Feel free to ask Myles

[alevinthal]

Originally posted by myles111:

alevinthal ...

 

Dan Torres is right on the money. Amps drift, and mostly because of AC variances. I always use a variac when I work on amps, as everytime something turns on or off, even if not on the same circuit, things go way off.

 

380 volts on EL-84's is also a bit high, so they will run hot also. Class A amps run a LOT hotter, and this heats up everything, not just the tubes. Remember, a class A amp with no signal, is running at 100%, flat out ... so use the standby switch when not playing. This is the reason that AC-30's used to actually catch fire in some cases.

 

You can also drop the heat by using a cooler range of output tubes with the Mesa amps, but the amp will distort more quickly.

 

Regards,

 

Myles

Hi Myles,

 

Thanks again for your time. What is your opinion about this idea:

 

since the RT30 sounds good when first turned on, but really sweet after running for an hour or so, might I put it on the bench, measure it at turn-on, run it into a load for an hour, measure it again, and then (maybe) figured out how to swap components to get it to run at those measured currents/voltages normally, and *then* try to keep it cool so it stays there? Is this likely to work?

 

If it does make sense, I could try it myself, but all I have is an EE degree, a basic iron/meter/scope, and limited knowledge of tubes and high voltage design. I am interested in trying, but I'm concerned about killing my best-sounding amp. Maybe Mr Torres can do this, but I don't know if he is willing to do this sort of 'experimental' work (or if I could afford it). Either way, I'll be trying a fan next time out.

 

just wondering,

 

-Adam-

 

P.S. The amp is supposed to be running at 350V B+ but I measured 380V, and I have felt the mains transformer get (too) hot, but it's intermittent. I suspect there might be a short in the primary windings of a turn or two. What would you suspect? I mean to replace it, but haven't gotten around to it.

 

P.P.S What do you think about implementing auto-bias in guitar amps with solid-state regulators? Here's a link to a paper on the subject: http://www.glass-ware.com/tubecircuits/Tube_Auto_Biasing.html

[myles_rose]

Originally posted by cereal:

Myles, I'm sure you have an opinion on this:

 

http://www.harmony-central.com/Newp/2002/RM50.html

\\

 

cereal ...

 

Haven't seen one of these yet, but its an old idea that has been done by a lot of others in the past.

 

Seymour Duncan did an amp like this, a combo, that was pretty cool. The problem was that they were pricy (but worth it for the work that went into making them), and complicated. The modules were also expensive too.

 

Generally, when you have more interconnects and things that move around, there is more that can go wrong.

 

The bottom line, is the concept is interesting, but as I said earlier ... it has been done before, and never seemed to gain a foothold.

 

These days, I would think that modeling amps would offer a lot of bang for the buck in this area. You can make a POD sound very nice now if you use something like a DITTO box on it, so the field is getting narrower all the time when it comes to being versitile in a compact package.

 

Myles

[myles_rose]

Originally posted by ehv:

Hi Myles, first post here.....

 

I am having a problem with my 94' Fender "Twin Amp" (not Twin Reverb) that I'm wondering if you can help with. When I turn my reverb level above about 4, I start getting a ringing/feedback/high-pitched tone. The higher I turn my reverb level, the louder the feedback gets (gets very loud at 10). If I turn the reverb level down to 4 or below, the feedback goes away. The feedback builds slowly in level, takes 10-20 seconds to build up. It does it whether I'm in channel 1 or 2. If the volume level is turned to 0, and the reverb level is turned up, it still feeds back.

 

Any idea what's causing this? If it's a potential tube problem, do you know which tube/tubes drive the reverb? I have schematics (though I don't know much about reading them) and my best guess is that V5 (12AT7) and /or V6 (12AX7) are the reverb tubes.

 

If it needs to be serviced, do you have any recomendations for an amp tech in the Denver/Boulder CO area?

 

From reading many of the above posts, I know it's been said many times, but it really is great of you to take your time to help so many people out here!

