Feel free to ask Myles

[surgevw]

Originally posted by myles111:

Seth

 

I would need to see this amp.

No problem. If I get a chance, I will post a schematic. If not, I will try some different tubes anyways. Can't hurt much other than the wallet.

 

And maybe I will build a tube rectifier stage, too.

 

Thanks,

 

Seth

[myles_rose]

Originally posted by J J:

Myles,

I was just searching around and I came across the amp brand "B-52." They're really cheap for what you get.

 

Just wondering if you have any info on them...

thanks,

JJ

 

oh yea, here's the one i was looking at B-52 Stealth Series

These amps are something of a steal that not too many people know about yet. You see them at Guitar Center but folks attention is generally drawn to the Marshall or big Crate stuff because folks see a big B-52 and many times don't check out the price.

 

They are all tube and really a great value. I have played with a few of them and they are built really nicely for their cost. I think they would be a really nice amp and would also be reliable.

[myles_rose]

Originally posted by surgevw:

Originally posted by myles111:

Seth

 

I would need to see this amp.

No problem. If I get a chance, I will post a schematic. If not, I will try some different tubes anyways. Can't hurt much other than the wallet.

 

And maybe I will build a tube rectifier stage, too.

 

Thanks,

 

Seth

Seth,

 

For a start, try a 12AY7 in V1.

[surgevw]

Thanks for the suggestion. The local store didn' t have a 12AY7, so I will have to order that and a matched phase inverter tube. They had a Groove Tubes 7025, so I picked that up to try, too.

 

They had Groove Tubes/Fender 6V6 "reds" so I popped those in on the output. I think they are quieter and distort earlier. They smell a bit, too as they break in. The shop guy said the reds were the "hottest" and would overdrive the earliest. Nothing ventured, nothing gained, and now I have some spares.

 

Thanks,

 

Seth

[myles_rose]

Originally posted by surgevw:

Thanks for the suggestion. The local store didn' t have a 12AY7, so I will have to order that and a matched phase inverter tube. They had a Groove Tubes 7025, so I picked that up to try, too.

 

They had Groove Tubes/Fender 6V6 "reds" so I popped those in on the output. I think they are quieter and distort earlier. They smell a bit, too as they break in. The shop guy said the reds were the "hottest" and would overdrive the earliest. Nothing ventured, nothing gained, and now I have some spares.

 

Thanks,

 

Seth

Seth,

 

Lots of wrong directions here....

 

The 7025 is the brightest of any of the 12AX7s.

 

The "red" 6V6's are the hottest .... BUT will break up the LATEST.... and .... you better check the bias as the reds (8-10), run VERY hot.

 

On rating numbers:

 

Basically, a #1 will distort sooner, and a #10 later. If, for example,

with a mid range tube, say a #5, makes your amp start to break in the

output section at a volume setting on the amp of "4", then with a lower

number tube, like a #2, your amp would have a same sort of break into

output distortion at say a volume setting of "3". With a higher tube,

such as an #8, then you amp would stay clean to about perhaps "6" on

the volume.

 

High rating numbers are not more or less powerful, they just distort

later. These are preferred by heavy rocker that want maximum clean

output, as they get their distortion and tone from effects or pedals.

These are not as touch dynamic.

 

Low number tubes are very touch dynamic, and more suited for a

lot of folks, for smaller venues and recording.

 

Most folks prefer the 4-7 range tubes, as they are the closest in character

and touch to what the amplifier designer had in mind. They are also the most

versatile.

 

On scale conversions:

 

On Fender amps, output tubes in newer amps are

color coded. The scale is:

 

Blue = GT 1-3 rating

White = GT 4-7 rating

Red = GT 8-10 rating

 

On Mesa Boogie amps there are six color codes.

All of them are in the GT 4-6 range. These amps

have a fixed bias to staying in this range is the

same as Mesa tubes.

 

Mesa vs Groove Tubes scale

 

Red 4

Yellow 4

Green 5

Gray 5

Blue 6

White 6

[surgevw]

Thanks for all the help Myles!

 

I found a box for the 6v6 tubes, it says Ip: 39 and Gm 3900. I am assuming 39mA of plate curent and a gain of 3900?

 

Looks like I am going to order some different tubes soon.

 

Thanks,

 

Seth

[myles_rose]

Originally posted by surgevw:

Thanks for all the help Myles!

 

I found a box for the 6v6 tubes, it says Ip: 39 and Gm 3900. I am assuming 39mA of plate curent and a gain of 3900?

