Feel free to ask Myles

[myles_rose]

Originally posted by phaetown:

I'm feeling kinda free right now, so i figured i should ask myles....

 

Myles,

I have a small practice amp: A 1975 Peavey Pacer SS-100

 

I know it's solid state, and it's nowhere near the caliber of units you normally service, but the principles will still apply.

 

It's got some pots on the front (primarily the pre-volume and master-volume) that seem to have some `angry spots' in them.

 

I.e. if you gradually turn up the "master" volume, the sound will get gradually louder (as it should), until you get to a few positions where it will drop off to a whisper, and a few others where it will be as if you've got it cranked. Yet other volume positions it will just sit and make this really strange squeaky hum. (not sure how else to describe the noise).

 

I know dirt in the pots can cause the dropouts in volume (gets between the contacts and increases the electrical resistance) but in the case where a few volume positions are much louder than what they should be (an internal short in the pot?) could this also be caused by dirt and/or some form of conductive contamination? Maybe rust? (the amp sat in storage for about 2.5 years)

 

I've had the amp apart once before (fixed a broken wire in the reverb circuit) and it looks like all the pots are soldered directly to a (suprisingly small) circuit boad. Desoldering/Resoldering new pots in may be a bit beyond my abilities, and my guess is the amp is probably not worth taking to someone. A Classic Series yes, a Pacer, no.

 

Should i try to `clean' the pots with some of that aerosol spray stuff, or will this be difficult/pointless? Are they already shot?

 

Even though it's all i have at the moment, you won't hurt my feelings if you have to tell me it's beyond reasonable repair and it should be thrown away.

 

I greatly appreciate your time, Myles.

phaetown ....

 

As far as your amp not being near the "caliber" of some of the amps I work on and design, I have to let you know that it is amps such as yours that end up in more touring bands hotel rooms for practice and writing than one can imagine.

 

Solid state amps are "not good"? That is what many think, but the JC-120, Polytone (the backbone of a lot of top jazz players), the Standel and Jordan amps of the mid 60's (the backbone on so many live performances), and at Woodstock (the 1969 one), we had walls of Acoustic 260 and 360 Solid State amps.

 

Your pots are dirty. You need to just spray some tuner cleaner and lube in there, and work the pots a few times. Don't use simple cleaner, as this will freeze up. You need a good cleaner and lubricant. This stuff is available from many sources. I geneally send my own personal clients to AES (antique electric supply). Their website is www.tubesandmore.com.

 

Pots are pretty easy to change, but I would first do the above, as I am pretty darn sure this will fix your problems.

 

Don't ever throw away an amp ... they all have their own sound and personality. I play one of my kid's Fender Squier Bullet SS amps all the time. It's a blast.

[myles_rose]

Originally posted by Dave th Dude:

Hey Myles,

 

In your reply to rsf1977 ....

 

"I use either a "Y" cord, and A/B/Y box or a mono in / stereo out pedal. I don't like to compromise the effects loops and have one amp's preamp coloration impact the other amp's, and this is what happens if you use the effects loop of one amp to drive the other."

 

First, why a 'Y' cord with the A/B/Y Box? I thought I would only need an A/B/Y Box to play through my JC55 and Randall Tube Pro.

 

Second, I was thinking specifically of purposely driving the preamp of the Randall with the guitar, coming out of the effects loop and then split (w/ A/B/Y Box) to both the JC55 (has EFX loop) solid state power output section and the Randall (has EFX loop) tube power output section to get a tube overdriven sound out of the JC55 (solid state). Should I reconsider? Will any damage occur?

 

Dave

Dave....

 

Sometimes the reason for the Y cord is just another feed if I want to go to some amps (on the A/B box, but also want a feed to a board.

 

Your proposed setup will work nicely, and there will be no concern for damage.

 

Hope that helped.

[myles_rose]

Originally posted by Compact Diss:

Please read my post "should we ban loveformusic" it's a poll and the majority has voted.

I am just ignoring that person. Hopefully others will do the same rather than responding to anything they say, and refrain from giving them any attention.

 

I do not care if they are banned or not .... if it is not guitar or amp related, they can take their views elsewhere.