 

Thanks for any help you can give on this!

 

Eric V

Eric ...

 

For your reverb problem, first replace the reverb driver tube with a new one. You may have too much gain. I prefer the 12AT7 as a reverb driver, and some folks just slap in a 12AX7.

 

Your tube chart will have the reverb driver (which parallels the two sides of the tube for send), and the return. You may want to just try to swap out both the send and return to save a bit of time.

 

I do not know of anybody in your area off the top of my head. Perhaps somebody else in here may have an idea, or post something over at www.harmony-central.com in their forum and ask there ... they are a good bunch for the most part too

 

Regards,

[myles_rose]

Originally posted by alevinthal:

Originally posted by myles111:

alevinthal ...

 

Dan Torres is right on the money. Amps drift, and mostly because of AC variances. I always use a variac when I work on amps, as everytime something turns on or off, even if not on the same circuit, things go way off.

 

380 volts on EL-84's is also a bit high, so they will run hot also. Class A amps run a LOT hotter, and this heats up everything, not just the tubes. Remember, a class A amp with no signal, is running at 100%, flat out ... so use the standby switch when not playing. This is the reason that AC-30's used to actually catch fire in some cases.

 

You can also drop the heat by using a cooler range of output tubes with the Mesa amps, but the amp will distort more quickly.

 

Regards,

 

Myles

Hi Myles,

 

Thanks again for your time. What is your opinion about this idea:

 

since the RT30 sounds good when first turned on, but really sweet after running for an hour or so, might I put it on the bench, measure it at turn-on, run it into a load for an hour, measure it again, and then (maybe) figured out how to swap components to get it to run at those measured currents/voltages normally, and *then* try to keep it cool so it stays there? Is this likely to work?

 

If it does make sense, I could try it myself, but all I have is an EE degree, a basic iron/meter/scope, and limited knowledge of tubes and high voltage design. I am interested in trying, but I'm concerned about killing my best-sounding amp. Maybe Mr Torres can do this, but I don't know if he is willing to do this sort of 'experimental' work (or if I could afford it). Either way, I'll be trying a fan next time out.

 

just wondering,

 

-Adam-

 

P.S. The amp is supposed to be running at 350V B+ but I measured 380V, and I have felt the mains transformer get (too) hot, but it's intermittent. I suspect there might be a short in the primary windings of a turn or two. What would you suspect? I mean to replace it, but haven't gotten around to it.

 

P.P.S What do you think about implementing auto-bias in guitar amps with solid-state regulators? Here's a link to a paper on the subject: http://www.glass-ware.com/tubecircuits/Tube_Auto_Biasing.html

Adam ...

 

I guess go and try ... cannot hurt.

 

As far as your transformer ... I would need to bench the amp and look.

 

Myles

[Oscar]

Myles,

 

On the one hand, I have box of old tubes, including:

-4 Siemens ECC83's

-a Brimar ECC83

-a Philips Miniwatt ECC83

-a Philips 12AT7 and a 12AY7

-a GE 6L6 GC

-a couple of Sylvania 6L6GC USA

-a couple of Philips EL34's

The pre-amp tubes are all in good shape, the power amp tubes vary. Some are worn, others are good.

 

On the other hand, I have a Fender HotRod Deluxe combo with Fender/Groove Tubes 12AX7's and 6L6's.

 

Now, how to combine the two....? Are the Siemens ECC83's, for example, to be used in stead of the Fender/Groove Tubes 12AX7's? What sound differences can I expect? Or would the Brimar be a great choice for V1, or which would be a good choice for the phase inverter, or, or, or....

 

***Oscar<---------option anxiety***

 

Any suggestions would be appreciated!

[myles_rose]

Originally posted by Oscar:

Myles,

 

On the one hand, I have box of old tubes, including:

-4 Siemens ECC83's

-a Brimar ECC83

-a Philips Miniwatt ECC83

-a Philips 12AT7 and a 12AY7

-a GE 6L6 GC

-a couple of Sylvania 6L6GC USA

-a couple of Philips EL34's

The pre-amp tubes are all in good shape, the power amp tubes vary. Some are worn, others are good.

