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    Amp noise and help reading the TSC LED check

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    proddy

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    Amp noise and help reading the TSC LED check

    Post by proddy on Wed Oct 18, 2017 4:55 pm

    Oh bum, my GM40 just started making nasty swelling hissing gurgling sounds, even with no input into the amp and running with Speaker Off direct into an audio interface.

    Doing the TSC check in Play/Standby off mode shows:

    LED 1 flashes 12 times
    LED 2 flashes 13 times
    LED 3 flashes 11 times
    LED 4 flashes 15 times

    The manual says the difference should be less than 4, so I should be ok. Still strange to see so much inconsistency. Is this normal?

    Amp is only 1 month old.
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    bordonbert

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    Re: Amp noise and help reading the TSC LED check

    Post by bordonbert on Thu Oct 19, 2017 12:26 pm

    Those TSC readings are fairly normal.  Matched valves does not mean both with exactly the same current in situ, it just means within a certain percentage of each other.

    If you are meaning running into your interface via the Red Box output then it leaves out the output valves as the problem anyway.  The Phase Splitter/Inverter is also after that output so it isn't the cause either.  Sounds like you may have an issue with one of your preamp valves.  Before you rush out and throw money at what we imagine is the solution, try just swapping each of the first two valves V1 and V2 in turn with V3 which is the Phase Splitter.  You are swapping an active valve which could cause the noise for one which is inactive and can't be causing it. Don't get them mixed up, it would be best to have them end up in their original sockets after you have finished.  Assuming that V3 is ok, you should notice the problem change, (hopefully go away), when a duff valve is swapped into the V3 socket.  It may only be the socket and valve pins being a little dirty, unusual in a new amp but not impossible.  And despite internet prattle touching the valves with clean fingers is NOT a problem!  They aren't coated in any way, they are just simple hardened glass bottles.

    Do you know the routine to take the lid off correctly to change the valves without voiding the warranty?  It's absolutely safe electrically, it just must be followed to leave the tamper indicator in place inside.
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    proddy

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    Re: Amp noise and help reading the TSC LED check

    Post by proddy on Thu Oct 19, 2017 2:49 pm

    Thanks bordonbert - I was hoping you would reply Wink

    So good to know even with the difference bias's the EL84's are healthy. I realised (stupidly) afterwards that the power section was bypassed anyway if only going via the Red Box.

    I'll swap out the 2 pre-amp valves with the V3 in turn and see if the noise goes, as you suggested. I found a few youtube vid's that show how to replace tubes (some using socks and pieces of string!). Also read that to keep the warranty seal from breaking I'll have to loosen the bottom screws just enough (max 9 turns).

    Two other related questions if you don't mind
    - is it worthwhile gentle taping on the valves when powered on to see if they're 'microphonic'
    - if some day I get bored, with which JJs would you recommend I replace the stock Chinese EL84/12AX7s ?

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    bordonbert

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    Re: Amp noise and help reading the TSC LED check

    Post by bordonbert on Thu Oct 19, 2017 9:21 pm

    Hi Proddy.  You will most likely find the "socks and pieces of string" are really unnecessary.  The valves just need the clips which are fitted over them lifted off.  I've never had a problem just pulling them upwards a touch and off to the side by hand.  Once the clip is off they are really easy to remove by just pulling up out of their sockets with a little gentle side to side wiggling at the same time.  They are pretty robust despite being made of glass and looking fragile.

    You got it right with the warranty issue, the bottom screws only need enough loosening for the end cheeks to fall outwards a cm or two so the lid can be slipped out.  It only takes me two or three turns.  And you don't need to touch the front screw of the handles, it only holds the handle onto the end cheek.  It's perfectly safe to run the amp with the lid off for short periods as you test as long as you keep small children and the cat out of the way.  You don't need the clips on the valves either of course to just run it up for testing.  You need to take care with the LED strip when you refit the lid but it isn't difficult once you know it is there.

