6550s and I don't like each other

[Mattfig]

Even with all the headroom 6550s provide for a great clean or recto tone...I just can't take the sterile tone...Mine are Tung Sol 6550s...I ALWAYS keep EL34s in the mix and I gotta go back to the 6L6STRs...As much as I should love the sound of those tubes - I have only liked them in bass rigs...What is wrong with me? What am I missing here 'cause I know a lot of you guys dig them....

Help me out...What should I like about them over 6L6s?

 

[kc2eeb]

You're not missing anything. 6550s, as well as KT88s, were specifically designed to be clean, really clean, to fix the "defects" found with 6L6s,
6CA7s aka EL34s, etc. That's why they're rated for 700-800 volts on the plates, so, when the "transform"-er converts the high voltage, low current to
low voltage, high current to drive speakers, there are more volts to start with.
Randalls run the plates around 500-520 volts, so the 6550/KT88s aren't even near being pushed. They could just as well be transistors.
The Ampeg SVT originally used 6146s, a RF transmitter tube, later changing to 6550s, six of them, to put out 300 watts RMS clean.

 

[JKMV12]

You're not missing anything. 6550s, as well as KT88s, were specifically designed to be clean, really clean, to fix the "defects" found with 6L6s,
6CA7s aka EL34s, etc. That's why they're rated for 700-800 volts on the plates, so, when the "transform"-er converts the high voltage, low current to
low voltage, high current to drive speakers, there are more volts to start with.
Randalls run the plates around 500-520 volts, so the 6550/KT88s aren't even near being pushed. They could just as well be transistors.
The Ampeg SVT originally used 6146s, a RF transmitter tube, later changing to 6550s, six of them, to put out 300 watts RMS clean.

I have the RM80 which if i remember correctly used to come stock with 6550's I know i liked the tone i got with the 6550's. Do you know if the RM80 circuit was designed for the higher plate voltage rating of the 6550's? I prefer the tone of the 6550's over the 6V6's and EL34 (which i currently have). The EL34's are ok...i am probably going to try 6L6's next. But at some point i will get another set of 6550's. The problem is that they are more expensive.

 

[kc2eeb]

The RM50 and RM80 are the same amp.
Later RM50s come with a reverb circuit on a board attached to ther reverb pan.

 

[JKMV12]

The RM50 and RM80 are the same amp.
Later RM50s come with a reverb circuit on a board attached to ther reverb pan.

So when i use 6550's i am not getting the most of out of them? Maybe when i get more experienced with tube amp circuits i can go in an make some modifications...**** me and my crazy ideas :lol:

Thanks,
John

 

[Nightdare]

Do you know if the RM80 circuit was designed for the higher plate voltage rating of the 6550's?

Now my degree of electrical engineering stops at super 5-way switches
but If I just use logical thinking, I suspect there will have to be very many parts swapped to higher voltage replacements and even after that, there still is the question if the PCB can handle the powerincrease

 

[JKMV12]

Do you know if the RM80 circuit was designed for the higher plate voltage rating of the 6550's?

Now my degree of electrical engineering stops at super 5-way switches
but If I just use logical thinking, I suspect there will have to be very many parts swapped to higher voltage replacements and even after that, there still is the question if the PCB can handle the powerincrease

true...of course if i try to do it i will consider all consequences of the mod. from what i know of pentodes/power beam tetrodes there are four sections that determine its performance (input grid circuit, cathode circuit, screen grid circuit, and plate circuit or the load). Then there is of course making sure that both tubes still work together as well as with the PI and OT. It would not be an easy task...but once i have the technical knowledge i will be able to better evaluate the plausibility of the idea.

 

[kc2eeb]

I would not increase the plate voltage on the RM50 with the pc board
layout as it is. Industry standard is to increase minimum electrical clearance by .0025mm per each volt over 500 volts. You won't get that
on the RM50 board.

 

[rblyn]

You're not missing anything. 6550s, as well as KT88s, were specifically designed to be clean, really clean, to fix the "defects" found with 6L6s,
6CA7s aka EL34s, etc. That's why they're rated for 700-800 volts on the plates, so, when the "transform"-er converts the high voltage, low current to
low voltage, high current to drive speakers, there are more volts to start with.
Randalls run the plates around 500-520 volts, so the 6550/KT88s aren't even near being pushed. They could just as well be transistors.
The Ampeg SVT originally used 6146s, a RF transmitter tube, later changing to 6550s, six of them, to put out 300 watts RMS clean.[/quot

Havent tried 6550's but KT88's are absolutely crushing....You are correct, very clean power but still very warm and a nice high end/mid range that doesnt get "ice pick" sounding at all, just sings and "thumps" at the same time. With the distortion coming from the preamps on the RM100, the KT88's work the best for me for live situations. Not for bedroom or any situation where cant at least push the master to 4 or 5...but **** good for gigs and rehearsals.

 

[Mattfig]

Thanks for all the great info guys! Yep, I've pulled them for good...In thinking about it, pairing 6550s w/EL34s is a bit too extreme and the 6L6s just fit that scheme better....Still get that low end thump and more headroom- just not so sterile...

 

[rblyn]

Even with all the headroom 6550s provide for a great clean or recto tone...I just can't take the sterile tone...Mine are Tung Sol 6550s...I ALWAYS keep EL34s in the mix and I gotta go back to the 6L6STRs...As much as I should love the sound of those tubes - I have only liked them in bass rigs...What is wrong with me? What am I missing here 'cause I know a lot of you guys dig them....