 

Looks like I am going to order some different tubes soon.

 

Thanks,

 

Seth

Seth,

 

Gm is Mu which is not really gain. The current... well since we do not know a plate voltage of the test or the bias voltage it's sort of a moot point.

 

True RCA book at 250 and -12.5 will yield 48mA.

[myles_rose]

bup for new folks

[Caevan O’Shite]

Say, Myles- would you mind popping in on this thread here?

 

(CLONK) http://www.musicplayer.com/ubb/icons/icon2.gifhttp://www.musicplayer.com/ubb/icons/icon5.gif "Amp and loads."

 

I know you're busy, but if you could be sure to scope-out the proposed DIY load-box plans there in particular...

 

I'd sure appreciate it if you chimed in there...

 

Thanks!

[myles_rose]

will do

[rudraksh]

tell me how to turn a simp elec guiar into a bass guitar ?

[myles_rose]

Originally posted by rudraksh:

tell me how to turn a simp elec guiar into a bass guitar ?

This is really not all that practible. They are different instruments.

 

It is like asking me how to turn a pickup truck into a mini-van.

[surgevw]

Myles-

 

Called Groove Tubes (no decent local deaters) and ordered some 6V6-S tubes, in a #2 or #3, a 12AX7 Matched Phase Inverter, a 12AY7 for preamp, and just so I have one, and ECC 83(?).

Will let you know how it goes. Thanks for the suggestions. I ordered from Rick- he mentioned the 6V6-S as being new.

 

Thanks,

 

Seth

 

 

 

[/qb]

Seth,

 

Lots of wrong directions here....

 

The 7025 is the brightest of any of the 12AX7s.

 

The "red" 6V6's are the hottest .... BUT will break up the LATEST.... and .... you better check the bias as the reds (8-10), run VERY hot.

 

On rating numbers:

 

Basically, a #1 will distort sooner, and a #10 later. If, for example,

with a mid range tube, say a #5, makes your amp start to break in the

output section at a volume setting on the amp of "4", then with a lower

number tube, like a #2, your amp would have a same sort of break into

output distortion at say a volume setting of "3". With a higher tube,

such as an #8, then you amp would stay clean to about perhaps "6" on

the volume.

 

[myles_rose]

Originally posted by surgevw:

Myles-

 

Called Groove Tubes (no decent local deaters) and ordered some 6V6-S tubes, in a #2 or #3, a 12AX7 Matched Phase Inverter, a 12AY7 for preamp, and just so I have one, and ECC 83(?).

Will let you know how it goes. Thanks for the suggestions. I ordered from Rick- he mentioned the 6V6-S as being new.

 

Thanks,

 

Seth

 

 

Seth,

 

Lots of wrong directions here....

 

The 7025 is the brightest of any of the 12AX7s.

 

The "red" 6V6's are the hottest .... BUT will break up the LATEST.... and .... you better check the bias as the reds (8-10), run VERY hot.

 

On rating numbers:

 

Basically, a #1 will distort sooner, and a #10 later. If, for example,

with a mid range tube, say a #5, makes your amp start to break in the

output section at a volume setting on the amp of "4", then with a lower

number tube, like a #2, your amp would have a same sort of break into

output distortion at say a volume setting of "3". With a higher tube,

such as an #8, then you amp would stay clean to about perhaps "6" on

the volume.

[/QB]

 

The 6V6S is a very strong 6V6. It is almost half way a step up to a 6L6. It also handles very high plate voltages (for a 6V6) over 475 plate volts. It's a great tube.

[surgevw]

Myles-

 

As I have a diode (versus tube) rectifier, then I assume that handling higher plate voltages is a good thing. I wasn't looking for more power, necessarily, but I am looking forward to trying them.

 

Seth

[myles_rose]

Originally posted by surgevw:

Myles-

 

As I have a diode (versus tube) rectifier, then I assume that handling higher plate voltages is a good thing. I wasn't looking for more power, necessarily, but I am looking forward to trying them.

 

Seth

When plate voltages are raised the bias needs to be readjusted.

[surgevw]

Ok, I (finally) found an online shematic for my amp. I have a prototype Ruetz Z20

 

http://www.diyguitaramp.com/z20_full_schematic.gif

 

or the webpage

 

http://www.diyguitaramp.com/z20.html

 

As of yesterday I installed a 12AY7 for the preamp and a 12AX7-MPI for the phase inverter. Haven't gotten the 6V6-S duet yet, have 6V6EH duet in there right now.