[myles_rose]

Originally posted by Da LadY In The Pink Dress:

By the way i have a dan electro mini amp(don't know what model but its plastic and it about the size of my hand yea it's a small bugger) and it sorta doesn't work liek when it's at certain angles it doesn't amplify the sound but sometimes it does. Do you think it's my cable thigny to my guitar? Thx myles.

Try a new cable.

[phaeton]

phaeton ....

 

As far as your amp not being near the "caliber" of some of the amps I work on and design, I have to let you know that it is amps such as yours that end up in more touring bands hotel rooms for practice and writing than one can imagine.

 

Solid state amps are "not good"? That is what many think, but the JC-120, Polytone (the backbone of a lot of top jazz players), the Standel and Jordan amps of the mid 60's (the backbone on so many live performances), and at Woodstock (the 1969 one), we had walls of Acoustic 260 and 360 Solid State amps.

 

Your pots are dirty. You need to just spray some tuner cleaner and lube in there, and work the pots a few times. Don't use simple cleaner, as this will freeze up. You need a good cleaner and lubricant. This stuff is available from many sources. I geneally send my own personal clients to AES (antique electric supply). Their website is www.tubesandmore.com.

 

Pots are pretty easy to change, but I would first do the above, as I am pretty darn sure this will fix your problems.

 

Don't ever throw away an amp ... they all have their own sound and personality. I play one of my kid's Fender Squier Bullet SS amps all the time. It's a blast.

 

 

Thanks Myles, you rule

 

And i don't think that *all* solid state amps are bad, just some are less good than others.

 

And it's a good thing you pointed out the clean+lube part, because i was about to just go out and buy the standard off-the-shelf spray and (probably) ruin ALL my pots.

 

Although tubesandmore.com seems to be no longer there... in any event, i can do some intelligent hunting for the right product.

 

Thanks again.

 

And fwiw, i totally side with you on the "should we ban posterX" issue.

[michael c]

Myles, have you ever heard the Little Lanilei Super 7? Curious what your thoughts are for finding the ultimate little practice amp with TONE.

[myles_rose]

Originally posted by phaeton:

phaeton ....

 

As far as your amp not being near the "caliber" of some of the amps I work on and design, I have to let you know that it is amps such as yours that end up in more touring bands hotel rooms for practice and writing than one can imagine.

 

Solid state amps are "not good"? That is what many think, but the JC-120, Polytone (the backbone of a lot of top jazz players), the Standel and Jordan amps of the mid 60's (the backbone on so many live performances), and at Woodstock (the 1969 one), we had walls of Acoustic 260 and 360 Solid State amps.

 

Your pots are dirty. You need to just spray some tuner cleaner and lube in there, and work the pots a few times. Don't use simple cleaner, as this will freeze up. You need a good cleaner and lubricant. This stuff is available from many sources. I geneally send my own personal clients to AES (antique electric supply). Their website is www.tubesandmore.com.

 

Pots are pretty easy to change, but I would first do the above, as I am pretty darn sure this will fix your problems.

 

Don't ever throw away an amp ... they all have their own sound and personality. I play one of my kid's Fender Squier Bullet SS amps all the time. It's a blast.

 

 

Thanks Myles, you rule

 

And i don't think that *all* solid state amps are bad, just some are less good than others.

 

And it's a good thing you pointed out the clean+lube part, because i was about to just go out and buy the standard off-the-shelf spray and (probably) ruin ALL my pots.

 

Although tubesandmore.com seems to be no longer there... in any event, i can do some intelligent hunting for the right product.

 

Thanks again.

 

And fwiw, i totally side with you on the "should we ban posterX" issue.

phaeton ....

 

The link for AES is at:

http://www.tubesandmore.com/

 

Another good place is Torres:

http://www.torresengineering.com/

 

Radio Shack also has good stuff of this sort.

[myles_rose]

Originally posted by michael c:

Myles, have you ever heard the Little Lanilei Super 7? Curious what your thoughts are for finding the ultimate little practice amp with TONE.

michael c ....

