just built a little tube amp 3 12AX7 + 2 EL84's pp. bugger me i cant find the cause of the hum. i know 50 hz is interferance and 100 hz is earth loop or bad power regulation. after fighting with this for a few weeks i must admit defeat (we all fail now and again). so now it's rip it all out and start afresh. the plan is a KLD kit (pva18h) but use my own transformers, chassis and front panel and using tube bridge rectification also an under sized output transformer but an over sized power transformer. Just for the potential interest of others here I will post the progress here. i alrady have a KLD amp modded to be more like an orange amp from the 70's this is the best amp I have had in 40+ years. "tight, punchy, resposive. etc etc etc" this kit is £137 inc tax,p+p,etc. this means i will have a couple of transformers for fleabay. an unusual thing about this amp is El84 pp but using a 5k ct output transformer ( so you don't need 8k ct as many experts state. ill udate as and when.
life's a *****
- Thread starter KLDVOX
- Start date
Help Support GroupDIY Audio Forum:
pucho812
Well-known member
what’s the layout?
all the info is on the kldguitar.com website.
pucho812
Well-known member
Help us help you.
Oh sorry I misread.I thought you were having an issue.
so the kit that has just cleared uk customs is this
the changes i will make are very minor ones.
1, 1st stage will get a bigger cathode capacitor and a differnt cathode resistor ( similar to fender bassman) and only one input socket.
2, fit a rotary switch with a couple of different capacitors right after the first stage (Orange style).
3, 3 tube bridge rectifier for the ht.
4, a smaller output transformer.
5, a power transformer capable of 50watts.
6, a stand alone heater transformer.
all simple stuff.
the changes i will make are very minor ones.
1, 1st stage will get a bigger cathode capacitor and a differnt cathode resistor ( similar to fender bassman) and only one input socket.
2, fit a rotary switch with a couple of different capacitors right after the first stage (Orange style).
3, 3 tube bridge rectifier for the ht.
4, a smaller output transformer.
5, a power transformer capable of 50watts.
6, a stand alone heater transformer.
all simple stuff.
Last edited:
thanks for the offer of help. but im just going to re-start from sratch
..@KLDVOX - remember, this forum not for marketing commercial stuff.
It's OK in white market though.
/Jakob E.
It's OK in white market though.
/Jakob E.
sorry mate , i was not advertising, selling or promoting anything. its just the same as saying i will use "tungsoll" tubes and build an amp with a "fender bassman" style output stage, but use "fane" speakers when i play my "gibson" guitar. mentioning the kit that i had bought was merely a statement of fact and i posted the schematic for the intrest of of other amp builders as this amp has a couple of interesting and unusual features.
scott2000
Well-known member
Your user name isn't tungsoll, fender, fane or gibson.... Maybe that's where the confusion lies..
life can be confusing for me sometimes.
as i was planning on posting details of this amp build in this board and nit picking all components etc. am i ok to continue the thread here or should i move it to another board?
im happy to have one of the mods move or delete my posts.
as i was planning on posting details of this amp build in this board and nit picking all components etc. am i ok to continue the thread here or should i move it to another board?
im happy to have one of the mods move or delete my posts.
Perhaps the confusion is because you chose user name Kldvox and started a thread about building amplifiers, then in this same thread there was discussion of a commercial company called KLD which sells amplifier kits.
right getting back to the kit i just bought.
you pretty much get what you pay for. first the eyelet board ( i prefer turrets myself ) the board is 2 mm thick with a division cut part way though, one part is for mounting the pots on ( doubt i will be using this part as the pots are only 16 mm i prefer the bigger ones i think they are more reliable ).
the board is clearly marked as to where all the components go..
it looks like this is their unversal board as its printed for other components not supplied.
the tansformers; the input transformer is quite heavy and i guess they supply this one with all of there kits i would estimate itwould be a little over 50 watts ( there is no power rating given ). as im planning to use a tube rectifier i will need qute a bit of power on the 6.3 windings so will not be using this transformer.
the output transfomer; im guessing about 20 to 30 watts. the inductance measures 5.5h aprx from one side to the ct, so 11h. but when i measure across the two phases the inductance shows as too much for my meter to record ( ie over 20h beats me ).
the other bits and pieces are what you would expect all cloe tollerance and high voltage. one thing i dont like is the quality of the plastic XLR for the line out. i have a few neutric ones in my shed.
this does not come with instructions you have to download a pdf.
if you plan to use their chassis it can only be supplied with the kit and not as an afterthought.
ill make a start on this over the weekend and post the problems that i find but will have to give it a rest for a few days after that. i have a small heart problem to get sorted ( nothing serious ) i have been told i will need to take it easy for a week or so.
you pretty much get what you pay for. first the eyelet board ( i prefer turrets myself ) the board is 2 mm thick with a division cut part way though, one part is for mounting the pots on ( doubt i will be using this part as the pots are only 16 mm i prefer the bigger ones i think they are more reliable ).
the board is clearly marked as to where all the components go..
it looks like this is their unversal board as its printed for other components not supplied.
the tansformers; the input transformer is quite heavy and i guess they supply this one with all of there kits i would estimate itwould be a little over 50 watts ( there is no power rating given ). as im planning to use a tube rectifier i will need qute a bit of power on the 6.3 windings so will not be using this transformer.
the output transfomer; im guessing about 20 to 30 watts. the inductance measures 5.5h aprx from one side to the ct, so 11h. but when i measure across the two phases the inductance shows as too much for my meter to record ( ie over 20h beats me ).
the other bits and pieces are what you would expect all cloe tollerance and high voltage. one thing i dont like is the quality of the plastic XLR for the line out. i have a few neutric ones in my shed.
this does not come with instructions you have to download a pdf.
if you plan to use their chassis it can only be supplied with the kit and not as an afterthought.
ill make a start on this over the weekend and post the problems that i find but will have to give it a rest for a few days after that. i have a small heart problem to get sorted ( nothing serious ) i have been told i will need to take it easy for a week or so.
