[RODA]

Hello

I'm currently building a Clarinet.
Bought it from a gay that gave up on the project.
EDIT: Not gay, GUY    

He had the half-kit, a cabinet and parts.

So, I assembled the kit, had to get some help determening which leads to use from the transformer. (not original)

I got it to play music, but unfortuneatly also buzz and hum......

A description of the differences from original.

- Not using the input, output, selection or balance soldering points on the circuit-board.

- Going directly from RCA-inputs to volumepot (Alps 100K)

- From volumepot to circuit-board, bypassing the first caps, since my source has no DC-offset.

- From output after caps, tapping onto the circuit-board leads (to have as short signalpath as possible) directly to the RCA-outputs.

- The transformer in the back of the cabinet instead of on top.

- RCA's isolated from chassis.

- Using RCA 5Y3GT rectifier-tube and Golden Dragon ECC82.

- Placed RCA's on the right side of the cabinet.

I have grounded like this:

Leads from:
- RCA in right ground
- RCA in left ground
- RCA out right ground
- RCA out left ground
- Circuit-board ground (using one of the ground connections for volumepot)
- Volumepot right ground
- Volumepot left ground
- Transformer ground
- Chassis ground

All of these are connected together.

Still its humming and buzzing......  (mostly buzz).

When I touch the cabinet, I get a "spark"-sound in the speakers....
The same when I touch ground on cd and amp.

The voltages are OK.
Filament voltage is 6,33v.

I love the sound from the system with the Clarinet connected, but the noise is irritating.

Any Ideas ?

A few pictures:










(RCA's moved after this pic)

And some pictures of the final design.
Still lacking mains input, but it's coming shortly.








(acryllic top-plate replaced with aluminium)

[/url]

[Eric H]

Since nobody else is responding to your post I'll offer some ideas...  assuming your voltages are all within spec, as you say they are, then it sounds like a ground-loop problem of some sort, or maybe some sort of PT wiring issue?  A common construction problem with these units it seems is accidentally grounding the RCA connectors... go through the archives...  also, there's a typo (I think/hope) near the beginning of your post that might discourage people from helping you out...

[RODA]

Since nobody else is responding to your post I'll offer some ideas...  assuming your voltages are all within spec, as you say they are, then it sounds like a ground-loop problem of some sort, or maybe some sort of PT wiring issue?  A common construction problem with these units it seems is accidentally grounding the RCA connectors... go through the archives...  also, there's a typo (I think/hope) near the beginning of your post that might discourage people from helping you out...

Thank you!

I'm not too good in the english-department  , please explain "PT wiring".

I have checked, and my RCA's are not grounded to the chassis.
Went through the archive prior to posting this.

Typo = typing error?
Please tell me....

During the weekend I tried to fix the problem.

Removed all the ground-connections, and grounded them to the original holes in the pcb.
   That helped!

I also scraped off the black anodized colour on connection-points in the cabinet.

A few pictures:

















I'm very pleased with the sound, an anxious to start rolling tubes.  
Any recomendations regarding tubes?

[mgalusha]

You might try adding a ground lift switch. Basically a switch that will connect and disconnect the circuit ground from the chassis ground. Of course the earth ground must be connected to the chassis at all times for safetly.

I built a Clarinet for an AC member and in his system it was horribly noisy. I had built in a ground lift switch but neglected to tell him about it. I had him flip the switch and it became very quiet. Note this is very system dependent. In my system the switch had very little effect and it was fine in either position.

Looking at your photos, it appears you have the circuit ground tied to the chassis with a braided cable. To implement a ground lift switch you will need to be sure that none of the circuit grounds are in contact with the chassis. This includes all of the threaded stand off's used for mounting the PCB.

Mike

[RODA]

Thank you, mgalusha

I will try this.

[Yoda]

Your transformer may also be causing some interference.  In the standard setup, Hagtech locates the power transformer outside of the metal chassis, presumably for shielding the internal components.  You may try relocating yours within your chassis and or shielding it from the circuit board.

Depending on your power amp, you may want to adjust the output impedance.  I have a tube pre-amp that is dead quiet with my decware tube power amps with no additional impedence on the output, but when I connected it to a set of solid state powered monitors, there was a noise.  There is a 600 ohm switch on the output, and that made it stable with the solid state gear.  

Matt

[RODA]

Thank you!

How do I incorporate this 600 Ohm swith?
In paralell or in series with the signal?
On the power-amp or the pre-amp?

Thank you for all help! This is fun!!

[Eric H]

Hi Rolf,

PT wiring = Power Transformer wiring, and the typo was "gay" instead of "guy"...

