Feel free to ask Myles

[myles_rose]

Originally posted by jross68052:

Myles,

 

Heres my question of the week. If you have a typical push pull amp and the phase inverter tube happens to be not balanced as it should, What would the amp sound like when it is turned up? Would this produce a non harmonic distortion?

 

The reason I ask is that my Marshall TSL60 sounds great at low volumes and the preamp out to a PA with digital effects sounds really great. But when I turn the amp up a bit, the power amp distortion sounds real nasty and not even musical in my opinion. I have ordered a balanced phase inverter tube for the amp.

 

Do you think this may improve the problem? Or am I on the wrong track?

 

Thanks,

 

Joe

I explain this in depth on my GAB website.

[Yuri T.]

Hi Myles,

I'm puttin new SED EL-34s in my Bogner Shiva. What would be your recommendation for bias point? I wonder if the higher voltage requires anything different. Any pre amp tubes I should use?

[myles_rose]

Originally posted by Yuri T.:

Hi Myles,

I'm puttin new SED EL-34s in my Bogner Shiva. What would be your recommendation for bias point? I wonder if the higher voltage requires anything different. Any pre amp tubes I should use?

Bogner recommends the Svetlana for their amps but I was never sure why. The real Svets (not the SED but the true St. Petersburg Winged C) are killer tubes but just about any EL-34 of good quality is more than up to the Bogner. They may say their plate voltages are high, and maybe by today's standards they are on the high side but by vintage Marshall standards they are nothing to worry about.

 

ANY EL-34 for the most part is up to the amp if properly biased.

 

I like 36mA in the Shiva. Hotter than that and the amp sounds harsh.

 

Preamp tubes ... really a user preference deal. For a British flair the ECC83S in V1 and V2 have that mid hump that is part of a British amp tradition. For a more linear and smooth amp the 12AX7C9 is a cool choice.

 

I love NOS RFT's or Brimars in V1 and V2 of these amps and when I need them I go to Mike at KCA ... www.kcanostubes.com

 

For the phase inverter, I prefer long plates as they go into distortion in a more smooth and linear fashion than short plates for the most part as a generality. Just make sure the PI has a transconductance of at least 1500 and at least 1.1 mA of current output at RCA book test spec. Most current production tubes fall far below this and the standard is 1600 and 1.2mA I see a lot of 0.6mA - 0.8mA and the amp will loose a lot of it's magic and just seem a bit dull and lifeless (but that is probably what is going on now anyway unless your PI was selected).

 

Happy playing.

[Yuri T.]

I found some old EL34s I pulled from a 70s Traynor head some years ago. Nothing on the glass just EL34M (could be an H, hard to read) in white on the black bases. Looks like tehy the Mullard V shaped metal at the top with square getters. Any idea who made these?

[myles_rose]

Originally posted by Yuri T.:

I found some old EL34s I pulled from a 70s Traynor head some years ago. Nothing on the glass just EL34M (could be an H, hard to read) in white on the black bases. Looks like tehy the Mullard V shaped metal at the top with square getters. Any idea who made these?

I would need photos.

 

I would not even try them unless they were first tested and within 10% of each other in current.

[MILLO]

Hello, Myles--

 

How's everything? I have an 80's Fender Twin Reverb II and its clean channel sounds really soft and volume doesn't seem to change when I crank it up. Almost no sound at all. Distortion channel seems to be working right, though. I guess it's a bad tube, but this thing has like 7 preamp tubes! Do you happen to know and/or can guess which is the clean channel tube?

 

Tomorrow (Saturday) morning I don't have that much time to experiment swapping tubes. It'd be better if I knew which one it was and swap it right away!

 

By the way, I just received a certain OD pedal w/ a ying-yang symbol on the control plate.

[Heatseeker]

Hey Myles,

I think I've ready to swap out the tubes in my AC30. The main problem is: I have no idea where to begin. I've looked around and most places say to change preamp and power tubes? First:

1. How should I take the amp apart to find where the tubes go?

2. Which tubes should I use for which places and what models?

 

All tube help would be greatly appreciated and any other info. you think I should know.

 

Thanks Myles!

[myles_rose]

Originally posted by MILLO:

Hello, Myles--

 

How's everything? I have an 80's Fender Twin Reverb II and its clean channel sounds really soft and volume doesn't seem to change when I crank it up. Almost no sound at all. Distortion channel seems to be working right, though. I guess it's a bad tube, but this thing has like 7 preamp tubes! Do you happen to know and/or can guess which is the clean channel tube?

