djk said:
I was servician (or technician or repairer , if you wish ) for years ;
during that time I stashed pile of various schematics ,but what I never do is making sort of "mail order" bussines ,where I sell something. now I'm techie in local radio station-for everything-from PCs to mix board........
what I usually do is to look at some (probably) good schmtc or project and collect ideas .
sometimes is more important figuring why some designer make particular compromise ,then figuring golden book value for some component.
besides-I'm from former Yu ,and just for evaluating purposes going through messy procedure of ordering pair of boards just for that is just silly.
do not act like having few boards is nuclear physic.
I pooged DH101 and DH200 15 yrs ago,even without net and even without knowing that somewhere in some magazine someone do the same .
making money is not always first thing for everyone
KarlDL,
Thanks for the thorough explanation of how you used the relay in your MC amplifier.
"The rated current for this DC coil is approximately 10mA. The 2K series resistor drops approx 20V at that current, hence the coil voltage is approx 110VDC under normal operating conditions."
I believe I can speak for Tom. He an I both appreciate your help.
Thanks for the thorough explanation of how you used the relay in your MC amplifier.
"The rated current for this DC coil is approximately 10mA. The 2K series resistor drops approx 20V at that current, hence the coil voltage is approx 110VDC under normal operating conditions."
I believe I can speak for Tom. He an I both appreciate your help.
DH 200
Hey:
I have a DH 500 modded by Musical Concepts that has an Inrush Limiter in series with the thermal switches that limits the current spike when turning the amp on. The Dynaco part number is RZ016. I cannot find a regular part number to correspond. Anyone?
This would of course work in any amp. It has a higher resistance when cold and goes to a low res. when warm. This works ok.
The amp sound as good as a Adcom GFA 7805 except that the volume is slightly lower and there is slightly less Bass. Just turn the vol up and the Bass up a little bit and the sound is similar. both are non fatuiging to listen to for long periods of time.
Hope this helps
Ed
Hey:
I have a DH 500 modded by Musical Concepts that has an Inrush Limiter in series with the thermal switches that limits the current spike when turning the amp on. The Dynaco part number is RZ016. I cannot find a regular part number to correspond. Anyone?
This would of course work in any amp. It has a higher resistance when cold and goes to a low res. when warm. This works ok.
The amp sound as good as a Adcom GFA 7805 except that the volume is slightly lower and there is slightly less Bass. Just turn the vol up and the Bass up a little bit and the sound is similar. both are non fatuiging to listen to for long periods of time.
Hope this helps
Ed
Hafler XL280 Upgrade
Hello,
I have a Hafler XL280 amp.
2 Questions
1. I want to upgrade to get the most out of the amp, the place I saw is:
http://www.musicaldesign.com/mc_amp_mods.htm
Does anybody know if they are a good place to upgrade with and what is worth upgrading.
2. I have a yamaha 600 CX Pre-amp, but want to get a Hafler 945 W/Tuner, is it a good pre-amp, and will the pre-ampmake a lot of difference?
Thanks
Mona979
Hello,
I have a Hafler XL280 amp.
2 Questions
1. I want to upgrade to get the most out of the amp, the place I saw is:
http://www.musicaldesign.com/mc_amp_mods.htm
Does anybody know if they are a good place to upgrade with and what is worth upgrading.
2. I have a yamaha 600 CX Pre-amp, but want to get a Hafler 945 W/Tuner, is it a good pre-amp, and will the pre-ampmake a lot of difference?
Thanks
Mona979
"I have a DH 500 modded by Musical Concepts that has an Inrush Limiter in series with the thermal switches that limits the current spike when turning the amp on. The Dynaco part number is RZ016. I cannot find a regular part number to correspond. Anyone?
This would of course work in any amp. It has a higher resistance when cold and goes to a low res. when warm. This works ok."
That came stock in later DH500s.
Switches and thermostats failed in those early amps after a period of time. If you beefed up the supply caps they failed even faster.
A better solution is to replace the two pole relay with a three pole type and the inrush limiter with the CL30 Keystone. The CL30 is 2R5 vs the CL100 being 0R5, it just doesn't do much.
This would of course work in any amp. It has a higher resistance when cold and goes to a low res. when warm. This works ok."
That came stock in later DH500s.
Switches and thermostats failed in those early amps after a period of time. If you beefed up the supply caps they failed even faster.
A better solution is to replace the two pole relay with a three pole type and the inrush limiter with the CL30 Keystone. The CL30 is 2R5 vs the CL100 being 0R5, it just doesn't do much.
Reply to mone979
mona,
I have used almost all the older Hafler amps but currently am using two of them with the Musical Concepts PA-3B circuit card mods and power supply cap upgrades. The MC mods are great, come in kit form, and have excellent installation instructions.