 

These amps were originally made for student of lap steel and Hawaiian guitar. They are GREAT. They were cool in the cabinets in some of them, made from a plastic sort of "mother of toilet seat" material, that was resonant and did not warp. They were pretty nicely made, especially for a practice amp. They are easy to work on, reliable, and with their lower voltages, tubes in them last for decades. If the amp has the original preamp tubes, they will probably test as new.

 

In any case, with your name ... just a question ... do you sell eye glasses? There is a Michael C optical store in the Valley, and that is where one of my kids get his glasses, and where I have gotten a set. With all the adjustments you may or may not have done for my son, if this is you, I owe you some free amp work!

[michael c]

Thanks for the info Myles. In the market for a great sounding practice amp and this seems like the ticket. Would you opt for the 7 watt or 33 watt? I'm more than likely only going to use it as a practice amp, but if the sound is great, should I opt for the bigger model just in case down the line I want to use it for a very quiet gig? BTW I'm a different Michael C!

[myles_rose]

Originally posted by michael c:

Thanks for the info Myles. In the market for a great sounding practice amp and this seems like the ticket. Would you opt for the 7 watt or 33 watt? I'm more than likely only going to use it as a practice amp, but if the sound is great, should I opt for the bigger model just in case down the line I want to use it for a very quiet gig? BTW I'm a different Michael C!

michael c ....

 

Personally, I'd go for the 7 watt. Small, light, easy to carry, breaks up great at rational volumes. Remember, on "Layla", Clapton and Allman used a 5 watt champ and a 10 watt tweed deluxe.

 

Since you are in Los Angeles, if you ever want to hear a 6 watt 6V6 amp compared to a Marshall JTM-45 as an example, I'd be more than happy to let you compare these, or a number of other amps of high and low power, all the way up to 400+ watt tube amp rigs.

[soulman]

Miles,

I've got a Fender Hot Rod DeVille that is acting weird. The amp has a static crackle only when playing certain chords or notes. specifically an A chord. Sounds strange huh? I don't really see any loose wires and the tubes seem pretty good to me although I am not an expert. The power tubes are relatively new. My guitar is fairly new too and I don't think that's the problem. Sounds kind of like a short or something but strange it only does it when I play in certain postions on the fretboard, Any suggestions? Thanks!

[myles_rose]

Originally posted by soulman:

Miles,

I've got a Fender Hot Rod DeVille that is acting weird. The amp has a static crackle only when playing certain chords or notes. specifically an A chord. Sounds strange huh? I don't really see any loose wires and the tubes seem pretty good to me although I am not an expert. The power tubes are relatively new. My guitar is fairly new too and I don't think that's the problem. Sounds kind of like a short or something but strange it only does it when I play in certain postions on the fretboard, Any suggestions? Thanks!

soulman ....

 

Right off the bat, swap V1, the first preamp tube, with any of the others.

 

Tell me what happened.

 

There is no adjustment needed.

 

If that does not help, try V2.

 

Call me at GT if you need help .... 1-800-459-5687.

 

You have a good amp that is generally pretty darn trouble free. This is probably something very simple and easy to remedy.

[soulman]

Miles,

 

It appears that the problem was/is in the power tube section. Although the tubes are seated well there seems to be some shorting sound when they are moved just a little. Not sure what to do about that. Right now it is OK but I definitely don't want to keep fiddling with the power tubes while playing. While I've got your attention. Do you think that 7025's in V1 and V2 and a 12AX7 in V3 are good choices for this amp. Would I be better served by a 12AT7 in V3? Thanks for all your help. It's nice to know that there are people out there that are genuinely interested in helping others with their expertise pro bono.

[myles_rose]

Originally posted by soulman:

Miles,

 

It appears that the problem was/is in the power tube section. Although the tubes are seated well there seems to be some shorting sound when they are moved just a little. Not sure what to do about that. Right now it is OK but I definitely don't want to keep fiddling with the power tubes while playing. While I've got your attention. Do you think that 7025's in V1 and V2 and a 12AX7 in V3 are good choices for this amp. Would I be better served by a 12AT7 in V3? Thanks for all your help. It's nice to know that there are people out there that are genuinely interested in helping others with their expertise pro bono.

soulman ....

