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leonard d rock
Silver Member
Philippines
301 Posts |
 Posted - 06/23/2009 : 10:06:09
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hello guys,
last year or so, there was some discussion on stacked opamp chips mostly for sd-1s. anybody still have them or got rid of them? i had one on an od pedal which i had already sold. i'm thinking about stacking again for another sd-1 and would like your insights, comments, criticisms etc.
ldr |
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cctsim
Silver Member
United Kingdom
418 Posts |
Posted - 06/24/2009 : 01:48:34
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I tried before to stack 2 RC4558p for my SD1 as suggested by Keeley but I found no noticeable improvement, if any, over the stock 4558DD.
The stock was more grainy in my view and more to my taste.
I remember long time ago, a Prof. mentioning that it is wise to have a small resistor, ~ 50-70 Ohm, between the opamp outputs but it is mechanically a challenge to do without a pcb. Maybe this will result in a better sounding combination, I haven't tried it though but its on my to try list. |
Edited by - cctsim on 06/24/2009 01:49:08 |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 06/24/2009 : 02:10:37
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quote:
Originally posted by cctsim
I remember long time ago, a Prof. mentioning that it is wise to have a small resistor, ~ 50-70 Ohm, between the opamp outputs but it is mechanically a challenge to do without a pcb. Maybe this will result in a better sounding combination, I haven't tried it though but its on my to try list.
This won't affect the sound - it's to stop the outputs from trying to drive each other. There will be minute differences in output voltage even with chip off the same wafer - giving a driving potential into effectively a short circuit.Hmmm... maybe it would affect the sound? One of the op-amps may be driven into current-limit condition by this effect, and that might "mellow out" the stacked sound? Dunno... just pontificating.
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cctsim
Silver Member
United Kingdom
418 Posts |
Posted - 06/24/2009 : 02:25:59
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To be honest, opamp stacking is not worth the effort. If there was even a minor improvement the manufacturers would have done it already inside the chip many times.
Stacking was invented by modders with commercial interests to get their business going. |
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IM28
Copper Member
26 Posts |
Posted - 06/25/2009 : 16:21:50
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quote:
Originally posted by cctsim
To be honest, opamp stacking is not worth the effort. If there was even a minor improvement the manufacturers would have done it already inside the chip many times.
Stacking was invented by modders with commercial interests to get their business going.
I would assume that the designers of opamps have already made improvements or new designs that would offer the equivalent benefits of stacking (whatever they may be)inside a single device. I think you could achive similar results sonically by substituting a device with the characteristics you want. Stacking creates a composite device with the main benefit of increased output current capability. With multiple stages in parallel with no isolation one of the stages will have a lower output impedance and would provide more output that the others which maybe not what you want. Jack Orman has a design on his site,http://www.muzique.com/lab/superbuff.htm, that parallels 4 opamps with each having a 100 ohm isolation resistor on the output. I don't know if Jacks design preceded the "boutique stacking", which was first brought to the attention of the diy community by Dave Barber. Creating composite devices by paralleling several is not really new,it has been already done in everything from digital fan outs to your basic 100 watt tube amp with 2 tubes on each push/pull section. |
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cctsim
Silver Member
United Kingdom
418 Posts |
Posted - 06/25/2009 : 19:49:51
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| Stacking is a very old concept. I studied EE in the early 90's and it was subject for audiophile discussion back then. |
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stacked chips updates?
