I have an old Rotel RC850 preamp that I am going to update
with new caps. Measuring the Vcc going to the opamps, I
find that the + and - are different. Vcc+ at pin 8 measures +20.5vDC and Vcc- at pin 4 measures -19.5vDC. How critical is it for these to be the same?
Re: Opamp Vcc
No problem at all!...But I presume that your CD use the NE5532 op amp ( a excelent choice)...but be aware that if you change for another op amp , a large number of them can't be feed with more than + - 18 Volts.
Thanks for the reply. I have been reading the posts about the 5532 & 5534 and was going to change it just to see if I hear any difference. I am considering the OPA275 which will take up to 22v
or the OPA2604 which will take up to 24v. The circuit is a preamplifier not a CD player. I know that fast recovery diodes
have been suggested as an improvement for CD players but for this application would these (replacing 1N4003 with MUR120's) be of any value? Thanks BL
I usually don't change the diodes but you can try the MUR 120 and see (hear..! ) if they make any diference. ;)
Is good that you find your own opinion and for that , there are only one way...try...try ...try!
hohohoo... Denon is a very goog pre-amp!
Many ideas i have to you:
Change the Caps To ELNA Cerafine model, and put more capacitance in the Power Supply...
Put Sockets on the op-amps, and change the op-amps to OPA627, OPA134, OPA134, when the OP-Amps are Dual Unit. Use the doubler socket to the OPA627... And the double versions of the OP-Amps, like OPA2227, OPA2132, OPA2134, and others... :smash:
Change the audio conections to silver wire.
When the transformer not a Toroid unit. Change to a toroid unit.
When the OP-Amps not operate at highter voltage, you can regulate it with 7812 and 7912... Put the Op-Amps in other board, and conect the conections of the op-amp in the principal board... Did you understand me?
I would hazard a guess that the reason for such high supplies is to ensure a sizeable overload margin for the phono preamp. This being the case you maywish to look at the LT1028 -A (From memory +/- 22V) which should justify the outlay. For line stages, without a schema and thus guessing, you could try the higher noise FET chips such as an OPA134 with regs as it offers excellent transparency.
The supply differences should have no effect.
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