DH-200 versus XL280 PS caps.
Help?!!
I've heard from another hafler fan the "280" caps are superior to any other DH series PS caps
DH-200 model# & other info: 3186EE103U075BMA2; 362 8902 56699; 7800 micro F
XL-280 model# & other info: 3186DE782U075BJA2; 362 8710 56699; 10K micro F
both have the same voltage & temp specs.
also how do I measure '280 channel bias? I see the adjustment pot and I'm acutely aware of the importance of same, about 330ma I think.
thnx in advance, tony
Help?!!
I've heard from another hafler fan the "280" caps are superior to any other DH series PS caps
DH-200 model# & other info: 3186EE103U075BMA2; 362 8902 56699; 7800 micro F
XL-280 model# & other info: 3186DE782U075BJA2; 362 8710 56699; 10K micro F
both have the same voltage & temp specs.
also how do I measure '280 channel bias? I see the adjustment pot and I'm acutely aware of the importance of same, about 330ma I think.
thnx in advance, tony
Here I meant "connecting the finals to the output jacks" Here I would use OFC 12ga
As for the Cat 5e, I have miles of it.
thanks tony
XL-280 stuff
Two items:
1. Looking for power supply improvements or upgrade ideas other than those on TnT-audio.com
2. On the XL-280 schematic I noticed 2 types of grounds.
(Pg 17 of the .pdf)
One looks like a bent pitch fork (chassis ground?) The other, an inverted pyramid.
What concerns me is the 100nF caps that appear to rely on a chassis ground* connected to the final's PS rails near the MOSFETs.
* grounded through the heat sinks attached to case w/sheet metal screws.
Is it worth it to improve it? Can I run a connection to where C20 & C21 are grounded? Or where the RCAs have a way-better chassis ground?
Thanks tony
Two items:
1. Looking for power supply improvements or upgrade ideas other than those on TnT-audio.com
2. On the XL-280 schematic I noticed 2 types of grounds.
(Pg 17 of the .pdf)
One looks like a bent pitch fork (chassis ground?) The other, an inverted pyramid.
What concerns me is the 100nF caps that appear to rely on a chassis ground* connected to the final's PS rails near the MOSFETs.
* grounded through the heat sinks attached to case w/sheet metal screws.
Is it worth it to improve it? Can I run a connection to where C20 & C21 are grounded? Or where the RCAs have a way-better chassis ground?
Thanks tony
What do you mean "~50W"? Lower power by way of lower rail voltage?
You're welcome to PM your reply
Thnx tony
Ok. That mention of "50 watts" threw me. I follow what you meant. I thought you drastically lowered your rail voltage to compensate for a higher-than-spec bias setting. I measured about 63V on 2 of my 280s. One of them idles hotter, not loaded, than the other at moderate volume levels.
Next stop is adjusting the bias on those amps.
Being a fellow 280 owner, can you tell me how to measure & adjust DC offset?
Thnx tony
Hi all,
I have a DH220 which sounds great and have no particular problem.
Though, i find the input stage a bit too noisy to my taste.
I think that's because the input transistors are not low noise ones. Though i might be wrong.
Is there a known mod to fix that?
I am too lazy to read the whole thread, so, help would be appreciated.
I have seen the XL280 uses cascoded jfets.
Should it be possible to cascode the input stage and use sk170/sj74 Jfets instead of those used in the XL280.
I have a DH220 which sounds great and have no particular problem.
Though, i find the input stage a bit too noisy to my taste.
I think that's because the input transistors are not low noise ones. Though i might be wrong.
Is there a known mod to fix that?
I am too lazy to read the whole thread, so, help would be appreciated.
I have seen the XL280 uses cascoded jfets.
Should it be possible to cascode the input stage and use sk170/sj74 Jfets instead of those used in the XL280.
DH200 in Class A
I have very efficient speakers (96db/1w/1m) and would like to play with a low power Class A using the Hafler DH200 chassis, heat sinks and outputs.
I have read this thread from one end to the other and the promise of new driver boards has never materialized.
Then I read the Pass forum F5 page and I think that driver board would be great to try here. I have a toroidal 24-0-24 vac transformer and plan on 4 39,000 uF of capacitance per Mr. Pass' F5 power supply design.
My question is do I need to change anything to drive 4 Mosfet outputs or due to the heat sinks should I only use a pair of outputs.
Also somewhere on the Pass forum I found this F5 mod and would like opinions. It shows only 20 VDC +- rails is that a problem as I will have 32 + - VDC? (see jpg)
I have very efficient speakers (96db/1w/1m) and would like to play with a low power Class A using the Hafler DH200 chassis, heat sinks and outputs.
I have read this thread from one end to the other and the promise of new driver boards has never materialized.
Then I read the Pass forum F5 page and I think that driver board would be great to try here. I have a toroidal 24-0-24 vac transformer and plan on 4 39,000 uF of capacitance per Mr. Pass' F5 power supply design.
My question is do I need to change anything to drive 4 Mosfet outputs or due to the heat sinks should I only use a pair of outputs.
Also somewhere on the Pass forum I found this F5 mod and would like opinions. It shows only 20 VDC +- rails is that a problem as I will have 32 + - VDC? (see jpg)
Attachments
Rush,
All of Pass's designs use vertical MOSFETs, not the lateral MOSFETs as in the Hafler amps.
I don't have engineering data but I can tell you from reading about using Hafler heatsinks in a class A amp, the heat sinks are just not large enough for any amp with a reasonable amount of watts.
All of Pass's designs use vertical MOSFETs, not the lateral MOSFETs as in the Hafler amps.
I don't have engineering data but I can tell you from reading about using Hafler heatsinks in a class A amp, the heat sinks are just not large enough for any amp with a reasonable amount of watts.
I know the heatsinks are smallish. I figure if you lower the voltage enough, you can get 5 or 10 watts and that is all I need. I have found that good sounding amps (the ones that sound powerful) all have great big large current power supplies whether they are tube or SS regardless of output wattage.
I currently use a 2 watt 45 tube amp with great success. The only thing I don't like about the 45 is the 60 hz hum due to the ac of the 2.5 volt heaters (please don't tell me how to DC the 2.5 volts, you really don't understand dht.) It really isn't noticeable when the music plays, but it is bothersome because I know it is there.
I currently use a 2 watt 45 tube amp with great success. The only thing I don't like about the 45 is the 60 hz hum due to the ac of the 2.5 volt heaters (please don't tell me how to DC the 2.5 volts, you really don't understand dht.) It really isn't noticeable when the music plays, but it is bothersome because I know it is there.