NAD + Need some opinions on tube swapping

[Dmoney]

Wow, they really should rethink the term "fixed" then, it's kind of misleading for most people with a non-technical background.

Yeah. it is one of those things that is very very commonly mixed up. pretty easy to see why!

[GuitarIv]

Ok guys, I'm back with some results:

I played the amp some more today and really toyed around with it, coming to the conclusion that the fizz is killing me. I really love the midrange and cut this thing delivers, note separation and clarity are superb, however there's this constant fizziness going on that neither the presence nor the treble control can tame. It's just disturbing. I'm sure in a band context it'll be fine, cut through and you wouldn't even notice it at all, but playing in front of the amplifier is a complete different story.

Some other weird things I noticed: When I turn on the standby switch the sound fades away whilst playing like it's supposed to, but when I turn the amp off and keep on strumming there is silence followed by a slowly building up sound of my playing coming out of the speakers again before it fades (with the amp in standby).

I played my RG with an EMG 81/85 set tuned to Standard D through it and it seemed to remove some of the fizz (guitar before was my Jackson Dinky with a Painkiller/Coldsweat Set tuned to E-Standard and although I know the Painkiller can create some fizz and the tuning might contribute to this it's just overkill) but not all of it. So the EMGs sounded better but the amp still did it's fizzy thing.

The Footswitch seems to be either broken or have a faulty connection as it first made the amp silent, no sound emerged until I hit the switch on the damn thing, then it reversed the drive and clean channel. (Judging from the LED on it that is supposed to be on only when the OD channel is engaged).


Don't get me wrong, I'm really trying to like the amp, but there are some obvious issues I can't and won't ignore. I still have the 30 Day Thomann money back guarantee and will send it back if following things don't work out:

Changing the Speaker Cab. I had some issues with my Laney before so maybe it's the cab. I'll ask a friend of mine to borrow me his Vintage 30 Cab so I can do a comparison.

Switching Preamp Tubes. I guess I'll try out some JJs as those are said to sound warmer and darker. Don't know if this will make my guarantee invalid though.

Get a technician to switch out the Preamp and Power Tubes and set a warm Bias? I'm sure I could do it on my own but if a technician does it maybe my guarantee stays valid?


Now I'm really not sure what to do. If I just keep the amp and experiment with a warmer Bias and better tubes I'll lose 300 quid in the worst case. Like Toe-Knee pointed out the cheap china tubes and the factory cold bias could contribute a great deal to the fizz and there are still tons of mods that can be done to the amp to make it better, I even looked up Mercury Magnetics and O'Netics Output and Power Transformers that should get you close to the real thing but in the end you get what you pay for and the amp was cheap. Maybe I'm overreacting but I'm trying to find out whether it's worth it messing around with the head or I shall just get my money back  :?


Thanks so far for all the input you have given me, especially Toe-Knee and Dmoney. More ideas what could be wrong are very appreciated. I might shoot you a p.m. anyway  :)

Cheers!

[darkbluemurder]

On the fizziness: keep in mind that the original SLO amps came with 5751 tubes in the preamp. The 5751 can be put in the amp without any changes but they have less gain (about 70 compared to 100 of a 12AX7). They also are warmer sounding. Try one in V1 and see if that's enough. If not, put one in V2, too.

Cheers Stephan

[Dmoney]

I've never played one so can't comment on the fizz, but the circuit isn't a fizzy circuit. My JCA22H was fizzy. Now it just has JJ ECC83S' in and it's fine. It is bright compared to 100watt big bottle versions of the same thing though I reckon. I don't really use bright guitars or pickups. My Vigier is pretty balanced and both the Les Pauls I have a darker. Both LPs have Nailbombs in the bridge.

Try the extra cab. I have no idea what 70/80's sound like.

With the footswitch, the light should be on when OD is engaged. It's a VERY simple pedal. One switch, an LED and a resistor. open it up and see if something looks bust. I can send you photos of mine. I removed the fixed cable and installed a jack so I could use any length cable with it.

