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General HIFI => Amplification (Pre/Power) => Topic started by: data on October 07, 2014, 01:16:39 AM

Title: one woofer pump_ground issue?
Post by: data on October 07, 2014, 01:16:39 AM
Hay guys

I'm at a lose on this one  :(

With the EAR Clone I have a touch of hum, slightly more in the right.

But the issue I'm trying to sort out (might be one and the same) is that when adjusting the volume pot on my main amp, the right speaker woofer pumps (left does not). There is a whooshing sound with it, move the volume up and pushes the cone outwards and move it down and it sucks it inwards. This only happens with the movement of the volume pot.

I think It's a grounding issue of the Clone as a CD played is OK, but wondering if the above symptom can narrow it down in any way?

The IEC earth goes to the ground post for the tables lead on the inside of the case, and this is the chassis ground point. I have tried it with the circuit ground (from PCB) tied directly from the RCA grounds to this point with and without a cap, and floating also, doesn't make any difference. table ground wire connected and not, still no difference.

Any ideas?

Thanks
Ian
Title: Re: one woofer pump_ground issue?
Post by: klackto on October 07, 2014, 07:57:36 AM
Sounds like there may be DC on the output of the pre. One of the coupling caps may be leaky.
Title: Re: one woofer pump_ground issue?
Post by: data on October 07, 2014, 01:29:30 PM
That would be a VSF cap :(

I'll swap them over and see what happens.

Cheers
Title: Re: one woofer pump_ground issue?
Post by: Tuyen on October 07, 2014, 01:40:03 PM
Does sound like a leaky output cap.

Fingers crossed it isn't a vsf.  In saying that, I've had two vsfs fail in the past. So I wouldn't be surprised.

Let us know how you go :)
Title: Re: one woofer pump_ground issue?
Post by: stevenvalve on October 07, 2014, 01:46:14 PM
Does sound like a leaky output cap.

Fingers crossed it isn't a vsf.  In saying that, I've had two vsfs fail in the past. So I wouldn't be surprised.

Let us know how you go :)
I to have had some fail, an expensive problem
Title: Re: one woofer pump_ground issue?
Post by: data on October 07, 2014, 02:05:53 PM
I'm not really surprised that I didn't (want), to consider it, but with no input caps on the amp, and only the VSFs on the output of the phono..... *sigh*

Will check them shortly, need to wake up fully first......yeah I know It's 1pm :)
Title: Re: one woofer pump_ground issue?
Post by: data on October 07, 2014, 02:38:11 PM
Doh!

Swapped the VSFs over for a pair of Dayton caps..........now It's on the other channel only  ::)

Edit: The VSFs test OK for capacitance measured out of circuit, but how the hell did it swap from one channel to the other with the caps change.......weird!
Title: Re: one woofer pump_ground issue?
Post by: data on October 07, 2014, 04:50:51 PM
The very good thing about this...

Is I found it before trying any of Steve's Red base lovely's in it :)
Title: Re: one woofer pump_ground issue?
Post by: data on October 07, 2014, 05:17:56 PM
My bad!

Showing my lack of knowledge again.

Pulling the valves is not what I should have done as I'll get peak voltages, and heaters are fine as being shared across the two of each valve means one is positive and one negative....nothing hurt luckily ;)

OK, so I'm back to this  pumping woofer again, so a grounding issue maybe.

I'll check the table, but as it changed from one channel to the other with the cap change I don't think so.

Edit: Going back to a cheap old CD player until I work this out :(
Title: Re: one woofer pump_ground issue?
Post by: data on October 07, 2014, 09:27:57 PM
OK, have reworked the connections for the musicaps, remounted the VSFs, and replaced the heater wires as they looked messy anyway.

The only thing I can think of that could have changed when the pumping changed to the other channel is the remounting of the RCA sockets. So making double sure that they are definitely isolated from chassis.

Fingers crossed

Oh, I confused myself (as I can do) about the heaters, they must be in parallel not series.
Title: Re: one woofer pump_ground issue?
Post by: data on October 07, 2014, 09:37:49 PM
It's still there, and back in the original channel.

Meh.....

