well few updates, I played with theese resitors from 2.2 to 10kohm. and listened for some critical recordings(recordings in which I ghave suspicion that sound become worse)
each time I will needed readjuste absolute dc ofset.
what I find that 3.3kohm worked best with my modified sonic frontiers sfd2 mk2 tube dac ,and 4.5kohm with solid state dac, going higher was not aceptable- sound has some strong improovements ,but also ver big minus I cant live with- rounded smooth sound. like tube amp. lack of resoliution. its just not right. my vote is arround 4kohm
each time I will needed readjuste absolute dc ofset.
what I find that 3.3kohm worked best with my modified sonic frontiers sfd2 mk2 tube dac ,and 4.5kohm with solid state dac, going higher was not aceptable- sound has some strong improovements ,but also ver big minus I cant live with- rounded smooth sound. like tube amp. lack of resoliution. its just not right. my vote is arround 4kohm
XA100 to XA200
Gl, I was looking at my aleph 1.2's yesterday and was thinking why not just upgrade them to the XA160/200. The rails are =/-
60volts and I have 2kva trannies (Plitron buzzards) which I would have to replace with quieter units. I though I could just mirror the aleph 1.2 circuit and rewire the outputs. Of course I would have to add the x circuitry and the infamous resistor. Is this how you started out with your design or did you just build from scratch??????????????? I could of course just use this amp chasis and outputs, power supply and build the 100 version with smaller trannies.
Gl, I was looking at my aleph 1.2's yesterday and was thinking why not just upgrade them to the XA160/200. The rails are =/-
60volts and I have 2kva trannies (Plitron buzzards) which I would have to replace with quieter units. I though I could just mirror the aleph 1.2 circuit and rewire the outputs. Of course I would have to add the x circuitry and the infamous resistor. Is this how you started out with your design or did you just build from scratch??????????????? I could of course just use this amp chasis and outputs, power supply and build the 100 version with smaller trannies.
Whoa! Put on the brakes!
60V rails for an Aleph-X will give you something like 800W per channel with power dissipation on the order of 2400W. That's not for the faint of heart.
I've never had a Plitron buzz in normal use. Are you sure that you don't have DC on your power lines and that your Alephs are functioning properly?
Grey
60V rails for an Aleph-X will give you something like 800W per channel with power dissipation on the order of 2400W. That's not for the faint of heart.
I've never had a Plitron buzz in normal use. Are you sure that you don't have DC on your power lines and that your Alephs are functioning properly?
Grey
XA100 to XA200
Grey, thanks for the response, my Plitron transformers are good for boat anchors nothing more. These are the standard series trannies not the newer potted ones that they now offer. My A75 amps transformer does not buzz nor do any of my others.
I thought about building a DC circuit but I never got around to it.
I think they buzz because of the class A load but they are rated for 2kva each.
You are correct I would have to get new trannies for the XA160/200 project but I could save on the chasis and output devices or just start over. I also like Erno Borbely's jfet class amp on his website but I am not sure if 80watts is enough for my line arrays.
I may also try to figure out if you can use Power Jfets to drive an
XA160/200 but I am not sure that I can get the devices. This means a lot of calculations to arrive at the right gain and feedback. With summer coming my motivation starts to wain.
You are correct regarding the wattage, I should have said +/-30volts or 60 peak to peak since the amp has balanced outputs.
The Aleph being single ended is 60v and starts to clip at 55 volts.
My Aleph's sound terriffic and I could buck up and get the better trannies. DC offset is between 20 to 40mv. If you know anyone who can use 90lbs of boat anchors let me know. dave
Grey, thanks for the response, my Plitron transformers are good for boat anchors nothing more. These are the standard series trannies not the newer potted ones that they now offer. My A75 amps transformer does not buzz nor do any of my others.
I thought about building a DC circuit but I never got around to it.
I think they buzz because of the class A load but they are rated for 2kva each.
You are correct I would have to get new trannies for the XA160/200 project but I could save on the chasis and output devices or just start over. I also like Erno Borbely's jfet class amp on his website but I am not sure if 80watts is enough for my line arrays.
I may also try to figure out if you can use Power Jfets to drive an
XA160/200 but I am not sure that I can get the devices. This means a lot of calculations to arrive at the right gain and feedback. With summer coming my motivation starts to wain.
You are correct regarding the wattage, I should have said +/-30volts or 60 peak to peak since the amp has balanced outputs.
The Aleph being single ended is 60v and starts to clip at 55 volts.
