Hi Jack,
First, I forgot to thank you for offering your "table scraps" to us hacks before tossing them in the bin
. Thanx also for posting the prints so quickly. As soon as my replacement credit card arrives (about a week) I will be ordering some of those 250W modules to play with.
I don't suppose you know the rail voltages? Trying to do a little prelim reverse engineering. I'm assuming something on the order of +/- 80V ?
FYI for others considering this amp:
These amps appear to be pretty long in the tooth, as such, almost all of the semi's are obsolete numbers. The good news however, is that http://www.electronix.com still carries everything except the BF422/423 semis in the protection circuit (the only ones that aren't obsolete), and the output pairs 2SA1302/2SC3281 have a direct replacement in the 2SA1943/2SC5200.
Casey
First, I forgot to thank you for offering your "table scraps" to us hacks before tossing them in the bin
. Thanx also for posting the prints so quickly. As soon as my replacement credit card arrives (about a week) I will be ordering some of those 250W modules to play with.I don't suppose you know the rail voltages? Trying to do a little prelim reverse engineering. I'm assuming something on the order of +/- 80V ?
FYI for others considering this amp:
These amps appear to be pretty long in the tooth, as such, almost all of the semi's are obsolete numbers. The good news however, is that http://www.electronix.com still carries everything except the BF422/423 semis in the protection circuit (the only ones that aren't obsolete), and the output pairs 2SA1302/2SC3281 have a direct replacement in the 2SA1943/2SC5200.
Casey
Hi guys,
The NPT-11-075-2 and the VT-3 amp is exactly what I am looking for to build my first twin box sub system, but I have no idea how to build a EQ by using a rectifier in a filter cap, can anyone help me here ?
My inner volume of each of the box is about 1.68 cubic ft, should I make these a sealed or vented system ?
Thanks.
Dave Chang
The NPT-11-075-2 and the VT-3 amp is exactly what I am looking for to build my first twin box sub system, but I have no idea how to build a EQ by using a rectifier in a filter cap, can anyone help me here ?
My inner volume of each of the box is about 1.68 cubic ft, should I make these a sealed or vented system ?
Thanks.
Dave Chang
Mr. Chang
With 1.68 cu ft per driver, you definitely need to keep the enclosure sealed.
You need to build a 2nd order HP filter (12dB/octave) with a corner frequency of 23Hz and a Q of 2.3. This filter can be placed inside the VT3 amplifier or in some other signal processor upstream.
The 075 driver in a 42l enclosure, with the filter from above will give you a -3dB frequency of 23Hz.
With 1.68 cu ft per driver, you definitely need to keep the enclosure sealed.
You need to build a 2nd order HP filter (12dB/octave) with a corner frequency of 23Hz and a Q of 2.3. This filter can be placed inside the VT3 amplifier or in some other signal processor upstream.
The 075 driver in a 42l enclosure, with the filter from above will give you a -3dB frequency of 23Hz.
Hi, Jack
Thank you for your fast responce and info, all sounded great what you sugested, eventhgough i have no idea how to build that filter. I figure some body out there may have something already buit, or will build it for me.
Please also let me know, how can order a pair of the drivers and the VT-3 from you, is it easier for you if i send you a check ?
If you can point me to the direction as how to build this filter,( such as components that I need, and where to get them, or if you can build this filter into the VT-3 and charge me for it.)
I am glad that SY recommented me to this forum and look into your drivers and amps. Thanks SY.
Can't wait to bild these subs...
Dave Chang
PS. If anyone can share any info how to build the filter Jack mentioned, It would be greatly appreciated, maybe I can return the favor by building a custom box in exchange, I work in a high end cabinet mfg, and have unlited free cut-off MDF and other materials.
Thanks guys.
Thank you for your fast responce and info, all sounded great what you sugested, eventhgough i have no idea how to build that filter. I figure some body out there may have something already buit, or will build it for me.
Please also let me know, how can order a pair of the drivers and the VT-3 from you, is it easier for you if i send you a check ?
If you can point me to the direction as how to build this filter,( such as components that I need, and where to get them, or if you can build this filter into the VT-3 and charge me for it.)
I am glad that SY recommented me to this forum and look into your drivers and amps. Thanks SY.
Can't wait to bild these subs...
Dave Chang
PS. If anyone can share any info how to build the filter Jack mentioned, It would be greatly appreciated, maybe I can return the favor by building a custom box in exchange, I work in a high end cabinet mfg, and have unlited free cut-off MDF and other materials.
Thanks guys.
DAVE CC said:
Hi Dave. Scroll to the bottom of Jack's sale page: http://home.comcast.net/~jhidley/ for terms and ordering information.