I think it's logical to guess that the problem might be related to the modifications...  the PT inside the chassis, as previously noted, and also the elimination of the balance and selector switches (I find the "micro" balance switch pretty nice, by the way).  Are there any unused traces that should be grounded that are floating?  Also, if you can characterize the hum/buzz in more detail that might help...  does it increase as you turn up the volume?  Have you tried grounding the inputs?  etc...

Eric

[RODA]

Hi Rolf,

PT wiring = Power Transformer wiring, and the typo was "gay" instead of "guy"...

I think it's logical to guess that the problem might be related to the modifications...  the PT inside the chassis, as previously noted, and also the elimination of the balance and selector switches (I find the "micro" balance switch pretty nice, by the way).  Are there any unused traces that should be grounded that are floating?  Also, if you can characterize the hum/buzz in more detail that might help...  does  ...

Ohhh. I don't know if the guy was gay.........

Yes, I am aware of the PT beeing inside the cabinet, and I belive this may be a future improvement to move it "outside".

Unused traces.
Do you meen I shuold ground the original traces from input to selection switch, and from selection sw. to balance?
These traces are not connected at all.
Neither signal or ground.

Humming.
My power-amp actually has some humming.
Thats why I don't beliveve (yet) that this is the biggest problem.

Buzzing/Noise.
This is what I feel is "a problem"
The noise is not heard when I play music, and not too annoying when I stop the music.
To describe it: It sounds like the "regular" noise coming from amps, but it also contains hizz (that I suspect is coming from worn-out tubes).

I think my power-amp (solid-state) has a fairly low input-impedance.
That's why I'm wondering how to try Yoda's tip.

Wil try to post a drawing of how I now have the connections.

Thank you for helping!!

[Yoda]

I think it's a modification you can try externally with your interconnect (IC) by adding a resistor between the signal and ground at the amp side.  You may want to test this on a cheap IC, or fabricate one with CAT5 cable and RCA jacks.

I have a Golden Tube Audio SEP-1SE (single ended 6922 based, transformer coupled pre-amp) which has jumpers for this, but the manual illustrates how to do this for the interconnect to match different amps.  I'll post a scan later of that part of the manual that designates the value of the resistor.

After re-reading your previous posts, I think having good ground and chassis connections would make a difference too.

Nice chassis--can you make one for me?

Matt

[mcgsxr]

mgalusha might be referring to the Clarinet that he built for me - using my higher efficiency Visatons, there was a buzzing that I could hear at the listening chair.

A quick email off to him, and an explanation of what that switch on the back was - click, silence.

I am no builder of these babies, but I can attest that the inclusion of this switch was exceptional foresight on Mike's part.

Great preamp, once you get it sorted.

[RODA]

Hello again!  

I Will have to try this "ground-lifting" then.  

I have made a drawing of the connections (signal/gnd) on my PCB.
This is the best configuration I have tried so far.

Do you see any obvious changes I should do?
Please let me know.

[Tone Deaf]

Hi Rolf - what a lovely job!  Looks much cooler than mine.  Shame to move the transformer outside the case, could you screen it where it is?

Probably make no difference, but personally I'd connect input ground near the input, ie through the volume pot.

I spent a lot of time trying to reduce noise when I built my Clarinet - I was convinced I'd done something wrong.  In the end I realised my old-fashioned power amp (a quad 405) was way to sensitive for it.  I reduced the gain of the quad's input stage & all's been well ever since.

Good luck - hope you fix it!
Glyn

[RODA]

Hi

Thanks for the nice comments, Glyn!  

I have tried the "ground-lift" yesterday, unfortuneatly that made no difference.

I hope to avoid moving the PT outside the box, but it will make no practical difference. I'm willing to go far to get rid of the noise-problem.

I will wait until I get my new tubes and then check the noise-level again.

How did you adjust the gain on the power-amp?

Suspect my power-amp to have the same "problem" as yours.
It's known to work fine with passive attuenators, and to respond to noise for example in the supply current.

You have all made me feel very welcome in this forum, it's good to be a newbie here  

Please keep the tips flowing.  

[Tone Deaf]

Hi Rolf,

input sensitivity for my power amp turned out to be 500mV for full output.  There was stacks of help on the net for modernising quad amps - I followed Bernd Ludwig's mods.

Glyn

[hagtech]

Hi, I'm back.  Buzz is usually caused by something "floating".  The anodized chassis pieces are a good example.  The buzz comes from the rectification in the heater circuit.  Large currents turning on and off.  This is all supposed to be localized and single point grounded, but there is always radiated emissions.