 

I don't remember which amp you had, but it may just be a need to retension the output tube sockets. This is pretty easy, you just have to drain the caps first to be safe.

 

In a lot of combo amps, power tubes can also be more microphonic than in heads.

 

On the 7025 ... they are a very bright tube. Generally too bright for a Marshall type of amp if a strat or tele is used. They are more of the brigher fender blackface era sound.

[soulman]

Miles,

 

The amp I have is the Fender DeVille 410. As I stated, I have 7025's in V1 and V2 and a 12AX7 in V3. Should I put a 12AT7 in V3? I kind of like the brightness of it but would also like to sweeten up the distortion channel on this amp as it is a little harsh sounding for my taste. How would a 12AX7C do in this amp in V1? And if I do change it should I change V2? I'm not really sure what you meant about "draining the caps" and that may go beyond my neophytic knowledge of amps. Thanks for your help.

 

Mike

[phaeton]

phaeton ....

 

The link for AES is at:

http://www.tubesandmore.com/

 

Another good place is Torres:

http://www.torresengineering.com/

 

Radio Shack also has good stuff of this sort.

Ahh.. thanks... the AES site must have been temporarily down, but it's back up now.

 

I take it i will find the cleaner and lubricant in the same can, such as the Jif-Action (S-C19-636) at AES. It appears to be cleaner with silicon lubricant.

 

While i'm at it i could probably hit the 5-way selector switch on my Strat and get those "out-of-phase" positions to work again too.

[myles_rose]

Originally posted by soulman:

Miles,

 

The amp I have is the Fender DeVille 410. As I stated, I have 7025's in V1 and V2 and a 12AX7 in V3. Should I put a 12AT7 in V3? I kind of like the brightness of it but would also like to sweeten up the distortion channel on this amp as it is a little harsh sounding for my taste. How would a 12AX7C do in this amp in V1? And if I do change it should I change V2? I'm not really sure what you meant about "draining the caps" and that may go beyond my neophytic knowledge of amps. Thanks for your help.

 

Mike

Mike,

 

In your amp, V1 is 85% of the gain and tone of the front end.

 

A 12AT7 in V3 will give a bit more clean headroom. This is the phase inverter in this amp. The need to change V2 is not a bit one, as these amps actually have a lot of solid state devices in the signal path ... that is how they get their overdrive, and the reverb is also driven by transistors rather than a tube circuit as the earlier fender amps and their pro tube series amps.

 

You do not need to worry about caps being discharged (drained), if it is just preamp tubes you are going to change.

 

Hope this helped.

[myles_rose]

Originally posted by phaeton:

phaeton ....

 

The link for AES is at:

http://www.tubesandmore.com/

 

Another good place is Torres:

http://www.torresengineering.com/

 

Radio Shack also has good stuff of this sort.

Ahh.. thanks... the AES site must have been temporarily down, but it's back up now.

 

I take it i will find the cleaner and lubricant in the same can, such as the Jif-Action (S-C19-636) at AES. It appears to be cleaner with silicon lubricant.

 

While i'm at it i could probably hit the 5-way selector switch on my Strat and get those "out-of-phase" positions to work again too.

phaeton ....

 

The AES folks have a lot of cool stuff.

[johnny5]

curious about the charector of EL84's as compared to KT66's. i know you have been asked this kind of question before and i know i have read it but something is not clear.

one of my amps has EL84's and the other KT66's and i find that when the EL84 amp gets into power amp distortion it kind of stays there (more compressed i guess, more saturated) and with the KT66 it tends to go in and out of distortion much quicker and easier (much less saturated and more of a loose bottom, deeper but looser).

 

anyhow, is what i am hearing a funtion of the power tubes? entire circuitry? partial to both? would a 6L6S behave a little more compessed/saturated and possibly have a tighter bottom as compared to the KT66?

 

i am realizing it takes a long time to get a grasp of all the nueances in amp technology.

