Hafler DH 220 amp sounds like tin can - diyAudio
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Old 19th December 2004, 07:14 AM   #1
Robcf is offline Robcf  United States
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Default Hafler DH 220 amp sounds like tin can

Just took possession of a Hafler DH220 amp and DH110 preamp. The DH220 sounds incredibly "tinny". Ran a couple of preamps through it so am sure it's the amp. The only way to get any decent low end is to turn the DH110 bass tone control to 10 and the treble to -2.

Intended to mod the amp with the Musical Concepts PA-3B boards, but now am wondering if I'm going to end up in the deep, dark, expensive mod-repair vicious cycle....

Anybody familiar with this problem in the DH220, or other solid states for that matter?

Thanks!!
RC
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Old 19th December 2004, 03:57 PM   #2
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there are two threads currently on this amp...

also, it shouldn't sound "tinny" - if anything a normal 220 sounds
a little bit fat and round...

I'd check the feedback network for yuks and the input cap(s) - perhaps someone has put in a cap as a HP filter for bi-amping duty??

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Old 19th December 2004, 05:11 PM   #3
Bogie is offline Bogie  United States
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Have you tried a different preamp? I just ebayed a 110 last week, and when it arrived, sounded VERY muddy on one channel - it's going back.

IIRC, John essentially guts the amps/pres anyway - replaces the boards, transformers, etc - I think about the only thing that's original are the mosfets...
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Old 19th December 2004, 06:43 PM   #4
Zen Mod is offline Zen Mod  Serbia
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Default Re: Hafler DH 220 amp sounds like tin can

Quote:
Originally posted by Robcf
Just took possession of a Hafler DH220 amp and DH110 preamp. The DH220 sounds incredibly "tinny". Ran a couple of preamps through it so am sure it's the amp. The only way to get any decent low end is to turn the DH110 bass tone control to 10 and the treble to -2.

Intended to mod the amp with the Musical Concepts PA-3B boards, but now am wondering if I'm going to end up in the deep, dark, expensive mod-repair vicious cycle....

Anybody familiar with this problem in the DH220, or other solid states for that matter?

Thanks!!
RC

if I understand corectly-volume is not in question , just quality of sound
?

if volume is low ,and sound is thiiiiiiiiiiiin! , then loudspeaker fuses are gone,and you have output through tiny capacitors, soldered in para with fuses.
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Old 20th December 2004, 12:59 AM   #5
Sze is offline Sze  Canada
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Quote:
also, it shouldn't sound "tinny" - if anything a normal 220 sounds
I have to agree with Bear. Must be something wrong with the amp.

I have a DH-220 modded to up to a Musical Concepts GXB mod at one time, until I accidentally blow it up. Slip of a meter probe. The mod made significant improvement to the stock amp. I rebuilt the amp to its stock state, save for the MC toroid, Supply caps and TRT wondercaps. Definitely not tinny sounding. Use it as back up if other projects are in working stages.
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Old 20th December 2004, 01:39 AM   #6
anatech is offline anatech  Canada
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Hi Robcf,
Your amp has open caps in the feedback to ground connection near the input transistor side. Easy to fix. Replace the other caps while you are there as they are commonly open or reduced in value. I've fixed many. As an added touch, match the transistors in the diff. pair locations. That is worthwhile. Then have a listen.
-Chris
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Old 20th December 2004, 03:30 AM   #7
fab is offline fab  Canada
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hi robcf

In addition to the other previous comments, if the "tinny" sound is present on both channels (L +R) then - unless the defective parts in respective channels have passed away a long time ago at different time - it is maybe a defective component that is common to both channels like: the power supply. With no input signal, check the DC voltage (maybe about 65V for a DH-220?) and the AC voltage (less than a few hundred mv).

Good luck!

Fab
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Old 20th December 2004, 05:39 PM   #8
Robcf is offline Robcf  United States
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Great feedback guys, really appreciate it!

I'm an audio engineer and occassionaly use the soldering iron on gear, but this might require someone more skilled then I. Been looking for a place that will work on this amp and haven't come up with a good source yet.

What a great forum, thanks for the assistance and happy holidays!
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Old 20th December 2004, 10:33 PM   #9
anatech is offline anatech  Canada
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Hey Robcf,
This is no more difficult than swapping the bad parts with good. Just mark the board where the line on the caps are (-). The values are on the parts. You will need 4 X 100uF 100V and 2 X 470uF 16V non-polarized. These are all radial lead, electrolytic capacitors. That will do you for both PC boards. The 470uF caps are the main culprit.

-Chris
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Old 21st December 2004, 02:05 PM   #10
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This is exactly how I got interested in DIY in the first place. I had two P230 Haflers that both played very distorted. I took them to a tech and he gave them back, after charging me to look at them, and told me he couldn't fix them because the trannies were bad and NLA. I found two NOS trannies on EBAY and bought them. After swapping one out I found no change. I started asking folks over at the JBL forum and they helped me find that it was bad Filter caps. I replace those and the amps play like new.

Since then I have fixed two Soundcraftsmen amps and am now nearly finished building an ESP P101 amp.

With all of the helpful folks here, I am not afraid to tackle things that used to make my head spin.

Thanks guys!

Terry
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