 

On the other hand, I have a Fender HotRod Deluxe combo with Fender/Groove Tubes 12AX7's and 6L6's.

 

Now, how to combine the two....? Are the Siemens ECC83's, for example, to be used in stead of the Fender/Groove Tubes 12AX7's? What sound differences can I expect? Or would the Brimar be a great choice for V1, or which would be a good choice for the phase inverter, or, or, or....

 

***Oscar<---------option anxiety***

 

Any suggestions would be appreciated!

Oscar,

 

Anything in the 12AX7 family (ECC83, etc.,) can be exchanged with no adjustment.

 

I prefer 12AT7's for phase inverters as they have about 10 times the current drive of a AX7, but a less gain. Its all personal preference.

 

I'd look at the 12AX7 section on my website, it may give you some ideas.

 

There are power tube areas on my website also.

 

Myles

[What Will Become]

Hi Myles-

 

I recently sold my 5150 II and have switched to a Triple XXX. I've found the Triple XXX has more low end crunch which better suits my needs as I use 7 strings and play very heavy music. Anyway I want to '86 my stock tubes and need help deciding if I should go with JJ 6L6's or E-34L's. I like a lot of low end and am afraid that the E-34L will lack bottom as opposed to the 6L6. I also hear that the E-34L has a way better definition as well. What would you do?

 

Thanks for any advice..

[Franknputer]

Hey Myles -

 

Sorry you couldn't make it - good food, good chattin'! Maybe next time.

 

Thanks for the tip on the amps - the THD looks interesting - I'll have to start saving my pennies.

 

Another warranty-voiding, don't-try-this-at-home-kids sort of question - currently, I have a Peavey Classic 30 (pretty nice for a REALLY cheap amp!). I've been wondering about the Mid Boost circuit - I've always thought that it should have been foot-switchable, rather than a pushbutton. I asked somebody at Peavey about this once, but they claimed it wasn't possible.

 

Personally, i thought he was BSing me in order to protect Peavey - any idea? Seems that, in theory, one switch should be replaceable with another, given appropriate rating, # of poles & type of switch - am I missing something here? Obviously, it would have to be wired to accept a jack, or hard-wired to a switch, but is there really any reason something like this should be "impossible"?

[myles_rose]

Originally posted by What Will Become:

Hi Myles-

 

I recently sold my 5150 II and have switched to a Triple XXX. I've found the Triple XXX has more low end crunch which better suits my needs as I use 7 strings and play very heavy music. Anyway I want to '86 my stock tubes and need help deciding if I should go with JJ 6L6's or E-34L's. I like a lot of low end and am afraid that the E-34L will lack bottom as opposed to the 6L6. I also hear that the E-34L has a way better definition as well. What would you do?

 

Thanks for any advice..

Pretty easy actually.

 

In most amps where you want the low and mids of the 6L6, but the articulation in the higher ranges when pushed of the EL-34, the 6L6S:

 

http://www.groovetubes.com/product.cfm?Product_ID=1680

 

is what I use in my clients amps. These bias closer to an EL-34 than a 6L6, and are also a 30 watt tube, rather than a 25 watter as most EL-34's and most 6L6's too. Be sure to check the bias. I use these in a #5 or #6, unless you want a LOT of volume and a LOT of clean headroom. If you get the version of this tube from JJ, be sure to get it from Bob Pletka over at Eurotubes (if you don't get it from Groove Tubes), and tell Bob to pick you a set that at 250 volts with a -14 bias, will run at about 80mA. The standard spec for a 6L6 is 72.0mA, and one at 78-82 will be right in the super range for your amp.

 

DO NOT use other vendors for the JJ 6L6S other than Eurotubes, Watford Walves, the folks on my website, or GT unless you have had good luck with them in the past on prior purchases.

