kt77 or el34 in an or120?

[Airburst]

anybody know the best valves to use for the 70's or120's?think im using 4 el34's and 2 12ax7's at the min.It also runs perfect with 15 and 5 amp fuses,anybody know why this is?

[Neiloler]

Well, if the amp takes a 5 amp fuse, and you put a 15 amp fuse in it, it won't blow for sure, but that also means that anything that was meant to blow a 5 amp fuse (because anything higher than 5 amps would hurt the amp) won't blow till it gets to 15 amps (3x the max current of the 5 amp fuse).

Use the right kind of fuse your amp desires, and don't skimp out simply because you didn't want to walk to radio shack to buy the right kind of fuse. $4 for a pack of fuses or your amp.

[Airburst]

Well, if the amp takes a 5 amp fuse, and you put a 15 amp fuse in it, it won't blow for sure, but that also means that anything that was meant to blow a 5 amp fuse (because anything higher than 5 amps would hurt the amp) won't blow till it gets to 15 amps (3x the max current of the 5 amp fuse).

Use the right kind of fuse your amp desires, and don't skimp out simply because you didn't want to walk to radio shack to buy the right kind of fuse. $4 for a pack of fuses or your amp.

yeah,ive got loads of fuses.i dont understand what you mean by the "right kind of fuse your amp desires" it says 3 and 1 amp but blows quicker when i put them in,and the 15 and 5 amp fuses last months longer..cheers for yer advice but im still very confused on the matter haha .

[Neiloler]

If you're blowing the rating of fuses that the amp is labeled for, then you've got a problem in the amp. You're risking things by running a higher rated fuse.

[Randy Bass]

See parallel (duplicate) topic in Technical:

http://forum.orangeamps.com/viewtopic.php?f=3&t=39678" onclick="window.open(this.href);return false;

This is getting confusing with all of the "Category Shopping" on the Forum where issues get posted in Technical section and then duplicated in the General Discussion if there isn't a lot of feedback. I know...nobody cares. My name is Randy Bass and I have a problem with Situational Disorder .

[Airburst]

See parallel (duplicate) topic in Technical:

http://forum.orangeamps.com/viewtopic.php?f=3&t=39678" onclick="window.open(this.href);return false;

This is getting confusing with all of the "Category Shopping" on the Forum where issues get posted in Technical section and then duplicated in the General Discussion if there isn't a lot of feedback. I know...nobody cares. My name is Randy Bass and I have a problem with Situational Disorder .

screw your situational disorder haha im having serious problems with this amp dude n posted it twice purely due to sheer fuckin confusion about my amp hah ...peace n all that pile of poop

[doomedfuzz]

anybody know the best valves to use for the 70's or120's?think im using 4 el34's and 2 12ax7's at the min.It also runs perfect with 15 and 5 amp fuses,anybody know why this is?

Simple answer to both your questions:

1. Write to Bob at Eurotubes (who sells JJ/Tesla tubes) and ask your question about tubes. He sells both and will be able to explain the subtle differences. But I can tell you, they are direct replacements for each other so it may not be as big of a difference between the two than you are expecting. Bob has always written me back in a timely fashion and always is helpful. Just be sure to be detailed with your question, don't just say, what do you think? You should state the desired tone you are looking for. [email protected]

2. Fuses, well its been explained pretty well already but it is this -- your amp is set up to run with certain amounts of voltage going through it. The fuse is there to protect the amp if something is wrong, it will keep your amp from getting fried. If you have the factory recommended fuse in there and it's blowing rapidly, you have a problem. Ignoring this issue and placing higher ampage fuses in there that won't blow is simply masking a problem and you are risking your amps well being. Honestly, what you are doing is really pretty stupid, let me be totally frank with you. I'd get it to a tech ASAP. Have them re-tube and bias it while you are at it.

[Airburst]

anybody know the best valves to use for the 70's or120's?think im using 4 el34's and 2 12ax7's at the min.It also runs perfect with 15 and 5 amp fuses,anybody know why this is?

Simple answer to both your questions:

1. Write to Bob at Eurotubes (who sells JJ/Tesla tubes) and ask your question about tubes. He sells both and will be able to explain the subtle differences. But I can tell you, they are direct replacements for each other so it may not be as big of a difference between the two than you are expecting. Bob has always written me back in a timely fashion and always is helpful. Just be sure to be detailed with your question, don't just say, what do you think? You should state the desired tone you are looking for. [email protected]

2. Fuses, well its been explained pretty well already but it is this -- your amp is set up to run with certain amounts of voltage going through it. The fuse is there to protect the amp if something is wrong, it will keep your amp from getting fried. If you have the factory recommended fuse in there and it's blowing rapidly, you have a problem. Ignoring this issue and placing higher ampage fuses in there that won't blow is simply masking a problem and you are risking your amps well being. Honestly, what you are doing is really pretty stupid, let me be totally frank with you. I'd get it to a tech ASAP. Have them re-tube and bias it while you are at it.

