Hi Samuel,
your report on sound quality difference changing from one output pair to three output pair is valuable.
It may be that single pairs do perform better in the quality stakes or it could be that the three devices have been crippled by poor selection of operating parameters.
I wonder if the three pair set-up is being affected by device matching?
Did you match some device characteristics?
Which did you match?
Which did you ignore?
What tolerance of macthing did you accept?
It might not get us any closer to a conclusion, but it will help put your report in context.
As an aside,
I am a believer in bi-amplification (not active speakers - Yet!).
Would the multiple output device amplifier suit driving the bass half of the crossover, another single pair amplifier driving the mid and/or the treble part of the crossover solve your problem?
Then you get that strong deep bass and nice delicate treble.
your report on sound quality difference changing from one output pair to three output pair is valuable.
It may be that single pairs do perform better in the quality stakes or it could be that the three devices have been crippled by poor selection of operating parameters.
I wonder if the three pair set-up is being affected by device matching?
Did you match some device characteristics?
Which did you match?
Which did you ignore?
What tolerance of macthing did you accept?
It might not get us any closer to a conclusion, but it will help put your report in context.
As an aside,
I am a believer in bi-amplification (not active speakers - Yet!).
Would the multiple output device amplifier suit driving the bass half of the crossover, another single pair amplifier driving the mid and/or the treble part of the crossover solve your problem?
Then you get that strong deep bass and nice delicate treble.
Samuel Jayaraj said:
It is quite possible that you have a grounding issue (or something similar) when two modules are commoned to the one ground. My stereo unit performs perfectly. Are you able to post an accurate drawing or photo of the wiring arrangement you used, i.e, power supply, ground speaker and input connections. Wiring and layout can do wierd things and a connection just a few centimetres away from the ideal location can increase distortion many times, particularly when more than one module is connected.
Cheers
Hi !
I see you are on line .What hapened with schematic of
LITTLE QUASI Amp.
Regards zeoN_Rider
I see you are on line .What hapened with schematic of
LITTLE QUASI Amp.
Regards zeoN_Rider
Re: Hi !
Well I suppose I better get cracking (busy)......
By the way how are your amps going? How many have you built?
Cheers
Q
zeonrider said:
Well I suppose I better get cracking (busy)......
By the way how are your amps going? How many have you built?
Cheers
Q
Hi Big"Q"
I'll made 7pcs . stereo amps.( with 6 Fets per Ch. ).
Nice power , nice sound, Good for PA aplication, but only with FAN cooling.First off all, thi is wery cheap amp. for made.
About shematic I, like to have full documentacion of all what I built.
Regards zeoN_Rider
I'll made 7pcs . stereo amps.( with 6 Fets per Ch. ).
Nice power , nice sound, Good for PA aplication, but only with FAN cooling.First off all, thi is wery cheap amp. for made.
About shematic I, like to have full documentacion of all what I built.
Regards zeoN_Rider
If i want to make this amp just with one pair o mosfet's and +/-40V ... for 65W , what mosfet should i use : IRFP450(460) or IRF840
@AndrewT
,😀 ...it seems you are right.
But do you think 540/9540 don't work.....?
If the gate (p channel.)will be on the emiter MJE350(pnp)...I think it work.
Also switch R28,R30 into source (S) of mosfet.
,😀 ...it seems you are right.But do you think 540/9540 don't work.....?
If the gate (p channel.)will be on the emiter MJE350(pnp)...I think it work.
Also switch R28,R30 into source (S) of mosfet.
Hi,
I can't answer for the designer on changing the topology from quasi to complementary.
If you don't have access to the knowledge then don't.
BTW,
is 9540 a complement (good match of parameters) to 540?
Based on other bad matches with vertical FETs, I suspect it isn't even close.
I can't answer for the designer on changing the topology from quasi to complementary.
If you don't have access to the knowledge then don't.
BTW,
is 9540 a complement (good match of parameters) to 540?