 

You will like them. If you are in the LA area, I would be happy to bias your amp gratis, as you are in this forum.

 

Myles

[myles_rose]

Originally posted by Christopher Kemp:

Hey Myles -

 

Sorry you couldn't make it - good food, good chattin'! Maybe next time.

 

Thanks for the tip on the amps - the THD looks interesting - I'll have to start saving my pennies.

 

Another warranty-voiding, don't-try-this-at-home-kids sort of question - currently, I have a Peavey Classic 30 (pretty nice for a REALLY cheap amp!). I've been wondering about the Mid Boost circuit - I've always thought that it should have been foot-switchable, rather than a pushbutton. I asked somebody at Peavey about this once, but they claimed it wasn't possible.

 

Personally, i thought he was BSing me in order to protect Peavey - any idea? Seems that, in theory, one switch should be replaceable with another, given appropriate rating, # of poles & type of switch - am I missing something here? Obviously, it would have to be wired to accept a jack, or hard-wired to a switch, but is there really any reason something like this should be "impossible"?

Christopher ...

 

Be sure to catch us next time ... it was a blast.

 

The THD is pretty amazing. If you are in my area, you are more than welcome to try mine.

 

The Peavey Classic 30 ... a really fun amp. I have a lot of clients with these that play gigs with them all the time, and in some fairly large venues. It is possible to add a mod to switch the mid boost, but would be more cost than it may be worth. Its a matter of a switch latch off the circuit. I'd leave the amp stock.

 

At the moment, I have a few folks out testing some new tubes off new tooling in "your" amp. I may post something soon on this new tube that may be stronger than the EL84S (JJ) tube. It would be nice to have three choices for new tubes for an EL84 ... although the current Russian tube is not a viable option in most cases.

 

Regards,

[What Will Become]

Thanks Myles. I ordered the 6L6's from Bob. Should I adjust the bias to the 33-44 MA range that he recommends?

[myles_rose]

Originally posted by What Will Become:

Thanks Myles. I ordered the 6L6's from Bob. Should I adjust the bias to the 33-44 MA range that he recommends?

You can go anywhere in that range, but it will work fine, not be great.

 

On the Fender test line, they have a procedure that for bias says .... "set to -52 volts". A 6L6 can bias between 46 and 62 volts ... so that is not the best sort of deal, as all tubes are different and all circuits a bit different.

 

Let me know your amp again, and if you can tell me your B+ voltage, that would be even better, and I will narrow that wide range way down for you. That is one reason some amps are magic and some are just nice.

 

Myles

[gearup]

I just put a pair of Tesla el-34s in a Blues Jr. I did not have the amp biased because Bob at Eurotubes said it would not be necessary. He sent me two tubes matched to within 1 milliamp. The rating he wrote on the boxes for these tubes was 37, I do not know what this means. If you know what it is , please help. Will these tubes be ok? The amp does sound very nice now.

[myles_rose]

Originally posted by gearup:

I just put a pair of Tesla el-34s in a Blues Jr. I did not have the amp biased because Bob at Eurotubes said it would not be necessary. He sent me two tubes matched to within 1 milliamp. The rating he wrote on the boxes for these tubes was 37, I do not know what this means. If you know what it is , please help. Will these tubes be ok? The amp does sound very nice now.

Bob is quite correct. I am not sure what his "37" is, but it may be the milliamp current. He uses different test equipment than I use, and he may use a higher plate voltage with a higher bias. My number that I look for is about 48, but I test at different spec.

 

Your tubes will work better than "ok" by a very wide margin. Any tubes we have ever gotten from Bob are of super quality and match, even when we get them from outside sources so he could not pick "ringers" for our testing.

 

Regards,

[gearup]

I was wondering if a Fender Blues Jr. will run a 4x12 cabinet. If so how will this affect the tone and overall volume vs. the single 12 that is in the BJ? If it will work well I will build my own cab. Does anyone know where I can get specs to build a cab?

