Feel free to ask Myles

[RG203]

Myles,

 

My amp (Ampeg VL-503) has a bad hum. The hum only goes away when the pot that controls the slope for the power amp is turned all the way left. I decided to replace the pot to see if that would fix the hum.

 

I managed to get the PCB board out without getting shocked and removed the pot. The problem is knowing what to replace it with. Ive called Ampeg and they are looking for a part number. However, they dont support this amp anymore and didnt give the impression they would be able to provide much help.

 

The following information is stamped onto the back of the pot:

 

70-105-22 9312 ROC

 

Im guessing the ROC means it was made it China. What do the other numbers mean? Any suggestions on what pot I can use if Ampeg fails to provide any help?

 

Thanks.

[myles_rose]

Originally posted by RG203:

Myles,

 

My amp (Ampeg VL-503) has a bad hum. The hum only goes away when the pot that controls the slope for the power amp is turned all the way left. I decided to replace the pot to see if that would fix the hum.

 

I managed to get the PCB board out without getting shocked and removed the pot. The problem is knowing what to replace it with. Ive called Ampeg and they are looking for a part number. However, they dont support this amp anymore and didnt give the impression they would be able to provide much help.

 

The following information is stamped onto the back of the pot:

 

70-105-22 9312 ROC

 

Im guessing the ROC means it was made it China. What do the other numbers mean? Any suggestions on what pot I can use if Ampeg fails to provide any help?

 

Thanks.

The other numbers may be date codes.

 

Meter out the pot if you do not know if it is a 1 meg vs 250k or whatever.

[cheesey]

Originally posted by myles111:

Originally posted by cheesey:

Hi Myles , I want to get a smokin set of tubes for my 1974x amp. 2 el84, 3 ecc83 and an ez81.

$200 max.

any favorites nos or current?

thanks

On the rectifier, if the stock one is working just keep it.

 

On the output tubes ... the EL84S in a 5-6 rating are great.

 

But .... for the front end hit Mike at www.kcanostubes.com and go for either Brimars or RFT NOS tubes.

 

A Brimar in V1 and RFT in V2 and V3 are great in these magic amps. If you talk to Mike tell him you want a balanced one for V3 ... he only charges about $2 more for a matched tube and does a great job.

Myles , I received the tubes from Mike

I got all 6 just so i'd have a back up for each

nos tesla el84's

nos brimar, 2 rft's one balanced and an rca 6ca4.

just a question , if I mainly use channel 2 does the brimar in v1 have any bearing on the sound .

i read you can jumper if primary input is ch 2 .

i just want to know that the $85 tube is working and not just sitting .

thanks

i'm just putting them in

[myles_rose]

Originally posted by cheesey:

Originally posted by myles111:

Originally posted by cheesey:

Hi Myles , I want to get a smokin set of tubes for my 1974x amp. 2 el84, 3 ecc83 and an ez81.

$200 max.

any favorites nos or current?

thanks

On the rectifier, if the stock one is working just keep it.

 

On the output tubes ... the EL84S in a 5-6 rating are great.

 

But .... for the front end hit Mike at www.kcanostubes.com and go for either Brimars or RFT NOS tubes.

 

A Brimar in V1 and RFT in V2 and V3 are great in these magic amps. If you talk to Mike tell him you want a balanced one for V3 ... he only charges about $2 more for a matched tube and does a great job.

Myles , I received the tubes from Mike

I got all 6 just so i'd have a back up for each

nos tesla el84's

nos brimar, 2 rft's one balanced and an rca 6ca4.

just a question , if I mainly use channel 2 does the brimar in v1 have any bearing on the sound .

i read you can jumper if primary input is ch 2 .

i just want to know that the $85 tube is working and not just sitting .

thanks

i'm just putting them in

The 18 and 20 watt Marhalls use all tubes for both channel. V1 uses one side of the tube for it's channel.

 

Here is a link to a schematic of the basic 18/20 watt family:

 

http://www.drtube.com/schematics/marshall/2022.gif

[Guitar55]

Hi Myles,

 

A friend lent me a Marshall JCM 900 50 Watt Hi Gain Dual Reverb 1x12 combo.

 

The impedance switch on the back is labeled "8" on one side and 4(16) on the other.

 

The manual says the combo is set for 8 or 4 ohms. So what does the "(16) mean? Can it be set for 16 ohms and,if so, how?

