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  1. #1
    Senior Member maxwedge's Avatar
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    Upgrading old amps?

    Is it worth it?

    I'm so attached to my my poor old Hafler P500's but I just picked up a QSC PL340 to run my 18's and the QSC is so much better sonically than the Hafler. Of course the QSC has a lot more power, but running them at lower levels the it still has a much nicer bass response than the P500.

    I've put some IXYS HyperFred bridge rectifier's in the P500's and maybe I should replace the power supply caps but that's all I could do that would be somewhat cheap. Driver board replacing gets expensive!

    I put the P500's at the bottom to anchor the rack down!
    Really got to get rid of that particle board!

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    Senior Seņor boputnam's Avatar
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    Quote Originally Posted by maxwedge View Post
    Is it worth it?
    In my opinion, yes - but pay attention to the Class of the amps you are deploying, and what your application is. A/B are best, sonically, to me, particularly in the home, but we use others in SR due to their efficiency.

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    Senior Member maxwedge's Avatar
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    Quote Originally Posted by boputnam View Post
    In my opinion, yes - but pay attention to the Class of the amps you are deploying, and what your application is. A/B are best, sonically, to me, particularly in the home, but we use others in SR due to their efficiency.
    I'm thinking the same.
    I bought the QSC because I have a minor ambition to rent out my gear out and play soundman and that amp is really light compared to the Haflers. I know a few bands I could maybe tag with and lugging 50 lbs amps around can be a pain.

    Plan of attack will be beef up the power supply's 1st then maybe some driver boards but the only place I've seen offering driver boards for diy is Musical Concepts and they run 400-500 a pair for theses Haflers, but I hear they sound good though.

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    Quote Originally Posted by maxwedge View Post
    .
    Plan of attack will be beef up the power supply's 1st then maybe some driver boards but the only place I've seen offering driver boards for diy is Musical Concepts and they run 400-500 a pair for theses Haflers, but I hear they sound good though.
    The Musical Concepts upgrade parts are really intended for home audio, not Pro. I think it would be a waste of money. If you had a broken amp, John probably has a few older (PA-3) boards in a box somewhere that could get it working, but short of that.....

    Now, if you wanted to turn one of those Haflers into a great home audio piece, fully rebuilt with his parts, they sound amazing.

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    Senior Member maxwedge's Avatar
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    Quote Originally Posted by rusty jefferson View Post
    The Musical Concepts upgrade parts are really intended for home audio, not Pro. I think it would be a waste of money. If you had a broken amp, John probably has a few older (PA-3) boards in a box somewhere that could get it working, but short of that.....

    Now, if you wanted to turn one of those Haflers into a great home audio piece, fully rebuilt with his parts, they sound amazing.
    Their not broken at all and I routinely set the bias and dc offset. They still kick hard.
    I don't really think that I plan to move these out of the house much and I like to work with electronics, so I think I'll work on improving them.

    John (Musical Concepts) really has some nice looking parts for these amps and I'm really itching to try out some of his power supply boards for 4-pole caps. They look really slick!

    Thanks for the replys

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    The QSC amps are great, I have many!

    I have a Hafler DH200 for my home stereo, same basic amp as yours only less power. I believe the front end of the amp uses the same board, no I take that back I believe it's the same board as the DH220 power amp. You may want to think about replacing the electrolytic caps on the boards. I just did that to my DH200 a month ago and it made a huge improvement! There were four electrolytic caps on each board. I ordered them from Mouser Electronics, total parts and shipping were about $15. I had notice the left channel starting to sound thin, the main problem was the input coupling cap on that channel that was a 10 uf actually measured about 100pf.
    I just took a quick look the DH500 schematic and there are six electrolytic caps on the each board.

    Replacing those caps would be worth it first before spending big dollars on main supply caps.

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