[johnny5]

myles, sorry to have so many questions but you have so much knowledge. my plate voltage / B+ voltage in the hellhound is about 480V. i tried the KT66 (not sure of the brand, they were my tech's) and they did not physically fit. i believe they might have a smaller bottle one. can i achieve a tighter, maybe slightly more throaty tone with a power tube change? if so, which direction should i look. i did have a bias pot installed so i have more room to work now.

 

i have Reverend Hellhound combo (2 6L6's, 60W, 1X12) that has Electro Harmonics 6L6's in it. i have read that these tubes are not very good. and in listening i notice that when these suckers are pushed, they get less and less sweet. almost flabby. i was looking the groove tubes site at the CB's looks like i can get a little more power tube distortion out of those.

 

any thoughts or recomendations?

johnny5 ...

 

The CB's are Chinese with a softer vacuum, but do have more mids than the EH's .... most 6L6 tube actually do.

 

In your amp my favorite tube is the KT-66HP, that is also now one of the least expensive in the GT line as we dropped price from $85 a duet to $60.00 a duet ( $5.00 cheaper than the Chinese KT-66 we also carry with the price drop now ).

 

I like these with a #5 rating in your amp and in the Dr. Z Route 66 amp (that was designed around this particular tube if you check with them). I also use this in a JTM-45 and a GT Solo 45.

 

Myles[/qb]why are the KT-66HP's your favorate in the hellhound? i'm looking for good rock / blues / rockin blues tone (FYI).[/qb]Its just personal preference.

 

Myles[/QB]

[johnny5]

Originally posted by myles111:

Originally posted by Christopher Kemp:

Hey Myles -

 

Sorry you couldn't make it - good food, good chattin'! Maybe next time.

 

Thanks for the tip on the amps - the THD looks interesting - I'll have to start saving my pennies.

 

Another warranty-voiding, don't-try-this-at-home-kids sort of question - currently, I have a Peavey Classic 30 (pretty nice for a REALLY cheap amp!). I've been wondering about the Mid Boost circuit - I've always thought that it should have been foot-switchable, rather than a pushbutton. I asked somebody at Peavey about this once, but they claimed it wasn't possible.

 

Personally, i thought he was BSing me in order to protect Peavey - any idea? Seems that, in theory, one switch should be replaceable with another, given appropriate rating, # of poles & type of switch - am I missing something here? Obviously, it would have to be wired to accept a jack, or hard-wired to a switch, but is there really any reason something like this should be "impossible"?

Christopher ...

 

christopher,

check out blueguitar.org. steve Ahola has got several cool mods on the Classic 30 (52 pages of discrptions to be exact), including a foot switchable boost circuit. lots of very tone improving tips. many of which are quite easy to do. i did alot of them on my C30. the amp is SOO much better now.

 

good luck,

john

 

Be sure to catch us next time ... it was a blast.

 

The THD is pretty amazing. If you are in my area, you are more than welcome to try mine.

 

The Peavey Classic 30 ... a really fun amp. I have a lot of clients with these that play gigs with them all the time, and in some fairly large venues. It is possible to add a mod to switch the mid boost, but would be more cost than it may be worth. Its a matter of a switch latch off the circuit. I'd leave the amp stock.

 

At the moment, I have a few folks out testing some new tubes off new tooling in "your" amp. I may post something soon on this new tube that may be stronger than the EL84S (JJ) tube. It would be nice to have three choices for new tubes for an EL84 ... although the current Russian tube is not a viable option in most cases.

 

Regards,

[myles_rose]

Originally posted by gearup:

I was wondering if a Fender Blues Jr. will run a 4x12 cabinet. If so how will this affect the tone and overall volume vs. the single 12 that is in the BJ? If it will work well I will build my own cab. Does anyone know where I can get specs to build a cab?

The Blues Jr. works nicely with a 4x12 cab, just make sure it is an 8 ohm cabinet. It will sound louder, but the sound image will be more constricted as it will probably be a closed back cabinet.