 

All this drives the (16 ohm nominal) output into a 8 ohm 10" Peavey Blue Marvel run with a series/parallel resistive & inductive load that eats ~5/6 of the output power. DC resistance of the setup with load and speaker is 14.5 ohms.

 

Myles- does this change your opinion on your suggestions any?

 

Thanks,

 

Seth

[Darklava]

Myles I did make that trade for that vibrolux

what would be a good power tube replacement?

I'm looking for a little more volume less

breakup if there is such a thing.

[Caevan O’Shite]

Psssst-

 

('Lava, get a "matched phase inverter" as well if you replace the output tubes, you won't regret it!)

 

(Always replace the phase-inverter/driver-tube along with the power-tubes; they work as a team, and wear out together.)

 

Now back to our Myles!

[myles_rose]

Originally posted by surgevw:

Ok, I (finally) found an online shematic for my amp. I have a prototype Ruetz Z20

 

http://www.diyguitaramp.com/z20_full_schematic.gif

 

or the webpage

 

http://www.diyguitaramp.com/z20.html

 

As of yesterday I installed a 12AY7 for the preamp and a 12AX7-MPI for the phase inverter. Haven't gotten the 6V6-S duet yet, have 6V6EH duet in there right now.

 

All this drives the (16 ohm nominal) output into a 8 ohm 10" Peavey Blue Marvel run with a series/parallel resistive & inductive load that eats ~5/6 of the output power. DC resistance of the setup with load and speaker is 14.5 ohms.

 

Myles- does this change your opinion on your suggestions any?

 

Thanks,

 

Seth

Seth -

 

This sounds fine to me but in the end it is all personal preference.

[myles_rose]

Originally posted by Darklava:

Myles I did make that trade for that vibrolux

what would be a good power tube replacement?

I'm looking for a little more volume less

breakup if there is such a thing.

Are you saying you now have a Vibrolux?

 

If yes ....

 

In V1 or V2 .... V1 is normal channel and V2 is Vibrato channel and they are not shared ....

 

A nice 5751.

 

For the output tubes for more power and these stay clean a long time too, the 6L6S (JJ) is a great tube in a #7-8 rating biased at 30mA. These are stronger than the GEs.

 

If you are anywhere near me I'd be happy to set the bias for free.

 

On the 5751 - go to www.kcanostubes.com and ask for Mike.

[myles_rose]

Originally posted by Caevan O'Shite:

Psssst-

 

('Lava, get a "matched phase inverter" as well if you replace the output tubes, you won't regret it!)

 

(Always replace the phase-inverter/driver-tube along with the power-tubes; they work as a team, and wear out together.)

 

Now back to our Myles!

You are 100% correct-o-mundo.

[Darklava]

We are so lucky to have you around Myles.

 

Thank Caevman you too

[myles_rose]

Darklava

 

Thanks a lot.

 

If you are near L.A. drop me a line.

[Teahead]

Hey Myles,

My '04 Korg Reissue AC30tbx blew a fuse the other evening, after about thirty minutes of rehearsals.

 

Upon further inspection I noticed R73, which I'm led to believe is a screen resistor relating to one of the output tubes, was "chipped" and had a small amount of scorching around it on the pcb.

 

I took it to the shop where the repair guy replaced the resistor and now the amp seems to be working fine, with all the same tubes it had when it failed.

 

Should I replace these tubes with my spares? Just to be safe? I don't want to run the risk of this happening again and if there's any chance the Mullard GZ34 or Brimar 6B5Q's are responsible I'd sooner swap them out.

 

What else could have caused the resistor to end up like it did, if not tubes?

 

Many thanks...

 

Tea.

 

edit...

 

I've just ran the amp again, with the chasis removed and after ten minutes I noticed some nasty tones, there was lots of noise coming from the rectifier.

 

I swapped the rectifier and all was well again, sounds better than ever in fact. I also then replaced the power tubes, just to be safe, but replacing the rectifier seemed to completely solve the problem by itself.

 

Should I try the other EL84s again in a few weeks, or maybe try to get them tested before attempting anything with them?

 

Could this suspect rectifier have caused the damage to the resistor? Or to the power tubes?

[myles_rose]

Originally posted by Teahead:

Hey Myles,

My '04 Korg Reissue AC30tbx blew a fuse the other evening, after about thirty minutes of rehearsals.

 

Upon further inspection I noticed R73, which I'm led to believe is a screen resistor relating to one of the output tubes, was "chipped" and had a small amount of scorching around it on the pcb.

