mlloyd1 said:
The servo 50 is appealing to me too but it may be even improved a bit using a regulated power supply for it. Maybe using the discrete regulator of the Borbely Millenium EB-201-168 and the Borbely DC-50 circuit but with a cascode VAS and an active bias circuit along with the mosfet buffer stage on the same pcb could be an idea...
if this a DH 200/220/500 only thread, please disregard. Otherwise...
I'm using two XL-280s to drive a pair of subs each having two 8* ohm drivers. My goals are better damping, more "thump," and operating more effectively in what some might call the forbidden zone.** Any suggestions, from mild to not-too-wild to "hot rod" them for this purpose?
* nominal; minimum 6.4 ohms
** 20 hz and below. With no EQ F3 is 22 hz
Right now they're XO'd* around 110 hz. Later I plan to XO* them around 50-60 hz with other drivers and amps covering up to 100 hz.
* 4th order
I'm sure new PS caps, and/or more capacitance would be a place to start. Transformers with higher VA rating wouldn't hurt either.
Also the speaker wire posts could handle larger wire. Right now I'm using 10 guage Monster cable with a separate, short run to each driver.
I'd appreciate specific models and "where to buy" ideas too.
Thanks for reading this far.
tony
I'm using two XL-280s to drive a pair of subs each having two 8* ohm drivers. My goals are better damping, more "thump," and operating more effectively in what some might call the forbidden zone.** Any suggestions, from mild to not-too-wild to "hot rod" them for this purpose?
* nominal; minimum 6.4 ohms
** 20 hz and below. With no EQ F3 is 22 hz
Right now they're XO'd* around 110 hz. Later I plan to XO* them around 50-60 hz with other drivers and amps covering up to 100 hz.
* 4th order
I'm sure new PS caps, and/or more capacitance would be a place to start. Transformers with higher VA rating wouldn't hurt either.
Also the speaker wire posts could handle larger wire. Right now I'm using 10 guage Monster cable with a separate, short run to each driver.
I'd appreciate specific models and "where to buy" ideas too.
Thanks for reading this far.
tony
fab:
interesting...
the servo 50 driver board that i purchased from borbely years ago has onboard discrete regulators. very simple - not as elaborate as the millenium.
the output stage is not regulated.
the VAS topology is already a folded cascode of sorts. are you saying an additional (conventional) cascode on top of that?
mlloyd1
interesting...
the servo 50 driver board that i purchased from borbely years ago has onboard discrete regulators. very simple - not as elaborate as the millenium.
the output stage is not regulated.
the VAS topology is already a folded cascode of sorts. are you saying an additional (conventional) cascode on top of that?
mlloyd1
servo 50
mlloyd1
yes I found the article and you are right the DC-50 is not the same as the servo 50. The servo 50 has in fact the same regulator as the millenium from my documentation. But the servo 50 has not exactly the same input stage arrangement as the DC-50. For the input stage, the DC-50 has a cascode jfet and not only a bjt cascode as the Servo 50. According to Erno, the jfet cascode reduces the input capacitance.
For the VAS I sm thinking of an additional (conventional) cascode on top of that.
Since the servo 50 has a lready the on-board regulator it is more appealing to me. Is it still available?
How did you incorporate it into the DH-200/220?
Can you describe the sound improvement (I suppose there is...)
In addition, seeing the recent post from tony I have checked the XL280 driver board schematics and it is very similar to the servo 50 board if you remove the DC-serco and on-board regulator... the XL-280 has also the buffer stage in front of the mosfet.
Thanks
mlloyd1 said:
mlloyd1
yes I found the article and you are right the DC-50 is not the same as the servo 50. The servo 50 has in fact the same regulator as the millenium from my documentation. But the servo 50 has not exactly the same input stage arrangement as the DC-50. For the input stage, the DC-50 has a cascode jfet and not only a bjt cascode as the Servo 50. According to Erno, the jfet cascode reduces the input capacitance.
For the VAS I sm thinking of an additional (conventional) cascode on top of that.
Since the servo 50 has a lready the on-board regulator it is more appealing to me. Is it still available?
How did you incorporate it into the DH-200/220?
Can you describe the sound improvement (I suppose there is...)
In addition, seeing the recent post from tony I have checked the XL280 driver board schematics and it is very similar to the servo 50 board if you remove the DC-serco and on-board regulator... the XL-280 has also the buffer stage in front of the mosfet.
Thanks
Xl-280
XL-280 or DH-200/220 are similar so this is a good place although I thought that you would have more responses.