 

If you ever want to hear something that will make your eyes pop out, hook your amp up to a THD 2x12 cabinet. They are stronger and fuller than any 4x12 around.

 

Myles

[myles_rose]

Originally posted by johnny5:

myles, sorry to have so many questions but you have so much knowledge. my plate voltage / B+ voltage in the hellhound is about 480V. i tried the KT66 (not sure of the brand, they were my tech's) and they did not physically fit. i believe they might have a smaller bottle one. can i achieve a tighter, maybe slightly more throaty tone with a power tube change? if so, which direction should i look. i did have a bias pot installed so i have more room to work now.

 

i have Reverend Hellhound combo (2 6L6's, 60W, 1X12) that has Electro Harmonics 6L6's in it. i have read that these tubes are not very good. and in listening i notice that when these suckers are pushed, they get less and less sweet. almost flabby. i was looking the groove tubes site at the CB's looks like i can get a little more power tube distortion out of those.

 

any thoughts or recomendations?

johnny5 ...

 

The CB's are Chinese with a softer vacuum, but do have more mids than the EH's .... most 6L6 tube actually do.

 

In your amp my favorite tube is the KT-66HP, that is also now one of the least expensive in the GT line as we dropped price from $85 a duet to $60.00 a duet ( $5.00 cheaper than the Chinese KT-66 we also carry with the price drop now ).

 

I like these with a #5 rating in your amp and in the Dr. Z Route 66 amp (that was designed around this particular tube if you check with them). I also use this in a JTM-45 and a GT Solo 45.

 

Myles

why are the KT-66HP's your favorate in the hellhound? i'm looking for good rock / blues / rockin blues tone (FYI).[/qb]Its just personal preference.

 

Myles[/QB][/QB]

 

That is one KT-66 issue ... their height. A problem in a lot of amps. There is a Sovtek version, that is not as nice, but still fun, that is shorter with a metal base. These are what I use at times when folks want KT-66's. A lot of folks these days are now switching to the GE's.

 

The EH's are perhaps my least favorite 6L6, but that is personal preference and bias from my testing.

 

The KT-66 is mostly personal preference in a lot of amps for me, but I also switch between those, GE's and 6L6S's.

 

Myles

[Jotown]

Myles.

 

I have a post called "Nashville Nails". So far no luck.

 

You are supposed to know everything so check it out and solve my problem.

 

Thanks in advance.

 

Jotown:)

[myles_rose]

Originally posted by Jotown:

Myles.

 

I have a post called "Nashville Nails". So far no luck.

 

You are supposed to know everything so check it out and solve my problem.

 

Thanks in advance.

 

Jotown:)

I don't know what you are talking about, and I do not know everything.

 

Myles

[Jotown]

I was trying to be funny with the "you are supposed to know everything remark", I guess I failed there.

 

About the Nashville Nails, did you read my post?

I know someone out there knows about it.

 

Sorry, did not mean to offend.

 

Jotown:)

[myles_rose]

Originally posted by Jotown:

I was trying to be funny with the "you are supposed to know everything remark", I guess I failed there.

 

About the Nashville Nails, did you read my post?

I know someone out there knows about it.

 

Sorry, did not mean to offend.

 

Jotown:)

Jotown ....

 

No offense was taken.

 

I try to have folks post here, as it forms something of an FAQ section for the benefit of others. I also check this post on a regular basis as I get email alerts.

 

So .... if you can just repost (just cut and paste) from wherever it is, I will try to answer what ever it is ....

 

Myles

[Jotown]

Here you go Myles:

 

Post 1

 

I was reading a article in Guitar Player about a year ago and there was an interview with a hot country guitar player whose name escapes me.

 

He refered to the term "Nashville nails". Because he plays with a pick and the nails on his other three fingers. He would get his nails done so that they woudl act like picks, and not break.

 

The reason I am interested is that last year I got my first new acoustic guitar in 20 years and I have been adding a lot of finger picking things into my show. Songst that I use to do years ago.