 

I took it to the shop where the repair guy replaced the resistor and now the amp seems to be working fine, with all the same tubes it had when it failed.

 

Should I replace these tubes with my spares? Just to be safe? I don't want to run the risk of this happening again and if there's any chance the Mullard GZ34 or Brimar 6B5Q's are responsible I'd sooner swap them out.

 

What else could have caused the resistor to end up like it did, if not tubes?

 

Many thanks...

 

Tea.

Tea,

 

This probably was one of the output tubes. I would replace them with EL84S #5-6 and then go have your tubes tested on a good tester, one that supplies real amp voltages (not an old tube tester).

 

Your Mullard GZ34 also will supply higher plate voltage than the GZ34's of today. That is also something to keep in mind but it will not cause any issues, will make the amp sound stronger and have a bit more output.

[Teahead]

Originally posted by myles111:

Tea,

 

This probably was one of the output tubes. I would replace them with EL84S #5-6 and then go have your tubes tested on a good tester, one that supplies real amp voltages (not an old tube tester).

 

Your Mullard GZ34 also will supply higher plate voltage than the GZ34's of today. That is also something to keep in mind but it will not cause any issues, will make the amp sound stronger and have a bit more output.

Hey Myles, thanks for the response and information. I must have been editing my post when you were typing your reply(!) If you don't mind checking back to my original post a moment?

 

Basically, I've since found the rectifier to be a source of excessive idling noise and rather nasty amp tones, but have replaced both it and the EL84s, just to be on the safe side.

 

Since doing this I've had no issues at all, it's running great. I suppose I should send the suspect Brimar EL84s off to Derek at Watford Valves and have him check them out?

 

Do you think it's more likely the rectifier would have harmed the output tube and resistor, or vice a versa?

 

Thanks again!

[myles_rose]

It could be either.

[surgevw]

A report back:

 

Installed a 12AY7 for preamp, a 12AX7-MPI for phase inverter, and amatched duet of the new 6V6-S output tubes in a #2 hardness.

 

Downstairs neighbors are gone, so I fired it up.

 

I still need earplugs, but at #7 on the dial I can go into nice overdrive. #8 on the dial and it gets more agressive with sustain. #9 and I can get crazy breakup.

 

NICE!!!

 

If I had a room where I could play 15 feet from the amp, I probably wouldn't need hearing protection (I am paranoid about this)

 

I wonder if a tube rectifier might add some compression to give a bit more sustained overdrive, as it is more pick-attack based right now.

 

Just thinking out loud, and not sure I will try that. I think I have done about as well as I can with this amp with just one pre-amp tube.

 

Thanks again for all the help, Myles!

 

Seth

 

 

Originally posted by surgevw:

 

 

Called Groove Tubes (no decent local deaters) and ordered some 6V6-S tubes, in a #2 or #3, a 12AX7 Matched Phase Inverter, a 12AY7 for preamp, and just so I have one, and ECC 83(?).

Will let you know how it goes. Thanks for the suggestions. I ordered from Rick- he mentioned the 6V6-S as being new.

 

Thanks,

 

Seth

 

 

[myles_rose]

Originally posted by surgevw:

A report back:

 

Installed a 12AY7 for preamp, a 12AX7-MPI for phase inverter, and amatched duet of the new 6V6-S output tubes in a #2 hardness.

 

Downstairs neighbors are gone, so I fired it up.

 

I still need earplugs, but at #7 on the dial I can go into nice overdrive. #8 on the dial and it gets more agressive with sustain. #9 and I can get crazy breakup.

 

NICE!!!

 

If I had a room where I could play 15 feet from the amp, I probably wouldn't need hearing protection (I am paranoid about this)

 

I wonder if a tube rectifier might add some compression to give a bit more sustained overdrive, as it is more pick-attack based right now.

 

Just thinking out loud, and not sure I will try that. I think I have done about as well as I can with this amp with just one pre-amp tube.

 

Thanks again for all the help, Myles!

 

Seth

 

 

Originally posted by surgevw:

 

 

Called Groove Tubes (no decent local deaters) and ordered some 6V6-S tubes, in a #2 or #3, a 12AX7 Matched Phase Inverter, a 12AY7 for preamp, and just so I have one, and ECC 83(?).

Will let you know how it goes. Thanks for the suggestions. I ordered from Rick- he mentioned the 6V6-S as being new.

 

Thanks,

 

Seth

 

 

Rick Benson is a cool guy. The 6V6S is a really nice 6V6 and can be pushed almost as hard as a lot of 6L6 tubes.