 

thanks,

john

[myles_rose]

Originally posted by johnny5:

curious about the charector of EL84's as compared to KT66's. i know you have been asked this kind of question before and i know i have read it but something is not clear.

one of my amps has EL84's and the other KT66's and i find that when the EL84 amp gets into power amp distortion it kind of stays there (more compressed i guess, more saturated) and with the KT66 it tends to go in and out of distortion much quicker and easier (much less saturated and more of a loose bottom, deeper but looser).

 

anyhow, is what i am hearing a funtion of the power tubes? entire circuitry? partial to both? would a 6L6S behave a little more compessed/saturated and possibly have a tighter bottom as compared to the KT66?

 

i am realizing it takes a long time to get a grasp of all the nueances in amp technology.

 

thanks,

john

johnny5 ......

 

These tubes are about as different as two tubes could be. Low vacuum vs. high vacuum .... large plates vs. light plates .... pentode vs. beam pentode.

 

It is almost like comparing a sailboat to a Cessna 172.

 

I'd need 5,000 words to try to give my take on this here

 

The 6L6S is more typical of a 6L6, where the KT-66 is a "kinlkess tetrode" that is more linear than the standard 6L6.

[srvfan51]

Dear Myles,

I was recommended to ask you this question:

Is there a better preamp tube that could brighten up the sound of the crunch channel of my brand new Marshall TSL 60 head?

As it is now, the crunch channel sounds very dark (no treble or presence) especially at low gain. As I increase the gain, the mids seem pushed to distortion first but not very smoothly and with no clarity.

The clean channel is great and the lead channel is OK.

All tubes currently in there are labeled as "Marshall".

Many thanks for your advice.

Tony

PS. I previously posted this message as a new topic by mistake; it was meant for this thread.

[johnny5]

Originally posted by myles111:

Originally posted by johnny5:

curious about the charector of EL84's as compared to KT66's. i know you have been asked this kind of question before and i know i have read it but something is not clear.

one of my amps has EL84's and the other KT66's and i find that when the EL84 amp gets into power amp distortion it kind of stays there (more compressed i guess, more saturated) and with the KT66 it tends to go in and out of distortion much quicker and easier (much less saturated and more of a loose bottom, deeper but looser).

 

anyhow, is what i am hearing a funtion of the power tubes? entire circuitry? partial to both? would a 6L6S behave a little more compessed/saturated and possibly have a tighter bottom as compared to the KT66?

 

i am realizing it takes a long time to get a grasp of all the nueances in amp technology.

 

thanks,

john

johnny5 ......

 

These tubes are about as different as two tubes could be. Low vacuum vs. high vacuum .... large plates vs. light plates .... pentode vs. beam pentode.

 

It is almost like comparing a sailboat to a Cessna 172.

 

I'd need 5,000 words to try to give my take on this here

 

The 6L6S is more typical of a 6L6, where the KT-66 is a "kinlkess tetrode" that is more linear than the standard 6L6.

thanks anyway. i was just curius. maybe i'll go buy some good book on the subject matter that is not too over the top.

 

john

[myles_rose]

Originally posted by srvfan51:

Dear Myles,

I was recommended to ask you this question:

Is there a better preamp tube that could brighten up the sound of the crunch channel of my brand new Marshall TSL 60 head?

As it is now, the crunch channel sounds very dark (no treble or presence) especially at low gain. As I increase the gain, the mids seem pushed to distortion first but not very smoothly and with no clarity.

The clean channel is great and the lead channel is OK.

All tubes currently in there are labeled as "Marshall".

Many thanks for your advice.

Tony

PS. I previously posted this message as a new topic by mistake; it was meant for this thread.

Tony,

 

The stock Marshall tubes are usually Ei's in the front end these days. They can also be Sovteks, I would need to see the tube to tell for sure.

 

If the preamp tube in V1 is an ECC83, this is a reason for the darker character. A 12AX7R3 (Electro Harmonix) would brighten things up a bit, or a 12AX7C (Chinese 12AX7) would give a more linear response.

