Feel free to ask Myles

[Bluesape]

Hey Myles,

 

I have an old, Montreal built Lifco Cobra head, with 2 6V6's and 1 12AX7 and 1 12AY7. My other guitarist says it is essentially a clone of an old Princeton circuit. He's quite a capable tinkerer with amps and pedals. The 2x12 cab I'm using with it is rated at 4 ohms, but the amp is at 8 ohms. He says I'm losing some output and clean headroom with this setup, and suggested replacing the tranny with a Hammond unit that has a 4 ohm lead to match the cab. He has spent many hours on this amp, and has developed a sort of crush on it. Last night he had it sounding better at our local jam than it ever has. He also thinks the plate voltage is around 300, and a better match in resistance should make the amp louder and cleaner. I'm told it was built by a long gone entity called Petco that built amps under a number of names in Montreal back in the '60's and 70's, and they used a lot of cheaper components in order to compete in price against the better known brands. I've never been happier with the sound than I am right now, and I'm wondering if I should leave it be, or would I be looking at a longer, more reliable lifetime with it if I make any further changes?

[myles_rose]

Hey Myles,

 

If you read the forum posts, you are probably aware that I just scored an Ampeg GVT15-112.

 

Like most players, I seek the "Jazz Holy Grail of Tone". I want a tone that is:

 

1. CLEAN!!!

2. Smooth

3. Liquid

4. Mellow

 

The tubes in the amp are as follows:

 

2-6V6

2-12AX7

 

Could you make any recommendations regarding tube substitutions that would contribute to achieving that tone?

 

Thanks for your help.

 

_________________________

If you play cool, you are cool.

 

 

[myles_rose]

Hey Myles,

 

I have an old, Montreal built Lifco Cobra head, with 2 6V6's and 1 12AX7 and 1 12AY7. My other guitarist says it is essentially a clone of an old Princeton circuit. He's quite a capable tinkerer with amps and pedals. The 2x12 cab I'm using with it is rated at 4 ohms, but the amp is at 8 ohms. He says I'm losing some output and clean headroom with this setup, and suggested replacing the tranny with a Hammond unit that has a 4 ohm lead to match the cab. He has spent many hours on this amp, and has developed a sort of crush on it. Last night he had it sounding better at our local jam than it ever has. He also thinks the plate voltage is around 300, and a better match in resistance should make the amp louder and cleaner. I'm told it was built by a long gone entity called Petco that built amps under a number of names in Montreal back in the '60's and 70's, and they used a lot of cheaper components in order to compete in price against the better known brands. I've never been happier with the sound than I am right now, and I'm wondering if I should leave it be, or would I be looking at a longer, more reliable lifetime with it if I make any further changes?

 

I am not sure what you are asking. If the speaker impedance does not match the OT change one or the other.

[myles_rose]

Hey Myles,

 

If you read the forum posts, you are probably aware that I just scored an Ampeg GVT15-112.

 

Like most players, I seek the "Jazz Holy Grail of Tone". I want a tone that is:

 

1. CLEAN!!!

2. Smooth

3. Liquid

4. Mellow

 

The tubes in the amp are as follows:

 

2-6V6

2-12AX7

 

Could you make any recommendations regarding tube substitutions that would contribute to achieving that tone?

 

Thanks for your help.

 

_________________________

If you play cool, you are cool.

 

 

Tubes are not going to change the basic character of the amp and the amp is a bit underpowered for jazz for most, better suited to blues or crunch.

 

You need more clean headroom. Try a 5751 in V1 and/or a 12AT7 in V2.

 

This will never be a clean amp other than at very low levels.

 

[Fred_C]

Hey Myles,

 

If you read the forum posts, you are probably aware that I just scored an Ampeg GVT15-112.

 

Like most players, I seek the "Jazz Holy Grail of Tone". I want a tone that is:

 

1. CLEAN!!!

2. Smooth

3. Liquid

4. Mellow

 

The tubes in the amp are as follows:

 

2-6V6

2-12AX7

 

Could you make any recommendations regarding tube substitutions that would contribute to achieving that tone?

 

Thanks for your help.

 

_________________________

If you play cool, you are cool.

 

 

Tubes are not going to change the basic character of the amp and the amp is a bit underpowered for jazz for most, better suited to blues or crunch.

 

You need more clean headroom. Try a 5751 in V1 and/or a 12AT7 in V2.

 

This will never be a clean amp other than at very low levels.