    As to what you will find in playing around with the valves, I would take a lot of what you will read online with a pinch of salt, especially in forums.  On the internet everyone is an expert in their own lunchtime because their mother's next door neighbour's postman's girlfriend's manicurist told them things were so so it must be.  Experts or not, there is only one criteria to use when you judge things like which type of valves to choose and aspects like microphony and the valves' "gain" (which doesn't exist!).  That is, does my amp sound good to me with this set of valves in it?  I know of people who actually love the sound of their original cheap Chinese ones which we all know are crap and prefer them to the usual suspects recommended as "the ones to go for" when rolling.  These people are not willing to wade into the mire that is "reasonable discussion" because they just get mockery and grief from the "experts" who have golden ears and the ultimate "common knowledge" of the subject.  They are happy with what they have and just enjoy it.  They are the sensible lucky ones!

    I can tell you that the valve manufacturer makes only a minor difference to an amp if any at all.  There are those who would passionately differ with me on that but the answer is in blind listening tests, not in swapping them and remembering what it sounded like a few minutes ago.  If there is a perceptible difference audibly then there must be a difference electronically to cause that.  If that is so it must be possible to identify it on the bench.  No one ever can!  My own experience, (and I have a lot of experience listening to and assessing hifi tweaks and mods for many many years as well as guitar gear), is that changing from the stock Chinese valves can remove some of the hardness that you may perceive in the top end of the H&K amps.  If you love that brashness then fine, (the designers at H&K Grosse Hauptquartier do), but if you don't you will want to swap out at some time.  There is no rush to do that.  I tried valves like Electro Harmonix and Marshall originals which I had around as well as the usual JJs and I came to the conclusion that the JJs were as good as any of them and anything I could hear elsewhere.  In fact there is only a whisker of a suggestion there may just be any difference at all between the 3 "better quality" ones I checked out if the listening conditions were just right.  There is absolutely no benefit to paying out huge sums of money for the latest NOS sensation of the month with the "flowery recessed mid range" and "velveteen mahogany bottom end" when you are going to be cranking the volume against a bass, keyboards and, God's own comedy hunchback torturer, the drummer.  That hint of "pink tinged lemon flavoured frothiness around 1kHz" you can perceive in the Clean channel in a quiet room late at night with the gain and volume down honestly vanishes when you get out in a pub brawling with the rest of the band, dimed and playing "Don't Fear The Reaper".  And if you play hearing only your irritating lack of Tinkerbell like sparkle at 4kHz then you aren't cut out to be a musician. Very Happy

    You need to do some assessment work first on this.  Check out the settings you end up using when you use your amp in real life with other musicians.  Are you constantly striving to tame too much gain?  Is that so acute you could consider 5751s to get lower amounts of gain on tap which opens up the bottom end of the Gain control?  Are you unhappy with the general tone in terms of raggedness or harshness in the upper registers?  That could point to a different valve make possibly helping you but....  Have you tried different speaker setups first?  That is MUCH more important and can genuinely make a huge difference to your sound.

    Yes, valve sets are much cheaper than new speakers but not if they end up making only a tiny difference if any at all, that way they are just more wasted money to no benefit.  And no one wants to admit they have been a dumbass and forked out cash unnecessarily once they have realised they have done it.  Hence most of the advice, "changing your valves out for a set of "NOS Yamatoshi Ninja Platinum Grid Super Large Anodes" will make your GM40 sound like Eddie Van Halen's Variac fed Marshall rig".  Once you have willingly made the same mistake would you be able to "out" the guy who advised you to go down that path? Wink And there is always the desire to be one of the guru group.  "A guru told me, so if I tell others that must make me a guru too!"  These are some of the reasons why all guitar gear myths are so easily propagated on the internet.  People basically want to believe and then don't want to own up to their own gullibility.

    On different models, my advice is very clear and based on understanding something of the ramifications of circuitry changes.  Do not go for 12AT7/12AU7/12AY7 type swaps, those valves are NOT anything like equivalents and everything the designer sets out to make reliable in a stage can change.  They make drastic changes in the setup of a stage designed for a 12AX7.  They may work happily and they may give you a sound you temporarily like but the result of putting them in there is not predictable and the circuit design may well become very susceptible to effects like ageing of components in a way it was not with its original design valve, a 12AX7.  The now well known 5751 IS a good close equivalent in all its parameters with the Amplification Factor μ (mu) dropped from about 100 to about 70.  The name Amplification Factor is what most people mistake for Gain.  It is not gain at all.  It does NOT mean the gain of the stage will drop from 100 to 70 or even by a factor of x0.7, life is more complicated than that.  You do get some relief in the GM36 when you swap out for 5751s.  It isn't so much tonally but the range of Gain (of the amp) becomes a little less overall but opens up at the bottom end of the control.  In other works it is like saying that with 5751s in place a lower portion of the Gain control's range spreads across the whole control to become 0-10 losing the upper end.  Some of us classic rock fogeys who don't do ultra high gain like that.

