Servo controlled Op Amp board on Ebay

The benefit of servo circuit on power amp is well document. Are there benefit to have servo on preamp board? I found 2 of these kits on Ebay. Any opinion or first hand experience?


OPA2604 Servo Preamplifier Kit AMP board kit for DIY


Top Preamplifier NE5532 Dual OP Amp And servo circuit kit for DIY

This is a cheap line amp board that may have a lot of use as output buffer. It is neither too cheap or too expensive. I have found some gems among the offers from these sellers and, obviously, burnt many times too.
 
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phase

Member
2004-10-04 11:59 pm
Are those 5v regulators I see?
Would think that a bit more would be needed to get decent sound from most popular op amps.
Neat board though, after adding an opa627, and Russian polystyrenes, may be good deal, and allow the use od a direct coupled amp.
 
This is a cheap line amp board that may have a lot of use as output buffer.
If you can make a PCB, a good buffer is simple a 5532 as a follower (output directly connected to input). It has very little voltage offset in this configuration and can drive pretty low impedance loads. Just make sure to put a 100nF cap directly across the power supply pins of the 5532.

My advice is to pass on the boards you linked to.
 
Are those 5v regulators I see?
Would think that a bit more would be needed to get decent sound from most popular op amps.
Neat board though, after adding an opa627, and Russian polystyrenes, may be good deal, and allow the use od a direct coupled amp.

The regulators are 15 volts. Agree with you that it would need to add a dual OPA627 to sound well.
 

Ian Finch

Member
Paid Member
2010-04-11 4:22 am
Coffs Harbour, NSW
The plan is to filter the supply tails at the opamp by shorting the noise between the rails, not contaminating ground as you would in a single rail microprocessor or logic chip supply. You save a wasted cap that way too. Normally, MKT film caps are an alternative used in audio applications. These are considerably larger but MKP is just impractical. See "bypassing" here: Audio Designs With Opamps
 
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