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Old 29th July 2004, 01:41 AM   #1
al2002 is offline al2002  India
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Default Hafler DH 200/220 Question

I'd like to know the DC rail voltages on the DH 200 power amp. The manual does not have this data and I don't have one to measure. Can anyone help?

I'd also like to know what the differences were between the various DH 220 driver boards. My unit has the PC 19s. Were there major circuit differences, or just minor changes?

Thanks.
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Old 29th July 2004, 08:36 AM   #2
djk is offline djk
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63V

First series changes were input cap changed to film type, cap in the feedback loop received film bypass.

DC off-set pot added.

Grounding scheme changed.

DH200s had a problem with the 2R2 resistor on the isolated RCA jack going open.

Later versions mounted the input jacks side-by-side and had a resistor between the signal grounds and the power grounds.

They just deleted the resistor on the last models.
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Old 30th July 2004, 02:14 AM   #3
fab is offline fab  Canada
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I have three DH-200 amps and they are all +/- 60 Vdc with no power delivered to loads (even sometimes during the winter since the line voltage is lower the voltage can drop to +/-58 Vdc). The DH-220 has a slightly higher voltage as indicated by djk.

Fab
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Old 30th July 2004, 03:47 AM   #4
al2002 is offline al2002  India
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Thanks for the info. So the the 200 has 60 V rails.

I was wondering about this as djk's post seemed to suggest that the 200 had 63V rails too, but I see now he was referring to the 220.

This is very helpful because I need to convert a 220 for use with 240 V mains, but have only been able to track down a DH 200 export transformer. Had to be sure that the 200 trannie could replace the 220 trannie, and it looks like it can.
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Old 30th July 2004, 03:54 AM   #5
al2002 is offline al2002  India
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Hi again fab.

Forgot to ask, what is the line voltage in your area? I got a private message from someone who said their DH 200 has +/- 62 V rails. Not that it matters, I just wanted to know.
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Old 30th July 2004, 06:50 AM   #6
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hi all

According to Van Alstine, the 200 has +/- 60v and
the 220 has +/- 65v. You could take a 200 transformer
and strap the primary for 220v to get a little more
juice for your 220.

BTW anybody know how to adjust bias or offset on
the 200? There's a pot P1 near Q9 for what I assume
is the bias. If the bias is adjusted will it affect the
DC offset at the outputs?

thanks
Bob
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Old 30th July 2004, 11:10 PM   #7
fab is offline fab  Canada
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Quote:
Originally posted by al2002
Hi again fab.

Forgot to ask, what is the line voltage in your area? I got a private message from someone who said their DH 200 has +/- 62 V rails. Not that it matters, I just wanted to know.
I just took a measurement and the line voltage is 122 Vac and the DH-200 voltage at the big caps is 59.1 VDC. There may be a slight variation in the transformer ratio or diode bridge from an amp to the other but the 3 amps that I got have similar DC voltage from what I remember.
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Old 30th July 2004, 11:24 PM   #8
fab is offline fab  Canada
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Quote:
Originally posted by CaliforniaBob
hi all

...BTW anybody know how to adjust bias or offset on
the 200? There's a pot P1 near Q9 for what I assume
is the bias. If the bias is adjusted will it affect the
DC offset at the outputs?

thanks
Bob
The driver boards (PC-6 type) in all my DH-200 amps do not include a pot for dc offset adjust. Typically, my stocks DH-200 amps had about 30 to 50 mv DC offset (before mods). I know that some of the DH-220 driver board types has a pot for dc offset adjust. Of course, you can use a DH-220 driver board in your DH-200 amp if you want too. P1 near Q9 in DH-200 driver board is for bias current adjust in the mosfets only. Normally. adjusting the bias current does not impact the DC offset since the latter is depending more on the lack of perfect balance of the input stage. The bias current must be adjusted by reading the DC supply fuse current. The value should be about 260 ma per rail as Hafler (Rockford-Fosgate) technical services indicated to me when I asked.

Fab
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Old 30th July 2004, 11:46 PM   #9
al2002 is offline al2002  India
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Thanks for the reply fab.

You seem to have modded your boards. Can you provide further details such as links, schematics, PC board layouts, etc?
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Old 31st July 2004, 12:01 AM   #10
fab is offline fab  Canada
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Quote:
Originally posted by al2002
Thanks for the reply fab.

You seem to have modded your boards. Can you provide further details such as links, schematics, PC board layouts, etc?
you are welcome.

There is already a thread I have started on this subject:
http://www.diyaudio.com/forums/showt...323#post359323

Fab
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