 

Thanks,

Dennis

[Trucks]

Hye Guitar55 as Myles doesnt seem to be about... I always thought it meant 4 ohm speakers in a set that make up 16 ohms alltogether.. Or something like that Im sure when Myles comes round he'll have a much more concise answer for ya (and one that is actually correct lol)

[myles_rose]

Originally posted by Guitar55:

Hi Myles,

 

A friend lent me a Marshall JCM 900 50 Watt Hi Gain Dual Reverb 1x12 combo.

 

The impedance switch on the back is labeled "8" on one side and 4(16) on the other.

 

The manual says the combo is set for 8 or 4 ohms. So what does the "(16) mean? Can it be set for 16 ohms and,if so, how?

 

Thanks,

Dennis

Dennis,

 

 

The strange switch setup on these amps was meant to work with the Marshall cab which has a stereo / mono setup.

 

Leave the amp set as per stock.

[Dr. Ellwood]

Myles, I'm posting this queston for Stratbluesman because he is having some trouble with the Forum format, he is new to the forum..here is his question: "hi there every one, new to this so you will have to bear with me.

i hope someone out there can help me with a problem that has recently started to happen with my fender deluxe 112 plus amp, at a couple of gig's it has started to lose volume and then every now and then it has come back with a bang, and it gets very warm on the top, any help would be much appreciated, i just hope that this is not one of them sites that is full of idiots saying things like, bin, buy a new one, and general crap like that.

thanks anyway all.

best regards"

[myles_rose]

Originally posted by ellwood:

Myles, I'm posting this queston for Stratbluesman because he is having some trouble with the Forum format, he is new to the forum..here is his question: "hi there every one, new to this so you will have to bear with me.

i hope someone out there can help me with a problem that has recently started to happen with my fender deluxe 112 plus amp, at a couple of gig's it has started to lose volume and then every now and then it has come back with a bang, and it gets very warm on the top, any help would be much appreciated, i just hope that this is not one of them sites that is full of idiots saying things like, bin, buy a new one, and general crap like that.

thanks anyway all.

best regards"

This could be many many things .... I'd take the amp to a tech.

[jzgtrguy]

Myles,

 

What if you were going to buy an amplifer with say 6V6 tubes but had the option of putting in a larger transformer say for a 50 or 100 watts. Then later on down the line you need more power so you switch out the 6V6'S for say 6L6's or EL34's. Now your already set up with a bigger transformer. You might have an impedance issue but you could get an extension cabinet and solve that.

 

Question, Would a larger transfromer say for 50 or 100 Watts make the lower powered 6V6's sound funny or differnt? Am I thinking straing here? See any problems with this train of thought

 

Thanks,

Jeff

[myles_rose]

Originally posted by jzgtrguy:

Myles,

 

What if you were going to buy an amplifer with say 6V6 tubes but had the option of putting in a larger transformer say for a 50 or 100 watts. Then later on down the line you need more power so you switch out the 6V6'S for say 6L6's or EL34's. Now your already set up with a bigger transformer. You might have an impedance issue but you could get an extension cabinet and solve that.

 

Question, Would a larger transfromer say for 50 or 100 Watts make the lower powered 6V6's sound funny or differnt? Am I thinking straing here? See any problems with this train of thought

 

Thanks,

Jeff

Jeff,

 

6L6's and 6V6's have different plate impedances. You cannot (or should not) use the same output transformer. As far as a power transformer, the typical 6L6 voltages are way too high for 6V6's

[jzgtrguy]

Thanks Myles,

 

I am looking at a Bluetron "Blueverb" It comes with several power tube options 6L6, EL 34, KT77 and 6V6. It was suggested to me that I could get a lower power version and if I needed more power swap out the tubes and solve the impedance issue by using an extension cabinet. I don't know how to build amps but I am kind of a gear head and I like to know how things work. The amp looks really interesting. I might just go with a 50 watter but I have not made up my mind yet one which amp to get.

 

Thanks for your help,

[myles_rose]

Originally posted by jzgtrguy:

Thanks Myles,

 

I am looking at a Bluetron "Blueverb" It comes with several power tube options 6L6, EL 34, KT77 and 6V6. It was suggested to me that I could get a lower power version and if I needed more power swap out the tubes and solve the impedance issue by using an extension cabinet. I don't know how to build amps but I am kind of a gear head and I like to know how things work. The amp looks really interesting. I might just go with a 50 watter but I have not made up my mind yet one which amp to get.