    Take this whole concept slowly, there is always time to get to grips with it and mistakes can be costly, especially if you find you didn't really need them after all.



    The Valve Wizard - from his book - Designing Valve Preamps for Guitar and Bass wrote:Some versions [of valves] are reputed to have a particular tonal character, and much has been written about the apparent superiority of, say, the Mullard ‘long plate’ ECC83, or the RCA ‘black plate’ 12AX7. These subjective differences are not a consideration for the circuit designer and will not be mentioned here again. So-called ‘tube rolling’ and ‘cork sniffing’ is fun, but is left to the discretion of the reader. Real tonal control comes from the choice of topology, manipulation of overdrive characteristics, voicing, and from a complete understanding of the circuit’s functionality, not from the particular manufacturer or vintage of the components used. This book will furnish the reader with this essential understanding, and the author will do his best to make it a painless experience.


    The Prosecution rests m'lud! Laughing
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    proddy

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    Re: Amp noise and help reading the TSC LED check

    Post by proddy on Wed Oct 25, 2017 1:34 pm

    bordonbert - Thanks for taking the time to put that explanation together, some great insights there and I love the way you write. I haven't gotten around to testing the 12AX7's as the gurgling noise is intermittent and I'm waiting on H&K support to acknowledge the issue. But if I get to exchange the valves I'll opt for the JJs (I'm less of a high-gain player too) and report back to the forum.

    watersnake

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    Re: Amp noise and help reading the TSC LED check

    Post by watersnake on Thu Nov 02, 2017 2:17 am

    Hi @all,

    quote 1:
    "... via the Red Box output then it leaves out the output valves as the problem anyway. The Phase Splitter/Inverter is also after that output ..."

    quote 2:
    "... that the power section was bypassed anyway if only going via the Red Box..."

    I may be wrong, but I do not agree with that.
    In my opinion none of the valves is bypassed if using the Redbox out.
    The audio transformer and the valves are all in the signal path.
    I guess the input for the Redbox circuitry of the amp is taken from the output of the audio transformer, which makes perfectly sense to me.
    Of course the output level of the audio transformer has to be reduced by certain degree,
    maybe by some resistors, so it can be used as a input signal for the Redbox circuitry.

    I am pretty sure, this is true for all the Meister amps.

    That means, if any of the valves is producing a noise like gurgling, hissing or whatever, this noise will be at the Redbox out, as well as at the speaker out.

    A simple test:
    switch the amp from play mode to standby mode - there will be no more sound at the Redbox Out, because the power valves are kind of not enabled in standby mode.

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    bordonbert

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    Re: Amp noise and help reading the TSC LED check

    Post by bordonbert on Thu Nov 02, 2017 8:07 am

    Hi Watersnake.  You are absolutely right with that, the Redbox is taken from the output transformer before the power soak and it follows the output valves and Tx.  I didn't make it at all clear what I thought I was actually responding to with those remarks.  Proddy said "...and running with Speaker Off direct into an audio interface."  I replied "If you are meaning running into your interface via the Red Box output then it leaves out the output valves as the problem anyway."  It would if the problem was that of a duff valve stopping the amp from working at all.

    I think I was locked onto the wrong problem at that stage.  Look at the time of post, it was the end of a "late nighter" working through.  What I was thinking was, and it was definitely the wrong advice for this situation at that time, that with a TSC problem bringing the output valves into question and with the Redbox output being taken from the absolute output of the amp just as you have pointed out, if it is working then the output valves and TSC must be working too.  Your point is absolutely sound, considering the other side of the problem described, with the problem of noise, the output valves COULD also be injecting it.  I confused those two issues.

