I must have done something wrong when building my C-lator because I get a bunch of weird stuff hapening when plugged into my OTS100. I have poured over the schematic and can see nothing wrong (argh!) Obviously tried different tubes too as well as lifting the mains ground temporarily: no luck... Can anyone diagnose what the problem may be?

1.) When turning the unit into standby sound passes through the unit. This is before the unit is actually on.

2.) When turning from standby to on (after the reccomended 30 secs warmup) there is a lot of noise. As I turn the "in" pot to maximum some weird thudding sounds occur (thought it was a bad pot, but read on). After about 3-4 mins this seems to stop so the pot is not to blame, its something electrical! Generally, the unit seems noisy (hiss) when on even after the 3-4 mins and it seems to cause some very high freq oscillation in the rest of the amp when the presence is high up.

3.) When I turn the unit back to standby sound still passes through it for about 3-4 mins (is it a coincidence that this is a similar time period to issue 1?)

4.) When I turn the unit totally off (even unplug it) then sound still passes through it exactly like issue 2 above.

5.) When working on the unit I realised it keeps voltage in its caps much longer than my amp, it seems to never fall when turning off, so I have had to bleed the caps each time I work with it.

I am at wits end with this one? Perhaps I have broken something whilst experimenting with the unit. I can certainly perform a fix, if I have some idea of what needs fixing!

Any help would be much appreciated.

Hi, thanks for the reply. Its a scratch build so it must be something I've done. Im just worried that I have damaged a component in initial testing. I will check the wiring again of course, but I'm pretty sure its OK. I'm really hoping for someone to give me a diagnosis based on the symptoms. My first guess is its a filter cap gone bad, but before I buy a replacement and rip out the board I would like to hear any suggestions.

EDIT

I've done some more tests to identify the problem and it seems to be something to do with the interaction between the c lator and my OTS100. It seems that the OTS bleeds signal from the preamp to the power amp when the poweramp in is plugged in but floating (e.g. just a cable in the poweramp in causes a large preamp signal to pass into the power stage). When the C lator is in standby it is essentially floating the amp's power amp in (the position of the out pot determines how much of this is bled to ground).

 For the distortion channel this bleed can be controled by the level control but the ratio and master do nothing. For the clean channel this bleed can be controlled by the master.

This is all a bit weird. I have tried identifying the leak in the amp itself but no luck. I've re-dressed all the wires and this makes no difference. The only thing I have determined is that grounding the floating power amp in causes the leak to stop.

Thanks,
Yes there appears to be two problems:
1.) The amp effect loop is at fault for the bleed aspect. Say I have the distorted channel on with a low master volume setting. When I plug a single cable into the PA return (not connected to anything, i.e. floating) the distorted signal from the Preamp bleeds into the PA. The bleed somehow bypasses the master volume and in the above scenario the distorted channel bleeds very loudly (much louder than the master volume is set). The C-lator interacts with this effect hence my initial observation of bleed in the C-lator, which I think isn't at fault here.

2.) The C-lator introduces quite a lot of hum and hiss when used. This seems to be hugely exacerbated when turning effects in the loop on. When using these same effects in the amp loop with no C-lator no noise seems to be introduced.

EDIT
Regarding issue 1 above I am starting to feel this is a "feature" of the amp rather than something I have done wrong in building it. What I observed was the plugging in a longer cable to the PA in causes the bleed to reduce. It doesn't matter whether the cable is (i.e. pointing the floating end closer to the amp does not increase the bleed). This indicates it is not EM crosstalk to the floating lead but rather the effect of cable capacitance forming a path to ground from the floating PA in (more cable means more capacitance hence more signal shunted to ground). The reason the bleed is so loud is that the power amp is so strong (100w) and sensitive that it is exagerated. As soon as I plug a CD player into the floating cable the bleed is dwarfed and cannot be heard.

Can anyone else confirm that plugging a floating cable into the PA in whilst using their amp cause the guitar signal to come through the speaker bypassing the master volume?