The power and standby switching is actually nicely done. They use DPDT switches to switch both the live and neutral wire going from your mains into the power transformer, where lots of amps normally just switch the live. They do the same thing with the high voltage secondary, switch both wires out of the power transformer into the rectifier. That leaves very little of the circuit at high potential (and still dangerous) when the amp is on. Normally a single pole switch is used after the first filter stage and in line with a fuse and the choke. That leaves the highest voltage node live when you switch the standby. It also means the switch is cutting DC voltage, which isn't always great. You can read about it all on the valvewizard site if you want. I wouldnt worry about it.

I think Jet City/Soldano stand by those transformers. O'netics and Merc's are probably worth twice the cost of the amp. I'm not sure if Merc Magnetics are worth the money either. As long as the OT isn't tiny then you should be getting a decent response from it and not loosing low end.

The bias recommendation I've seen for other soldano amps is 26mA idle current. Which is on the cool side, but I think it's chosen for a couple of reasons. It's not TOO cold by most peoples standards, It gives your power valves longer life and a more reliable set of conditions to work in. In comparison a 5150 i have in my flat is biased around 14mA per valve. 60% in that amp would be around 35mA each. If i got the scope on it I'd probably see a lot of crossover distortion in it. 70% is most peoples rule of thumb. A lot of people just bias using a scope and not looking at idle current. Some people do it totally by ear! I usually go lower than the 70% mark for my own amps. Also, in some amps when you add a bias test point from pins 1&8 you actually end up measure the plate and screen current draw summed together which means you usually end up biasing a few miliamps cooler than you think, unless you work out the screen current draw in advantage and take that away from what you read at the cathode.

[dave_mc]

are you using 70/80s? It's ages since I've tried them, but I remember not being too fussed. They certainly don't have a great rep as far as celestions go. And certain speakers (looking at g12t75s here) can definitely add their own fizz that you can't dial out. maybe the 70/80s are similar. maybe not. I dunno :? :lol:

If your friend's v30s are broken-in, that should help.

i should probably add though that fizz doesn't really annoy me. I quite like a bit of fizz. :lol:

and yeah mine makes a noise when i switch off, even when i've switched to standby first. Dmoney will know more about the technicalities than I will, lol, so listen to him. I just assumed it was normal.

If you really aren't getting on with it, though, by all means send it back. it doesn't matter if I like it if you don't. :)

[Alex]

Sure Thomann will give you the cash back after you've done all those changes to it? if there's such issues, just send it back right away and get something different. I had the same with the laney I had and I'm glad I sent it back and did not tinker with it for ages.

[Dmoney]

Like Alex says too, if you don't think it's gonna work out, don't try anything too invasive and get it sent back. Best option if you've bought online.

[GuitarIv]

Ok, so I have an update: on Monday I'm borrowing my mates Engl 4*12 with broken in Vintage 30s. This should give me a definite answer if it's the cabs fault or not.

Stephan, Dmoney: Preamp tubes aren't expensive and if they really can cut out the fizz like you say I guess this would be the next step after messing around with the cab.

Thinking that I could still get my money back after fiddling around with the internals of the head was kinda stupid I admit, I just don't wanna take the easy way out and give up by sending a basically good amp back because it doesn't appeal to me stock. If a few euros for new tubes can remove the fizz (and that's the only thing that disturbs me) and changing my Painkiller for the Holydiver again can fatten the sound up, I see no reason why I shouldn't try it. I guess right now I need to decide wether to take the risk of loosing 300 quid or just let it be. I know myself well, so it's probably gonna be the former...

Regarding the footswitch I'll open it up and see if anything is loose.

I've just started my journey of delving into the world of amplifiers and how they work, so I will certainly consult the Valvewizard site, the more information I get, the better  :D

The idea with the transformers was actually just... well an idea. Maybe I'll end up building my own SLO Clone one day anyway, that is if I gather the knowledge that's required.

The biasing will be the first big step I'll do after trying the cab and new preamp valves out. I'll certainly open up a thread/shoot some messages when the time is right.

Well, seems like I have already made a decision. I think I'll keep the amp. News on Monday  :D

Cheers!

[Toe-Knee]

Ok, so I have an update: on Monday I'm borrowing my mates Engl 4*12 with broken in Vintage 30s. This should give me a definite answer if it's the cabs fault or not.