    In picking up the problem late at night I got my head around it the wrong way and I think I was focusing on the fact that the TSC was in question.  Apologies for that, you are quite right, it could have been the output valves causing the noise.

    But I had better point out to stop Proddy worrying, as we found out later on, the fact that it is strongly affected by which channel is selected rules that out and points clearly to the preamp valve as the prime suspect.




    EDIT:  (And I should say thanks for pointing out my bad advice in such a sensitive diplomatic way.  It takes skill to say "You're wrong." without saying "You're a bloody idiot".  Very Happy )
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    proddy

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    Re: Amp noise and help reading the TSC LED check

    Post by proddy on Mon Nov 27, 2017 2:48 pm

    Hi,

    thought I'd just feedback on my original thread and say I ended up sending the GM40d back for repair (under warranty) and the nice folk at H&K gave me spanking new one in return. I guess more things weren't quite right with the amp. 3 weeks later, all is good. Now where was I?......
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    bordonbert

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    Re: Amp noise and help reading the TSC LED check

    Post by bordonbert on Tue Nov 28, 2017 6:52 am

    That's a bit of a double edged sword Proddy. It's great for you as you got your amp back in full working order and can rock on into the night without any issues, it's frustrating for us as it means we don't get to know what the actual cause was. Very Happy

    I think H&K took the sensible route just swapping it out and it points to the general quality of their after sales service. It's easy to knock them when you are losing it because your new purchase has just developed a fault and they don't swap it out immediately but we have to keep in mind that what counts is the percentage of faults occurring in their line, and they are very low compared to many other well known brands, and the percentage of happy conclusions when they do occur. Unlike many of your average Marshall or Fender class amps, these amps are not a bodgers' paradise! They are ultra modern in construction, well designed and well built and they require engineering knowledge to dive into reliably. All of the sums have been done correctly and random changes can upset that. This means that once they develop a fault there is a limit to the amount of repair work the average player can do, and that isn't helped by the usual plethora of unsound bumbling advice which is often handed out in chat rooms. There is a lot more that can be done with a unit once an engineer has it on the test bench in front of him and the scope probes in his hands.

    It is easily possible that if they choose to, knowing the circuitry as they do, they can just do a couple of simple tests with a scope on fixed test points and see exactly where in the circuit the noise is being generated. For them, it is then an easy job to replace whatever is causing it, that is if it is worth it. Let's be honest, if it is just a valve they have lost nothing as it just needs a swap out. If it is in one of the solid state stages or the power supply which is very possible, the repair would be more awkward and they would have had to take it back anyway.

    Many thanks for getting back to us to let us know how it ended up, not everyone does that and it is appreciated. It all helps others around you when they may have a similar problem. Do keep in touch and let us know how the amp fits in with your playing as you get to grips with it.
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    proddy

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    Re: Amp noise and help reading the TSC LED check

    Post by proddy on Thu Nov 30, 2017 3:54 pm

    Yes I would have loved to have known the original fault. Thinking about it I had problems with the MIDI too (connected to a Focusrite usb audio interface into my DAW) with random cut-outs and midi signals so I expect something else was skew-whiff in the circuitry. I'm not sure you can tell the production date from the serial number but just maybe it was a known problem from a bad batch.

    I'm still trying to find my tones and tend to linger between gained up cleans and crunch. Then I found a gem of a tone in the Ultra channel with really low gain (6%). Most of my cleans are at 40W, the rest 5W with Master set to 10:00 and the preset volume rolled off a little to compensate. Not sure if its right but thats how far I've got without blowing the windows out at home.

    In the last 25 years I've gone from a brief period with a Marshall JMP-1 pre-amp/9000 poweramp to many years on a Mesa Boogie triaxis/simul 2:90 poweramp rack (from my Dream Theater days) then to a smaller Boogie Rectifier, then sold everything and went digital with the AXE-FX, sold all that and downsized to a Laney Ironheart combo. Now I'm just with the H&K and matching TM212 cab. Sold most of my pedals too and kept my home built overdrives and wah. With age comes simplicity I guess.

    I do have a question about volume pedals (25k expression vs analogue in the fx loop) but will post a separate topic on the forum.


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