My Aleph's sound terriffic and I could buck up and get the better trannies. DC offset is between 20 to 40mv. If you know anyone who can use 90lbs of boat anchors let me know. dave
You didn't answer either of my questions regarding your Alephs. I'm still not convinced that everything is okay. It's not impossible that you might have bad transformers, but it strikes me as highly improbable. There are other things I would look into before condemning the Plitrons.
While I'm sure the newer audio transformers are wonderful, I've never used them. All mine are the standard ones.
As for the power JFETs, everything you need to know is in the Lovoltech thread in the Group Buy forum.
Grey
While I'm sure the newer audio transformers are wonderful, I've never used them. All mine are the standard ones.
As for the power JFETs, everything you need to know is in the Lovoltech thread in the Group Buy forum.
Grey
ax100
Grey, I hooked up my signal generator and scope and ran some frequency tests with a 250watt 5ohm resistor (both sine and square wave). In comparing input and output traces everything looked ok, all the voltage and current checks against the schematics are ok. The driver board is located about 18 inches from the center of the transformer.
I hooked the Aleph's back up and I noticed I was getting a low level buzz (probably 120hz in my mid range driver). I retested and added another 1mh inductor so now I have a clclc PS. Ripple was almost non detectable at jus a few mv measured at the last cap.
I put some sound absorbant material under the Plitrons (the gooey stuff used to damp car doors which have speakers). I still get the buzz in the speakers and now I am thinking of the following:
1. I plug the amps into different outlets in the house so I may be getting a low level ground loop. I have to check this out further but my other amps do not display this problem. The chasis are connected to safety ground and the amp is star grounded per the schematic on the Pass web site.
2. I am not sure how to measure DC on my 120 volt lines so I cannot really tell.
3. I have line level filters on the inputs to the ps that I got at fair radio for a few bucks each but they don't remove dc.
4. If I remove the output bias the bussing stops but of course I don't have much of a load.
5. I got my PS caps at Fair radio so who knows how old they were when I bought them but they came sealed, I have used the
amps for 7 years now. Perhaps my ps caps are going bad?
I called plitron and they told me put the amps in a different room!!! These transformers throw off a large magnetic field and should be shielded (they weigh 45lbs each).
I saw somewhere a design for a dc protector box (I hate messing with ac) and I will try to find it here on the site. If it isn't to complicated I can try making one and fitting into the chasis.
Have you ever used one and did it work?
I will measure the total current draw for the amp through my monster 7000 ac ps since it has this convient feature just to see if I am leaking current to ground somewhere. I highly doubt this.
The amp is almost the equal of the Pass 350.5 except it is not as quiet. More to come--thanks for the support. dave
dave
Grey, I hooked up my signal generator and scope and ran some frequency tests with a 250watt 5ohm resistor (both sine and square wave). In comparing input and output traces everything looked ok, all the voltage and current checks against the schematics are ok. The driver board is located about 18 inches from the center of the transformer.
I hooked the Aleph's back up and I noticed I was getting a low level buzz (probably 120hz in my mid range driver). I retested and added another 1mh inductor so now I have a clclc PS. Ripple was almost non detectable at jus a few mv measured at the last cap.
I put some sound absorbant material under the Plitrons (the gooey stuff used to damp car doors which have speakers). I still get the buzz in the speakers and now I am thinking of the following:
1. I plug the amps into different outlets in the house so I may be getting a low level ground loop. I have to check this out further but my other amps do not display this problem. The chasis are connected to safety ground and the amp is star grounded per the schematic on the Pass web site.
2. I am not sure how to measure DC on my 120 volt lines so I cannot really tell.
3. I have line level filters on the inputs to the ps that I got at fair radio for a few bucks each but they don't remove dc.
4. If I remove the output bias the bussing stops but of course I don't have much of a load.
5. I got my PS caps at Fair radio so who knows how old they were when I bought them but they came sealed, I have used the
amps for 7 years now. Perhaps my ps caps are going bad?
I called plitron and they told me put the amps in a different room!!! These transformers throw off a large magnetic field and should be shielded (they weigh 45lbs each).
I saw somewhere a design for a dc protector box (I hate messing with ac) and I will try to find it here on the site. If it isn't to complicated I can try making one and fitting into the chasis.
Have you ever used one and did it work?
I will measure the total current draw for the amp through my monster 7000 ac ps since it has this convient feature just to see if I am leaking current to ground somewhere. I highly doubt this.
The amp is almost the equal of the Pass 350.5 except it is not as quiet. More to come--thanks for the support. dave
dave
uptate Aleph 1.2's to XA100 or better
GL and GR, yes I am going to do it!! I have made a decision to update my Aleph 1.2's to the XA 100 to 160. My initial thoughts are:
Remove the Aleph Driver Board
Remove the Aleph Plitron 2kva transformers.