 

Myles,

 

Thanks for getting back to me. I just need clean tone at "living room" levels. Thanks for the advice. So, you prefer the AT7 over the AY7 that Caevan recommended?

[myles_rose]

AT7 only in the phase inverter position. It is an awful tone generator for the first tone and gain stage.

 

A 12AY7 is a nice V1 tube but you will lose some level at a given volume position on the amp pot.

[Bluesape]

Hey Myles,

 

I have an old, Montreal built Lifco Cobra head, with 2 6V6's and 1 12AX7 and 1 12AY7. My other guitarist says it is essentially a clone of an old Princeton circuit. He's quite a capable tinkerer with amps and pedals. The 2x12 cab I'm using with it is rated at 4 ohms, but the amp is at 8 ohms. He says I'm losing some output and clean headroom with this setup, and suggested replacing the tranny with a Hammond unit that has a 4 ohm lead to match the cab. He has spent many hours on this amp, and has developed a sort of crush on it. Last night he had it sounding better at our local jam than it ever has. He also thinks the plate voltage is around 300, and a better match in resistance should make the amp louder and cleaner. I'm told it was built by a long gone entity called Petco that built amps under a number of names in Montreal back in the '60's and 70's, and they used a lot of cheaper components in order to compete in price against the better known brands. I've never been happier with the sound than I am right now, and I'm wondering if I should leave it be, or would I be looking at a longer, more reliable lifetime with it if I make any further changes?

 

I am not sure what you are asking. If the speaker impedance does not match the OT change one or the other.

 

 

 

I guess the short answer does sum it up - match impedances - thx.

[Fred_C]

Hey Myles,

 

Thanks so much for the expert advice. Regards.

[myles_rose]

You are quite welcome

[Caevan O’Shite]

Myles,

 

Thanks for getting back to me. I just need clean tone at "living room" levels. Thanks for the advice. So, you prefer the AT7 over the AY7 that Caevan recommended?

 

For what it's worth, a good up-to-spec 12AU7 was one of the two tubes that I recommended for the Phase-Inverter/Driver position, and not a 12AY7.

 

 

I DID suggest the 12AY7 as the second of a couple of options for V1, my first suggestion for V1 being a 5751.

[myles_rose]

12AU7 is too weak unless the amp was designed for it as is an Ampeg SVT. You will lose level, life and character.

[Caevan O’Shite]

For what it's worth, a good up-to-spec 12AU7 was one of the two tubes that I recommended for the Phase-Inverter/Driver position, and not a 12AY7.

 

12AU7 is too weak unless the amp was designed for it as is an Ampeg SVT. You will lose level, life and character.

 

Oops! Thank you for that correction, then, Myles! I had mistakenly thought that since either a nice 12AX7, 5751 or 12AU7 will work well as a Driver for my Fuchs Lucky 7- the 12AU7 being a nice option for Jazz tones- that a 12AU7 would make a good candidate for a Phase-Inverter/Driver tube here in his Ampeg GVT15-112 for clean, smooth Jazzy tones.

[haywired2]

Hi Myles, what do you know about these "New" Tung-Sol EL84s? I saw someone asking about them on another thread for their Classic 30.

 

http://tubedepot.com/ts-el84.html

 

Thanks

Scott

[myles_rose]

Hi Myles, what do you know about these "New" Tung-Sol EL84s? I saw someone asking about them on another thread for their Classic 30.

 

http://tubedepot.com/ts-el84.html

 

Thanks

Scott

 

Nothing but a new name and logo on an old tube that is dark.

 

Something else to consider .... If they cannot even keep the bottle diameter to spec what hope would you have that the other items had proper attention paid to them?

 

It is all personal taste and preference when it comes to tone but I don't like them. The fact that they cannot even follow design spec (and it is the tube not the amps they mention) then I would not give them a second thought. Garbage.

 

[haywired2]

Something else to consider .... If they cannot even keep the bottle diameter to spec what hope would you have that the other items had proper attention paid to them?

 

Good point. Thanks.

[Caevan O’Shite]

Something else to consider .... If they cannot even keep the bottle diameter to spec what hope would you have that the other items had proper attention paid to them?

 

Good point. Thanks.

 

The size issue here and incompatibility with a large number of known and popular amps are indeed bad enough red flags...

 

The Ruby EL84CZ and JJ EL84 (same tubes, different labels) are an excellent tube that can be had in matched duets and quartets for reasonable prices from the likes of Doug's Tubes and KCA NOS Tubes. I can't believe how long a of GT branded quartet of these has lasted for me, and they made my amp sound a LOT better, too!

