g. TPA3116, TPA3130 etc.

It's just these pro-audio power amps I'm wondering about ... are you commenting from an electronic knowledge of these amps or practical experience e.g. you've turned them on many times with no load attached and nothing bad has happened?

I'm still getting about a 50/50 split of opinion ... if it's safe to turn these on with no load then what in the design makes it safe because it looks very similar in schematic to other amps that are recommended not to be used without load?

This post is not a criticism I'm just seeking a better understanding of the situation.

jim h
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Re: Ok to run IPR-1600 without speakers connected?

Post by jim h » Fri Jul 22, 2022 9:14 am

I've been designing products at Peavey with class d amps for the last 20 years...including one of the IC's you mentioned. TPA3116

I've run every one of them on my bench with no load with no problems. The problem with unloaded class d amps is the output filter (LC) gain at 50kHz or so. When that tank is excited, there is a great amount of gain at that point. The excitement happens when you drive it with a square wave. The signal/load levels this creates is way too much power for the components used in the output section and can damage them. We've found some workarounds for this situation in newer designs, but it's still not a good idea to over-drive an unloaded channel.

Why not just turn down the level of the unloaded channel?

check12
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Re: Ok to run IPR-1600 without speakers connected?

Post by check12 » Fri Jul 22, 2022 5:38 pm

jim h wrote:
Fri Jul 22, 2022 9:14 am
I've been designing products at Peavey with class d amps for the last 20 years...including one of the IC's you mentioned. TPA3116
Thanks for getting back it would've saved time if you'd said that in 1st post.
jim h wrote:
Fri Jul 22, 2022 9:14 am
I've run every one of them on my bench with no load with no problems. The problem with unloaded class d amps is the output filter (LC) gain at 50kHz or so. When that tank is excited, there is a great amount of gain at that point. The excitement happens when you drive it with a square wave. The signal/load levels this creates is way too much power for the components used in the output section and can damage them. We've found some workarounds for this situation in newer designs, but it's still not a good idea to over-drive an unloaded channel.
That's confusing? ... I'm not overdriving anything ... but there is always square wave reaching the output filter albeit @ much higher frequency from pin13 (VS) ... so when does 50kHz PWM happen? ... is there less gain at the higher frequency so it's ok to have no load?
jim h wrote:
Fri Jul 22, 2022 9:14 am
Why not just turn down the level of the unloaded channel?
??? I haven't mentioned turning up either of the channels when unloaded ??? ... talk about a "loaded question" LOL ... :D

Are you one of the designers then of the IPR-1600?

If so I've noticed the amp ic's (30418651) run pretty warm at almost 60c? (no input signal, unloaded with full attenuation & warmer 65c when loaded with 8ohms and driven with typical unclipped music to the point just before the DDT led's light) on my thermal imager (which tests accurately compared to the other contact probes I've got here). I'd include images but I can't attach them.

Is that the normal temp range for the amp IC's? ...

I'm even more confused now ... how do you stop square wave getting to the output filters when the amp is switched on?

It's not clear to me whether you are talking about clipped input signal (into the amp) or square wave into the output LC filter when you talk about overdriving the output filter with square wave?

Stryker57
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Re: Ok to run IPR-1600 without speakers connected?

Post by Stryker57 » Fri Jul 22, 2022 8:29 pm

it dont look like it would have saved any time if he said that in the 1st post because you continue on to ask question on his answers anyway.

just what do you want to know? you ask a really good question is it ok to run an ipr 1600 without a speaker.
he answers ,"Under normal conditions it is safe to run class d amplifiers with no load."

he then goes further and answers "However, there is one situation where it can be dangerous to the amplifier. If there is no load and the signal is over-driven to the point of square waves, there can be damage done to part of the output filter."

but thats not good enough so you now decide to now include "Do you mean pro-audio power amps with that comment or ALL Class D amps?"