Keep everything else.
I have 24 out put devices per mono amp, I would rewire them into 4 quads with 6 devices each.
I will keep the PS caps, chasis and heat sinks.
I have to make up new driver boards but I would like a bit more power so I was thinking of about +/- 30 to 35 volt rails.
I will have to purchase some new audiophile grade xformers that are not the buzzards I have now. The Aleph 2kva (+/- 60v dc) xformers can be sold, saved or used as boat anchors.
My Alephs were built in 2000 and have given me 7 years of music harmony.
Risks and questions:
I will use the schematic that GL has proven works well to start and go from there.
I have followed the threads regarding how to adjust the current sources to 50% but I have never done it so I will make sure I understand this well before attempting it.
I hope the XA series can drive 7ohm impedance. I will use this as a full range amp or in a bi-amp mode with my Pass 350.5 driving the mid basses. For the biamp mode I am not sure what the total impedance of my 12 fountek ribbons per side is as I don't have an impedance meter and I can't get a dc reading because the drivers have impedance matching transformers.
I think I understand well enough the issues regarding DC offset. Needless to say, I must design this thing so I don't get thumps on turn on and turn off. I will protect my tweeters in my line array with a 20uf cap.
I have a lot of leftover parts with 9610's and resistors so the first job is acquiring the rest of the parts. The xformers will be the most expensive issue. I will reuse my AC input filters and hexfred diodes. I have 6-15,000uf caps in the PS hooked up in a clclc arrangement using 1mh iron core inductors. If there is room in the chasis I may add some extra caps. Or I could add some caps right at the drains. I will keep the grounding arrangemens but disconnect the speaker output grounds.
Since this is a balanced bridged design I am not sure how to calculate the output power. My Aleph's are biased at about
.33ma per device x 24 =7.9amps or 3.8A per side. The heat sinks get to about 55 deg C. When calculating the output watts rms into 8 ohms (I am going on memory) I got a bit over 200watts with clipping at 55v p-p.
The other option is to go out and help NP's bottom line and buy another 350.5. The last time I did this I had to convince the audio salesperson that he and I were related through DNA evidence back to Italy in the 15th century and that "you wouldn't take advantage of your brother would you"!! I also found a nick on the face plate and dust on the heat sinks which of course means a huge discount. I also must convince the Prime Minister at home that she can put off some vacation plans or furniture acquistions.
If you have any suggestions let me know. My time frame is to get the boards done and tested this summer but I have vacation and business trips which will interfere. Wish me luck, dave
GL and GR, yes I am going to do it!! I have made a decision to update my Aleph 1.2's to the XA 100 to 160. My initial thoughts are:
Remove the Aleph Driver Board
Remove the Aleph Plitron 2kva transformers.
Keep everything else.
I have 24 out put devices per mono amp, I would rewire them into 4 quads with 6 devices each.
I will keep the PS caps, chasis and heat sinks.
I have to make up new driver boards but I would like a bit more power so I was thinking of about +/- 30 to 35 volt rails.
I will have to purchase some new audiophile grade xformers that are not the buzzards I have now. The Aleph 2kva (+/- 60v dc) xformers can be sold, saved or used as boat anchors.
My Alephs were built in 2000 and have given me 7 years of music harmony.
Risks and questions:
I will use the schematic that GL has proven works well to start and go from there.
I have followed the threads regarding how to adjust the current sources to 50% but I have never done it so I will make sure I understand this well before attempting it.
I hope the XA series can drive 7ohm impedance. I will use this as a full range amp or in a bi-amp mode with my Pass 350.5 driving the mid basses. For the biamp mode I am not sure what the total impedance of my 12 fountek ribbons per side is as I don't have an impedance meter and I can't get a dc reading because the drivers have impedance matching transformers.
I think I understand well enough the issues regarding DC offset. Needless to say, I must design this thing so I don't get thumps on turn on and turn off. I will protect my tweeters in my line array with a 20uf cap.
I have a lot of leftover parts with 9610's and resistors so the first job is acquiring the rest of the parts. The xformers will be the most expensive issue. I will reuse my AC input filters and hexfred diodes. I have 6-15,000uf caps in the PS hooked up in a clclc arrangement using 1mh iron core inductors. If there is room in the chasis I may add some extra caps. Or I could add some caps right at the drains. I will keep the grounding arrangemens but disconnect the speaker output grounds.