[haywired2]

Something else to consider .... If they cannot even keep the bottle diameter to spec what hope would you have that the other items had proper attention paid to them?

 

Good point. Thanks.

 

The size issue here and incompatibility with a large number of known and popular amps are indeed bad enough red flags...

 

The Ruby EL84CZ and JJ EL84 (same tubes, different labels) are an excellent tube that can be had in matched duets and quartets for reasonable prices from the likes of Doug's Tubes and KCA NOS Tubes. I can't believe how long a of GT branded quartet of these has lasted for me, and they made my amp sound a LOT better, too!

 

I found some Rubys yesterday at my local mom and pop, The Fret House, and road tested them last night and the Classic 30 never sounded better

[davidm]

Myles,

 

Do you have any advice for running a Boss DD3 Digital delay through a Rivera Quiana effects loop? I followed the instructions in the Rivera manual, but can't get a good sound out of it. Its sounds okay through the clean channel, but unusable through the distorted channel. I used this delay through a Marshall Jubilee for a couple of years and it worked fine. It also woked great through a Marshall 30th Anniversary, which had a parallel loop, but doesn't sound good through the Rivera loop or straight into the amp for that matter.

[myles_rose]

I generally put any Boss effects into the input jack. Their levels are not suited to effects loops in some amps.

[davidm]

Myles,

 

Would a rack mount unit like a Lexicon or Midiverb work well through the Quiana loop? Is that what the loop was mostly designed for? I'm convinced there must be a way to get a nice delay sound out of this amp.

 

Thanks Myles.

[myles_rose]

Myles,

 

Would a rack mount unit like a Lexicon or Midiverb work well through the Quiana loop? Is that what the loop was mostly designed for? I'm convinced there must be a way to get a nice delay sound out of this amp.

 

Thanks Myles.

 

Yes. Both of those work really nicely in the loop. Keep in mind that the levels on the units will need to be adjusted for optimum performance and s/n ratio. The two channels will work differently as the gain structure is different.

 

[Caevan O’Shite]

Hey, Myles. Time to replace the output-tubes and MPI in my Carvin Vintage 33!

 

Years ago, I put a matched quartet of GTEL34 S's and a GT12AX7M/MPI in there that you'd picked for me, along with a SAG-MHG set. I have loved 'em all!! Thanks again, again!! Excellent "Play The Amp" and "Touch" all week!! (I only use the "Soak" Channel, too, turning down my guitar's volume-knob for cleans.) I can't believe how long they've held up!! People always ask me what boutique pickups and/or speakers I'm using (both stock), or if I had someone "Hot Rod" the amp...

 

I will most likely be replacing the output-tubes with a matched quartet of Ruby EL84CZ's from Doug's Tubes, in an "Average" rating, unless you would suggest something else.

 

Now- for the MPI, what would you suggest for the most dynamic, "play the amp" response, rich harmonic-overtones, with plenty of overdrive/distortion and compression/roundness when pushed hard?

 

Another long-plate Sovtek 12AX7LPS, with "Balanced" triodes, with at least 1.0mA or more of plate current output? Or, something else? Would High-Gain (and Matched Gain) be of any benefit for a MPI in my Carvin Vintage 33?

 

I have loved and been VERY happy with that GT12AX7M/MPI that you picked for me years ago; but I'm not so sure that I trust (Fender)/GT the way I used to anymore.

 

 

I am also wondering about the reverb-tube in this amp (currently a GT12AX7R originally purchased a good decade ago or so); what characteristics/specs would I look for in a tube for good, strong reverb? (I believe that V4B is the Reverb Send, and V4A is the Reverb Return.)

 

THANKS FOR YOUR TIME!!

[myles_rose]

Hey, Myles. Time to replace the output-tubes and MPI in my Carvin Vintage 33!

 

Years ago, I put a matched quartet of GTEL34 S's and a GT12AX7M/MPI in there that you'd picked for me, along with a SAG-MHG set. I have loved 'em all!! Thanks again, again!! Excellent "Play The Amp" and "Touch" all week!! (I only use the "Soak" Channel, too, turning down my guitar's volume-knob for cleans.) I can't believe how long they've held up!! People always ask me what boutique pickups and/or speakers I'm using (both stock), or if I had someone "Hot Rod" the amp...