 

Tomorrow (Saturday) morning I don't have that much time to experiment swapping tubes. It'd be better if I knew which one it was and swap it right away!

 

By the way, I just received a certain OD pedal w/ a ying-yang symbol on the control plate.

Take a known good fresh 12AX7 and start at V1 and swap in and out of each position. It is probably not V1 as if it was all funtions would be sub standard.

[myles_rose]

Originally posted by Heatseeker:

Hey Myles,

I think I've ready to swap out the tubes in my AC30. The main problem is: I have no idea where to begin. I've looked around and most places say to change preamp and power tubes? First:

1. How should I take the amp apart to find where the tubes go?

2. Which tubes should I use for which places and what models?

 

All tube help would be greatly appreciated and any other info. you think I should know.

 

Thanks Myles!

Power tubes are first.

 

Preamp tubes are probably fine.

 

Get somebody to help as the back panel has to be pulled and the entire chassis removed.

 

This is easier shown that written ... it is not that hard.

[Proglodyte]

Hi Myles, A few of us on the forum were talking about reverb and tremolo. My question: In a Fender Twin Reverb amp, does the tremolo stage come before or after the reverb stage? I'm asking just so that I have a frame of reference when I'm working with these effects in my home studio. Thanks.

[SF audio]

Hi Miles,

 

My univalve has a scratchy hotplate knob - the volume also cuts in/out when using at the lowest setting. It definitely needs to be replaced.

 

Do you know a total repair cost, including shipping both ways?

 

thanks!

Aaron

[MILLO]

Originally posted by myles111:

Take a known good fresh 12AX7 and start at V1 and swap in and out of each position. It is probably not V1 as if it was all funtions would be sub standard.

It was a GT 12 AX7-M. Got it. The Zendrive sounds pretty good through this head.

 

I should probably go ahead and find out what each of these tubes do. I know the fx loop is "tube-buffered" or whatever the term is.

[myles_rose]

Originally posted by Proglodyte:

Hi Myles, A few of us on the forum were talking about reverb and tremolo. My question: In a Fender Twin Reverb amp, does the tremolo stage come before or after the reverb stage? I'm asking just so that I have a frame of reference when I'm working with these effects in my home studio. Thanks.

Email me and I will send you a print.

[myles_rose]

Originally posted by SF audio:

Hi Miles,

 

My univalve has a scratchy hotplate knob - the volume also cuts in/out when using at the lowest setting. It definitely needs to be replaced.

 

Do you know a total repair cost, including shipping both ways?

 

thanks!

Aaron

I have no idea ... check with THD.

[davidm]

Hi Myles,

 

What changes in channel 1 and 2 could I expect if I changed the Sovtek 6L6WXT+s in my Quiana Studio 112 to KT66-Cs?

 

Thanks,

 

Dave

[jross68052]

Originally posted by myles111:

Originally posted by jross68052:

Myles,

 

Heres my question of the week. If you have a typical push pull amp and the phase inverter tube happens to be not balanced as it should, What would the amp sound like when it is turned up? Would this produce a non harmonic distortion?

 

The reason I ask is that my Marshall TSL60 sounds great at low volumes and the preamp out to a PA with digital effects sounds really great. But when I turn the amp up a bit, the power amp distortion sounds real nasty and not even musical in my opinion. I have ordered a balanced phase inverter tube for the amp.

 

Do you think this may improve the problem? Or am I on the wrong track?

 

Thanks,

 

Joe

I explain this in depth on my GAB website.

Thanks for the advice. In installed a balanced JJ phase inverter tube before my gigs this weekend. The Marshall TSl tone and power were right on.

 

Joe

[myles_rose]

Originally posted by davidm:

Hi Myles,

 

What changes in channel 1 and 2 could I expect if I changed the Sovtek 6L6WXT+s in my Quiana Studio 112 to KT66-Cs?

 

Thanks,

 

Dave

The amp will just sound much bigger ... firmer mids and lows too.

 

Don't forget to rebias as a KT66C will put out about 10 more milliamps if the bias is left stock and this is way too hot.

 

Bias at 32mA

[Satsloader]

Hi Myles,

 

While building Marshall 50 watt clones, I've moved the bias supply to the hot side of the standby switch, but I've wondered about the following..