 

My problem is that I am always breaking nails which really sucks. I have used Nutri-nails and a couple of othet clear products, but my nails are stil cracking.

 

Anybody out there know what I am talking about?

 

Thanks in advance.

Post 2

 

The Nashville Nails article was refering to a kind of nail polish that is extremely durable.

 

The truth is I usually break a nail moving my gear into a gig, not playing.

 

Hard is not good because hard cracks.

Durable is the key.

 

The search continues.

Thanks for your response Myles,any info would be helpful.

[myles_rose]

Originally posted by Jotown:

Here you go Myles:

 

Post 1

 

I was reading a article in Guitar Player about a year ago and there was an interview with a hot country guitar player whose name escapes me.

 

He refered to the term "Nashville nails". Because he plays with a pick and the nails on his other three fingers. He would get his nails done so that they woudl act like picks, and not break.

 

The reason I am interested is that last year I got my first new acoustic guitar in 20 years and I have been adding a lot of finger picking things into my show. Songst that I use to do years ago.

 

My problem is that I am always breaking nails which really sucks. I have used Nutri-nails and a couple of othet clear products, but my nails are stil cracking.

 

Anybody out there know what I am talking about?

 

Thanks in advance.

Post 2

 

The Nashville Nails article was refering to a kind of nail polish that is extremely durable.

 

The truth is I usually break a nail moving my gear into a gig, not playing.

 

Hard is not good because hard cracks.

Durable is the key.

 

The search continues.

Thanks for your response Myles,any info would be helpful.

Jotown ...

 

Sorry ... I cannot help you here ... I am more of a technical type. Maybe somebody else around here will be able to answer this.

 

My wife is always getting on my case for not even knowing many of the folks I work with, as far as what band they are in, etc. I generally know folks as "steve ... plays a 5150 .... rocker ... high gain type ... 6L6GE's @ 34mA .... 470 B+ ... 12AX7R3 in V2 at 108/100 .... etc..

 

Myles

[johnny5]

myles,

i promise this is the last. i asked groove tubes but they would not give me a straight answer. i would like to know the idle (approx.) bias current for KT66-HP and 6L6S, given i'm running a plate voltage of 480V and both tubes are #5 GT rated.

 

would appriciate the help,

thanks

[myles_rose]

Originally posted by johnny5:

myles,

i promise this is the last. i asked groove tubes but they would not give me a straight answer. i would like to know the idle (approx.) bias current for KT66-HP and 6L6S, given i'm running a plate voltage of 480V and both tubes are #5 GT rated.

 

would appriciate the help,

thanks

johnny5 ....

 

If you asked Groove Tubes and did not get a straight answer, who did you talk to? I happen to be "Groove Tubes" and I don't remember talking to you.

 

In any case.... on each of these tubes, the milliamp draw at idle will be the same, although the bias voltage will be different to get the same ID on the tubes.

 

It also depends a bit on the amp ....

 

but ....

 

For the KT-66HP:

 

50% 60% 70% Idle dissapation

 

26 31 36 milliamps

 

I like these at 32-34mA at your plate voltages.

 

What amp? and did you measure B+ with ALL the tubes in place? If you pulled one tube to read pin 3 to ground, the loss of one tube in the circuit will cause a false high B+ reading.

 

For the 6L6S:

 

50% 60% 70%

 

31 38 44

 

I like these at 34-36mA personally, at this sort of plate voltage in most amps.

 

Next time you need to talk to GT, either ask for me directly, or email me from the GT website (techsupport@groovetubes.com)

 

Myles

[Jotown]

Hey Myles,

Thanks for the response.

[myles_rose]

Originally posted by Jotown:

Hey Myles,

Thanks for the response.

You're welcome ... any time.

[ManInTheBox]

Myles, I have a loud anoying hum in channel one only. What could cause this problem, and how do I rtemedy it? I have a Crate Blues Voodoo 6212 combo. Thanks for your help.