Pre-amp alternative

[Forever Young]

Technics preamp seems to be on it's way out. I keep losing treble on the right channel. I've tried my spair power amp, swapping leads over, speaker wires over, speakers over. It's always on the right. There was no obvious place to spray switch cleaner.

I mainly use it as a volume control, source select, and phono stage. Been thinking about getting a dedicated headphone amp.

I'm looking for something to switch between my DAC and a seperate phono stage on the input side. A spare input would be nice. Then, to switch between my power amp and seperate headphone amp. Ideally, it would have a built in volume control. I also want to connect my subwoofer via RCA. The DAC can connect via RCA or XLR. Or should I get my technics repaired?

Any ideas welcome.

 

[insider9]

Losing treble on one channel sounds like an issue with a tweeter. Have you ruled out speaker issue?

 

[Forever Young]

Yes. I've swapped the speakers over, moving the one on the right to the left, and left to right. I still get intermittent treble. I don't always notice it go off, but I notice it come on.

 

[Forever Young]

Switch cleaner seemed like it helped a bit, for a little while. But there was no obvious place to spray it in anywhere.

 

[insider9]

It's really difficult to say. I guess it depends on what level of gear you're talking. If it's a very vintage and desirable model then I'd definitely look to fix it. Other than that I'd look at alternatives. As an example I'd be reluctant to spend £50 fixing a £100 pre.

 

[Forever Young]

It's an Su-C1000M2. I never got around to replacing the battery. I've got the matching power amp. The amp needs it's LEDs replacing in the VU meters. The Technics amp is just sitting around. I've been using the Technics pre with my NAD amp. It's second output goes to my active sub.

 

[shadders]

Hi,
Do you have a tone control defeat button ?. I get this issue sometimes on my Cambridge Audio Azur 650A amplifier - i switch in and out the tone control defeat button and there are static clicks, and it seem to resolve.

The other issue is where the inputs switch- i leave it on the same input, and one channel goes/reduces, and sometimes the treble seems to be cut too. So i quickly switch the inputs which operates the relays and this resolves the issue.

So, it could be a dry joint on the PCB, or relays issue, or a switch problem.

Regards,
Shadders.

 

[Forever Young]

It has got tone defeat. I never use the tone controls. There's no way to avoid the balance control, which would be good. I never use that either. There are no static noises. I get the old equipment, background "shhhh", but only if I turn it up pretty loud. That's not coming from the NAD amp. I was getting it switching source on its own. It hasn't done that for a while, and I'm not sure why it's improved. It tends to get left on the same input, which is the one the DAC goes into. Occasionally, I'll switch over to phono.

 

[shadders]

It has got tone defeat. I never use the tone controls. There's no way to avoid the balance control, which would be good. I never use that either. There are no static noises.

Hi,
Have you operated the tone defeat multiple times ?. Is there any change when you turn it on and off again, multiple times ?

Have you switched the inputs such as to Aux, then back to CD etc., multiple times when you get the issue, and if so, does it have an effect ?

Regards,
Shadders.

 

[Forever Young]

I'm sure I have, but I can't remember. It seemed like all the drivers in the speaker stay on when it occurs. I tend to notice it most if I'm streaming from the PC, via the DAC. I struggle to hear what the actors are saying and don't notice until it comes back and I can hear again. It can work fine for an evening, be playing up for the evening, or keep going in and out for short periods of time. I'm currently sitting on the floor by my right speaker, trying to make it do it. I've just fiddled with all controls and not getting static sounds. The source selector is working perfectly. I'll keep trying.

 

[shadders]

Hi,
To take this further - take off the lid of the unit and tap the insides with a piece of plastic. Do not use a pencil, as the lead conducts electricity.

If the changing of the inputs whilst playing audio has no effect, then it may be an opamp failing, or a conductive path problem - so tapping the insides of the amplifier will show up any dry joints etc.

If you are switching the inputs when listening to a degraded sound, or operating the tone defeat at the same time, and no change, then the above is the next stage,

Regards,
Shadders.

 

[Forever Young]

Thanks for your help in trouble shooting. I'm listening to a 1khz tone on repeat. I've got the balance all the way to the right. So far its once gone silent. Switching source made no difference. I tried everything. It came back on after I turned the balance knob. I'm waiting for the tone to go silent again and I'll go straight for the balance knob. I don't yet know if it's the balance or just a coinsedance.

 

[shadders]

Hi,
It is difficult to say what it is. Tapping the balance pot, tone control pots, and other areas on the PCB will help. Moving the balance control rapidly multiple times may clear the issue. Tapping the PCB/electronics/pots inside the amplifier - will locate the problem, if it is mechanical.

Regards,
Shadders.

 

[Forever Young]

It hasn't done it again. Further investigation required. I did find that the balance is behaving strangely. It doesn't cross fade smoothly or consistently, from left to right. There is a dirty connection (static like) sound at the extreme left (anticlockwise). I guess I should take the lid off, like you suggested. It's probably time for a clean out anyway. I'll check for dry joints. I expect this pot needs replacing. I don't know if that's possible? This Technics isn't like the old 70s stuff I had before it. They were large, metal and open. They were easy to clean out. This thing has small, enclosed pots. There's not even a squirt hole.