 

Your output tubes are also critical in the amp for sound. If they are the current Sovteks, this can be improved with most any other EL-34. The Sovteks are nice and sturdy (as were Russian airplanes in WWII and today), but sonically, there are a bit "unsophisticated". Most of my personal clients use the E34L or E34Ls. These are made in the JJ factory, the Ls version being off GT tooling, and a 30 watt tube, rather than a 25 watt EL-34 as the JJ E34L or other EL-34 tubes. This is the tube used by folks like Slash, Joe Walsh, Billy Gibbons, Joe Perry, and Matchless in their EL-34 based amps. They have stronger mids and are stronger all around, than other EL-34's, but may be too aggressive for some players that are used to the 25 watt EL-34's.

 

For the E34Ls, a bias adjustment is a MUST, and turn the bias all the way up BEFORE inserting the tubes, as you want the highest negitive voltage before attempting to set the bias. These fellows draw a lot of current, and are 20% stronger than other EL-34's.

 

Now .... even though I work for GT as well as myself, I would be amiss if I did not mention the Ruby Tubes EL-34BSTR. This is a new tube off new China tooling. It is a 25 watt tube, with all the curves and flair of an old Siemens. If you want the original Marshall sound, this is the killer tube today for the 25 watters. It is more consistant than any of the current Russian offerings, including the Svetlana or new EH. It holds up to high plate and screen voltages, and is really a terrific tube. They are also not very expensive as a side benefit. They are not the same as other Chinese EL-34's as these were done with backing from Magic Parts (Ruby Tubes) to develop the tooling for this new tube.

 

I did a battery of tests on these a bit ago, and they are posted on my own website in the EL34 / EL84 area.

 

By the way, this tube is about 15% stronger than the current Russian EL-34's, as Chinese quality went up a bit, and Russian quality has either not improved over the last six months on power tubes, or declined a touch. I guess the Russians are spending money on aircraft engines, as the metal in the new master wrist pin for the engine on the plane I fly is a work of art. Maybe they will do that with tubes.

 

By the way, the latest Russian Electro Harmonix 12AX7EH is a jewel, so I am mainly talking power tubes here.

 

Hope this helped.

[Space_Ace113]

I just bought a 1986 laney pro tube lead ant the thing rips, however i am still looking for some new tubes for it any reccomendations it uses 4 12ax7's and 4 el34's.

Kevin

PS anyone know where to get a Gibson Les Paul Custom in trade for a 91 les paul studio with di marzio super distortions and some cash.

[halcyon]

hi myles. i bought a musicman 75 head about a month ago and it needs new tubes. it has a pure solid state preamp and 2 6L6's in the power amp. i heard this amp has a plate voltage of 750 volts. I talked to the guy at KCA NOS Tubes and he said he didnt think he had anything that would be reliable in my amp. are there any tubes that will work for my musicman? thanks.

[myles_rose]

Originally posted by Space_Ace113:

I just bought a 1986 laney pro tube lead ant the thing rips, however i am still looking for some new tubes for it any reccomendations it uses 4 12ax7's and 4 el34's.

Kevin

PS anyone know where to get a Gibson Les Paul Custom in trade for a 91 les paul studio with di marzio super distortions and some cash.

Space_Ace113 ....

 

In your amp I like the EL-34C as they are now the most linear of the 25 watt EL-34's and the most "brit sounding" tube.

 

In the front end, I prefer the ECC83's if you are going for the brit sound, but 12AX7C9's if you want a warmer, more linear, and more versitile amp.

 

If you want to go all out, then the E34Ls's are the way to go in a #6 rating.

 

Bottom line here though, it is all personal taste.

 

The 12AX7C9's are available from Ruby Tubes and Groove Tubes, they are the only folks with 12AX7's off that version of tooling.

 

The ECC83's are available from a lot of folks, Bob Pletka at Eurotubes always has these at great prices, as does Doug Preston. Doug can only be reached via email at: djp@optonline.net Doug is who I use for my east coast clients. He also uses a VTV tester to grade preamp tubes.

 

The EL34BSTR (Chinese latest EL-34C) is available from Ruby Tubes, and I have a review on this particular tube in the EL-84 / EL-34 area of my personal website.

 

The E34Ls is a GT tube of their tooling and is not the same as the JJ E34L, so this is a single source tube also.

 

I have a lot of 12AX7 / 7025 / ECC83 reviews at the bottom of the area on my website in the 12AX7 section. This mostly shows that you should know your vendor pretty well to avoid inconsistancy problems.