 

1. It would be easy to change the bias supply from half wave to full wave. Is this benificial?

 

2. The 1986/87 wiring diagrams show the .5amp fuse after the 1st filter capacitor. If this cap shorts, we are relying on the increase in current to blow the main fuse on the primary side of the power transformer, which stresses the PT and could damage it. Moving the .5amp fuse to the "hot" side of the 1st filter cap would eliminate this, at the risk of popping the fuse when switching from "standby" to "on" due to inrush current ( which I am assuming is why Marshall placed the fuse after the 1st cap, is this correct? ). If so, wouldn't another fuse (in-line type ) installed before the 1st filter cap, say a 1amp value, be a smart idea?

 

Bill

[myles_rose]

Originally posted by Satsloader:

Hi Myles,

 

While building Marshall 50 watt clones, I've moved the bias supply to the hot side of the standby switch, but I've wondered about the following..

 

1. It would be easy to change the bias supply from half wave to full wave. Is this benificial?

 

2. The 1986/87 wiring diagrams show the .5amp fuse after the 1st filter capacitor. If this cap shorts, we are relying on the increase in current to blow the main fuse on the primary side of the power transformer, which stresses the PT and could damage it. Moving the .5amp fuse to the "hot" side of the 1st filter cap would eliminate this, at the risk of popping the fuse when switching from "standby" to "on" due to inrush current ( which I am assuming is why Marshall placed the fuse after the 1st cap, is this correct? ). If so, wouldn't another fuse (in-line type ) installed before the 1st filter cap, say a 1amp value, be a smart idea?

 

Bill

Bill,

 

Unless you are an experienced amp designer and have sound ideas why you are making these changes ... DON'T.

 

I will not comment on any of this because there is a danger that you may cause yourself bodily injury or electical shock.

 

If you want a Marshall 50 watt clone follow the electrical diagrams to the letter and stick to the changes you desire to be signal caps or tone caps.

[Satsloader]

In Today's lawsuit-happy world I don't blame you for your response, although I wouldn't sue someone for my own mistakes in life, I'm funny that way..

 

I do feel my questions are valid ones though, and ask questions like these to explore the possibility of building better and safer designs. I should have pointed out that I have experience building various electronic devices, starting with my first kit radio when I was 9 years old. I've felt the business end of high voltage and developed safe habits and practices, including checklist's, to avoid killing myself in the process of enjoying this hobby we love.

 

I should also point out that in my second question I was suggesting simply adding an additional in-line fuse prior to the 1st filter cap. In re-reading the question I realised it could be misinterpreted, sorry if there was any misunderstanding to anyone reading it.

 

Cheers,

 

Bill

[mdrs]

Myles....I just got a THD Univalve...

 

I'm interested in obtaining a NOS Mazda 6V6, and would also like to have a quality 12 AX7, and a 12AT7.

 

Where would you suggest I buy these?

 

Thanks!

[myles_rose]

Originally posted by Satsloader:

In Today's lawsuit-happy world I don't blame you for your response, although I wouldn't sue someone for my own mistakes in life, I'm funny that way..

 

I do feel my questions are valid ones though, and ask questions like these to explore the possibility of building better and safer designs. I should have pointed out that I have experience building various electronic devices, starting with my first kit radio when I was 9 years old. I've felt the business end of high voltage and developed safe habits and practices, including checklist's, to avoid killing myself in the process of enjoying this hobby we love.

 

I should also point out that in my second question I was suggesting simply adding an additional in-line fuse prior to the 1st filter cap. In re-reading the question I realised it could be misinterpreted, sorry if there was any misunderstanding to anyone reading it.

 

Cheers,

 

Bill

Bill,

 

I am always reluctant to answer question such as these in a forum. There are many things to consider and if something is not clear others go off and do who knows what.

 

If you contact me via by normal email at GAB I will give you my phone contact and we can talk about this one on one.

 

Myles

[myles_rose]

Originally posted by mdrs:

Myles....I just got a THD Univalve...

 

I'm interested in obtaining a NOS Mazda 6V6, and would also like to have a quality 12 AX7, and a 12AT7.

 

Where would you suggest I buy these?

 

Thanks!

Mike at KCA .... www.kcanostubes.com

[Paul24]

Hi Myles,

I wonder if you can shed some light on the following.I have just purchased a Rivera Pubster 25 with an FX loop.Normally I would normally use the following effects in this order plugged into the Amp

Guitar -> Dunlop Wah Wah pedal ->Marshall Compressor -> Marshall Guvner 2 (distortion) ->Behringer digital delay -> Amp

How do i go about setting these up for fx loop ? as i believe there are some fx that shouldn't go in a loop ?