 

Thanks for your help,

I do not know this particular amp. I also do not know your application. I personally steer clear of any amp over 50 watts in most cases.

 

The output tube selection should be based on many factors such as tone and how you play and the amps design. Is this a high front end gain amp? Is is a great amp with pedals? Are you going to use pedals? Is there a master volume? There are about 30 more questions I would need to ask you to make an informed recommendation.

[jzgtrguy]

Thanks Myles,

http://www.bluesamps.com/development/default.asp

 

is the URL. I linked to them through the Tonequest Report web site. I think it is basically a Fender circut like a Super Reverb but wiht more controls. There is a volume knob for every gain stage and two masters one before and one after the phase inverter. Yes I use a few pedals, an OCD and a Magic stomp for some light delay and very light chourus. this amp has no effects loop. I listened to the sound clips but it is hard to tell on the internet even with broadband.

 

I am currently using a Rivera Quiana Studio 112. I play mostly rock, blues and fusion with either a Strat or a Les Paul. I have the hardest time dialing in home on this amp. Sometimes I really like it and other times it sounds thin and farty especially in the low end. The Les Paul washes out and the strat gets farty. Some of the high gain stuff is good though.

 

Thanks,

 

Jeff

[myles_rose]

Originally posted by jzgtrguy:

Thanks Myles,

http://www.bluesamps.com/development/default.asp

 

is the URL. I linked to them through the Tonequest Report web site. I think it is basically a Fender circut like a Super Reverb but wiht more controls. There is a volume knob for every gain stage and two masters one before and one after the phase inverter. Yes I use a few pedals, an OCD and a Magic stomp for some light delay and very light chourus. this amp has no effects loop. I listened to the sound clips but it is hard to tell on the internet even with broadband.

 

I am currently using a Rivera Quiana Studio 112. I play mostly rock, blues and fusion with either a Strat or a Les Paul. I have the hardest time dialing in home on this amp. Sometimes I really like it and other times it sounds thin and farty especially in the low end. The Les Paul washes out and the strat gets farty. Some of the high gain stuff is good though.

 

Thanks,

 

Jeff

Jeff,

 

I would look at this amp as I would look at any Fender tolex BF era amp .... and think of it as having the same tone stack design, that is, not high gain and an amp that should stay clean. I do not like EL34's on this type of amp ... stick to 6L6's.

 

Keep in mind ... the more knobs the more pots ... the more pots the more resistors in the signal path and other components. The more components the less touch sensitivity and articulation for the player. A general rule but true over 95% of the time.

[jzgtrguy]

Myles,

 

Thanks! That is a good rule of thumb about the knobs. I am all over the place as far as a new amp goes. Here are a few I am considering;

 

Talos Basic (two knobs gain and volume three modes)

Mesa Boogie Lone star special

Guytron GT20 combo (found some great clips for this)

Fuchs OD50 (great clips on the web site)

Blankenship

Skrydstrup OD50

Kingsley Deluxe 30 or 50 (great clips)

Bluetron

Dr. Z Maz (Romance classifieds!)

 

Lots to choose from, probably all good. I went to the amp show and was really impressed by the blankenship. I got to make a decision eventually.

Thanks for your help.

 

Jeff

[myles_rose]

Originally posted by jzgtrguy:

Myles,

 

Thanks! That is a good rule of thumb about the knobs. I am all over the place as far as a new amp goes. Here are a few I am considering;

 

Talos Basic (two knobs gain and volume three modes)

Mesa Boogie Lone star special

Guytron GT20 combo (found some great clips for this)

Fuchs OD50 (great clips on the web site)

Blankenship

Skrydstrup OD50

Kingsley Deluxe 30 or 50 (great clips)

Bluetron

Dr. Z Maz (Romance classifieds!)

 

Lots to choose from, probably all good. I went to the amp show and was really impressed by the blankenship. I got to make a decision eventually.

Thanks for your help.

 

Jeff

Jeff,

 

You have some great stuff there....

 

Here is a bit of my feedback on some of them:

 

Talos Basic (two knobs gain and volume three modes) - I do not know this amp.

 

 

Mesa Boogie Lone star special - Fun amps but very complex front ends. The amp also has a very unconventional output section. If you like it then that's great. If you expect it to be able to sound like other classic EL84 amps that will not happen. I also have had a few reliability issues with these amps on the road such as internals vibrating loose during transportation.

 

 

Guytron GT20 combo (found some great clips for this) - I think all of his amps are pretty darn nice.