When I plug just a cable in the pre-out its like no change to the amp. It still passes signal as it with no cable in the pre-out. When I plug just a cable in the PA-in I get signal from the guitar to the speaker and it is really loud (turning the master volume has no effect on the volume of this signal, is this the same for you?). With floating cables in both pre-out and pa-in its just like a single cable in the pa-in. As soon as the something is plugged in to the other end of the pa-in cable the guitar signal no longer comes through and is replaced by whatever is plugged in (e.g. CD player). Because of this, when my c-lator is off, the behaviour is very similar to just having floating cables in both pa-in and pre-out (i.e. guitar signal bleeds through the amp but much more quietly though still not affected by the master volume control).

As for the C-lator I tried the supplied JJ tube as well as a sylvania and mullard I have lying around. All the same...

Hmm, interesting that you have the same effect on opposite jack. Even if our layouts are the same it could be a difference in switches (e.g. yours may break on the right-side looking at the top whereas mine may break on the left...) I don't know if nik might have changed supplier or something... My layout seems to match the photos on the ceriatone website. Anyway, I've attached a pic of my amp fx loop wiring. Its not the best quality as I only have my phone to take photos!

EDIT: When I look into the hole on my jacks, looking at the silver bands at the top, my break is on the left side. Is this the same with yours?

Hi,
I've been checking my relays just now actually and can see no probs. Orientation is deff fine too.

I have looked at the hrm layout. Its clearly different with respect to the relay switching config. I am pretty sure you are right about this causing the difference in our observations.

I think it be possible that whatever cross talk is happening in both of our cases is occuring within the relays themselves. I have tried swapping the two relays in the amp to make see if it might just be a leaky relay, but both behave the same, so chances are this is a design issue. I still can't explain why either of our amps leaks this signal (although in different ways). I have tried moving wires around to see if I can lessen the effect through lead-dress but not a single one has made any difference.

Because the HRM circuit is so different in the switching area I cannot see a direct way to change my circuit to closer match yours (basically, you seem to have your master connected before the relay hence any attenuation it provides also attenuates the cross-talk whereas my master is after the relay and hence any cross talk may be amplified?). I think i would rather have my amp behaving like yours in this respect as the bleed issue makes it harder to debug my C-lator (the bleed essentially running in parallel with the loop). I will have a think to see if I can come up with an improved switching scheme for the non-HRM which circumvents this issue.

Perhaps I shouldn't worry too much about this and focus instead on the noise that my Clator introduces (which I suspect may be a ground loop issue). Maybe others with non-HRM models can confirm my observations?

Once again, sorry about the pic it's very grainy. The mv connects to the connection between the preamp out tip and pa in break.

I've talked to nik and we dont know why I am getting the bleed that I am getting. Its something inside the amp causing it. Not sure what....

Just one thing nik menitoned which may be interesting. I wondered why you were seeing the same symptoms as me but on a different jack.... Nik made the point that a floating cable at the pre-amp in doesn't break the signal through the amp so your behaviour is normal and expected. I thought you may have the same problem as me because your master did not change the level of the "bleed" but of course, as your amp is HRM, the master doesn't impact the level of the distortion channel anyway!

I think this problem is either something unique to my amp or perhaps something to do with the non-HRM design...

Also, I have realised that this bleed in my amp is what is causing the bleed in the c-lator. With the c-lator not plugged into the mains and all capacitors drained (0v at all nodes in the c-lator) signal passes from guitar to speaker. The c-lator out control is connected to the PA in and therefore can be used to shunt the leak to ground (although the signal level still does not respond to the master volume! argh...

EDIT:
I have found an interesting bit of behaviour which may help narrow down the problem. It seems that with a cable in the PA in pin 2 (grid) of the PI becomes hyper sensitive, the cable leading to it makes loud noises when tapped with a chopstick. The same is true for the ground lead going to the 390 ohm resistor in the PI network. This is much more sensitive than pin 7 which suggests a huge PI imbalance (only when PA in has a floating lead!). This sensitivity does not occur when the PA in is removed and the amp is set to top volume so its obviously behaving abnormally in my scenario.... the search goes on.

Regards.