Since this is a balanced bridged design I am not sure how to calculate the output power. My Aleph's are biased at about
.33ma per device x 24 =7.9amps or 3.8A per side. The heat sinks get to about 55 deg C. When calculating the output watts rms into 8 ohms (I am going on memory) I got a bit over 200watts with clipping at 55v p-p.
The other option is to go out and help NP's bottom line and buy another 350.5. The last time I did this I had to convince the audio salesperson that he and I were related through DNA evidence back to Italy in the 15th century and that "you wouldn't take advantage of your brother would you"!! I also found a nick on the face plate and dust on the heat sinks which of course means a huge discount. I also must convince the Prime Minister at home that she can put off some vacation plans or furniture acquistions.
If you have any suggestions let me know. My time frame is to get the boards done and tested this summer but I have vacation and business trips which will interfere. Wish me luck, dave
Hi Dave,
Sorry I haven't replied sooner but I have been on vacation myself for the last 11 days. Fact is I was in the same area as NP if you can believe that.
I have never heard 1.2's so I can't say whether you are going to hear an improvement or not. I do know that you have always spoken very glowingly of your Aleph's so this is clearly a hard decision for you to make. I am still very happy with the AX100's and will be glad to help you through the build process.
There are a number of discussions on this site on how to adjust the Aleph CCS gain. There is even a synopsis on this thread somewhere in the first few posts. If you change the number of output devices from the 5 per quadrant that I used to 6 to take advantage of your current 1.2 build than you will need to re-adjust the CCS. But that can be done after the amps are built and even used for a while.
Please note that the transformer secondary voltage I used is not commonly available. If you want to duplicate the PS voltages I used you will need to order a custom unit perhaps from Victoria Magnetics. Your extra LC section will also cause a bit more voltage drop so that will need to considered too. Anyway if you end up with a DC voltage between 25V and 32V in the end, and if the power dissipation per output device is tolerable then you're good to go - so don't sweat it.
The rest of your plan sounds fine. Seven ohms is not a problem. I think you can probably find a parallel/series arrangement for the Founteks that will yield a reasonable impedance. It's the AC impedance that counts - not the DC resistance. The Founteks won't be operating anywhere near DC so that's not important. By all means use the cap - at least to start with.
I think you meant .33 amps - not milliamps.
If you can swing it I think that another 350.5 would be truly killer.
Cheers,
Graeme
Sorry I haven't replied sooner but I have been on vacation myself for the last 11 days. Fact is I was in the same area as NP if you can believe that.
I have never heard 1.2's so I can't say whether you are going to hear an improvement or not. I do know that you have always spoken very glowingly of your Aleph's so this is clearly a hard decision for you to make. I am still very happy with the AX100's and will be glad to help you through the build process.
There are a number of discussions on this site on how to adjust the Aleph CCS gain. There is even a synopsis on this thread somewhere in the first few posts. If you change the number of output devices from the 5 per quadrant that I used to 6 to take advantage of your current 1.2 build than you will need to re-adjust the CCS. But that can be done after the amps are built and even used for a while.
Please note that the transformer secondary voltage I used is not commonly available. If you want to duplicate the PS voltages I used you will need to order a custom unit perhaps from Victoria Magnetics. Your extra LC section will also cause a bit more voltage drop so that will need to considered too. Anyway if you end up with a DC voltage between 25V and 32V in the end, and if the power dissipation per output device is tolerable then you're good to go - so don't sweat it.
The rest of your plan sounds fine. Seven ohms is not a problem. I think you can probably find a parallel/series arrangement for the Founteks that will yield a reasonable impedance. It's the AC impedance that counts - not the DC resistance. The Founteks won't be operating anywhere near DC so that's not important. By all means use the cap - at least to start with.
I think you meant .33 amps - not milliamps.
If you can swing it I think that another 350.5 would be truly killer.
Cheers,
Graeme
aleph 1.2's to AX100
Gl-thanks, yes I meant 33ma or .33amps.
I got started down this road because I cannot get my plitron transformers to quit buzzing. I have tried isolating them with sound absorbant material etc. I did call plitron and the engineer did admit that under heavy load that these xformers can buzz and he suggested that I put them in another room. Grey thinks I have dc coming in on the ac line. However, neither my 350.5 amp or my 92 vintage A-75 Pass/tharagard class A amps have any noise or buzzing. I could build a dc blocking circuit but I am not convinced this will work.
There is a response from NP on another thread in which he states that the XA100 was not recommended for low impedances and he suggested the XA100.5 but I don't know what the difference is between the two models that would account for this.