 

Hope this helped.

[myles_rose]

Originally posted by halcyon:

hi myles. i bought a musicman 75 head about a month ago and it needs new tubes. it has a pure solid state preamp and 2 6L6's in the power amp. i heard this amp has a plate voltage of 750 volts. I talked to the guy at KCA NOS Tubes and he said he didnt think he had anything that would be reliable in my amp. are there any tubes that will work for my musicman? thanks.

halcyon ....

 

Great amps ... tough spot.

 

These do have very high plate voltages, and not too many tubes can handle that anymore as far as those made today.

 

You can go the 6550 route, and try to stick with GE NOS ones ... pricy.

 

There are the KT-88's, and the new ones will work, but I'd stay with the SV's:

 

http://www.groovetubes.com/product.cfm?Product_ID=1701

 

Either of these will work, but not sound like the amp did originally.

 

For the original sound, you really need 6CA7s. 6CA7's are an EL-34 sort of tube, but with a larger bottle generally, much higher vacuum (they were generally USA made), and with an active beam forming element, that the EL-34's do not have.

 

DO NOT try any new "6CA7's" such as those sold by Ei or anybody else. They are not even as nice as current EL-34's from just about anybody, and will blow at at least a few hundred volts below what you amp can do.

 

Check with Mike at KCA ( http://www.kcanostubes.com ) and hope he can find you some real 6CA7's.

 

Check with Charlie Kittleson at Vacuum Tube Valley - http://www.vacuumtube.com and maybe he can help.

 

Check with George Low at Vintage Electron ( http://www.vacuumtube.com )

 

Or last case, wait at least six months until we have the GE 6CA7 production line up and running as we will be making the GE's again, as we did with the 6L6GE.

 

Hope this was of some help.

[Blue Note]

Myles,

 

I read the post about the Music Man 75 and has got me a little concerned I have a Music Man HD-150 head that I love and don't want to damage it. Is there danger in harming a amp if the tubes blow. Also it has a low,stanby, high selection switch which seems to make no difference to the sound or the volume, will it be best to always play this amp in the low position.

 

Thank You.

[myles_rose]

Originally posted by Blue Note:

Myles,

 

I read the post about the Music Man 75 and has got me a little concerned I have a Music Man HD-150 head that I love and don't want to damage it. Is there danger in harming a amp if the tubes blow. Also it has a low,stanby, high selection switch which seems to make no difference to the sound or the volume, will it be best to always play this amp in the low position.

 

Thank You.

Blue Note ...

 

If the amp has the proper fuse ratings, most of the time you will be lucky. A lot of amps did not have HT or B+ fuses, so if a tube shorted, the AC line fuse would hopefully shut down the amp in time (if the proper rating) on a tube short. (This is one reason that it pays to get output tubes that have been tested for gas leakage and low vacuum).

 

If the tube just burns out, the end result is not as critical, but an internal short can have other more extensive results. Most of the time the amp will just stop playing properly, or altogether. If it is a short, it can be a different story.

 

On the high plate voltage amps, the best bet is to try to find NOS GE or other real 6CA7's or very good EL-34's from a known vendor that will really test these for low vacuum, gas leakage, and grid leakage. There are very few vendors that do this as it takes very expensive equipment and is time consuming. Most vendors have a warranty, and they rely on that ... when a tube fails (because it was generally not tested for anything more than simple current draw at best), they are more than happy to replace it. That is cheaper than testing the tubes properly. The harder part is fighting with them when the bad tube takes out your output transformer.

 

Music Man amps are great, and most have replaced output transformers actually. The originals went out pretty darn fast, and when they were replaced with after market ones, they stayed alive and well after that replacement.

 

You can also rebias and use a KT-88SV, but the amp will not sound the same. Some folks like the sound even more, so it is all personal taste. You need to have the bias checked and adjusted if you do this.

 

Hope that was of some help.

[Nollykin]

Hey myles. I have a bit of a problem with a Marshall AVT 150 - could you please check out my post - " Problems with d/o. "? Twould be appreciated.

 

Nolly