Based on other bad matches with vertical FETs, I suspect it isn't even close.
quasi said:
Marus, Quasi,
I am pressed for time until at least Friday evening. This research will take a bit of time. I have not had the time the last couple days. If Friday is too busy for me, I will be able to do it Saturday evening EST (-05:00 GMT) if that is ok with you gents.
Samuel Jayaraj said:
Samuel,
I find your findings for the single pair of IRFP460 vs IRFP450 most interesting. It appears for some reason the IRFP460 was superior to the IRFP450 as single pair. This seems interesting as the IRFP460 has a higher Ciss and slower Ton/off Tr/f times compared to the IRFP450. I have a number of APT4025BNs that in many respects I like to use in single pair configuration. I have some IRFP450 that will enable me to test in single pair as well. I think a store downtown has some IRFP460 or IRFP461's. Maybe I should pick up a couple pairs to do a comparison.
In my opinion, power handling aside, I think the best choice is the IRF640N. If you have access to a pair of those it might be worth a go to try a single pair of IRF640's and compare. If you do not, but have a pair of IRF540s or IRF540Ns that might be interesting to try as well.
I assume your results were from listening tests of music you are familar with? I know some may say not possible, but did you let either of the IRFP450s or IRFP460s burn in for any time? I know many say that sort of phenomena does not exist, but I had a recent first hand experience where it clearly did make a difference over several hours of amp use before the sound settled in to its very nice final form. Some of the time leading up to was a bit up and down. This phenomena may not strickly be the semi-conductors, but still a actual experience on whole.
marus said:
Marus,
Vdss Id/25C Id/100C Pd Derate Pd/70C Pd/60C Ciss Td(on) Tr Td(off) Tf
IRF450 500 14.0 8.7 180 1.5 112.5 127.5 2400 17 47 92 44
IRF840 500 8.0 5.1 125 1.0 80.0 90.0 1300 14 23 49 20
I would say use the IRFP450, but be careful not to use speakers/pasive crossover below impediance of 7 ohms.
AndrewT said:
Andrew,
Vdss Id/25C Id/100C Pd Derate Pd/70C Pd/60C Ciss Td(on) Tr Td(off) Tf
IRF540 100 28.0 20.0 150 1.0 105.0 115.0 1700 11 44 53 43
I would say the IRF540 would only be able to handle 55W for a >= 8 ohm rated impedance. To handle 4 ohms you will need two pairs of IRF540s/IRF540Ns.
Regards,
John L. Males
Willowdale, Ontario
Canada
17 January 2007 17:47
17 January 2007 17:49 Typo correction
felixx said:@AndrewT
But do you think 540/9540 don't work.....?
If the gate (p channel.)will be on the emiter MJE350(pnp)...I think it work.
Also switch R28,R30 into source (S) of mosfet.
Yes this would work, but no benefit would be gained. Indeed it could be better to place the P-channel FET on the positive rail and gain full rail to rail swing.
AndrewT is quite right, when you look at the P-channel specifications and charts there are quite a few differences between seemingly complementary devices.
Anyway, the amp was designed to make use of many N-channel FETs I have (or had) in my possesion. Similarly the reason for the small version is to take advantage of commonly available TO220 N channel FETs that many DIY'ers seem to have laying around without the need to find complementary P-channel devices.
Cheers
Q
Hi Key,
I assumed that with +-40Vrail the proposed speaker load was 8ohm and the target was 65W. 540 meets that (just).
If the rails are reduced (~+-25Vdc) to achieve 64W into 4ohm speakers then the 540 is still suitable with just ONE PAIR.
My data shows them to be 150W 28A 175degC 0.08ohm devices, is your data the same?
I assumed that with +-40Vrail the proposed speaker load was 8ohm and the target was 65W. 540 meets that (just).
If the rails are reduced (~+-25Vdc) to achieve 64W into 4ohm speakers then the 540 is still suitable with just ONE PAIR.
My data shows them to be 150W 28A 175degC 0.08ohm devices, is your data the same?