The 080 was used in the VT3, VR3 and VC3 as a midrange. The 081 was used in the VS2.4 and VT2.4 as a woofer/midrange. I'm 99% sure that they are the exact same driver. We probably gave the 080 a different part number, because we QCed it to a tighter standard. I'm trying to confirm the difference now, but this is from two owners ago.
I received my VT3 amp yesterday. I rewired the RCA jack, hooked up the output wires to the binding posts, and soldered the jumper wire in place. When I turned on the amp, I measured 270mV of DC on the output. I verified with an old speaker and there is in fact enough DC to cause issues. I tried hooking up a source, a source with a low-pass filter, and a short at the input, but I still measured (and saw in the speaker) approximately 270mV of DC. It seems to be amplifying correctly, as I saw higher amplitude AC when playing the source, but the DC offset is still there. I tried disconnecting the jumper and had the same results.
Would adjusting the V+ or V- offset trimmers (as seen on http://home.comcast.net/~jhidley/SubTwoi_Amplifier.pdf) allow me to reduce this offset, or is my amp damaged?
Would adjusting the V+ or V- offset trimmers (as seen on http://home.comcast.net/~jhidley/SubTwoi_Amplifier.pdf) allow me to reduce this offset, or is my amp damaged?
An unconventional 3-way
Hi all:
I've designed the basics of an unconventional 3 way using the 5.25" peerless and the 10" Foster (the $20 unit). This is going to my not-for-profit day job, for use to be built by the students, and for use with some of their new media gear in the classrooms. We're building a 3 way with these two drivers and a tang band W2-803SM 2" Driver. The idea is for pretty decent power handling through the mid/tweet, so we're using the 2" and crossing over low. Ragged 10k-20k response but we can live with that. Another nice feature of the 2" is the small frame- much smaller than most 1" domes, giving us good driver-driver spacing for better point source behavior.
We're figuring on first order at 1.2k and 2nd order at 300Hz, which should keep the cones all pretty much in pistonic mode up until the 2" breaks up. The only real limitation is the power handling down low- the 10"s would max out with some serious movie bass, but if they're playing loud enough to max out two 10" subs.... something's wrong
These will also be used as stage monitors and other types of usage in the school.
A triangular cabinet is being planned, I may post some drawings and other info if people are interested later on. These are made to be used up against walls (or the floor), so there's no baffle step compensation. Sub will be somewhere between max flat and .55 Qtc, sealed.
Hi all:
I've designed the basics of an unconventional 3 way using the 5.25" peerless and the 10" Foster (the $20 unit). This is going to my not-for-profit day job, for use to be built by the students, and for use with some of their new media gear in the classrooms. We're building a 3 way with these two drivers and a tang band W2-803SM 2" Driver. The idea is for pretty decent power handling through the mid/tweet, so we're using the 2" and crossing over low. Ragged 10k-20k response but we can live with that. Another nice feature of the 2" is the small frame- much smaller than most 1" domes, giving us good driver-driver spacing for better point source behavior.
We're figuring on first order at 1.2k and 2nd order at 300Hz, which should keep the cones all pretty much in pistonic mode up until the 2" breaks up. The only real limitation is the power handling down low- the 10"s would max out with some serious movie bass, but if they're playing loud enough to max out two 10" subs.... something's wrong
These will also be used as stage monitors and other types of usage in the school.
A triangular cabinet is being planned, I may post some drawings and other info if people are interested later on. These are made to be used up against walls (or the floor), so there's no baffle step compensation. Sub will be somewhere between max flat and .55 Qtc, sealed.
Whatever you do, don't mess with the V+ and V- adjustments!
The amplifier uses a power supply that tracks the audio output voltage requirements. It's target is to keep about 6V across the output devices at all times. This keeps the output devices in their SOA. Since there is so little voltage drop across the output devices, the amplifier needs less heatsink and is more efficient. If you adjust the V+ and V- controls, you can increase the standoff voltage enough to blow the outputs under the right conditions.
The 280mV or so at the speaker output is there as a bootstrap voltage used to start up the - tracker. It can't be removed or the amplifier won't function correctly.
I ran some measurements with the 10" Foster woofers. With 270mV DC across the woofer coil and the driver mounted axis horizontal in free air, the DC causes a cone displacement of 0.45mm. This is the worst case condition. Place the driver in a sealed box and the displacement will drop down below 0.2mm.
If the amplifier had an output relay, which it doesn't, the DC might be an issue from a turn on/off noise standpoint. You would get a nice audible DC step at the off/on or on/off time. The trackers and the amplifier form a feedback system that takes some time to stabilize during turn on. During this time, the output voltage swings around quite a bit. The small amount of DC present after things have stabilized is completely masked.