New PS caps, and/or more capacitance and transformers with higher VA rating is surely good if you find the place in the chassis. A good VA/size ratio is a toroidal transfo plus they are more efficient:
www.plitron.com/
www.avellindberg.com/
www.hammondmfg.com/182.htm
Regarding the damping I am surprised that you find it not appropriate since according to XL-280 spec it is about 300 at 1 KHz which is not bad at all. Based on the schematics I see an output fuse. I would replace the fuse if it is old and use a high current one to reduce the output impedance of the amp. In fact I am surprised that Hafler could guaranty a damping factor of 300 with an output fuse. Can someone who owns an XL-280 can really confirm that the fuse is at the output of amp?
In the DH-200/220 the fuse is in the feedback path so the impedance is reduce by the feedback factor to not affect the damping of the amp.
Are you sure that what you dislike is caused by the amp damping factor? There may be other reasons. If you want to use the amp at very high power level make sure that your speakers ar up to it too. Speakers power ratings are indicated for not damaging them and does not mean that the speaker will still sound good at high power.
good luck
gp4Jesus said:
XL-280 or DH-200/220 are similar so this is a good place although I thought that you would have more responses.
New PS caps, and/or more capacitance and transformers with higher VA rating is surely good if you find the place in the chassis. A good VA/size ratio is a toroidal transfo plus they are more efficient:
www.plitron.com/
www.avellindberg.com/
www.hammondmfg.com/182.htm
Regarding the damping I am surprised that you find it not appropriate since according to XL-280 spec it is about 300 at 1 KHz which is not bad at all. Based on the schematics I see an output fuse. I would replace the fuse if it is old and use a high current one to reduce the output impedance of the amp. In fact I am surprised that Hafler could guaranty a damping factor of 300 with an output fuse. Can someone who owns an XL-280 can really confirm that the fuse is at the output of amp?
In the DH-200/220 the fuse is in the feedback path so the impedance is reduce by the feedback factor to not affect the damping of the amp.
Are you sure that what you dislike is caused by the amp damping factor? There may be other reasons. If you want to use the amp at very high power level make sure that your speakers ar up to it too. Speakers power ratings are indicated for not damaging them and does not mean that the speaker will still sound good at high power.
good luck
Yes, the fuse on the back of the amp is in series with the output to the speaker. Other amps, such as the DH-120, Hafler 9130/9180, Hafler Pro1200, etc., all have this fuse in series with the output.
Only the DH-200/220 amps put it in the feedback loop. Interesting.
I re-wired a DH-220 and bypassed the speaker feedback loop and put the fuse in series with the speaker. The amp sounded a little different, I guess. I think it sounded a little better with the fuse in the feedback loop.
Only the DH-200/220 amps put it in the feedback loop. Interesting.
I re-wired a DH-220 and bypassed the speaker feedback loop and put the fuse in series with the speaker. The amp sounded a little different, I guess. I think it sounded a little better with the fuse in the feedback loop.
Thanks for all of your replys
Just got to looking at this thread... ...been busy.
A new transformer (toroids are cool w/me) and new (more) capacitance; I knew this would be a good place to start. I thought the PS was a little wimpy. How high a VA rating and how much capacitance will bring me to the point of diminishing returns? I don't mind spending a few dollars to make sure it's more than adequate. I got a reality check on power supplys after reading links* @ tnt audio and zero distortion about "getting fancy" with PS designs and mods. Would really appreciate some feed back from you all on their ideas.
* http://www.tnt-audio.com/clinica/ssps1_e.html and http://www.zero-distortion.com/techno/powersupply/powersi.htm
I'm interested in improving all aspects of XL-280 bass perfomance to drive my subs.
For a long time I've belived fuses can mess up performance particulary damping. I've read articles that agree and disagree to same. I'm glad to hear from someone in the real world I was right. I haven't taken the time to study the scematic to know what the fuses (it has several) do to protect whatever...
Ultimately, I'll XO them around 55-60 hz. I've discussed what I'm going to do to cover the frequency band above the XO in a previous reply.
So any ideas to improve bass performance in the lowest octaves are welcome.
thanks for reading this far
Tony
Just got to looking at this thread... ...been busy.
A new transformer (toroids are cool w/me) and new (more) capacitance; I knew this would be a good place to start. I thought the PS was a little wimpy. How high a VA rating and how much capacitance will bring me to the point of diminishing returns? I don't mind spending a few dollars to make sure it's more than adequate. I got a reality check on power supplys after reading links* @ tnt audio and zero distortion about "getting fancy" with PS designs and mods. Would really appreciate some feed back from you all on their ideas.
* http://www.tnt-audio.com/clinica/ssps1_e.html and http://www.zero-distortion.com/techno/powersupply/powersi.htm
I'm interested in improving all aspects of XL-280 bass perfomance to drive my subs.