 

I will most likely be replacing the output-tubes with a matched quartet of Ruby EL84CZ's from Doug's Tubes, in an "Average" rating, unless you would suggest something else.

 

Now- for the MPI, what would you suggest for the most dynamic, "play the amp" response, rich harmonic-overtones, with plenty of overdrive/distortion and compression/roundness when pushed hard?

 

Another long-plate Sovtek 12AX7LPS, with "Balanced" triodes, with at least 1.0mA or more of plate current output? Or, something else? Would High-Gain (and Matched Gain) be of any benefit for a MPI in my Carvin Vintage 33?

 

I have loved and been VERY happy with that GT12AX7M/MPI that you picked for me years ago; but I'm not so sure that I trust (Fender)/GT the way I used to anymore.

 

 

I am also wondering about the reverb-tube in this amp (currently a GT12AX7R originally purchased a good decade ago or so); what characteristics/specs would I look for in a tube for good, strong reverb? (I believe that V4B is the Reverb Send, and V4A is the Reverb Return.)

 

THANKS FOR YOUR TIME!!

 

If there are no issues with the preamp tubes leave them alone.

 

If you want to replace the PI look at the Sovtek 12AX7LP and JJ ECC803S, both longer plate tubes. Assure they have proper current drive, at least 1.1mA and are closely balanced.

 

High gain for driver tubes (even your reverb driver) is not as important as current drive.

 

On output tubes I prefer JJ EL84S as they are still the most long lived tube but that is personal taste. The Ruby CZ is the JJ tube and Ruby does an excellent job of testing and matching. Yes, an average rating .... proper plate current. High and low ratings indicate that a tube was improperly manufactured.

 

I am not a Fender/GT tube fan. The ten point spread was course enough but at least when I was their QA/QC I could assure a "6" was always a 6. Now with just three ratings there is almost no chance that an output set will match. Today's better vendors match by the milliamp, not a wide range envelope.

 

 

[Caevan O’Shite]

Thanks, Myles!

[Caevan O’Shite]

Hey again, Myles.

 

So I tried a fresh Ruby 12AX7AC5 HG+ ("High Grade Plus") for the reverb (V4 B & A) in my Carvin Vintage 33.

 

It definitely drove the reverb-springs harder, giving a brighter, ringing-upper-midrange, classic bf Fender sort of reverb; almost splashy and crashy in-a-good-way, heading into surf territory when the reverb was cranked. It also had excellent low noise characteristics.

 

Overall, this was a good thing, particularly with the amp's clean/"Rhythm" Channel set clean, clear and bright.

 

=BUT=

 

- I found that I actually preferred the general tone of the reverb with a fairly old GT12AX7R; it certainly fits the lead/"Soak" Channel much better, with a darker, warmer, softer, smoother reverb-tone. I'd just like a little more of it on-tap, with a little longer reverb "Dwell" time...

 

My question is, what might I look for to get stronger drive hitting the reverb for a little more/longer "Dwell", while still having a darker, warmer, softer, smoother reverb-tone, and reasonably low noise? Perhaps strong plate-current output with medium-ish gain on V4B (rev-drive), and medium to high-ish gain on V4A (rev-recovery)? Any tips, or tube recommendations?

[myles_rose]

You cannot change dwell or basic nature of the reverb by changing tubes. Change the tank.

 

[Caevan O’Shite]

You cannot change dwell or basic nature of the reverb by changing tubes. Change the tank.

 

Aaaaaahh... Thanks!

[Caevan O’Shite]

What cable and plugs would you recommend for DIY instrument cables, Myles?

 

I need some new instrument cables, including a roughly 2' one with right-angle plugs at each end, to go from the guitar's output-jack to a strap-born gizmo, and then another 10' with right-angle-to-straight plugs to go from there to pedals or amp; and also a pair of longer ones- 10' or 20'- for the amp's effects-loop, and another one, not quite as long, maybe 6' to 10', to go from pedals to amp-input.

 

Now, I've been looking at offerings from various makers and retailers, and I've come to think that I'll get closer to what I want- and hopefully at a more reasonable cost- if I just buy 40 to 65 or 70 feet or so of some good quality cable, some good right-angle and straight plugs, and make my own to the lengths that I need.

 

Thank you once again for your time and effort!

[myles_rose]

George L stuff is pretty decent for do it yourself but I prefer soldered connections personally.

[Caevan O’Shite]

...but I prefer soldered connections personally.

 

Same here...