The amplifier uses a power supply that tracks the audio output voltage requirements. It's target is to keep about 6V across the output devices at all times. This keeps the output devices in their SOA. Since there is so little voltage drop across the output devices, the amplifier needs less heatsink and is more efficient. If you adjust the V+ and V- controls, you can increase the standoff voltage enough to blow the outputs under the right conditions.
The 280mV or so at the speaker output is there as a bootstrap voltage used to start up the - tracker. It can't be removed or the amplifier won't function correctly.
I ran some measurements with the 10" Foster woofers. With 270mV DC across the woofer coil and the driver mounted axis horizontal in free air, the DC causes a cone displacement of 0.45mm. This is the worst case condition. Place the driver in a sealed box and the displacement will drop down below 0.2mm.
If the amplifier had an output relay, which it doesn't, the DC might be an issue from a turn on/off noise standpoint. You would get a nice audible DC step at the off/on or on/off time. The trackers and the amplifier form a feedback system that takes some time to stabilize during turn on. During this time, the output voltage swings around quite a bit. The small amount of DC present after things have stabilized is completely masked.
thanks for the explanation Jack. I think it makes sense that this amount of offset should have minimal impact. After all, using the simple V^2/R formula for power, there is only 15mW of power going into the offset.
I got my MDF cut for my SubTwo clone. Hopefully, I'll have them assembled this weekend!
Jack, you mentioned that the EQ circuit for the SubTwo was not optimal. Do you have a recommendation for the EQ parameters for a homebuilt one that is about the same size as the original (i.e. 1.2 cu ft per speaker)?
I got my MDF cut for my SubTwo clone. Hopefully, I'll have them assembled this weekend!
Jack, you mentioned that the EQ circuit for the SubTwo was not optimal. Do you have a recommendation for the EQ parameters for a homebuilt one that is about the same size as the original (i.e. 1.2 cu ft per speaker)?
I've updated the sale website with information on the npt-11-080-1 driver. It is in fact different than the npt-11-081-1 driver.
The EQ circuit in the Sub 1 and 2 controllers is optimal from a shape standpoint. It is not optimal from a circuit design standpoint. If you want to tweak the shape of the curve at all, it takes a lot of trial and error. I would just use any of the free speaker design programs/spreadsheets out there to determine what eq settings you need.
The EQ circuit in the Sub 1 and 2 controllers is optimal from a shape standpoint. It is not optimal from a circuit design standpoint. If you want to tweak the shape of the curve at all, it takes a lot of trial and error. I would just use any of the free speaker design programs/spreadsheets out there to determine what eq settings you need.
Jack,
I currently have a set of SB2's and a SC1 center channel. I like them quite abit, but I want a to built a three way to amtch them as losely as I can for fronts. I also want to build a three center to replace the SC1. Can you make any suggestions from the drivers that are for sale.
Thanks
Todd
I currently have a set of SB2's and a SC1 center channel. I like them quite abit, but I want a to built a three way to amtch them as losely as I can for fronts. I also want to build a three center to replace the SC1. Can you make any suggestions from the drivers that are for sale.
Thanks
Todd
Todd,
If you use a pair of npt-11-079-1 6.5" woofers, one npt-11-080-1 5.25" midrange and one npt-11-096-1 tweeter, you will have built virtually a VC3 or VR3 speaker. The 096 isn't the original tweeter, but it is very close. I can even supply an exact crossover schematic. You will only have to modify it for the small tweeter differences.
If you want to build a smaller version, you could just use one of the npt-11-079-1 woofers. This will make the crossover entirely new though.
If you use a pair of npt-11-079-1 6.5" woofers, one npt-11-080-1 5.25" midrange and one npt-11-096-1 tweeter, you will have built virtually a VC3 or VR3 speaker. The 096 isn't the original tweeter, but it is very close. I can even supply an exact crossover schematic. You will only have to modify it for the small tweeter differences.
If you want to build a smaller version, you could just use one of the npt-11-079-1 woofers. This will make the crossover entirely new though.
Jack,
Thanks for your reply and time. I will probably be placing an order for the 80 and 81 drivers and the tweeter sometime today. I would like to get a copy of the crossover schmatic from you when I place the order. I was going to have a custom builder build the cross over for me because I have never done it before, but if I have the design why not go ahead and try it. Thanks again.
Todd
Thanks for your reply and time. I will probably be placing an order for the 80 and 81 drivers and the tweeter sometime today. I would like to get a copy of the crossover schmatic from you when I place the order. I was going to have a custom builder build the cross over for me because I have never done it before, but if I have the design why not go ahead and try it. Thanks again.
Todd