YOU asked about a specific amp and model and now want an answer on all class d amps.

LOL its ok if you are wanting to learn, but this time you are talking to an expert in Jim h,
you'll learn alot, just stay on point
dont throw in a bunch of what ifs and whys .... go through them slowly, so to limit confusion,

check12
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Re: Ok to run IPR-1600 without speakers connected?

Post by check12 » Fri Jul 22, 2022 9:01 pm

Stryker57 wrote:
Fri Jul 22, 2022 8:29 pm
it dont look like it would have saved any time if he said that in the 1st post because you continue on to ask question on his answers anyway.

just what do you want to know? you ask a really good question is it ok to run an ipr 1600 without a speaker.
he answers ,"Under normal conditions it is safe to run class d amplifiers with no load."

he then goes further and answers "However, there is one situation where it can be dangerous to the amplifier. If there is no load and the signal is over-driven to the point of square waves, there can be damage done to part of the output filter."

but thats not good enough so you now decide to now include "Do you mean pro-audio power amps with that comment or ALL Class D amps?"

YOU asked about a specific amp and model and now want an answer on all class d amps.

LOL its ok if you are wanting to learn, but this time you are talking to an expert in Jim h,
you'll learn alot, just stay on point
dont throw in a bunch of what ifs and whys .... go through them slowly, so to limit confusion,
This is a forum, not a fan club ... I don't understand, you've just picked out certain things that I've said?

I'm looking for more detail because I didn't know Jim was a design engineer and as such I'm sure he'll understand my interest in detail.

What have I done wrong? Do you inspect all his posts like this? :roll:

Stryker57
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Re: Ok to run IPR-1600 without speakers connected?

Post by Stryker57 » Sat Jul 23, 2022 12:21 pm

lol nope, i dont inspect anything just didnt care for your tone of

"Thanks for getting back it would've saved time if you'd said that in 1st post."

just saying if you wish to learn,
stay on issue dont bounce around,
so to keep things clearer.

sorry if i hurt your feeling,
after reading that ...i figured you had tough enough skin to handle it.,
:D

jim h
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Re: Ok to run IPR-1600 without speakers connected?

Post by jim h » Sun Jul 24, 2022 8:54 am

You're right in that the amplifier is constantly putting out rail to rail square waves...however, they are at 400kHz. Not in the range of the LC tank circuit, where the extra gain is located.

The 50kHz comes when you apply a signal that is grossly overdriven or clipped. Once a signal flat tops, it generates harmonics. Some of these harmonics will fall in that 50kHz range where the gain is applied and the next thing you know, poof.


"??? I haven't mentioned turning up either of the channels when unloaded ??? ... talk about a "loaded question" LOL ... :D"

The channel would have to be turned up to cause a problem...so my assumption is there is a channel turned up...so why not just turn it down?


That is a normal temperature range for the IC...as I said earlier, they are always working, whether there is audio or not.

check12
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Re: Ok to run IPR-1600 without speakers connected?

Post by check12 » Sun Jul 24, 2022 7:22 pm

Hi Thanks for reply JimH ... first I'd just like to say that I've only just joined this forum and have no idea which members are "punters" and which are experienced Peavey staff, there was nothing to show you are Peavey staff so I was trying to confirm the knowledge behind your initial comments. You could have been somebody who had no idea what they were talking about.

I've got no idea what the other guy wants to achieve with his strange comments, I went into more detail when I found out you were a designer. If I've offended you by not realising who you were then I'd like you to know that wasn't intended ... but that would seem as ridiculous to me as the way this other attention seeking guy is going on.
jim h wrote:
Sun Jul 24, 2022 8:54 am
You're right in that the amplifier is constantly putting out rail to rail square waves...however, they are at 400kHz. Not in the range of the LC tank circuit, where the extra gain is located.

