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Old 16th April 2003, 04:20 PM   #1
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Default What is your Gainclone Configuration?

Since alot of people are building these bad boys I thought I would see what configurations are out there and what people thought of the results.

I'm running the LM3875 with a single Avel Lindberg 330va w/ 25+25 on the secondarys and dual bridges. I'm using 8800uf for the power supply. Chip schematic is below.

I am definitely not done tinkering. I plan on going to dual 18v transformers, using smaller caps in the supply, and maybe getting rid of the cap at the input.


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Old 17th April 2003, 08:46 AM   #2
miguel2 is offline miguel2  Portugal
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I used a 2.2 uF film cap in the input. I just dont like electrolytics there

Miguel
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Old 17th April 2003, 12:54 PM   #3
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You can remove 6k8 resistor and connect + input to ground directly (I noticed improvement), you don't really need 22k resistor to ground on the input. Also, if your source is OK with DC coupling cap is not required (I don't use it). So your GC practically comes down to two resistors and PS. I like to use 1000u for filter caps. First, it is very pure and simple path for the currents (the leads are 1/2" and connected directly to chip pins) and I didn't noticed much difference when connected additional 1000cap in parallel, and I noticed degradation in sound when connecting 10,000 caps. Use MUR or MSR860 On Semi diodes as they influence sonics and if using sparate PS, experiment with a cable, as this inluences the sound as well.
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Old 27th April 2003, 07:13 PM   #4
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I removed the 6.8k and the 22k resisitors and the sound did open up. I will also try removing the cap to see if I can hear any improvement.

I am getting the parts together to build the JLTi Hybrid, it will be interesting to see if there as any noticeble improvement.
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Old 27th April 2003, 09:13 PM   #5
Bricolo is offline Bricolo  France
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Quote:
Originally posted by Peter Daniel
You can remove 6k8 resistor and connect + input to ground directly (I noticed improvement), you don't really need 22k resistor to ground on the input. Also, if your source is OK with DC coupling cap is not required (I don't use it). So your GC practically comes down to two resistors and PS. I like to use 1000u for filter caps. First, it is very pure and simple path for the currents (the leads are 1/2" and connected directly to chip pins) and I didn't noticed much difference when connected additional 1000cap in parallel, and I noticed degradation in sound when connecting 10,000 caps. Use MUR or MSR860 On Semi diodes as they influence sonics and if using sparate PS, experiment with a cable, as this inluences the sound as well.
peter: you prefer 1000uF, but on what volume?
maybe 1000 is better on low volume, and higher capacitance can help on higher volumes
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Old 27th April 2003, 10:23 PM   #6
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I prefer 1000u on all volumes and I usually listen at full volume, industrial stuff like Front 242 and Apoptygma Berzerk

But I'm using BG and some say they actually show more capacitance then regular caps in a same circuit
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Old 28th April 2003, 07:54 AM   #7
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So in general folks seem to feel that the zoebel on the output is superfluous as well?

Can someone explain how both the inputs can be connected correctly to ground (ie without either the 6.8k or 22k in cct) without having the inverting and non inverting inputs of the chip effectively connected tohgether? I don't understand.

Looks to me like they'd be linked at the ground point in which case the amp would get equal and opposite inputs and hence produce nada???

Pls slap me if I've missed something obvious from "Gainclones for Dummies"

Drew
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Old 28th April 2003, 09:25 AM   #8
Paulr is offline Paulr  United Kingdom
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Hi Drew,

The 22K to ground on the inverting input is removed completeley. i.e. no not connect to ground at all.

I have seen similar resistors put in as a static volume reduction on the circuit (does a similar job to a 100K pot to ground if you think about it)

Cheers

Paul
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Old 28th April 2003, 09:26 AM   #9
Bricolo is offline Bricolo  France
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Quote:
Originally posted by Peter Daniel
I usually listen at full volume
Don't you cara becoming deaf?
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Old 28th April 2003, 02:02 PM   #10
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Taking the signal directly from a DAC and using 91dB speakers, it's not loud at all
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