 

 

Fuchs OD50 (great clips on the web site) - Andy's stuff is all quite nice too. His OD series are classics that are based somewhat on a Dumblesque flair.

 

 

Blankenship - Roy is another one of those builders that does things very well. He is up at the top of the list. His stuff has had no reliability issues as a side note.

 

 

Skrydstrup OD50 - Don't know this amp but if it another "Dumble Clone" go th Fuchs route as he has been around a long time and his service is excellent.

 

 

Kingsley Deluxe 30 or 50 (great clips) - Steer clear of sound clips. They tell you nothing about how the amp responds to the player and this is what makes a great amp rather than a good amp.

 

 

Bluetron - Don't know the amp.

 

Dr. Z Maz (Romance classifieds!) - This is a lot of bang for the $$$$ and you could not beat it at two times the price. It is one of the most versitile amps on the planet and can cover the tonal scale for the most part. With an open back 4x10 it will sound like a Fender BF Super Reverb. It can get those very agressive tones with Celestions. It has a master volume that works very nicely. Listen to anything by Buddy Whittington or Michael Burks. As a side note, Michael used to play real Dumbles. His main amp now is the MAZ Sr 2x12 combo and he just smokes.

 

Good luck in picking one

[jzgtrguy]

Thanks Myles,

 

I have to unload some gear first. I think I am going to revamp everything. Maybe that will inspire me to play more too.

 

FYI the Skrydstrup is sort of like a Dumble but is supposed to do more kind of like a fuchs only more $$$

 

Kingsleys seem Fender like but with just more of everything. Smoother distortion.

 

The Talos Basic has only a Gain and volume knobs and several imputs that give you different power amp configuration Pentode, Partial triode and triode with a couple switches that boost treble or something and the knobs push pull for different boost. Very simple and very short signal path. I am not sure it can give me all the gain I want to have on tap.

 

Good advice on the sound clips. There are some amazing player out there whose farts probably sound pretty damn good! Wish I could play them all. I have tried the boogie and the blankenship and that is it. All three of the Blankenship amps were great the Leeds, Fatboy and the Variplexi.

 

Thanks for your help

 

Jeff

[jzgtrguy]

Myles,

 

One last thing. I have exchanged a few emails with the builder of the Bruetron amps and he seems like a real stand up sort of guy. This is what he had to say about the 6V6 and 6L6's and the trannies which started this whole thread.

 

FYI:

Yes. 6V6s do have higher plate impedances. The manufacturers recommended plate impedance for a given voltage at a specific bias point is max power at minimum distortion. The distortion figure is the total of second and third harmonic. Lower impedances result in lower third harmonic distortion and higher second harmonic distortion. Since the second harmonic is the octave, it is quite pleasing in guitar amps.

 

Yes. You are correct to think of it as a tonal compromise in the sense that if you wanted the 6V6 output tubes to run with max power and minimum distortion. If that were the case you would most likely just populate the output section with 6L6s and be done with it. But you want a smaller amp with more "tube sound" at lower volumes than a 6L6 provides, so 6V6s with more second order harmonics may be the preferred compromise. Follow my logic?

 

A lot of guys like the sound. Guys with Super Reverbs are doing this regularly now.

 

Yes. 6V6s call for lower plate voltages. Guitar manufactures have exceeded this for generations. The JJ 6V6 is particularly stout and can handle very high plate voltages quite easily. Some consider it to be more like lower wattage 6L6. The actual plate impedance for the JJ 6V6 at 450 volts has not been measured by anyone that I know of. Based upon sonics, though it may be closer to a 6L6 than we think.

 

At this point I am going to recommend a Twin Reverb output transformer for the most flexibility. You will have almost two months to change your mind after you place your order due to the backlog. During that time we will be exploring other aspects of your tone to determine the best voicing and speaker choice.

 

Thanks again now I'll leave you alone and go practice.

 

Jeff

[myles_rose]

Jeff,

 

Keep in mind that a 6V6 and EL84 share the same output transformer ... that means in a manner of speaking, that the cool chime you get out of many EL84 amps will also come from many 6V6 amps.

 

A 6L6 on the other hand has a very different output transformer requirement.

[jross68052]

Hey Myles,

 

My question of the week. Can I remove two power tubes from my 100 Watt Marshall JCM800 and get the eqivalent of a 50 Watt JCM800? Will this damage the amp?