Back to the sweeter sounds of the phono. I'll need to redo the phono section point to point in the future, seems to be something up with how it is now but I can't see the cause of that strange woofer/volume adjust thing. At least there is nothing amiss with the sound or the drivers outside of this.
Title: Re: one woofer pump_ground issue?
Post by: kajak12 on October 08, 2014, 11:00:27 PM
It's still there, and back in the original channel.

Meh.....

Back to the sweeter sounds of the phono. I'll need to redo the phono section point to point in the future, seems to be something up with how it is now but I can't see the cause of that strange woofer/volume adjust thing. At least there is nothing amiss with the sound or the drivers outside of this.
Just get digital you have less problems
Title: Re: one woofer pump_ground issue?
Post by: data on October 09, 2014, 01:10:10 AM
Just get digital you have less problems
Mario..... not going to help, as the stylus will just slid all over those little shinny drink coasters ;)

The problem here isn't the turntable, It's a tube phono, maybe I should go SS instead?
 :D
Title: Re: one woofer pump_ground issue?
Post by: data on October 10, 2014, 12:39:00 PM
Eek!

Just measured for DC on the output RCAs of the phono stage, .65vdc on one and 45vdc on the other  :o

Something very odd here!
Title: Re: one woofer pump_ground issue?
Post by: Tuyen on October 10, 2014, 12:51:22 PM
The output cap is not doing its job! :o
Title: Re: one woofer pump_ground issue?
Post by: data on October 10, 2014, 12:55:54 PM
It's strange though as when I pulled the VSF they measure correct in capacitance and when subbed with some Dayton's that high DC moved to the other channel.

Needless to say, i won't be using the pbono stage until I nut this out.............the nut possibly being me  :D
Title: Re: one woofer pump_ground issue?
Post by: data on October 10, 2014, 12:58:37 PM
I may need to order some new (not Duelund) output caps.

But I'll have yet another good look over the PCB  ::)

Have a couple of pairs of Russian PIOs here suitable, so will replace the VSFs with those and see what I read.
Title: Re: one woofer pump_ground issue?
Post by: data on October 10, 2014, 01:55:16 PM
OK, with the PIOs in place while the reading is a little erratic, one reads between 25mv to 35mv and the other between 2mv/3mv and 15mv

The Duelunds were mounted underneath the PCB while these are mounted on top, I guess that has no bearing on the readings, does this mean the VSF's are stuffed?

OK, no strange woofer action when adjusting the volume now, but DAMN! Russian PIOs are no substitute for VSFs  :'(

Edit: hmm...I'm still wondering if the issue was mounting the caps on the underside of the PCB  :-\
Edit part 2: I'm near certain that it was the mounting on the underside that was the issue (nothing else makes sense to me), picking up interference, but no where else to mount the VSFs. The PIOs are OK but a definite step back. looks like I need to rebuild this thing soonish, that way I can construct it point to point while at it.
Title: Re: one woofer pump_ground issue?
Post by: data on October 11, 2014, 11:43:43 PM
OK, I tried mounting the VSF off to the side & shielded with mu-metal, with leads running a short distance across the upper PCB and no go. Again over half a volt on one and 46v on the other.

Damn!
I might wait a bit and see the comparisons with the Jupiters before replacing the Russian PIOs, don't like the PIOs but not willing to risk Duelunds again.

Drove down for some smokes just before, and took the VSFs with me and tossed them in the dumpster. Was going to go into the bins downstairs, but I know myself and would have obsessed on them and fished them out in more fruitless attempts to use them  ::)
Title: Re: one woofer pump_ground issue?
Post by: stevenvalve on October 12, 2014, 02:10:47 PM
Don't throw them away, you can use them in a crossover and other applications, in a crossover they work in a different way, and will work perfectly. I had some faulty one's. they had AC on the output but in my crossover they worked fine.
Title: Re: one woofer pump_ground issue?
Post by: data on October 12, 2014, 02:34:19 PM
 :o

Hmm...looks looks like a dumpster dive tonight  :D

LOL
Probably buried under a heap of crap by now, oh well....weren't going to suit what I needed them for anyway. But thanks for that heads up all the same, Steve.
Title: Re: one woofer pump_ground issue?
Post by: omodo on October 12, 2014, 06:16:57 PM
wow binned them, that's a bit drastic!!  :-[

only one was bad? wouldn't a single replacement would be around the same $ as a pair of Jupiters?
Title: Re: one woofer pump_ground issue?
Post by: data on October 12, 2014, 07:13:18 PM
The other was still allowing over a half volt of DC pass (0.68v), not acceptable when there are no blocking caps on the input of my amp....or is it?