Yeah its been with a tech for a very well known music shop for a long time and it was him that did this to my amp,he also says its kickin out almost 200 watts.He also tried to put it back to 120 but couldnt do it.this guy is the man for valve amps and he was stumped!... plus i originally used jj tesla kt77 and the amp sounded great and then my tubes fried and he said they were the wrong tubes as they were originally fitted with mullards but being hard to obtain n expensive he opted for el34's

[Nork]

dude, i posted in the tech forum too, but i'll say it again - get a second opinion. that dude may be the bees knees for amps, but so far he's done a couple things that could really damage you and your amp. like a doctor, i would take it somebody else. another perspective on it may be a good idea.

[doomedfuzz]

anybody know the best valves to use for the 70's or120's?think im using 4 el34's and 2 12ax7's at the min.It also runs perfect with 15 and 5 amp fuses,anybody know why this is?

Simple answer to both your questions:

1. Write to Bob at Eurotubes (who sells JJ/Tesla tubes) and ask your question about tubes. He sells both and will be able to explain the subtle differences. But I can tell you, they are direct replacements for each other so it may not be as big of a difference between the two than you are expecting. Bob has always written me back in a timely fashion and always is helpful. Just be sure to be detailed with your question, don't just say, what do you think? You should state the desired tone you are looking for. [email protected]

2. Fuses, well its been explained pretty well already but it is this -- your amp is set up to run with certain amounts of voltage going through it. The fuse is there to protect the amp if something is wrong, it will keep your amp from getting fried. If you have the factory recommended fuse in there and it's blowing rapidly, you have a problem. Ignoring this issue and placing higher ampage fuses in there that won't blow is simply masking a problem and you are risking your amps well being. Honestly, what you are doing is really pretty stupid, let me be totally frank with you. I'd get it to a tech ASAP. Have them re-tube and bias it while you are at it.

Yeah its been with a tech for a very well known music shop for a long time and it was him that did this to my amp,he also says its kickin out almost 200 watts.He also tried to put it back to 120 but couldnt do it.this guy is the man for valve amps and he was stumped!... plus i originally used jj tesla kt77 and the amp sounded great and then my tubes fried and he said they were the wrong tubes as they were originally fitted with mullards but being hard to obtain n expensive he opted for el34's

The amp could be biased incorrectly first of all. Again, Bob can answer questions such as this (concerning biasing), I am no tech but know enough to be dangerous. Forget about brands for a minute (JJ, Mullard, etc.), and concentrate on the tube type itself. KT77 is a direct replacement for an EL34. There should be no issue dropping those in at all. How they should be biased, that is for someone more qualified than myself to answer. You could have other problems though, perhaps the OT is going bad. And as mentioned above, get a second opinion. I was using one tech exclusively for a while who had a great reputation, but I wasn't happy with some of the results I was getting after he worked on my old RV50 (picked up from the shop and one channel didn't work!). So I use a different tech now and am very happy with his work on vintage amps and on modern Orange amps. Second opinions are a great thing.

I saw somewhere that the KT77s in an OR120 should be biased at about 65% dissipation and will hold up well. I've also read that in OR120s, the voltage is generally around 600V which should be enough to kick the KT77s into high gear (they perform well around 500V and up, below that they are lifeless). Almost sounds like your amp is running way to high of voltage! Kind of scary actually.

[Airburst]

Thanks for all the feedback dudes,ill be sure to take it to another tech asap

[bassdrop]

Ted Weber's site has a list of amp techs by geographic area. I found a great tech that way.

[jontheid]

Hi all,
I've tried Genalex KT77s in my 1979 Orange Super Bass (very similar design to OR120 with a few bass-specific bells and whistles) and I didn't get very good results at all. The sound was ok but lacked volume overall.

I scoped the output with a dummy load and found I was only getting 100W output. With Shuguang EL34Bs I get 150W clean output power no problem. My plates run at 500V so high enough really.

I don't really think that KT77s are a 'drop in' replacement for EL34s. KT77s have a higher plate resistance than EL34s (23kohm vs 15kohm at 250V plate) and maybe this accounts for the loss in power. The difference in power is not bias related - you can bias proper KT77s all the way up to 32W dissipation (and they don't red-plate, honest) - I tried from cold to sizzling and it made no difference in total power output, it just changed where crossover distortion started creeping in.

Maybe a bit less power is what you are looking for though?

Anybody else measured power output of OR120s running KT77s, either Genalex or JJ?

Cheers
Jon

ps. I'm no expert on valve amps but I do all my own repairs and those of my bandmates, because I am cheap, i.e. free. I do have a degree in electronics, but they don't teach you anything about valves these days . . .

[jontheid]

Further to my post above:

I am using reissue Genalex KT77s, just in case there was any doubt.


A question for AIRBURST. What country are you in, and what is the voltage selector on the back plate of the amp set to? I know this might sound like a ridiculous question, but if the voltage selector is set too low (e.g. 200V instead of 240V) you would get a higher than normal plate voltage, and would also probably blow fuses a bit more often than normal.

Jon

[Orphin]

dude, i posted in the tech forum too, but i'll say it again - get a second opinion. that dude may be the bees knees for amps, but so far he's done a couple things that could really damage you and your amp. like a doctor, i would take it somebody else. another perspective on it may be a good idea.

Yeah, I agree.
If a tech can't fix a pretty simple, or should we say "primitive" amp as old Orange, I wouldn't consider him a great tech tbh.