I'm still fairly new to DIY audio and had a quick question (that may fall into "there are no stupid questions, but this one is stupid").
I have a TOA P-300D I am using as a sub amp, I do realize it is not the best amp but it was part of audio lot being sold by my local school. I do not think it has been serviced in quite some time but it is in operable condition. My question is will servicing the amp have a chance to improve the headroom of the amplifier. Within its limits it sounds fine but once it crosses over into clipping (even for brief transients, like a kick drum) the distortion really picks up.
Or is it simply just the wrong tool for the job? My guess is this is an amplifier more for a paging/intercom (very compressed signals or speech) in its design where it can provide its maximum RMS power forever, just don't ask for more. The user manual does show the power curves vs distortion and past its rated power there is a huge almost vertical spike in distortion. So maybe it is only operable for 1/4 of its RMS rating for musical applications.
I know some of the other more dramatic symptoms of an amp needing service but I'm not sure if this is one or not.
Any input will be greatly appreciated, thanks in advance!
Also incase it would help with the question, the amp is running a jbl 2242 in a 9 CF box tuned to 25hz, with B6 alignment (almost like a 4645C), but it is 1 CF larger so it would have the same footprint of the Altec 518 cabs (speakers that came with the amp). I know the 2242 are not the ultimate in VLF reproduction, but once again the price was right ($200 for an unopened box NOS pair)
I have a TOA P-300D I am using as a sub amp, I do realize it is not the best amp but it was part of audio lot being sold by my local school. I do not think it has been serviced in quite some time but it is in operable condition. My question is will servicing the amp have a chance to improve the headroom of the amplifier. Within its limits it sounds fine but once it crosses over into clipping (even for brief transients, like a kick drum) the distortion really picks up.
Or is it simply just the wrong tool for the job? My guess is this is an amplifier more for a paging/intercom (very compressed signals or speech) in its design where it can provide its maximum RMS power forever, just don't ask for more. The user manual does show the power curves vs distortion and past its rated power there is a huge almost vertical spike in distortion. So maybe it is only operable for 1/4 of its RMS rating for musical applications.
I know some of the other more dramatic symptoms of an amp needing service but I'm not sure if this is one or not.
Any input will be greatly appreciated, thanks in advance!
Also incase it would help with the question, the amp is running a jbl 2242 in a 9 CF box tuned to 25hz, with B6 alignment (almost like a 4645C), but it is 1 CF larger so it would have the same footprint of the Altec 518 cabs (speakers that came with the amp). I know the 2242 are not the ultimate in VLF reproduction, but once again the price was right ($200 for an unopened box NOS pair)
Since it's for a sub, you could try running it in bridged mono mode which will give you 960 watts into 8 ohms according to the data sheet. This is more in line with the power handling of the JBL 2242.
If it still clips in mono mode then there may be something wrong inside the amp. Also make sure the signal driving the amp (pre-amp) in not clipping.
If it still clips in mono mode then there may be something wrong inside the amp. Also make sure the signal driving the amp (pre-amp) in not clipping.
I did run it in mono and it did provide a better output, I was trying to stay in stereo mode due to having 2 subs running on the same amp. I will probably need to go through the signal chain again (really wish I paid the extra for the HD versions of miniDSP 2x4) I have a clean box pro running to the amp and my signal could be too hot. I also have a PV-8.5C laying around, I might do a quick comparison between the two and see the performance. I think it might go back to just wrong tool for the job, where the musical power and rms power of the amp is probably essentially the same.
This is a 300W per channel amplifier, so if it is badly clipping, you are demanding way too much of it.
I do realize that it is a 300W amplifier, but depending on the design of the amp, you can get 300 watts for continuous power and an allowance peaks (lets say +6 db). But there seems to be no headroom in this amp. I think it is by designed like this for its purpose. Or maybe there are bad caps that are not storing excess energy for peaks. That is why I was asking if lack of head room could be a symptom of getting it serviced. If it isn't, I was just planning on saving that money for a new amp. But with being a class AB design I was hoping for a little headroom from the amp.
So right now its more like a 75/50 watt RMS amp for sub use at the moment with 300 watts provided for the peaks. Then, yes I am asking too much for it.
So right now its more like a 75/50 watt RMS amp for sub use at the moment with 300 watts provided for the peaks. Then, yes I am asking too much for it.
You can measure the power supply voltage to estimate the "peak" power, but +6dB on peaks would be very unusual.
If the power supply voltage rises 10% for brief transients compared to rated rms power, that would be about the most
that you could expect. That would be more like 360W. Any greater difference would indicate a poorly designed power supply.
If the power supply voltage rises 10% for brief transients compared to rated rms power, that would be about the most
that you could expect. That would be more like 360W. Any greater difference would indicate a poorly designed power supply.
Thanks! That's good to know!