The 50kHz comes when you apply a signal that is grossly overdriven or clipped. Once a signal flat tops, it generates harmonics. Some of these harmonics will fall in that 50kHz range where the gain is applied and the next thing you know, poof.
Yes ok I see now you meant clipped amp input signal harmonics exciting the filter resonant frequency ... the detailed answer is much more interesting and valuable to me. I've been doing pro sound since the 80's I would not be sending clipped signal anywhere :)

To avoid confusion ... I am a 35+ year sound engineer/guitar tech. ... I also studied Music Technology & Electronics in the early 90's but put the electronics aside till about 5 years ago when I started getting asked to do electronic repairs again locally and this has increased since. This is only the 3rd Class D power amp I've seen for repair (about here it's still mainly AB, G ,H) but there will be a lot more soon as the warranties run out. I was given this amp as a gift to work on so decided to learn as much as I could from it so I've been studying it in spare time for the past few weeks. It came with the SMPS blown & the gate driver IC and fets on one side of the amp blown, it's all fixed now and I'm a lot more confident about fixing future Class D but I was left with just a couple of unanswered questions which I've asked here. I've got the basics but still got a lot of little details about Class D to get straight.


*****"??? I haven't mentioned turning up either of the channels when unloaded ??? ... talk about a "loaded question" LOL ... :D"******

That was me trying to be funny ... not meant to offend.
jim h wrote:
Sun Jul 24, 2022 8:54 am
The channel would have to be turned up to cause a problem...so my assumption is there is a channel turned up...so why not just turn it down?
I'm still mixed up as to where this has come from I've never mentioned any problem ... the amp is working fine ... I just wondered about turning on with no load attached as the manual would suggest is ok and then the separate gate driver IC temperature question was asked when I found out you are a Class D designer.
jim h wrote:
Sun Jul 24, 2022 8:54 am
That is a normal temperature range for the IC...as I said earlier, they are always working, whether there is audio or not.
Thanks for that, yes I understand the switching is constant but it has been really hard to confirm the temperature range. I even wrote to Infineon who gave a very cryptic reply, didn't answer the temperature question but suggested that I reduce VCC to 12V.

One other thing you could maybe give advice on is ... 1st time power up after replacing output fets .... for other amp classes I have a variac and dim bulb limiter but with class D using SMPS the variac is pointless so I've been doing initial power up on just the dim bulb to spot any obvious shorts, then if ok switching to full mains voltage. This was another point where I had been wondering if it would be best to have a non-inductive load attached or not.

Is there any better way to do this?

jim h
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Re: Ok to run IPR-1600 without speakers connected?

Post by jim h » Mon Jul 25, 2022 8:37 am

check12 wrote:
Sun Jul 24, 2022 7:22 pm
Yes ok I see now you meant clipped amp input signal harmonics exciting the filter resonant frequency ... the detailed answer is much more interesting and valuable to me. I've been doing pro sound since the 80's I would not be sending clipped signal anywhere :)
I'm sure you wouldn't, I didn't think it was fair to say it is perfectly safe when I know of a condition that can cause problems.

check12 wrote:
Sun Jul 24, 2022 7:22 pm
I'm still mixed up as to where this has come from I've never mentioned any problem ... the amp is working fine ... I just wondered about turning on with no load attached as the manual would suggest is ok and then the separate gate driver IC temperature question was asked when I found out you are a Class D designer.
Maybe I misunderstood your initial question, were you asking about just turning it on or actually sending signal to it?

check12 wrote:
Sun Jul 24, 2022 7:22 pm
One other thing you could maybe give advice on is ... 1st time power up after replacing output fets .... for other amp classes I have a variac and dim bulb limiter but with class D using SMPS the variac is pointless so I've been doing initial power up on just the dim bulb to spot any obvious shorts, then if ok switching to full mains voltage. This was another point where I had been wondering if it would be best to have a non-inductive load attached or not.

Is there any better way to do this?
Yes, please email me through the forum...I have something that might help.
Jim

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