Hi Andrew,
Yes, you are correct my comments were as the original question posed for IRF540 at +-40VDC rails. I was not thinking at time of my reply as I was very tired to realize +-40V rails might exceed the 65W power requirement. I think the +-40VDC rails are still the required rail voltage as the 65W is likely referring to 65W RMS. This would translate into 130W Peak, which before losses would be about 32V. It would seem that there is an assumption of about a 8VDC loss which may be a bit too optimistic. I think maybe it needs to be clarified if marus meant 65W peak or 65W RMS.
I do not have the time to look at the datasheet and so I am not sure of the IRF540 Rds off hand, but all the other specs you listed were part of the specs I posted in my reply. Sadly the forum software takes out all the spacing I had between the headings and spec values that it makes it much harder to see. I have these specs in a text file as part of the parts list so I have such information quick and handy and some calculated values as Pd at 70C and 60C.
I am sure your calculation at ~25VDc rails and conclusions for single pair are correct. That said if the intent is for the 65W rating as as peak power then your calculations I am sure are on money. This would of course mean the RMS power would be about 33W RMS for a rail of about 25VDC.
I need to run, shower and get out door for day and I have some important matters to do in next day or two, so I may not be able to reply for a day or two to any followup to the discussion as well as my outstanding research "job" for quasi.
Regards,
John L. Males
Willowdale, Ontario
Canada
18 January 2007 05:19
18 January 2007 05:21 Typo corrections
Yes, you are correct my comments were as the original question posed for IRF540 at +-40VDC rails. I was not thinking at time of my reply as I was very tired to realize +-40V rails might exceed the 65W power requirement. I think the +-40VDC rails are still the required rail voltage as the 65W is likely referring to 65W RMS. This would translate into 130W Peak, which before losses would be about 32V. It would seem that there is an assumption of about a 8VDC loss which may be a bit too optimistic. I think maybe it needs to be clarified if marus meant 65W peak or 65W RMS.
I do not have the time to look at the datasheet and so I am not sure of the IRF540 Rds off hand, but all the other specs you listed were part of the specs I posted in my reply. Sadly the forum software takes out all the spacing I had between the headings and spec values that it makes it much harder to see. I have these specs in a text file as part of the parts list so I have such information quick and handy and some calculated values as Pd at 70C and 60C.
I am sure your calculation at ~25VDc rails and conclusions for single pair are correct. That said if the intent is for the 65W rating as as peak power then your calculations I am sure are on money. This would of course mean the RMS power would be about 33W RMS for a rail of about 25VDC.
I need to run, shower and get out door for day and I have some important matters to do in next day or two, so I may not be able to reply for a day or two to any followup to the discussion as well as my outstanding research "job" for quasi.
Regards,
John L. Males
Willowdale, Ontario
Canada
18 January 2007 05:19
18 January 2007 05:21 Typo corrections
Hi Key,
I would never write ?W (with or without peak) when I mean ?Wpk.
In fact that even that would, in my view, be confusing and I would tend towards using ?Vpk to avoid the ambiguity. Similarly I write Ipk when I mean that.
I would never write ?W (with or without peak) when I mean ?Wpk.
In fact that even that would, in my view, be confusing and I would tend towards using ?Vpk to avoid the ambiguity. Similarly I write Ipk when I mean that.
Hi Quasi,
funny co-incidence.
I just happen to have 3pair apt30 in my Bensen spreadsheet.
It shows 300W into 4ohm @ 60degree phase angle, Tc<=53degC and it stays inside the DC SOAR.
The apt30 were added when Workhorse? was advocating their use some months ago.
Do you want the numbers for 100mS? since this fits your reliability criteria more closely.
funny co-incidence.
I just happen to have 3pair apt30 in my Bensen spreadsheet.
It shows 300W into 4ohm @ 60degree phase angle, Tc<=53degC and it stays inside the DC SOAR.
The apt30 were added when Workhorse? was advocating their use some months ago.
Do you want the numbers for 100mS? since this fits your reliability criteria more closely.
I just use the Quasi Power Matrix when i said 65W....
I think it's about TRUE RMS POWER those watts
This is what i will do : 😀
I will make a test PCB just with the low power section ... without power transistors and i'll try all transitors ( mosfet's and bipolars) to find one who works better. (single pair!)