About your pre-amp question. What do you need to pre amplify? Are you still spinning vinyl? Most CD players have sufficient output to directly drive most amps to full power. Many find that all they need is a passive stereo line control center. The main criteria for this device being successful are short low capacitance interconnects, a quality selector switch and a volume control potentiometer that leaves little sonic signature on the signal.
Hope this helps.
mona,
I have used almost all the older Hafler amps but currently am using two of them with the Musical Concepts PA-3B circuit card mods and power supply cap upgrades. The MC mods are great, come in kit form, and have excellent installation instructions.
About your pre-amp question. What do you need to pre amplify? Are you still spinning vinyl? Most CD players have sufficient output to directly drive most amps to full power. Many find that all they need is a passive stereo line control center. The main criteria for this device being successful are short low capacitance interconnects, a quality selector switch and a volume control potentiometer that leaves little sonic signature on the signal.
Hope this helps.
Question for djk
djk,
I have a pair of devices that sure look like a thermistor. On each are the letters and numbers:
KKK
C30-18
and they measure 2-3 ohms resistance cold.
Are these the CL30 you and others recommend. Mine don't have the "L" in their description but I assume they are the same thing. Am I correct?
Thanks.....
djk,
I have a pair of devices that sure look like a thermistor. On each are the letters and numbers:
KKK
C30-18
and they measure 2-3 ohms resistance cold.
Are these the CL30 you and others recommend. Mine don't have the "L" in their description but I assume they are the same thing. Am I correct?
Thanks.....
XL-280 transformer question
As long as we are doing some thread hijacking please permit me to ask a question about the XL-280 Hafler amp.
I have a pair of power supply transformers that were used in the Dynaco ST-150 and ST-300 amplifiers, both solid state amplifiers. They are a little larger than the stock XL-280 transformer and weigh a little more and info I read about them in an old Audio Amateur issue indicates they have an equal if not larger VA rating.
These Dynaco center tapped transformers have a booster winding to provide either 50 VDC or 70 VDC +/-.
I would like to make a dual mono pair of XL-280 mono amps and have the parts and chasses to do so. What I lack is the 2nd XL-280 transformer. How about using these Dynaco transformers? I can drive their circuit cards with 70 VDC but what happens if I drive the output MOSFETs with only 50 VDC?
Will I only just observe a reduction in power because of the reduction in voltage from 65 to 50 VDC? If so, I can accept this. But, will the differential between the designed 65 and my 50 VDC create a problem when working with the circuit card driven at 70 VDC?
Thanks for your help.
As long as we are doing some thread hijacking please permit me to ask a question about the XL-280 Hafler amp.
I have a pair of power supply transformers that were used in the Dynaco ST-150 and ST-300 amplifiers, both solid state amplifiers. They are a little larger than the stock XL-280 transformer and weigh a little more and info I read about them in an old Audio Amateur issue indicates they have an equal if not larger VA rating.
These Dynaco center tapped transformers have a booster winding to provide either 50 VDC or 70 VDC +/-.
I would like to make a dual mono pair of XL-280 mono amps and have the parts and chasses to do so. What I lack is the 2nd XL-280 transformer. How about using these Dynaco transformers? I can drive their circuit cards with 70 VDC but what happens if I drive the output MOSFETs with only 50 VDC?
Will I only just observe a reduction in power because of the reduction in voltage from 65 to 50 VDC? If so, I can accept this. But, will the differential between the designed 65 and my 50 VDC create a problem when working with the circuit card driven at 70 VDC?
Thanks for your help.
Dick,
This is not hijacking to discuss mods on a thread titled "Hafler" "mods"!
I can not see problem with running the driver board 5vdc more than the stock XL-280 supply since all components on the board are rated with a big voltage margin. However, I saw in the manual that the XL-280 has the big 7800uf caps rated at 75vdc. The voltage margin between 75V and 70V is not that much if you consider that the main 120Vac voltage has variation and also during power up you can have short spikes. I do not know the real effect on long term operation. Check on the caps if they are rated 75vdc (as nominal) but max voltage 90 Vdc (transient).
I can not see a problem running the output stage including the MOSFET and their associated driver transistors Q14 and Q15 with a lower voltage. As you have indicated you will loose a lot of max output power (maybe only about 85 W rms clean power compared to the rated 140W rms with the original transfo).
Fab
This is not hijacking to discuss mods on a thread titled "Hafler" "mods"!
I can not see problem with running the driver board 5vdc more than the stock XL-280 supply since all components on the board are rated with a big voltage margin. However, I saw in the manual that the XL-280 has the big 7800uf caps rated at 75vdc. The voltage margin between 75V and 70V is not that much if you consider that the main 120Vac voltage has variation and also during power up you can have short spikes. I do not know the real effect on long term operation. Check on the caps if they are rated 75vdc (as nominal) but max voltage 90 Vdc (transient).