For a long time I've belived fuses can mess up performance particulary damping. I've read articles that agree and disagree to same. I'm glad to hear from someone in the real world I was right. I haven't taken the time to study the scematic to know what the fuses (it has several) do to protect whatever...
Ultimately, I'll XO them around 55-60 hz. I've discussed what I'm going to do to cover the frequency band above the XO in a previous reply.
So any ideas to improve bass performance in the lowest octaves are welcome.
thanks for reading this far
Tony
Using an XL-280 just for the bottom 1 or 2 octaves is really a waste of its better characteristics. You might be better off getting a big plate amp specifically designed to drive subwoofers. These plate amps might be cheaper, run cooler, take less space, etc.
If you beef up the XL-280 with too much PS capacitance and a toroidal transformer you risk blowing the power switch and the bridge diode in the power supply unless you also incorporate a soft start circuit. Also, the PS caps are in a tight spot which requires them to be a specific size not only to fit but to allow the top plate to attach and allow space for the other little power supply that drives the two circuit cards. PS caps will not be cheap.
Again, if you just want more power for the lowest 1 or 2 octaves, get a plate amp. My $0.02
If you beef up the XL-280 with too much PS capacitance and a toroidal transformer you risk blowing the power switch and the bridge diode in the power supply unless you also incorporate a soft start circuit. Also, the PS caps are in a tight spot which requires them to be a specific size not only to fit but to allow the top plate to attach and allow space for the other little power supply that drives the two circuit cards. PS caps will not be cheap.
Again, if you just want more power for the lowest 1 or 2 octaves, get a plate amp. My $0.02
gp4Jesus,
Dick has good arguments there. Although I do not know what is a "plate amp". I suppose that the XL-280 has impressive characteristics like frequency bandwidth so its use for only sub frequency will not take advantage of its full potential. I suppose that you have verified that your mid/hi freq amps are better than your XL-280?
In my DH-200 amps I have not change the transformer due to space limitation. I saw one implementation using a big toroidal where the chassis had to be cut to install it. However, I have changed to power caps from (2x) 10000 uF to (2x) 30000 uf while keeping the same size factor. In my other DH-200 I used (4x) 14000 uF and 2x 35A diode bridge. AS Dick said, the XL-280 uses a pcb on top of the power caps so you better stay with same form factor. I had this caps setup for several years with no problem. Increasing the transfo VA rating may require an "in-rush" limiter. Also, from the user manual the XL-280 has 2 separate windings for 2 available voltages (driver stage with a slight highest voltage and power stage voltage). You may have problem to find the same output voltages unless you use 2 transformers but again space limitation inside the chassis is again a problem.
"How high a VA rating and how much capacitance will bring me to the point of diminishing returns?"
I would put the highest value caps that fit into the XL-280 and make sure you use the same voltage ratings.
Dick has good arguments there. Although I do not know what is a "plate amp". I suppose that the XL-280 has impressive characteristics like frequency bandwidth so its use for only sub frequency will not take advantage of its full potential. I suppose that you have verified that your mid/hi freq amps are better than your XL-280?
In my DH-200 amps I have not change the transformer due to space limitation. I saw one implementation using a big toroidal where the chassis had to be cut to install it. However, I have changed to power caps from (2x) 10000 uF to (2x) 30000 uf while keeping the same size factor. In my other DH-200 I used (4x) 14000 uF and 2x 35A diode bridge. AS Dick said, the XL-280 uses a pcb on top of the power caps so you better stay with same form factor. I had this caps setup for several years with no problem. Increasing the transfo VA rating may require an "in-rush" limiter. Also, from the user manual the XL-280 has 2 separate windings for 2 available voltages (driver stage with a slight highest voltage and power stage voltage). You may have problem to find the same output voltages unless you use 2 transformers but again space limitation inside the chassis is again a problem.
"How high a VA rating and how much capacitance will bring me to the point of diminishing returns?"
I would put the highest value caps that fit into the XL-280 and make sure you use the same voltage ratings.
that was a long time ago- i don't think so, but i'm not sure. i think i just got a parts placement diagram in addition to the article on the website.
the PCBs had more jumpers than i would prefer to have. i always thought about redoing them but that has obviously gotten VERY low on my priority list.
the PCBs had more jumpers than i would prefer to have. i always thought about redoing them but that has obviously gotten VERY low on my priority list.
fab said:
I have modelled the DH-200 on Switchercad SPICE but cannot find models for the 2SK134 or 2SJ49 output MOSFETS. I was able to find models for 2SK1058 and 2SJ162 MOSFETS and used these as substitutions. Even with these substitued parts the model seems pretty accurate (I also substituted 1N4740A diodes for the 1N5240B zeners and estimated coil L1 at 1.5uH). I modelled the amp in the hope of getting a better idea about the various parts substitutions recommended. Besides it was an easy exercise and kind of fun.
