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Old 27th October 2005, 03:56 AM   #1
jleaman is offline jleaman  Belgium
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Default No bass / No Treble But Bass And treble Help!

OK well I have been fighting this a few weeks now and have no clue how to help my self. Could it be a impedance problem Or ?

Note all equipment is working properly.

Ok scenario..

I have :

LG DVD player with digital out and RCA out with built in DAC..
Dual TDA 1541a's DAC
Tube Buffer that goes with the DAC witch uses 6DJ8's.
Aleph Mini A's
50K Alps Passive Pot.

First Iíll describe the problem and some things I have tried.

The tube DAC is suppose to go along with the digital to analogue DAC. It goes from Digital out on my LG to > DAC then from DAC analogue out > to tube buffer then to Passive Pot > mini A's.

LG > DAC > tube > Passive pot > mini A's

If this is like this i get no bass maybe a squeak or so.
If i go LG > DAC > Passive pot ? mini A's I get bas clarity but hardly any volume but good sound.

If I go LG > DAC> pot tube buffer > mini A's I get all bass no treble.

Now if i go I-Pod > tube Buffer > mini A's then I get clear sound bass treble and etc etc.

Any ideas what to do here. ?

I could post any info needed upon request..
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Old 27th October 2005, 05:17 AM   #2
jleaman is offline jleaman  Belgium
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Any one ?
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Old 27th October 2005, 08:06 PM   #3
jleaman is offline jleaman  Belgium
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Default Inside

Inside The pot.
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File Type: jpg inside.jpg (81.7 KB, 333 views)
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Old 27th October 2005, 09:00 PM   #4
sek is offline sek  Germany
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Default Re: No bass / No Treble But Bass And treble Help!

Hi Jason,

As you mentioned impedances, let me try to figure out some questions:

Quote:
LG > DAC > tube > Passive pot > mini A's

i get no bass maybe a squeak or so.
You mention the pot to be 50k. Depending on the way you connect it, are you maybe loading the tube buffer too heavily (so that it can't deliver enough current/voltage for larger amplitudes)?


Quote:
LG > DAC > Passive pot ? mini A's

I get bas clarity but hardly any volume but good sound.
Maybe because your DAC doesn't suffer from the pot impedance (due to higher current capability/lower output impedance, compared to the tube stage).
But this time, the maximum output level of the DAC might not be sufficient to drive the mini-A with larger voltage levels (not enough overall gain).

Quote:
LG > DAC> pot tube buffer > mini A's

I get all bass no treble.
Might the pot form an RC filter with the input (capacitance) of the tube buffer, implementing a low pass filter?

Quote:
I-Pod > tube Buffer > mini A's

I get clear sound bass treble and etc etc.
Sure, because the iPod has a fairly low output impedance (try driving the speakers directly, you'll be surprised) and the pot doesn't interfere with the tube.


All in all, I'd say you really have a problem with impedance matching between the stages. Depending on your needs either a higher or lower pot value might help (try different cheap ones both before and after the tube buffer), but you should post the schematics before I could guess any better.

Ciao,
Sebastian.
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Old 27th October 2005, 09:55 PM   #5
jleaman is offline jleaman  Belgium
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Default Re: Re: No bass / No Treble But Bass And treble Help!

But i tried 3 pots lastnight.. I even tried wireing them diferent too. still same problem what can i do to fix this ?
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Old 28th October 2005, 12:59 AM   #6
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Default Re: Re: Re: No bass / No Treble But Bass And treble Help!

Quote:
Originally posted by jleaman
But i tried 3 pots lastnight.. I even tried wireing them diferent too. still same problem what can i do to fix this ?
I suppose you have an output coupling cap after that tube, on your dac?
What's the value of that cap?
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Old 28th October 2005, 01:45 AM   #7
jleaman is offline jleaman  Belgium
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This was already lokoed at and was not a answer to solve this ..
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Old 28th October 2005, 06:18 PM   #8
Raj1 is offline Raj1  United Kingdom
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Hi,

I didn't realise you had already posted here, the posts above reflect some of what I posted on Chung's forum.

I still think the output impedence of that tube buffer is not sufficient to drive a passive pot without an additional gain stage.

Either way it's going to cost money, it's all to do with budget and what seems reasonable and affordable to you. Of course the need for extra expense is unfortunate, but perhaps not strictlty nesessary, if you choose to live with the SS output only.......


Thanks
Raja
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Old 28th October 2005, 06:22 PM   #9
jleaman is offline jleaman  Belgium
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Quote:
Originally posted by Raj1
Hi,

I didn't realise you had already posted here, the posts above reflect some of what I posted on Chung's forum.

I still think the output impedence of that tube buffer is not sufficient to drive a passive pot without an additional gain stage.

Either way it's going to cost money, it's all to do with budget and what seems reasonable and affordable to you. Of course the need for extra expense is unfortunate, but perhaps not strictlty nesessary, if you choose to live with the SS output only.......


Thanks
Raja
What are my options to fix this then ?

New thing :

If i turn the pot up when connected dac then pot then tube buffer then ( any power amp ) if it is a low volume there it so much bass no treble if i turn it up say half and alittle more i get treble bass and lots of gain if i go louder ( eek ) i get all the signal with trebble bass and hi gain.. HUMM>>:scratch :
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Old 28th October 2005, 09:01 PM   #10
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I suspect the pot.
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