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Laurie
Double Platinum Member
Canada
4854 Posts |
 Posted - 01/08/2009 : 16:07:24
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quote:
Originally posted by zerksies
wouldn't a ls-2 do the trick
An LS-2 can be made to do the same job but it needs a specially wired external cable.
This thing is true bypass, and will also double as a 2 channel mixer, and an ultra-clean one or two channel booster.
Oh... and it has a phase reversal switch, which the LS-2 does not. If the extrnal pedal inverts the phase (some of them do) you need this because the mix will be subtractive rather than additive without it.
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Edited by - Laurie on 01/08/2009 16:17:04 |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 01/08/2009 : 16:10:28
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quote:
Originally posted by Dr. Bob
Hi Laurie
Once again, nice work.
quote:
working through getting rid of some low-level thermal noise (that "bacon frying" sound).
Once you get it into a properly shielded enclosure, like the Hammond's that you use, A lot of the circuit noise will disappear.
Some of that Bacon Sizzle, is probably induced from the gears on & around your Lab bench, & especially those 40 watt overhead fluro's.
I always mount my proto's onto a slightly larger Hammond box,
with a number of assorted holes drilled in it, for mounting various pots, sockets & switches.
It make a big difference.
I sometime even tape or screw on the back plate/lid to see how much quieter the project will become.
Regards & just my 2 cents worth.
Dr. Bob 
Hi Dr. Bob!
I'm using fairly high value resistors around the opamps (typically 470k) that will inherently ad thermal noise because they are so high. I will lower those values and switch to metal film, and I think that should get rid of most of it. If not, I'll try it shielded - thanks for the heads up!
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 01/08/2009 : 16:13:20
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quote:
Originally posted by DeFrag
Laurie's boutique shop of horrors!
Great project & excellent job. 
Thank you 
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 01/08/2009 : 16:45:03
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Hi Laurie
quote:
I will lower those values and switch to metal film, and I think that should get rid of most of it. If not, I'll try it shielded - thanks for the heads up!
Long ago when it was still a new toy, I did some tests with my HP N&D Analyzer.
In some cases I saw an 18dB to 20dB improvement in the noise floor
when using Metal film, verses carbon comp.
But it also depends on the brand, of mental metal film, generally most are good.
I guess it depends on how much gain you are trying to get out of the op-amps, & they type of op-amp.
It will be interesting to hear (not a pun) how much improvement, the metal films made.
Regards Dr. Bob
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Edited by - Dr. Bob on 01/09/2009 05:50:14 |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 01/08/2009 : 17:05:16
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| Interestingly, I swapped the original 4558 opamps for OPA2124's and it made very little difference. Anyway, I'll keep prodding along at it and it will sort itself out. |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 01/09/2009 : 05:31:17
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Noise is gone - it was the high value feedback resistors on the opamps.
So now it is quiet, the levels are all set, and the bias points are all adjusted. I can crank out over 5V peak-to-peak undistorted with an 8V supply.
Next step is to put it into a housing and onto the pedal-board with my PH-1R.
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Edited by - Laurie on 01/09/2009 05:39:42 |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 01/11/2009 : 07:06:51
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The finished product...
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DeFrag
Moderator
USA
3409 Posts |
Posted - 01/11/2009 : 09:03:03
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That is so freakin' sweet!
Great final pics as well. Kudos  |
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archimedes
Silver Member
United Kingdom
191 Posts |
Posted - 01/11/2009 : 11:30:07
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quote:
Originally posted by Laurie
The finished product...
That is a great idea and neat looking final product. |
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Topic |
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Looper/mixer
