My first mod

On my new amplifier the signal path is:

RCA
Input PCB, relay
2 x 30cms wire to pot, (volume set to max it is not big problem)
2 x 30cms wire back to amp-in (crossing twice the amplifier)
16 solder points

+ 1 meter of wire back and forward from input PVC to source selector, across the amplifier, (not on signal path, but can cause interferences)

Going to change to:

RCA
2 x 5cms wire to amp-in
8 solder points

Removing the input PCB and all the wire crossing the amplifier.

If this "tweak" doesnt improve the sound I will eat my hat...

Obviously I use it only as power, and even if I want to sell it later, not many people will want an integrated without remote control, and if someone does, it is easy to put back what I removed...

 

The biggest difference will come from bypassing the pot, not so much from extra wire and longer signal paths, but that may make a little difference.

 

What souce would you like with your hat sir? Fries?

 

I dont have an hat...

 

It is over one meter of wire, probably not as well isolated as good ICs, and running close to tubes, transformers, etc...

Cannot do any good to the sound...

Relays could also pose some problems, every thing added sure does, if I will be able to hear it, is another story, but at least I wont be thinking about it...

 

dont forget that you will need to simulate the inpedance of the pot .ie if its a 50k pot drop a 50k res from signal to ground .

also look at the input cap and consider a film cap or pio ...

 

Hmmm... now I use it at max volume, does it still have impedance... Where is the input cap...

Dont push me too hard, it is only my first mod...

Anyway, I asked the seller about my plan, he mods hifi, so hoppefully will know what I have to do in this particular unit...

 

the vol pot has three terminals per chanel signal wiper and ground. The value of the pot is seen by the source not just the value on the wiper...a your connected to signal and ground by the ic.

the input cap should be the first thing the signal encounters after switching.

 

I only see 2 terminals per channel, looking at the pic on the first post, I see WIMA red caps, arent they at least reasonable...

 

look closely at the alps pot and you can see six solder connetions..three per side!

see here for a better view of the first row

http://www.hificollective.co.uk/components/potentiometers.html

 

Now I am confused, maybe this is too much for me after all, doesnt a RCA connection only have 2 wires...

As for caps, there are some cylindrical here and there, where I could read the brand, I saw ELNA or KME, Samsung on the two large, but I will not risk changing caps, too much for the first mod...

 

imagine that the incoming signal enters the top leg of a capital E, the bottom leg is to ground and the middle leg is the wiper or signal out ...the resistance between the top leg and bottom leg is normally 50k or the value stamped on the case, the resistance between the top leg and middle leg is the attenuation of the signal.

the resistance between top and bottom leg is seen by the curcuit regardless of the level of attenuation.

 

Not inserting the resistance, it says 100k on the pot, will make a noticeable difference in the sound quality ? Or just means that I have to use less "volume" from the pre...

 

the 100k is in effect part of the curcuits impedance.....its not all in the signal path, with the volume pot turned to max there should be no attenuation but the 100k is still seen by the rest of the curcuit and attached devices.

as to the sonic effects yes no maybe ...but if it was designed with it in place it was meant to be there!

if you need two good 100k resistors pm me I've got some dale vishay and holco's you can have.

 

I think I understand now, and it is not that much extra complication, thanks...

 

The specs of the amp say 100k input impedance, same as Leben CS-660P, does the pot contribute a lot for this, I know impedance should be high, at least much higher than pre output...

 

Yes it does,; usually the pot dominates this if the input is switched directly to the volume control (i.e. no buffer before the vol control). Without the volume pot in this situation the input impedance will be even higher - not necessarily a bad thing

but

depending on the source's output stage design and the amps input stage design, the volume pot (or an equivalent resistor as suggested by Zanash) may be needed to control leakage currents/avoid 'pops' when switching sources. That's all. 100K is a good safe value to try.

 

Apparentely there is nothing but relays and small resistors on the input PCB, and, unless they hidden parts under the main PCB, input PCB is switched directely to the volume control...

 

that sound and look about right ....

I'd agree that the impedance is set by the vol pot...but every component will add to it however small.

there will be an input dc blocking cap at some point ..it may even be after the volume pot ...

the designer has the choice of placing the vol pot in three places
a. as in this case post input selection
b between buffer and out put stage [like the incatech claymore ?]
c after the output stage ....can't think of an example off the top of my head.

the amp looks very nicely built.....

 

Thanks,

I see two pairs of caps in the photo, the red WIMA and the small cylindrical purple, close to the input board, I will ask in another forum for the brand and specs...