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Old 21st November 2002, 05:36 PM   #1
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Exclamation Voltage regulator help!

I want to change the voltage regulators in my Classé preamp, they dont seem to be of the best kind.

It uses L7815CV (+15V 1.5Amax) and a L7915CV (-15v 1.5Amax).
The powersupply supplies +-25V to the regulators.

What regulators should i look at?
Im really intrested in those sulzer types, anyone with schematics and layout?

Nothing is overkill =D


regards - kasra
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Old 23rd November 2002, 06:29 AM   #2
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Hello!

The 78xx and 79xx-series of regulators are in fact good chips.


Best regards\Morello
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Old 23rd November 2002, 10:06 AM   #3
joensd is offline joensd  Germany
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A lot of people recommend changing the voltage regulators to chips from Linear Technology.( for example LT1086 for positive rail).
I have to admit I never done this mod so I can´t tell if it´s worth.
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Old 23rd November 2002, 10:16 AM   #4
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Default Improving regulators

[QUOTE]Originally posted by kasra
I want to change the voltage regulators in my Classé preamp, they dont seem to be of the best kind.

It uses L7815CV (+15V 1.5Amax) and a L7915CV (-15v 1.5Amax).
The powersupply supplies +-25V to the regulators.

What regulators should i look at?
Im really intrested in those sulzer types, anyone with schematics and layout?

Nothing is overkill =D


For upgrading regulators you have several paths, some quite discussed on this Forum. So first of all do a search here.

Going from generic 7X15 to adjustable types, like 3X7 or LT1085/1033, should be a great improvement. At least it was on all places I did that replacement.

The next option are the Pooge 5.51 supplies, also mentioned in this Forum. Look for that reference.

Next come Sulzer supplies. You can go see a complete building project for the Sulzer here:

http://hitechnetworks.net/bwaldron/a..._regulator.htm

Then come Jung/Didden supplies, also dissected in this Forum.

Go have a look and take your pick.


Carlos
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Old 23rd November 2002, 10:42 AM   #5
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Thank you for all the replys.

I have ordered a pair of Didden/jung PCB´s.
It seems to be the easiest solution.

regards - kasra
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Old 23rd November 2002, 10:53 AM   #6
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Default Re: Voltage regulator help!

Quote:
Originally posted by kasra
I want to change the voltage regulators in my Classé preamp, they dont seem to be of the best kind.

It uses L7815CV (+15V 1.5Amax) and a L7915CV (-15v 1.5Amax).
The powersupply supplies +-25V to the regulators.
Kasra, we have had a discussion privately but you seem not be satisfied with my answers.

First of all: what is the main goal? The main goal is to create a stable DC-wise and AC-wise voltage source. You want also little noise = low internal impedance at all frequencies

What is "bad" with the 78xx and 79xx? Rather high internal current consumption, not so fast, high drop-out voltage, not very stable voltage reference.

For preamps with rather constant current consumption the important parameters are rejection of incoming disturbance, low noise output. The easiest way to achieve this (in a already built amp) is to add passive components before and after the regulator. You will get the best effect if the components are added after. Decouple every opamp locally with 10-100 ohms in series plus 100-470 µF maybe also add 10-100 nF small polyester or ceramic cap bown to signal ground.

If the pre amp is opamp based the importance of clean voltage is less than if the amp is made by descrete parts, check for intance Pass Lab's RIAA amp with FET's.

Before you ruin your fine Classé amp totally (I've seem the pictures), maybe the amp design is wrong? The voltage is maybe alright? You are digging in the wrong end? Maybe you should design your own amp in order to get satisfied?
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Old 23rd November 2002, 11:35 AM   #7
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Per,

You have stated my goals.

However dont like to mess around with the existing design by adding / removing components due to little knowledge about the design. I have no own experiences from changeing 78xx and 79xx but there are som many things thats pointing on them and their implements to partly be the bottleneck in this design.

If i was going to change the regulators to 108x or 337 or others which are proved better, i still would need to change some components, and add some, on the board which im not found of - just to get them optimized..

The best / easiest? thing would be to simply build a new powersupply, perhaps external.

>Decouple every opamp locally with 10-100 ohms in series plus >100-470 µF maybe also add 10-100 nF small polyester or >ceramic cap bown to signal ground.

These things you mention about optimizing the opamp are all partly done, they all made the preamp better.
However i still feel the sence that i have some HF-noise and "övertoner(=D)" from the supply, which from what i know all partly points to the regulators

As you mention, the single best thing would be to build a completely new unit. Unfortunately i dont have the time to do that. Perhaps sometime in future i will.

best regards - kasra
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Old 23rd November 2002, 02:07 PM   #8
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Quote:
Originally posted by kasra
"övertoner"
= harmonics
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