Still might dive in and see if I can get them out, luckily It's Sunday so may not be difficult or messy :)

But with my plans, and these being 1.5uf I doubt I'll use them unless I go with a SS player or DAC.......not likely for myself.

Edit: Ah bugger it, can't bring myself to dumpster dive to get them back.
Title: Re: one woofer pump_ground issue?
Post by: omodo on October 12, 2014, 07:44:25 PM
http://www.freelancer.com.au

 ;D
Title: Re: one woofer pump_ground issue?
Post by: Rob181 on October 12, 2014, 07:44:48 PM
Edit: Ah bugger it, can't bring myself to dumpster dive to get them back.

Jeez I would...its Sunday & I wouldn't care anyway...
Title: Re: one woofer pump_ground issue?
Post by: data on October 12, 2014, 09:58:30 PM
OK...Ok, went down and had a go.

First I would like to say that I'm about to have a very thorough shower shortly, but have them back, only an extra issue now with one, fishing them out and one has a leg snapped off at the body...maybe from the ompact of when they went in  :D

I don't even know if it is the better one or not.
Title: Re: one woofer pump_ground issue?
Post by: Rob181 on October 12, 2014, 10:50:01 PM
OK...Ok, went down and had a go.

First I would like to say that I'm about to have a very thorough shower shortly, but have them back, only an extra issue now with one, fishing them out and one has a leg snapped off at the body...maybe from the ompact of when they went in  :D

I don't even know if it is the better one or not.

That's better...

Once you have showered...relax...& enjoy some music...
Title: Re: one woofer pump_ground issue?
Post by: data on October 12, 2014, 11:17:37 PM
Oh god, Rob, the things we do for audio parts, even dodgy ones ;)

Had a shower and did a.......repair of the leg as best I could, so now they go in the cupboard until and if i have a use  ::)

They look worse for wear....as expected after being in and out of a few different builds, and a dumpster also.
Title: Re: one woofer pump_ground issue?
Post by: zenelectro on October 13, 2014, 12:33:58 PM
The other was still allowing over a half volt of DC pass (0.68v), not acceptable when there are no blocking caps on the input of my amp....or is it?

Still might dive in and see if I can get them out, luckily It's Sunday so may not be difficult or messy :)

But with my plans, and these being 1.5uf I doubt I'll use them unless I go with a SS player or DAC.......not likely for myself.

Edit: Ah bugger it, can't bring myself to dumpster dive to get them back.

Data,

You should really just get a tech to check it out, anyone who knows what they are doing will have the problem diagnosed very quickly.

If you are measuring DC on the OP of the pre amp this can be purely because there is no ground reference resistor at the OP to pull it to ground.
There should be a resistor -after- the OP cap going to ground but some equipment don't always have one,  they rely on the gear that the
pre is feeding to have an IP ground ref resistor which will pull it to ground. 

If there is no resistor to ground after the OP cap, solder a 1 meg R there to gnd and re measure.

If you have a decent size OP cap and the OP resistor is also large say >1.0uF and 1 Meg R then you may measure some
DC there that is constantly slowly hunting around because of very low frequency drift. But it will be 'hunting' around zero going + and -
to some small degree - this is normal.

Other causes of DC offset are a leaky grid on the IP tube that connects to the 'wiper' of the volume pot - assuming the vol pot
is right at the IP feeding the first tube.

There are some cases where a high frequency oscillation can measure as a DC offset with a multi meter and where the oscillation can
actually cause some DC offset, however this is not common and since you don't have an oscilloscope lets doubly hope so. :)

In the end you are better off just getting someone who knows what they are doing to check it out, you will save a lot of time.

cheers

Terry 
 

Title: Re: one woofer pump_ground issue?
Post by: data on October 13, 2014, 02:59:23 PM
Wow!

Some stuff to take in, but very good stuff!

Thanks, mate......I'll look into those things and if need be I'll look for someone to have a look at it.

