Grandmeister Deluxe 40 review since first arriving and troubles

I wrote some quick words on Sweetwater when I first received my Grandmeister Deluxe 40 in the US as a review.

First off I had said this (In a nut shell)....
1) Great tone
2) Can get all the sounds I want from clean to modern distortion.
3) It would be nice to have built in Tuner at the least. A built in Compressor and Wah would be cool too. I can see the H&K adding some of this as the technology progresses in future models.
4) Being able to control the master volume using Yamaha FC7 would be very useful.

After using this for a while my biggest gripes are.
1) Not being able to control the Master Volume with a pedal. Would be very useful.
2) In a band with 2 guitars the boost is almost useless. I wish I can program the Volume/Gain for a set DB gain globaly. It would be very useful then to me.
3) They should have an app for a PC. I know Fredo has one that will be ready soon.


So here is the drama that went on....
First off Sweetwater is probably the best company I ever dealt with for anything. I plan to make all musical purchases through them.

So after a couple weeks of having the amp, I turned it on one day and the TSC came on and stayed on. Reading the manual it likely is a power tube issue and that an internal fuse would need to be replaced.

So I called Sweetwater and they gave me a couple of options after the rep talked with their tech support. They could send me a new set of power tubes or swap out the amp. I went for swapping the amp because I had a gig coming up and wanted to use the new equipment. Also they weren't doing anything about the fuse because the tech said it doesn't usually blow.

The new amp arrived and I played through it for 2 days. I had decided it sounded like crap and if this was the first amp I had received I would have returned it and been totally unhappy with H&K products. I play in a 90's rock cover band and the low end sounded really flubby (Flabby). Palm mutted chunking sounded terrible. But I remembered what the original amp sounded like (Amazing) so I didn't give up. I made the decision to use the replacement amp to fix the original amp. I swapped the power tubes and my original amp still didn't work. I then found one of the internal fuses was blown so I swapped that. Now my original amp worked again and sounded amazing again. I suspect since I did not mess with the preamp tubes that the preamp tubes in the replacement amp may have caused it to sound bad. So I guess the moral of this is Sweetwater Rocks, The H&K amp Rocks, and when people say they swapped out tubes in the amp after receiving it and that the amp came alive I believe them. I believe that they were unlucky with the first Chinese tubes they received originally in the amp. There is a possibility that maybe it wasn't the preamp tubes and instead something to do with the transformers, resister values, or rectifier in the replacement amp but I think it's more likely to have something to do with the preamp tubes.

Worried that Sweetwater wouldn't be happy with may choice to take them apart I called them up to tell them what I did. The answer I got back from them was "As long as the amp is complete so we can send it back to H&K that is fine." I needed to have this discussion so they would understand why I sent back the amp with the same serial number they just sent me.

One other thought on this amp or modeling amps..... My own thinking outside the box. I wish amps which you are likely to program many patches had a meter or some sort of volume matching so you can easily match the volumes between presets. I have used an spl meter in the past.

I hope this helps someone and is the reason for writing this lengthy post.

Thx SMS

Commiserations on your problems and congrats on fixing it.  I do have to say though that you are assuming a lot about what caused this issue in the first place.  Sounds like you had an anode fuse go out on you. It isn't common but it is known in new GM36s. It can happen to any amp if the valves have debris inside, and that can happen with almost any make at new not just the cheap Chinese valves that H&K use. I've personally had it with JJs. A flash and it generally clears. The reason they use Chinese cheapies is that they know that the average user will swap out the valves as his first act of supplication to the mojo Gods, so they reckon it isn't worth putting in a set of valves that is better quality at the factory. If they gave us JJs then so many would want Groove Tubes or Electro Harmonix or something treated in a Scandinavian nuclear powered fridge which the salesman has told them they really cannot do without, (Emperor's new clothes!) It simply helps to keep the amp costs within spec to give someting cheap knowing it will be thrown away immediately anyway. If everyone hadn't leaped onto the valve rolling bandwagon so easily they would have had to include a decent set from teh off. Anyway, a couple of points which might help.

We don't have a clue what is going on inside the GM40 yet but the GM36 is an opened can of beans now.  I would also suggest that the basic principles of operation are not too different, anyone who thinks that the GM40 is a completely new amp is on slightly dodgy ground. Use the GM36 forum to look for technical info on how the amp is set up and how to get the best out of it, it will translate directly to the GM40 in most things.