I did hear a rumor from a dealer that NP was coming out with new circuits for the XA line and I wouldn't be surprised if we see the Power J-fet invlolved somehow. I also thought of using power Jfets for the differential pair but I am not sure if they can drive all these output devices even if you run up to 20ma through them. I would definetly have to do some experimenting to get this to work.
Another less important reason for udating the Aleph's is grounding. The Pass 350.5 is a balanced bridge design with no speaker ground. All my other amps use the convential positive and speaker ground connections. I just wanted some symetry.
In biamp mode the tweeter and midbass driver circuits don't see each other but they are connected to the same DEQX preamp crossover system. Hopefully I am worried about nothing.
dave
Gl-thanks, yes I meant 33ma or .33amps.
I got started down this road because I cannot get my plitron transformers to quit buzzing. I have tried isolating them with sound absorbant material etc. I did call plitron and the engineer did admit that under heavy load that these xformers can buzz and he suggested that I put them in another room. Grey thinks I have dc coming in on the ac line. However, neither my 350.5 amp or my 92 vintage A-75 Pass/tharagard class A amps have any noise or buzzing. I could build a dc blocking circuit but I am not convinced this will work.
There is a response from NP on another thread in which he states that the XA100 was not recommended for low impedances and he suggested the XA100.5 but I don't know what the difference is between the two models that would account for this.
I did hear a rumor from a dealer that NP was coming out with new circuits for the XA line and I wouldn't be surprised if we see the Power J-fet invlolved somehow. I also thought of using power Jfets for the differential pair but I am not sure if they can drive all these output devices even if you run up to 20ma through them. I would definetly have to do some experimenting to get this to work.
Another less important reason for udating the Aleph's is grounding. The Pass 350.5 is a balanced bridge design with no speaker ground. All my other amps use the convential positive and speaker ground connections. I just wanted some symetry.
In biamp mode the tweeter and midbass driver circuits don't see each other but they are connected to the same DEQX preamp crossover system. Hopefully I am worried about nothing.
dave
Re: aleph 1.2's to AX100
Hopefully.
The XA .5 product is different, the output stage having more
similarity to the original Aleph 0 with a Class A PP follower stage
in parallel with a smaller single-ended bias, and is capable of 40
amps output peak. The only JFETs are in the front end.
daly41k said:
Hopefully.
The XA .5 product is different, the output stage having more
similarity to the original Aleph 0 with a Class A PP follower stage
in parallel with a smaller single-ended bias, and is capable of 40
amps output peak. The only JFETs are in the front end.
Hi Nelson,
Man I don't know if it would be possible to leak out the XA.5 news any slower. Talk about painful. That being said it appears that there is now enough info on the table for the aggressively inclined folks around here to start generating their "How's about this?" schematics.
I recall you writing about the early days of experimenting with SuSy circuits and how too many stages compromised the principle. The time period implied suggests that you were using the Aleph 0 as a test bed and that 3 stages was the point where problematic issues started to arise. All of the SuSy Passlabs designs I can think of offhand are 2 stage - even the ones with followers. So I find your reference to the Aleph 0 very interesting. The fog is definitely lifting.
Hi Dave,
I think your fears about balanced/unbalanced speaker connections and the DEQX connections are unfounded.
Cheers,
Graeme
Man I don't know if it would be possible to leak out the XA.5 news any slower. Talk about painful. That being said it appears that there is now enough info on the table for the aggressively inclined folks around here to start generating their "How's about this?" schematics.
I recall you writing about the early days of experimenting with SuSy circuits and how too many stages compromised the principle. The time period implied suggests that you were using the Aleph 0 as a test bed and that 3 stages was the point where problematic issues started to arise. All of the SuSy Passlabs designs I can think of offhand are 2 stage - even the ones with followers. So I find your reference to the Aleph 0 very interesting. The fog is definitely lifting.
Hi Dave,
I think your fears about balanced/unbalanced speaker connections and the DEQX connections are unfounded.
Cheers,
Graeme
Manu said:have found this on the web.
How beautiful
Yep thats a beauty, allright
Counting 4 IRF's in TO220 case, and I bet to spot 2 Toshiba dual J-fets in there. 2SJ109's? The pic is a bit blurry. What is the Thermistor doing on the amp board? Temp. stabilizing of some sort? Also, thats a lot of outputfets Steen
beautiful is a good word for it indeed
Originally posted by steenoe
Yep thats a beauty, allright
likely the n and p jfets for the ugs driver stage discussed elsewhere in the forum.
The pic is a bit blurry. What is the Thermistor doing on the amp board? Temp. stabilizing of some sort?
looks to me like it's doing something for the meter, but what do i know....
Also, thats a lot of outputfets
yup!
mlloyd1
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