I wish you were local ;)

Thanks again
Ian

Edit: the Schamatic shows a 220k resistor to ground.
(Sub ECC83 with 6SL7)

(http://www.jogis-roehrenbude.de/Leserbriefe/Carsten-RIAA/Schaltung.png)
Title: Re: one woofer pump_ground issue?
Post by: data on October 13, 2014, 06:00:41 PM
OK, I'm going to search out a competent Tech' to look at this pre. I didn't like that he had the circuit ground tied directly to chassis as from reading up this is not a safe practice? but if I put a C/R in between (.047 & 39ohms) it has no music and DC pulses on the left channel  >:(

Anyone know of a good tube tech' in Brisbane?
Title: Re: one woofer pump_ground issue?
Post by: Jehuty on October 13, 2014, 07:36:57 PM
OK, I'm going to search out a competent Tech' to look at this pre. I didn't like that he had the circuit ground tied directly to chassis as from reading up this is not a safe practice? but if I put a C/R in between (.047 & 39ohms) it has no music and DC pulses on the left channel  >:(

Anyone know of a good tube tech' in Brisbane?

Paul Baker. He's near Gold Coast though....But he's always worth a visit  8)
Title: Re: one woofer pump_ground issue?
Post by: data on October 13, 2014, 07:53:48 PM
Cheers mate :)

Will need to wait a few weeks to engage him for the job, but this thing is a POS, taking everything back to how it was and worked and still a pulse in the left channel and no sound.

I might even just scrap the home made PBC and just go without and rebuild the bloody thing in a better case, as It's not that complicated a circuit......I think his layout/build on this PBC is part of the problem.

But who knows.
Title: Re: one woofer pump_ground issue?
Post by: Jehuty on October 13, 2014, 08:06:33 PM
If you want a nice case, Paul Baker can get you a very nice one like this (borrowed pic from gamve):
(http://i480.photobucket.com/albums/rr165/gamve/P9242429_zps2d33dbde.jpg)
Title: Re: one woofer pump_ground issue?
Post by: data on October 13, 2014, 08:19:27 PM
Looks cool  8)

I'll have a think about things and work out what fits my budget, and when... before deciding what way to go.

Edit: My bad!
A ground wire that looked connected was actually broken :(

Working again..........silly me, as usual the problem was me  ;D

Will still rebuild the thing in the near future. It's also a good thing that I can laugh at my own mistakes.
Title: Re: one woofer pump_ground issue?
Post by: data on October 27, 2014, 03:25:37 PM
Damn it! had to try the Duelunds one last time, and one leaks far too much.

But I definitely need more (maybe RS) as they cream the Russian PIOs  >:(
 :D
Title: Re: one woofer pump_ground issue?
Post by: stevenvalve on October 27, 2014, 11:32:58 PM
Damn it! had to try the Duelunds one last time, and one leaks far too much.

But I definitely need more (maybe RS) as they cream the Russian PIOs  >:(
 :D
It's a problem, Duelunds are usually the only game in town.
Title: Re: one woofer pump_ground issue?
Post by: klackto on October 28, 2014, 07:10:23 AM
Has anyone tried the RS series?
Title: Re: one woofer pump_ground issue?
Post by: data on October 28, 2014, 09:11:40 AM
It's a problem, Duelunds are usually the only game in town.
Seems so Steve, I'll wait and get some in the new year.
8)
Title: Re: one woofer pump_ground issue?
Post by: data on October 28, 2014, 09:14:05 AM
Has anyone tried the RS series?
Mike Lenehan has been using them I think.

Maybe Bill has hear them...
Title: Re: one woofer pump_ground issue?
Post by: data on January 08, 2015, 09:24:00 PM
OK, this is oscillating still i think.

A whooshing sound from speakers at low level that increases with volume, and checking the outputs for DC shows symptoms of RF with small but erratic DC readings, between about .7mv and 15mv. The low whooshing is variable like the variation of those DC readings.

Damn it, just when i was going to get some RS caps for it, so now that will have to go towards sorting this.

Edit: Now not doing it, this stage drives me nuts at times, but great when it is not  :D
Title: Re: one woofer pump_ground issue?
Post by: data on January 13, 2015, 05:16:50 PM
Hmm...oriented the board a different way and things seem more stable and hum is near non existent.

Meh...It's a forward step anyway :)