Stephan, Dmoney: Preamp tubes aren't expensive and if they really can cut out the fizz like you say I guess this would be the next step after messing around with the cab.

Thinking that I could still get my money back after fiddling around with the internals of the head was kinda stupid I admit, I just don't wanna take the easy way out and give up by sending a basically good amp back because it doesn't appeal to me stock. If a few euros for new tubes can remove the fizz (and that's the only thing that disturbs me) and changing my Painkiller for the Holydiver again can fatten the sound up, I see no reason why I shouldn't try it. I guess right now I need to decide wether to take the risk of loosing 300 quid or just let it be. I know myself well, so it's probably gonna be the former...

Regarding the footswitch I'll open it up and see if anything is loose.

I've just started my journey of delving into the world of amplifiers and how they work, so I will certainly consult the Valvewizard site, the more information I get, the better  :D

The idea with the transformers was actually just... well an idea. Maybe I'll end up building my own SLO Clone one day anyway, that is if I gather the knowledge that's required.

The biasing will be the first big step I'll do after trying the cab and new preamp valves out. I'll certainly open up a thread/shoot some messages when the time is right.

Well, seems like I have already made a decision. I think I'll keep the amp. News on Monday  :D

Cheers!

Preamp valves can make or breakj an amp.

For me any chinese valve completely destroys the tone fizz, compression & really shrill high end.

In fact electro harmonix valves also do the same thing!

[richard]

I'm wondering what the 'fizz' is that you're hearing.

To me , this is a fizzy amp:

https://www.youtube.com/watch?feature=player_embedded&v=aAE3NMERwGw#t=263

Is this anything like your Jet City ?

Personally, I don't like what I've heard of the Soldano high gain channel. I watched some clips of EC and Gary Moore in their Soldano days and hated the lead tones.

Like this, too MUCH fizz:

Eric Clapton and Mark Knopfler - Cocaine

I quite like a little fizz but there are limits. It could be the amp circuit. However, it's worth trying tube swaps and, as long as you put the originals back, there's no way of telling that you've done this so no worries about the warranty - as long as you've got time.

[Dmoney]

Here's a bit of trivia, I have the details somewhere but... Clapton's SLO100s (or some of them at least, dunno how many he had but it was at least two) had an extra valve added to them to give them a different loop circuit. It was designed by Pete Cornish as a post master volume loop that worked at a level require for the huge Pete Cornish rack system clapton used, which also had all manner of gain controls for each effect in and out (I believe). I have a copy of the manual for it somewhere and a few more details. The circuit modification is not used by Soldano and the post master loop circuit they use is implemented differently without the addition of a valve, which reduces noise in comparison to the head in the EC rig. 

[dave_mc]

Like Alex says too, if you don't think it's gonna work out, don't try anything too invasive and get it sent back. Best option if you've bought online.

agreed.

might as well try the v30s and new preamp valves, though, i suppose.

[Dave Sloven]

I find that my Peavey tends to be fizzy at 'house volumes', but when you get up to proper operating volume the fizz subsides substantially.

Or that could be an effect of the earplugs ...

[GuitarIv]

Richard: the fizz is in the background, "behind the sound" if that makes any sense.

Regarding the Preamp Tubes my local Music store has Sovteks, Tung-Sols, TADs, Mesa Boogies, Electro Harmonix and Groove Tubes in stock. I guess I'll get myself a Tung-Sol and a Sovtek to see how those sound. Would like to try JJs as well but those need to be ordered online.

[chopeth]

I understand completely what you are talking about. My previous amp ( jvm 205 ) has an awful, annoying fizz sound in the background...well, i changed all the tubes for TAD tubes and problem solved ! I sold the amp and the next two amps ( engl savage special edition and bogner uberschall clone ) has TAD tubes in all the positions and , dispite of using extreme high gain with ods, eq, sonic maximizer...they hasnt any kind of fizz sound. It doesnt matter the extreme amount of distorsion or if the guitar has extreme output pups ( like the ceramic warpig ) i think it worth the change ! the sound is more powerfull, thick, balance, organic and out of fizz !!