The boost/buffer in the GM36 is not just a clean boost, it is actually a very simple single opamp Tubescreamer zener diode feedback clipping type circuit which is the first stage of the amp.  It has enough clean headroom to act as a clean boost if you use it right, then as signal increases it drives one side of the signal into clipping and finally clips both sides. There is then a second solid state gain circuit before the valve stages. With boost off the first stage acts as a clean input buffer with a gain of about 4x to achieve the levels the later stages are set to expect.  There are two protection setups around this stage.  One is across the input itself and will clip input at around 3.3V peak in both directions before it even goes into the buffer.  This is absolutely inactive under any sensible normal conditions and is there only to protect the circuitry against stupid application of gain before the amp, there is plenty of gain everywhere inside this amp I promise you.  The other is in the feedback around the boost stage and clips the signal assymetrically at about 6V stage output in one direction and around 12V in the other.  This feeds in even harmonic distortion first, the musical kind, and then serves to prevent the opamp clipping internally which is the source of all of the hype and guff talked about opamps colouring sound in guitar amps.  That's good design on H&K's part.

When the boost is kicked in the stage has a mechanism which increases the gain a lot starting at about 10x at 72Hz and increasing to about 25x at 720Hz, it's a frequency dependent gain increase, it gradually increases more and more as frequency goes up.  H&K like doing things this way as they are fanatical about keeping the bottom end crisp on high gain settings, part of the reason you can do modern rock beautifully but can't do classic rock too well with this amp, it just sounds thin.  If you are not getting enough boost out of that circuit then it could be because you have such high settings in other areas, maybe pedals before the amp or high gain set within it, so that there is very little increase in internal signal level left to make when the boost kicks in.  How much distortion can an amp and associated gear generate before you start not noticing too much more difference?  I mean, if 1V clips the signal severely, then how different would 2V sound to that? It's still going to clip to the same level so the signal is actually getting no bigger inside it's just clipping more of it off at the same overall level. And how much different would 3V sound to that?  Try this, it isn't anything to do with the type of sound you should use but just as a test. Do you get significant change in volume if you play on Clean with the Gain at a reasonable level, then kick in just the boost? If you do then the boost is actually doing its job, the way you are currently using it may be preventing that.

The H&K boost may have no controls of its own in the amp but it is very well controlled by just the volume knob on your guitar.  We all learned a while back with the GM36 to use that to drive the input circuitry to get the sound as we wanted, then the Gain control has ample range to claw back anything you may be losing by turning down at the guitar.  It gives a great range of tone and distortion and is much more sensitive than the average amp, as I said.

There are many aspects of using the H&K amps which you have to retrain yourself on to get the best out of them, because of the flexibility of their design they do not respond exactly as much simpler amps will.  I promise you, if you can take the time to get used to them then you have so much more on tap than with most other gear.  I would be absolutely flabbergasted if you were to find that the GM40 is really different to the GM36 in its basic internal circuitry.  It may have been voiced very differently as they claim, (nothing so far has shown that to me but that could just be the internet).  I would spend a lot of time in the GM36 forum looking at all of the info available there from way back as to how to get the best sounds out of it, the processes will be the same.  You have loads of info already available even though there is very little specifically on the new GM40 at the moment.

Bordonbert,
Thank you for the awesome explanation on this. And honestly I have an associate degree in electronics so I totally understand what you are saying.

I will play with the clean and the boost as you say, just to see. While I'm thinking about it with the music we are playing I'm always trying to boost a high gain setting for a solo.

I do like the amp and am very happy with it so far. I can see how this amp is going to grow as time goes on. Like adding a tuner and etc. IMHO this amp has the best of both worlds, It's almost a modeling amp(Digital effects) with the tone of a tube amp. Like you said it's a different animal and I need to take time to learn it's nuances. You have helped me a lot on that front already.

I have rebuilt 2 super reverb's that I bought off a guy that had them sitting in a shed for years (I bought the rat droppings too . Those respond wonderfully to the volume on the guitar. I also have a Vox AC50 that I used for a while.

Now for the 90's rock I have been playing I have a Fender Mustang III which is a good combo modeling amp. However, it does not respond well to the volume on the guitar. So I'm used to having different patches for boost programmed.

I wish I had something to compare the sound of different tubes in the GM40 before ever buying a new set. I used JJ's in the super reverbs.

I have a gig this Saturday at the local bar and plan to use the GM40. Any amp can have an issue right before a gig, but after this last issue it makes me a little uneasy feeling. At least until this proves to me that it is very reliable. At some point I will have a backup fuse and a backup set of tubes.

Anyway thanks for taking the time to write that reply. I appreciate it....

Thx SMS