Help me out...What should I like about them over 6L6s?

Matt-Nothing wrong at all...everyone likes something different and styles, technique, cabinets, speakers all affect what you're liking...I've used el34's for awhile but after trying KT88's, I wouldnt go back. The 34's have a sweet mid-range but so do the KT's....6l6's sound "boomy" to my ears through my Mesa cab but always sounded killer in my Triple Rectifier.

 

[JKMV12]

I would not increase the plate voltage on the RM50 with the pc board
layout as it is. Industry standard is to increase minimum electrical clearance by .0025mm per each volt over 500 volts. You won't get that
on the RM50 board.

well there is my answer...though that doesn't mean i can't make an amp specifically for 6550's. though i need to do a lot of studying and experimenting before i can make a full amp. My first task is to learn about power supplies. I am trying to start a project with a friend to make a variable DC power supply. I am thinking about having several channels (say three or four) that each can put out 0-600VDC. It will also have three secondary outputs of 5V, 6V, and 12V. One of my goal for this is to have a device that i can use to help me design gain stages by trying different plate voltage. I know that designing a gain stage involves more than just the plate voltage and that the other components depend on the plate voltage. Mainly i think it would be a good learning experience.

 

[Rod]

I have been using KT66's and KT77's in my RM50's and like these tubes much more than either 6l6's or EL34's.. They seem more musical and the overdrive is fuller and the highs are more pleasing to the ear..... Just thought I'd throw this info out there for you guys. As for KT88's, I haven't tried these yet..

 

[hunter]

Sometimes I think people running huge KT88/6550 amps would be better off using transistor power amps. They give very little coloration, which IMO is a bad thing for guitar.

 

[rblyn]

Sometimes I think people running huge KT88/6550 amps would be better off using transistor power amps. They give very little coloration, which IMO is a bad thing for guitar.

Hunter- I respectfully disagree with that. Have you tried these tubes? Looks like your playing an RM22 (I have an RM20 t00, killer amp!) and prefer my RM100 with the KT88's over my RM20 with JJ EL84's any day. Ive seen some of your youtube clips and your rig sounds really good ..I dont think my power tubes are being pushed very hard in the RM100 but they have a nice mid punch/smooth top end, bottom end is super tight and the KT88's are very warm, musical and everything sounds BIGGER..It actually changed the sound of preamps and as they used to sound more alike with high gain, they are now each sounding very different. (Could be because of the super clean power that these tubes provide? not sure) This has also translated into my rig just crushing our other guitar player's Triple Recitifier in tone, flexibility and overall cut in the mix. We are both using Mesa cabs as welll with V30's.I have used both amps in a band situation and there's no comparison at least to me...I've owned, played and toured with about a dozen different tube amps/rack setups and this is the first time I've had a chance to try these out...Very pleased...but to each his own, especially when it comes to tone.

 

[Nightdare]

Sometimes I think people running huge KT88/6550 amps would be better off using transistor power amps. They give very little coloration, which IMO is a bad thing for guitar.

coloration characteristics is still something different from overdrive characteristics
even the various tubetypes driven 'clean' give a certain (different) character

 

[hunter]

Sometimes I think people running huge KT88/6550 amps would be better off using transistor power amps. They give very little coloration, which IMO is a bad thing for guitar.

Hunter- I respectfully disagree with that. Have you tried these tubes? Looks like your playing an RM22 (I have an RM20 t00, killer amp!) and prefer my RM100 with the KT88's over my RM20 with JJ EL84's any day. Ive seen some of your youtube clips and your rig sounds really good ..I dont think my power tubes are being pushed very hard in the RM100 but they have a nice mid punch/smooth top end, bottom end is super tight and the KT88's are very warm, musical and everything sounds BIGGER..It actually changed the sound of preamps and as they used to sound more alike with high gain, they are now each sounding very different. (Could be because of the super clean power that these tubes provide? not sure) This has also translated into my rig just crushing our other guitar player's Triple Recitifier in tone, flexibility and overall cut in the mix. We are both using Mesa cabs as welll with V30's.I have used both amps in a band situation and there's no comparison at least to me...I've owned, played and toured with about a dozen different tube amps/rack setups and this is the first time I've had a chance to try these out...Very pleased...but to each his own, especially when it comes to tone.

I take that experience from trying a Shiva 20th with both, KT88 and EL34. KT88 sounded dead clean to me, EL34 rocked. I also played a 6x6550 Herbert and thought it sounded and felt like solid state.

Matter of taste for sure. Guess those 6550s are great for fast metal stuff.

 

[eyeball987]

I used 6550's for a while and thought they were great. Went to a mix of 34's and 6550's and liked it better. Tried all 34's and the 6550's sat in their box for a while.

I think I might end up with all 34's again but had a set give up the ghost on me so I am 34 and 6L6 at the moment. I thought the 6L6's were too boomy but the tone has grown on me even with my Marshall tuned ear.

I don't think I can give up keeping at least one set of 34's in the RM100. I have tried to steer away from tone chasing over the past 6 months or so and have been happier and less critical as a result. I do need another set of power tubes around, just in case, since I only have 6550's on back up but I have not been serious enough about it to pull the trigger. My eye has caught a couple sets of Winged C 34's at decent prices though.

 

[GtrGeorge!]

I love it when u guys talk Tubes. Its an expensive thing to try every kind of tube so all discussion is helpful to me.
Tanks!

GtrGeorge