I guess I was expecting too much from it. I thought with the new power rating of most new (class D especially) amps where they state some crazy watt number that sometimes exceeds the power that can be supplied from the outlet that some of the older amps with RMS ratings had a bit more reserves for transients. I was wrong.
I guess I was expecting too much from it. I thought with the new power rating of most new (class D especially) amps where they state some crazy watt number that sometimes exceeds the power that can be supplied from the outlet that some of the older amps with RMS ratings had a bit more reserves for transients. I was wrong.
which version of the MINI DSP do you have? The original only outputs 900millivols on a good day at clipping. I have one and it clips at 880millivolts output with an external regulated 6Volt DC power supply. 5 volt ps is recommended. Your amplifier according to the pdf spec sheet says
An input of +4dB (1.23V), ±0.5dB, produces an output of 300 watts into 8-ohm, INPUT ATTENUTOR set for maximum level
you will never clip the power amp if you have an older version of the MINI DSP 2x4. I had to increase the gain on my diy power amps and it's louder but the mini dsp still clips first.
An input of +4dB (1.23V), ±0.5dB, produces an output of 300 watts into 8-ohm, INPUT ATTENUTOR set for maximum level
you will never clip the power amp if you have an older version of the MINI DSP 2x4. I had to increase the gain on my diy power amps and it's louder but the mini dsp still clips first.
I have the .9 V version. that is why I have the clean box pro in the signal chain. Right now I have a sony TA-E1000ESD (1V out iirc) to the miniDSP and then to the Art clean box pro to boost the .9V out pf the miniDSP closer to +4db
The main speakers are Altec 817a (107.5 db/m) with 291s on mrii594 (108 db/m), running with those high efficiencies the art clean box was pretty much a must. But with that there is another item in the gain structure to check and it might be sending a clipped signal to amp. Plus the boost from the B6 could be wrecking havoc on the gain structure.
The main speakers are Altec 817a (107.5 db/m) with 291s on mrii594 (108 db/m), running with those high efficiencies the art clean box was pretty much a must. But with that there is another item in the gain structure to check and it might be sending a clipped signal to amp. Plus the boost from the B6 could be wrecking havoc on the gain structure.
you are going to have to scope out your signal chain to see where its clipping. Are you using too much bass boost. Try cutting off everything below 35 Hz.
re-reading your original post have you built 2 sub cabinets with 1 JBL woofer in each to bring up the bass to match the 817a cabinets. You may need a few more sub cabinets.
re-reading your original post have you built 2 sub cabinets with 1 JBL woofer in each to bring up the bass to match the 817a cabinets. You may need a few more sub cabinets.
No, you can NOT.
If you expect 300W output and want +6dB "allowance"/headroom, you need a 1200W RMS amp.
Math 101
Not at 25Hz, no way.
And if you heavily boost them to reach that low, consider this: for every 1 dB you electronically boost, you are losing 1 dB headroom, because you are pulling that output out of thin air, the speakers are definitely not giving it on their own.
Your amp is not broken, you simply are asking too much and it shows.
Yeah right now the boost is to provide "level-ish" response for the tuning. Tuning more towards the 2242s intended use of a PA speaker around 40hz may have been the way to go but right now I'm with a 25 hz tuned box. I thought since the 4645c was a proven design I would replicate that. I don't listen to too much music that has plenty of sub frequencies, so when they play the signal could be clipped before it reaches the amp.
Instead of extra subs, I think I'll go more toward double/quadrupling the power as the cheaper option with inuke or xls amps. I've heard the 2242 on macrotech-2400s, so I have some reference on what they are capable of.
Yes I realize now that most amps max allowance are at RMS values. Once again, I wasn't sure because of the way amplifiers are rated now as to previous ratings and was also mistaken that class AB amps had more of a tolerance/reserve from RMS ratings than class D.
The altecs are 107.5 db/m, 2x515-16g loaded in them, they are doing mid-bass duty, I'm not asking the altecs to reach 25 hz (it would require like 35 db of padding), I'm using the JBLs to fill in the bottom octaves.
Instead of extra subs, I think I'll go more toward double/quadrupling the power as the cheaper option with inuke or xls amps. I've heard the 2242 on macrotech-2400s, so I have some reference on what they are capable of.
Yes I realize now that most amps max allowance are at RMS values. Once again, I wasn't sure because of the way amplifiers are rated now as to previous ratings and was also mistaken that class AB amps had more of a tolerance/reserve from RMS ratings than class D.
The altecs are 107.5 db/m, 2x515-16g loaded in them, they are doing mid-bass duty, I'm not asking the altecs to reach 25 hz (it would require like 35 db of padding), I'm using the JBLs to fill in the bottom octaves.
Cheaper? Sure, today power is a cheap and abbundant commodity.
But you´ll run out of excursion, there is only so much air those pistons can push and no electrical power can solve that.
You can´t escape the physical fact that at low frequencies you need to move air, lots of it.