The transformer looks beautiful.  I don't suspect it as a problem.  Make sure all chassis pieces are connected to a common ground.  Look for wiring loops in the cables (to/from RCA jacks) that might get close to diodes or tranny.  Keep inner loop area low.

Could be the shaft of the ALPS floating?  You can trace down this sort of problem by touching various parts to see what effect there is to the buzz.  What happens if input to tubes is shorted (after ALPS)?

jh

[RODA]

hagtech
Hi, I'm back.  Buzz is usually caused by something "floating".  The anodized chassis pieces are a good example.
Hi
Thanks for answering my tread.
Read your answer in another tread about scraping off the black colour on the caninet joints, and did so. I believe it helped, but it's a bit difficult to A-B test....

The buzz comes from the rectification in the heater circuit.  Large currents turning on and off.  This is all supposed to be localized and single point grounded, but there is always radiated emissions.
Ok.
Could it be the diodes are the wrong type?
When I got the kit, the parts were already soldered onto the pcb.

The transformer looks beautiful.  I don't suspect it as a problem.
Thank you, don't know the brand....
So I shouldn't worry to much about moving it out of the cabinet?

Look for wiring loops in the cables (to/from RCA jacks) that might get close to diodes or tranny. Keep inner loop area low.
Sorry for the incompetence.......Wiring loops, by that you mean cables from one point to another an the to gnd, instead from each point directly to gnd?
Inner loop area low = shortest possible cables?

Should I use the original gnd points for signal in out, or find gnd close to the inputs/outputs where they now are placed?

Could be the shaft of the ALPS floating? You can trace down this sort of problem by touching various parts to see what effect there is to the buzz. What happens if input to tubes is shorted (after ALPS)?
Yes, the shaft of the Alps is floating.
Makes no difference though, wether it's grounded to chassis or not.
Should I ground the pot-chassis to pcb-gnd?

Touching. Sounds dangerous..... I guess you mean chassis, rca-input/output.....
Will have to try this shortening of inputs to see(hear) what happends.

Hope to make it "buzz-free".
Really enjoy the sound of the Clarinet.
Thanks for sharing this design with us!   [/b]

[hagtech]

Could it be the diodes are the wrong type?

Probably fine.

So I shouldn't worry to much about moving it out of the cabinet?

I think it will be ok as is.  If anything, maybe orient it 90 degrees, but I think you have the best direction right now.

Wiring loops, by that you mean cables

Each input or output should have it's own return (ground) wire going with it.  Try and not separate all of these too far from each other, as ground loops are made as soon as you plug in the interconnects.  In fact, does buzz change if you unplug one of the channels?  Is there buzz without any input?

Should I ground the pot-chassis to pcb-gnd?

You'll know by touching it.  Now don't go touching any traces or high voltage.  I meant touching the various grounded chassis pieces, or RCA shields, or tranny bells, etc.  If something is floating and picking up a field, then tying it down will help.

jh

[RODA]

Each input or output should have it's own return (ground) wire going with it. Try and not separate all of these too far from each other, as ground loops are made as soon as you plug in the interconnects. In fact, does buzz change if you unplug one of the channels? Is there buzz without any input?

I have them separated, so there's one source for buzzing.
No changes when unplugging input (one or both) or shortening the inputs.

You'll know by touching it. Now don't go touching any traces or high voltage. I meant touching the various grounded chassis pieces, or RCA shields, or tranny bells, etc. If something is floating and picking up a field, then tying it down will help.

The pot hasn't been properly attached to the chassis yet, so if the pot-chassis is not in contact with the chassis i can hear some noise in the speakers when touching it.

Here's the "spooky" part:
I have a Sony XA-30ES cd-player.
It has a "puck" to put on the cd in the tray. (brass-puck I think)
When I touch the puck, I can hear a (very low) sound/noise in the speakers.
It's hard to describe the sound, but it's a short "tap" "burst" like when I touch it, it gets "connected".
This sound was much higher and noticeable before I did the latest changes on the cabinet an gnd-layout (pictures in this tread).

I'm also beginning to believe that the buzz is just me, and that this is my first tube-equipped component.
My power-amp is known to work well with passive attenuators, and I suspect it to have lots of gain.
The speakers are only 83dB sensitivity, but with lots of gain both in the Clarinet and the power-amp......?
This, plus the fact that the preamp I used before the Clarinet was op-amp based maybe made me a little "buzz-allergic"  

I will have a go at shortening the inputs after the alps, and tell you if it made a change.

Thanks again for all help!

[RODA]

Hi

Tried to shorten the inputs, after the pot.
Didn't help at all!  

What do try/do next?