 

Hope you can help me on this

 

Paul

[myles_rose]

Originally posted by Paul24:

Hi Myles,

I wonder if you can shed some light on the following.I have just purchased a Rivera Pubster 25 with an FX loop.Normally I would normally use the following effects in this order plugged into the Amp

Guitar -> Dunlop Wah Wah pedal ->Marshall Compressor -> Marshall Guvner 2 (distortion) ->Behringer digital delay -> Amp

How do i go about setting these up for fx loop ? as i believe there are some fx that shouldn't go in a loop ?

 

Hope you can help me on this

 

Paul

Paul,

 

This is really a lot of trial and error and personal taste. Some effects don't like being in some loops as they expect a high impedance load on their output, like an amp input.

 

Some effects, weather in a loop or used in the before the amp signal chain prefer to feed or be fed with different effects and turning them around will do different things ... and ... once you add more in the chain other changes may be noted in earlier or later effects in the chain.

 

This has been an issue from the first pedals even before effects loops and continues today.

 

The only effects I like in a loop are those that were intended to be rack mounted units where you can adjust the input level to the effect and the effect's output level back to the return of the amplifiers effects loop.

 

Then again, doing things in a very wrong way on purpose can sometimes lead to some pretty cool and unique sounds.

 

In the "old days" I would chain two or more Dynacomps and crank the two knobs on each unit to about 3:00 and get some very heavy tones ... part coming from overdriving the input of compressor 2 in the chain and a lot from overdriving the amplifiers input. I used this setup in the mid 70s with a Dual Showman. Whoever thinks Fender amps cannot sound like metal monsters or hard rock amps never tried this. In 1968, Jimi Hendrix used four dual showman heads at the Hollywood Bowl concert. Not a Marshall in sight. He still sounded just like always if you ask folks that were there.

[mdrs]

Originally posted by myles111:

Originally posted by mdrs:

Myles....I just got a THD Univalve...

 

I'm interested in obtaining a NOS Mazda 6V6, and would also like to have a quality 12 AX7, and a 12AT7.

 

Where would you suggest I buy these?

 

Thanks!

Mike at KCA .... www.kcanostubes.com

Thanks Myles. I found that they have a NOS Mazda 6V6G for sale. Is this the same as a NOS Mazda 6V6, or is it a different tube, with different tone characteristics. I'm looking for a blues tone in my Univalve, using a 12AX7, and 12 AT7, and a NOS Mazda 6V6.

 

Will the NOS Mazda 6V6G do the trick?

 

Don

[myles_rose]

Originally posted by mdrs:

Originally posted by myles111:

Originally posted by mdrs:

Myles....I just got a THD Univalve...

 

I'm interested in obtaining a NOS Mazda 6V6, and would also like to have a quality 12 AX7, and a 12AT7.

 

Where would you suggest I buy these?

 

Thanks!

Mike at KCA .... www.kcanostubes.com

Thanks Myles. I found that they have a NOS Mazda 6V6G for sale. Is this the same as a NOS Mazda 6V6, or is it a different tube, with different tone characteristics. I'm looking for a blues tone in my Univalve, using a 12AX7, and 12 AT7, and a NOS Mazda 6V6.

 

Will the NOS Mazda 6V6G do the trick?

 

Don

Mazda had a number of 6V6 tubes ... straight bottle and coke bottle ... all terrific.

 

Be sure to use any 6V6 in the low voltage setting ONLY on the Univalve.

[mdrs]

Thanks Myles! I didn't realize about the low voltage setting issue. Thanks for the heads up.

[myles_rose]

Originally posted by mdrs:

Thanks Myles! I didn't realize about the low voltage setting issue. Thanks for the heads up.

You are quite welcome.

 

Using a 12AY7 in V1 and 12AX7 in V2 with a 6V6 as the output tube is my personal favorite setup by the way.

 

You can also get a 8 to 9 pin adaptor and then also on the low setting use an EL84 and that is also a blast.

[mdrs]

Originally posted by myles111:

Originally posted by mdrs:

Thanks Myles! I didn't realize about the low voltage setting issue. Thanks for the heads up.

You are quite welcome.

 

Using a 12AY7 in V1 and 12AX7 in V2 with a 6V6 as the output tube is my personal favorite setup by the way.

 

You can also get a 8 to 9 pin adaptor and then also on the low setting use an EL84 and that is also a blast.

I'm in trouble!!

 

By the way, Mike was very quick to answer several e mails, and I've already placed an order! As a developing vintage "ampaholic", I thank you for your help, and appreciate the referal to Mike!

 

Now, I'll be e mailing Mike about the adaptor and the EL84.....