 

Thanks,

 

Joe

[myles_rose]

Originally posted by jross68052:

Hey Myles,

 

My question of the week. Can I remove two power tubes from my 100 Watt Marshall JCM800 and get the eqivalent of a 50 Watt JCM800? Will this damage the amp?

 

Thanks,

 

Joe

There is extensive info on this on my GAB website in the 50 vs 100 watt writing.

 

This is safe if you change the amps impedance selector to half the speak cab value but in the end it will backfire on you.

[jross68052]

Myles,

 

I read your piece about removing two tubes. I will ax that idea. How about using four THD Yellow Jackets in a Marshall 100 Watt JCM800? Any experience with this?

 

Thanks again,

 

Joe

[myles_rose]

Originally posted by jross68052:

Myles,

 

I read your piece about removing two tubes. I will ax that idea. How about using four THD Yellow Jackets in a Marshall 100 Watt JCM800? Any experience with this?

 

Thanks again,

 

Joe

Joe,

 

That works great. You can also leave in the center two regular tubes and use the YJ's in the outer two positions or visa versa. The cathode bias operation of the YJ's will give you a more complex tone at lower levels which can be what you are really after moreso than lower overall wattage.

[PBBPaul]

Hi Myles,

 

I've been gigging with my home-built "twin" amp that is based on an old Bogen PA amp chassis. It uses 7868 power tubes and I really love the sound of this amp. The 7868's seem to be fairly rare but I'd like to get a backup set. Do you have a reasonably priced source that you would recommend? Or do you have any kicking around the shop that I could buy?

 

By the way, I was in the L.A. area last week and almost found the time to stop by and say hello. Unfortunately, it didn't happen. Perhaps next time.

 

Thank you,

 

Paul

[myles_rose]

Originally posted by PBBPaul:

Hi Myles,

 

I've been gigging with my home-built "twin" amp that is based on an old Bogen PA amp chassis. It uses 7868 power tubes and I really love the sound of this amp. The 7868's seem to be fairly rare but I'd like to get a backup set. Do you have a reasonably priced source that you would recommend? Or do you have any kicking around the shop that I could buy?

 

By the way, I was in the L.A. area last week and almost found the time to stop by and say hello. Unfortunately, it didn't happen. Perhaps next time.

 

Thank you,

 

Paul

Paul,

 

This is a pretty obscure tube and not widely used. Antique Electric Supply (www.tubesandmore.com) has them for about $50 each!

 

You might also look on my website in the tube vendors area and find George Low ... Vintage Electron and give him a call as he may have some also.

[Cheo]

Hey Myles. I'm looking to buy an amp head and a cabinet for my church. My church is so hollow is not even funny it's 70' long, 40'wide, and the ceiling is 25' high. This is just the inside. We seem to have a lot of difficulty with the amps we have. The type of music we play is very clean, so I don't think we'll need distortion or nothing like that yet. What do you recommend?

[myles_rose]

Originally posted by Cheo:

Hey Myles. I'm looking to buy an amp head and a cabinet for my church. My church is so hollow is not even funny it's 70' long, 40'wide, and the ceiling is 25' high. This is just the inside. We seem to have a lot of difficulty with the amps we have. The type of music we play is very clean, so I don't think we'll need distortion or nothing like that yet. What do you recommend?

Jose,

 

There are way too many choices to just try to take a stab at this in the dark. Let me know what you have seen that you have considered.

[Cheo]

Than Myles. Well I was looking at the Marshall MG100HDFX/MG412 Slant Cab Half Stack Package

It has very good reviews and seems powerful enough for my church. Also I was recommended a fender twin head or something like that, but I looked it up online and they no longer make it. I don't need anything too fancy but it has to be good and reliable. I'm willing to go more expensive that that first one that I told you. It's 599 retail. Ihope this is enough info. I appreciate you taking time to help.

[myles_rose]

Originally posted by Cheo:

Than Myles. Well I was looking at the Marshall MG100HDFX/MG412 Slant Cab Half Stack Package

It has very good reviews and seems powerful enough for my church. Also I was recommended a fender twin head or something like that, but I looked it up online and they no longer make it. I don't need anything too fancy but it has to be good and reliable. I'm willing to go more expensive that that first one that I told you. It's 599 retail. Ihope this is enough info. I appreciate you taking time to help.

Do you really need something as large and complex as the Marshall? Fender never made a Twin "head" for the most part (unless you think that a Showman head is actually a Twin).

 

Is there a reason something like a Fender Hot Rod Deluxe 1x12 will not work in this application?