I can not see a problem running the output stage including the MOSFET and their associated driver transistors Q14 and Q15 with a lower voltage. As you have indicated you will loose a lot of max output power (maybe only about 85 W rms clean power compared to the rated 140W rms with the original transfo).
Fab
fab,
The stock XL-280 has circuit cards designed to operate at 75VDC. The stock XL-280 transformer has two sets of secondaries, one to provide around75VDC, the other to provide 65 VDC for the output stage. Therefore, there is no concern about using my XL280 circuit cards with 70 VDC.
Also, the 75WVDC rating of the PS caps is not a problem as the output stage of the stock XL-280 runs at the same voltage as the DH-200 and DH-220.
As you know, the XL-280 has an input circuit that runs at 5-10 VDC higher than the output stage. This compensates for the 5 VDC gate voltage to get the MOSFETs to conduct. This design gets the max power out of the components, chassis and heat sink size, possible.
Thanks for the data about power reduction using 50 VDC instead of 65 VDC for the output MOSFETs. I can live with 80 or so watts as my speakers are efficient and I am not a loudness freak. I hope that the dual mono amplification will provide an enhanced sound stage and clarity that overcomes any problems with an occasional lack of power.
Well, whatta' hobby! Right?
The stock XL-280 has circuit cards designed to operate at 75VDC. The stock XL-280 transformer has two sets of secondaries, one to provide around75VDC, the other to provide 65 VDC for the output stage. Therefore, there is no concern about using my XL280 circuit cards with 70 VDC.
Also, the 75WVDC rating of the PS caps is not a problem as the output stage of the stock XL-280 runs at the same voltage as the DH-200 and DH-220.
As you know, the XL-280 has an input circuit that runs at 5-10 VDC higher than the output stage. This compensates for the 5 VDC gate voltage to get the MOSFETs to conduct. This design gets the max power out of the components, chassis and heat sink size, possible.
Thanks for the data about power reduction using 50 VDC instead of 65 VDC for the output MOSFETs. I can live with 80 or so watts as my speakers are efficient and I am not a loudness freak. I hope that the dual mono amplification will provide an enhanced sound stage and clarity that overcomes any problems with an occasional lack of power.
Well, whatta' hobby! Right?
dual mono amp
Dick,
it is surely a good idea to have individual power supply for each channel since it mainly prevents modulation of the power supply (of one channel) by the other channel musical signal. Do you intent to increase the caps bank value as well?
I have not done this mod but only thought about it. Keep us informed on the "before and after mod" difference (with same musical material and source of caourse).
I would also consider regulating the driver voltage since you have a lot of margin (75V to 50V) to be able to still keep the max power unchanged. Even a regulated 65V would be fine. By the way the SK134 and SJ49 are lateral mosfets and they are polarised to about 0.75Vdc (check R36 voltage that is probably to about 1.5 Vdc for bias of about 280 ma) and not 5Vdc as V-mosfet type.
fab
Dick,
it is surely a good idea to have individual power supply for each channel since it mainly prevents modulation of the power supply (of one channel) by the other channel musical signal. Do you intent to increase the caps bank value as well?
I have not done this mod but only thought about it. Keep us informed on the "before and after mod" difference (with same musical material and source of caourse).
I would also consider regulating the driver voltage since you have a lot of margin (75V to 50V) to be able to still keep the max power unchanged. Even a regulated 65V would be fine. By the way the SK134 and SJ49 are lateral mosfets and they are polarised to about 0.75Vdc (check R36 voltage that is probably to about 1.5 Vdc for bias of about 280 ma) and not 5Vdc as V-mosfet type.
fab
The HV winding on an XL280 transformer is only rated to run the front end cards, 100mA or so.
Remember: 134/49 devices are only rated at 140V MAXIMUM and 135/50 devices should be used with the Dynaco 300 ±70V windings.
Sound Valves has some XL280 transformers left if you really want to go dual mono with your pair of XL280 chassis.
"Are these the CL30 you and others recommend. Mine don't have the "L" in their description but I assume they are the same thing. Am I correct?"
Sounds like a similar part from a different vendor, I would probably use it.
I would save the pair of Dynaco 300 transformers for a different project.
Remember: 134/49 devices are only rated at 140V MAXIMUM and 135/50 devices should be used with the Dynaco 300 ±70V windings.
Sound Valves has some XL280 transformers left if you really want to go dual mono with your pair of XL280 chassis.
"Are these the CL30 you and others recommend. Mine don't have the "L" in their description but I assume they are the same thing. Am I correct?"
Sounds like a similar part from a different vendor, I would probably use it.
I would save the pair of Dynaco 300 transformers for a different project.
I realize my post about using the Dynaco transformer contained too many parts for most to read carefully.
I do not intend to run the output MOSFETs at more than 50VDC.