It has been instructive to see how changing various caps and resistors changes (not much admittedly) the frequency response of the unit. I am still a SPICE novice so haven't run distortion simulations yet.
Right now the model runs "hot"-- that is, at the middle of P1's adjustment range bias is running around 450 mA. Since this does not accurately simulate the actual circuit I am trying to figure out why but my guess is that this is due to the use of the wrong output devices.
If anyone has models for the 2SJ49 and 2SK134 MOSFETS I would much appeciate it.
I'd also be happy to share the DH-200 model with anyone else who is interested.
Terry Ilardi
It has been instructive to see how changing various caps and resistors changes (not much admittedly) the frequency response of the unit. I am still a SPICE novice so haven't run distortion simulations yet.
Right now the model runs "hot"-- that is, at the middle of P1's adjustment range bias is running around 450 mA. Since this does not accurately simulate the actual circuit I am trying to figure out why but my guess is that this is due to the use of the wrong output devices.
If anyone has models for the 2SJ49 and 2SK134 MOSFETS I would much appeciate it.
I'd also be happy to share the DH-200 model with anyone else who is interested.
Terry Ilardi
Hey all. Some of you remember me with the DH-200 switch that went bad. You all helped me out GREATLY. Thanks!!
I have read though this WHOLE thread. WOW, what great info.
I want to change out my inputs and outputs on the amp. I want to go with maybe gold plated. Better than what the originals are. What do you all recomend? The originals are starting to corode.
I deal alot with www.partsexpress.com . Do you all know if anything from there would work? Somehting that would be a "drop in" fit?
Jake
I have read though this WHOLE thread. WOW, what great info.
I want to change out my inputs and outputs on the amp. I want to go with maybe gold plated. Better than what the originals are. What do you all recomend? The originals are starting to corode.
I deal alot with www.partsexpress.com . Do you all know if anything from there would work? Somehting that would be a "drop in" fit?
Jake
Or www.mouser.com or ww.radioshack.com . Thay all seem to carry one type or another. Just wondering which one was the best fit. Also about the speaker output, I would like to go with the same style, just maybe gold plated. Something that would also accept bananna plugs.
ilardi:
if you have good models for the 2SK1058/2SJ162, then you have good models for the 2SK135/2SJ50 (the 2SK134/2SJ49 are the lower voltage siblings).
hitachi used the same die in different physical packages.
it is indeed a fun circuit to simulate. some years ago, a person i met in the high end audio newsgroup sent some notes he prepared because he taught about the hafler design in an electronics class. i've got to find it and see if he'll let me share it.
mlloyd1
if you have good models for the 2SK1058/2SJ162, then you have good models for the 2SK135/2SJ50 (the 2SK134/2SJ49 are the lower voltage siblings).
hitachi used the same die in different physical packages.
it is indeed a fun circuit to simulate. some years ago, a person i met in the high end audio newsgroup sent some notes he prepared because he taught about the hafler design in an electronics class. i've got to find it and see if he'll let me share it.
mlloyd1
ilardi said:
to Dick West:
Yeah I'm crazy
tony
What's a plate amp?
this part I get.
I think this will fill the soft start need. http://www.sound.westhost.com/project39.htm Upgrading the bridge diode is easy and low $. If I have to mount add'l caps out side the case...
Yeah I'm crazy
tony
Go here for an example of a Plate Amp:
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=300-794
For a subwoofer you don't need to be quite so concerned about purity of sound. Most of the value of the XL-280 is wasted if it only drives a subwoofer.
Parts Express has a variety of plate amps. Go to the discussion board at Parts Express and read the mail, check the searches and archives, and ask a question. The guys who hang there are very expert in subs and with plate amps.
http://www.pesupport.com/cgi-bin/config.pl
Many plate amps provide features to enhance the use of a subwoofer that your XL-280 lacks -- such as a variable phase control to help the sub better blend with your other speakers.
Sell your XL-280 amps, buy a couple of plate amps, and smile all the way to the bank plus enjoy better sound with less fuss and worry.
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=300-794
For a subwoofer you don't need to be quite so concerned about purity of sound. Most of the value of the XL-280 is wasted if it only drives a subwoofer.
Parts Express has a variety of plate amps. Go to the discussion board at Parts Express and read the mail, check the searches and archives, and ask a question. The guys who hang there are very expert in subs and with plate amps.
http://www.pesupport.com/cgi-bin/config.pl
Many plate amps provide features to enhance the use of a subwoofer that your XL-280 lacks -- such as a variable phase control to help the sub better blend with your other speakers.
Sell your XL-280 amps, buy a couple of plate amps, and smile all the way to the bank plus enjoy better sound with less fuss and worry.