Bare Knuckle Pickups Forum
Forum Ringside => Guitars, Amps and Effects => Topic started by: gwEm on December 13, 2005, 02:38:50 PM
-
After all the positive discussion regarding the advantages of valve amplifiers on this forum, I invested in a little H&K valve amp on ebay.
It arrived last night, and so far i'm disapointed... However I strongly suspect the valves are shot.
Not knowing anything about valves, I'm posting here ;)
What I experience is a tone somewhat like my lame Yamaha practise amp (complete with belt clip! and overdrive button ;) ) when the batteries are close to running out.
At low gains, the amp works as I might have reasonably expected valves to sound (violin sounding distortion, subtly sustaining notes). But at higher gains it becomes progressively more fuzzy, the tone become glitchy and breaks up in an incredibly cheap sounding way.
When I tap the valves with my finger they are not microphonic, and they glow strongly.
The unit is a 'cream machine', I brought it because H&K are not known for cr@p gear... but maybe someone knows different?
-
I guess the 1st question is: is the amp all valve, or a hybrid?
Also, power tubes don't have to be dim in order to be dead ... they will still glow even if the filament inside is dissintegrated.
Can you take any pics of the amp?
-
it has a solid state buffer on the front end.
this is then followed by a 12ax7 preamp and a 12au7 configured as a 1watt power amp.
that goes into an output transformer, and if you like into a speaker.
or you can use the built in 'power break' (actually a 10ohm resistor) and 4x12 simulator.
i was using it in the 4x12 simulator configuration so far.
-
Hmm, have you tried it through an actual speaker cab yet?
-
Check the make of the valves and look up the characteristics here:
http://thetubestore.com/12ax70ectyp.html
or here:
http://www.watfordvalves.com/home.asp
If your sound differs from the described characteristics, then getting new tubes is an easy upgrade. If gain is the problem, then I might be tempted to change the valves to use a 5751, which will cut the gain to 70% of the AX7. This will give less drive and should give a less fuzzy tone.
-
perhaps one thing that should be pointed out it that valve amps come alive when the valves are hot - which is usually through volume rather than just gain. alternatively use something like a tubescreamer to push the amp into overdrive at a lower level - most overdrive/distortions work best with a valve amp.
-
I'd email the eBay seller and ask when, and if, he last changed the tubes. H&K are my favourite amps (the big, expensive ones, anyway) and I don't think it should sound cr@ppy unless there's something wrong.
-
thanks for all the advice
regarding the tubes, they are the original H&K items which suggests they might be getting on a bit. however, the previous owner claimed he hardly used it. certainlly the tubes are neither very noisy nor microphonic.
i'll try with a speaker this evening.
i was mainly wondering if my symptoms sound like a typical tube reaching the end of its life?
-
think it could be the valves:
http://www.harmony-central.com/Guitar/Data/Hughes___Kettner/Cream_Machine-1.html
loads of actual user reviews, the amp seems to be good for a few people :)
-
When I tap the valves with my finger
It wont make any difference but you're supposed to tap valves with a chop stick or something similar. Don't want you frying your fingers now. :)
-
well last night i plugged the thing into my 'new' 1x12 which chrisola sold me. its sounding considerably better like this... even it its still somewhat fuzzy at times. i can see what people say now when they talk about valves reacting to your playing.
floyd pepper: It wont make any difference but you're supposed to tap valves with a chop stick or something similar. Don't want you frying your fingers now.
i used my guitar hand hehehe ;))
philking: If your sound differs from the described characteristics, then getting new tubes is an easy upgrade. If gain is the problem, then I might be tempted to change the valves to use a 5751, which will cut the gain to 70% of the AX7. This will give less drive and should give a less fuzzy tone.
yes mate. this seems like an incredibly perceptive comment. after trying with a speaker i can clearly hear the 12ax7 gives way too much gain in the Cream Machine. i think i'll try a 12at7.
chrisola: loads of actual user reviews, the amp seems to be good for a few people
yes, i was encouraged by these reviews too! the amp was just 60 pounds on ebay, including postage. the 1watt of power through your old 1x12 would be easily loud enough to make my neighbours (i live in a flat)
as i said before, though the speaker its much better, but still rather fuzzy and too much gain. as the harmony central reviews say, the built-in 4x12 emulator isn't great and now listening through the speaker it seems reasonably clear that 12ax7 preamp needs taming at least. i might as well change the poweramp at the same time.
thanks for all advice!
i must say the fuzziness gives a pretty 70s edge to my tone though... i can do a great "sad wings of destiny" sound ;)
"Whisky woman dont you know your driving me INSAAAAANE!!" :twisted:
-
if you want to take the edge off an ECC83, try a 5751 - less gain (popular with SRV in his Fenders)
:twisted:
-
why would you want less gain???
-
some people find ECC83s too gainy/buzzy - a 5751 has slightly less gain and can smooth out the tone to suit some players tastes.
:twisted:
-
I take it you don't have a valve based power amp. This is where you reallt get the true valve amp sound, pre-amp valves mean nothing, it's all about what valves you have in the power amp stage of your amp (what makes the amp loud, rather than what makes it distorted).
-
ok, so i have changed the tubes and its much nicer now ;) maybe i should have done it straightaway, but not being experienced in how valves 'should' sound, i thought it best to ask. anyway, i learnt some things from the discussion so no regrets.
t3haze: it has a valve power amp and output transformer, read up the thread for full details ;)
heavier than hell: thanks for this tip, maybe i can use it in the future.
tweboss: actually i have replaced the 12ax7 with a 12at7 and its still gainy as hell ;) the solid state input stage already has a pretty high gain in the cream machine. even now its impossible to get a totally clean sound without rolling down the volume on my guitar slightly. maximum gain setting drives the preamp into over the top spitting and fuzzy saturation.
i understand op-amps pretty well at least, so time to whip out the soldering iron...
-
There is the 12AY7 - this gives about 45% of the gain of the 12AX7. Don't know if it would help though if the sound is already boosted before it gets here. There is also a possibility that you could try this pr a 12AV7 as the power tube to give you more headroom. But I am not sure of the build of the Cream Machine, so I would see if there is a forum somewhere that might help you.
-
you read my exact thoughts philking :)
actually i get the feeling from playing the amp that the 12AU7 tube is working really well in the power amp.
i tried the old 12AU7 in the preamp, and it was not enough gain (would be good for blues though i reckon). which suggests the 12AY7 to me also. its good to know i'm thinking on the right lines.
anyway, i found the schematics for the box, so it shouldn't be too hard to make adjustments. i have the hunch the solid state gain stage is pushing the first half of the preamp valve into saturation. the gain control is between both halves of the 12A?7 preamp, which backs up this impression.
-
The EH English Muff'n has one 12AX7 and one 12AY7, and is supposed to be really nice.
-
There is the 12AY7 - this gives about 45% of the gain of the 12AX7
PhilKing, Can any amp that takes 12AX7s take 12AY7s? Can I put 12AY7s in my Marshall for example?
-
Usually you can swap the 12A-7 series, the 12 gives you the heater voltage. Going with a lower gain should not be a problem, but HJM is more up on the specifics of this than I am.
-
was playing the cream machine with the new 12at7/12au7 all morning. on consideration its pretty sweet like this, and i think i might leave these valves in for a while, as i can get a number of cool tones. i especially think the 12au7 power amp is great :)
it does need a gentle touch to get a clean tone, but thats nice somehow.
really enjoying my little rig:
-
Nice wall paper. :)
-
yeah, its listed in the inventory too ;) no chance to change it :(