The Dynaco trans. has two sets of secondaries, one provides 70VDC the other 50VDC. The circuit cards will run at 70VDC and the output MOSFETs at 50VDC. That is what I intend to do. That pair of old Dynaco transformers really bug me and I want to find a reasonable way to use them.
I do not intend to run the output MOSFETs at more than 50VDC.
The Dynaco trans. has two sets of secondaries, one provides 70VDC the other 50VDC. The circuit cards will run at 70VDC and the output MOSFETs at 50VDC. That is what I intend to do. That pair of old Dynaco transformers really bug me and I want to find a reasonable way to use them.
fab,
For several years here I ran a pair of monoblocks made from a DH-200. Each had its own power supply with the heatsink on the left and the tranformer on the right to balance the weight. In between was 80,000 mfd of PS capacitance and a soft start surge resistor/time delay relay
The monoblocks threw a big wide soundstage though in retrospect it was a little diffuse. Then along came a MusicalConcepts amp with the PA-3B circuit cards and 50K uF in the PS. This amp's soundstage was almost as large as that of the DH-200 monoblocks but it was more detailed, more subtley nuanced, not diffuse, and with better placement of sound images. It became my reference amp.
Now, into the two empty chasses I could mount the XL-280 cards with the Dynaco transformer and the 80K PS capacitance and maybe even regulate the front end voltage from 70 down to 60 VDC to make sure it gets not only regulated but decoupled from the 50vdc windings that run the outputs.
The bottom line, however, how will I like the XL-280 sound compared to that of the MC amp? Mybe I should just split the MC amp and make it dual mono, run everything at 70VDC and use the matched triplet sets of 2SK176/2SJ56 MOSFETs recently acquired.
But, how does the "sound" of the XL-280 compare to that of a MC amp with the PA-3B circuit cards?
Any comments about the XL-280 "sound?"
For several years here I ran a pair of monoblocks made from a DH-200. Each had its own power supply with the heatsink on the left and the tranformer on the right to balance the weight. In between was 80,000 mfd of PS capacitance and a soft start surge resistor/time delay relay
The monoblocks threw a big wide soundstage though in retrospect it was a little diffuse. Then along came a MusicalConcepts amp with the PA-3B circuit cards and 50K uF in the PS. This amp's soundstage was almost as large as that of the DH-200 monoblocks but it was more detailed, more subtley nuanced, not diffuse, and with better placement of sound images. It became my reference amp.
Now, into the two empty chasses I could mount the XL-280 cards with the Dynaco transformer and the 80K PS capacitance and maybe even regulate the front end voltage from 70 down to 60 VDC to make sure it gets not only regulated but decoupled from the 50vdc windings that run the outputs.
The bottom line, however, how will I like the XL-280 sound compared to that of the MC amp? Mybe I should just split the MC amp and make it dual mono, run everything at 70VDC and use the matched triplet sets of 2SK176/2SJ56 MOSFETs recently acquired.
But, how does the "sound" of the XL-280 compare to that of a MC amp with the PA-3B circuit cards?
Any comments about the XL-280 "sound?"
XL-280 - MC
Dick,
unfortunately I can not really provide a valuable opinion on the sound between these options since I have not heard either of them. However, I know that the circuitry of the MC PA-3B circuit includes a cascode VAS which might (it is only a possibility not a verified fact for the MC) be partially responsible of the "more detailed, more subtley nuanced, not diffuse, and with better placement of sound images." In 2 of my DH-200 amps, this is one of the mod I have done and I can say that I have the same comments on the sound as you when I have compared with the stock DH-200. However, I have performed several mods so it might be other mods that really made the difference also.
fab
Dick West said:
Dick,
unfortunately I can not really provide a valuable opinion on the sound between these options since I have not heard either of them. However, I know that the circuitry of the MC PA-3B circuit includes a cascode VAS which might (it is only a possibility not a verified fact for the MC) be partially responsible of the "more detailed, more subtley nuanced, not diffuse, and with better placement of sound images." In 2 of my DH-200 amps, this is one of the mod I have done and I can say that I have the same comments on the sound as you when I have compared with the stock DH-200. However, I have performed several mods so it might be other mods that really made the difference also.
fab
fab,
As I recall from a post many months ago you toyed with the idea of making a PCB that encompasses your DH-200 mods onto a circuit card which others can use to enjoy the fruits of your labor and knowledge. Any further thoughts on this?
I praise MC circuit cards highly but the price of their kit is more than I want to pay, at least not pay frequently. How about a PCB from you?
As I recall from a post many months ago you toyed with the idea of making a PCB that encompasses your DH-200 mods onto a circuit card which others can use to enjoy the fruits of your labor and knowledge. Any further thoughts on this?
I praise MC circuit cards highly but the price of their kit is more than I want to pay, at least not pay frequently. How about a PCB from you?