Last edited:
Electrobumps
Well-known member
yes this is true, but other things can cause this
you might be better figuring out what you have done wrong/or what component is at fault. If you build again you might just do exactly the same thing again or have the same issue.
You need to start with the basics and determine what section of the amp introduces the hum. Be methodic take notes pull tubes, chopstick lead dress and work out where it's being introduced. At pre-amp, PI, or output. Is it heater hum, tube hum, lead dress hum, bias hum.
I’ve been there with an AB763 build twin reverb build. Building the amp was relatively quick compared to working out issues and chasing hum.
This is a really good place to start with fault-finding.
https://robrobinette.com/Amp_Stuff.htm
Last edited:
so i built the mainboard today. no problems a couple of small caps had been replaced with similar value but higher voltage rating.
i guess its astock control issue. no problem in itself except for the slightly larger diameter causing some components to be bunched up.
missing items,,, no hookup wire included luckily i have some 18 gague solid wire knocking around.
a couple of the eyelets have been replaced with turrets
the small changes i have made upto now the 1st stage has a 100k anode reesistor ( not 220k) cathode resistor is 2k2 (not 1k5) cathode cap is a massive 220uf (not1uf) these are close to fender bassman values and ive always found these work well (im not an electronics guy so please dont quizz me on the gain or headroom).
another small mod is.the blocking cap after the 1st stage is replaced with a smal bunch of caps and a rotary switch similar to what Orange used to fit on the early 70's 100 & 120 overdrive amps. im only using a 4 position switch orange use a 6 position switch (4 is enough) the switch im using was far too stiff and designed for a 40mm knob so ive replaced the spring with a softer spring making the switch easy to turn.
all simpe stuff.
i guess its astock control issue. no problem in itself except for the slightly larger diameter causing some components to be bunched up.
missing items,,, no hookup wire included luckily i have some 18 gague solid wire knocking around.
a couple of the eyelets have been replaced with turrets
the small changes i have made upto now the 1st stage has a 100k anode reesistor ( not 220k) cathode resistor is 2k2 (not 1k5) cathode cap is a massive 220uf (not1uf) these are close to fender bassman values and ive always found these work well (im not an electronics guy so please dont quizz me on the gain or headroom).
another small mod is.the blocking cap after the 1st stage is replaced with a smal bunch of caps and a rotary switch similar to what Orange used to fit on the early 70's 100 & 120 overdrive amps. im only using a 4 position switch orange use a 6 position switch (4 is enough) the switch im using was far too stiff and designed for a 40mm knob so ive replaced the spring with a softer spring making the switch easy to turn.
all simpe stuff.
Last edited:
so after being zapped with a couple of hundred joules in the arithmia clinic ( quite shocking really ) i found a few hours to build this little kit,
thankfully it all went together well. i have used an all tube bridge rectifer this seems to compress the volume a little when i crank the amp up. i made a few small mods ( nothing spectacular ) i swapped the 1st tube with an ecc82 as i think they sound nice, ive altered a couple of the resistors around this tube so i still get a high gain input stage. a small mod for the future is to put a couple of low value caps ( in the post ) across the anode resistors on the first 2 stages to improve stability at extreme settings.
although the output tranny has 4,8 & 16 ohm outs i only fitted a jack to the 8 ohm as once this is in the rack it will be plugged into a dummy load with the line out going to the rack mixxer then into my power amp ( 400w & 400w ) i sometimes play loud 102db for 1w@1m
i like the kld stuff so this will be going in my rack along with my other kld amp and my little vox amp
aparently these amps are based on a marshell tmb 18watter. i dont know about that but i like this little amp.
thankfully it all went together well. i have used an all tube bridge rectifer this seems to compress the volume a little when i crank the amp up. i made a few small mods ( nothing spectacular ) i swapped the 1st tube with an ecc82 as i think they sound nice, ive altered a couple of the resistors around this tube so i still get a high gain input stage. a small mod for the future is to put a couple of low value caps ( in the post ) across the anode resistors on the first 2 stages to improve stability at extreme settings.
although the output tranny has 4,8 & 16 ohm outs i only fitted a jack to the 8 ohm as once this is in the rack it will be plugged into a dummy load with the line out going to the rack mixxer then into my power amp ( 400w & 400w ) i sometimes play loud 102db for 1w@1m
i like the kld stuff so this will be going in my rack along with my other kld amp and my little vox amp
aparently these amps are based on a marshell tmb 18watter. i dont know about that but i like this little amp.
Last edited:
