Feel free to ask Myles

FishWater · April 17, 2003

Fabulous! I must've died and gone to Free Information Heaven. Thank you so very much. I'll follow your advice.

myles_rose · April 17, 2003

Originally posted by FishWater:
Fabulous! I must've died and gone to Free Information Heaven. Thank you so very much. I'll follow your advice.

FishWater........

You are more than welcome.

If you do not have my 24 page tube and amp document, just email me at techsupport@groovetubes.com and ask for one, and I will send it as an attachment.

PBBPaul · April 18, 2003

Myles,

As I'm contemplating doing the recap job on my Bandmaster, it occurred to me, what's the best solder to use for max conductivity? I should know this from all the hours I've spent with a soldering iron in my hands but I don't. Is silver solder better than the tin/lead?

Thanks again,

Paul

FishWater · April 18, 2003

Looking for your recommendation re: preamp and driver tubes for my '63 Princeton modded to run JAN Phillips 6L6 outputs (per Jonathan Hill of Mill Hill Audio). She's pushing a Jensen C12N in a repro brown Deluxe cabinet. Ideas?

Frank C · April 20, 2003

Hey Myles,

I have a line on some phillips nos 6L6WGB's that I'm thinking of using in a fixed bias Mesa 290.What are some difference's between svetlana 6L6 and phillips and what rating's should the phillip's be if tested on a digital maxi matcher.Any Problem using them in 290? Thanks Frank C.

myles_rose · April 21, 2003

Originally posted by PBBPaul:
Myles,

As I'm contemplating doing the recap job on my Bandmaster, it occurred to me, what's the best solder to use for max conductivity? I should know this from all the hours I've spent with a soldering iron in my hands but I don't. Is silver solder better than the tin/lead?

Thanks again,

Paul

Paul,

What the amp was done with originally, was conventional everyday solder as you find in most electronics stores.

I'd steer clear of silver solder, sure it is great, but required higher temperatures to work, and this can damage other components nearby.

myles_rose · April 21, 2003

Originally posted by FishWater:
Looking for your recommendation re: preamp and driver tubes for my '63 Princeton modded to run JAN Phillips 6L6 outputs (per Jonathan Hill of Mill Hill Audio). She's pushing a Jensen C12N in a repro brown Deluxe cabinet. Ideas?

FishWater ......... that all boils down to presonal taste. I personally love the C12N speaker in many amps.

myles_rose · April 21, 2003

Originally posted by Frank C:
Hey Myles,
I have a line on some phillips nos 6L6WGB's that I'm thinking of using in a fixed bias Mesa 290.What are some difference's between svetlana 6L6 and phillips and what rating's should the phillip's be if tested on a digital maxi matcher.Any Problem using them in 290? Thanks Frank C.

Frank,

The Svets and Philips are the same design spec wise for the most part. Just find mid rating Philips, and in the Mesa you will be fine.

gearup · April 21, 2003

Hey Myles,

I was wondering if there was any reason or benefit to replacing ALL your pre-amp tubes at the same time. If you know you have a bad tube and just change it will that somehow hasten the demise of the others?

Thanks,

Loren

KHAN · April 21, 2003

Myles, thank you for your recommendation of Doug Preston at Dougs Tubes .

I just placed an order with him, and I must say, he is a pleasure to deal with. I told him that you recommended him.

On your advice (from a previous post), I'm getting (balanced triode) JAN Philips 12AX7WA and JAN Philips 12AT7WC tubes for my '68 (AB763) Bandmaster.

I also ordered a Sovtek 12AX7LPS (balanced) for the phase inverter on my 410 Hotrod Deville.

When I can afford it, I want to get the JAN Philips 6L6WGB's you mentioned earlier.

I made a mistake (before I went deep on your site) and got a matched pair of Svetlana 6L6GC's from The Tube Store .

They seem to be OK, and assuming that I won at "Russian Roulette" (literally ...Svetlana ...Russian Roulette ...get it??? ...never mind)

In general, what do you think of the Svets??

Thank for all your great info. It is very appreciated.

myles_rose · April 21, 2003

Originally posted by gearup:
Hey Myles,

I was wondering if there was any reason or benefit to replacing ALL your pre-amp tubes at the same time. If you know you have a bad tube and just change it will that somehow hasten the demise of the others?

Thanks,
Loren

Loren,

I replace the phase inverter whenever I replace power tubes, as it is a very hard worked tube.

V1 and at times V2, are the main tone and gain stages, and where most noise will start. These are good to replace if you want to change your tone or have a problem, but other than that, if things sound fine, leave them alone.

Tubes for reverb, effects, trem, etc., .... if there is not a problem, leave them alone, and save the money to take you "significant other" out for dinner.

myles_rose · April 21, 2003

Originally posted by KHAN:
Myles, thank you for your recommendation of Doug Preston at Dougs Tubes .

I just placed an order with him, and I must say, he is a pleasure to deal with. I told him that you recommended him.

On your advice (from a previous post), I'm getting (balanced triode) JAN Philips 12AX7WA and JAN Philips 12AT7WC tubes for my '68 (AB763) Bandmaster.

I also ordered a Sovtek 12AX7LPS (balanced) for the phase inverter on my 410 Hotrod Deville.

When I can afford it, I want to get the JAN Philips 6L6WGB's you mentioned earlier.

I made a mistake (before I went deep on your site) and got a matched pair of Svetlana 6L6GC's from The Tube Store .

They seem to be OK, and assuming that I won at "Russian Roulette" (literally ...Svetlana ...Russian Roulette ...get it??? ...never mind)
In general, what do you think of the Svets??

Thank for all your great info. It is very appreciated.

Khan,

Doug Preston at dougstubes.com is a pretty cool fellow. I send most of my East Coast folks to him, and have had nothing but great feedback.

Doug is one of the folks that has great Philips 12AX7 tubes. He tests them very well, and after they go through his VTV unit, they are pretty remarkable. By the way, Mike at www.kcanostubes.com is one of the few other folks that has one of these testers, so he is another source of great tubes, so at least there is more than one choice of folks.

On the LPS for the phase inverter .... make sure this was checked for current, not just gain or TC, as there are a bunch of them out there from a batch that was very low on current drive (the opposite of what we need for a phase inverter), and were VERY inconsistant.

I do not know how this will cut and paste over here, but the test results from the common batch that is not out there in big numbers is as follows:

DATE TUBE B+ volts BIAS volts mA actual TC actual mA spec TC spec Comments

10/23/02 12AX7R2 Sovtek LPS long plate 250 -2 1.0 1440 1.2 1600

1.1 1670

1.2 1690

1.3 1830

0.8 1350

0.7 1320

0.5 1160

0.7 1370

0.5 1110

0.6 1240

Average 0.8 1418 70.00% <- Output average compared to spec tube

High mA % 1.3 108.33% <- Range above of spec tube highest tube

Low mA % 0.5 41.67% <- Range below spec tube lowest tube

Tolerance Range 66.7% 67% <- Lower number is best

The JAN Philips 6L6WGB is killer in your amp.

On The Tube Store, let me just say nothing in regard to them over here ....

The Svet 6L6 and EL-34 tubes can be wonderful, but date codes before mid/early 2002 are a lot better, at least when it comes to testing. These need to be really well tested if new.

KHAN · April 21, 2003

Myles. Thank you for your response. Most people who have valuable info want to keep it that way. You are to be commended for giving away yours so freely.

I look forward to learning more from you in the future.

-KHAN

myles_rose · April 21, 2003

Originally posted by KHAN:
Myles. Thank you for your response. Most people who have valuable info want to keep it that way. You are to be commended for giving away yours so freely.

I look forward to learning more from you in the future.

-KHAN

Khan,

It is really nothing more than self preservation. When I go to a concert with my wife or friends, and the amp is "off", or just night anywhere close to being "right", I complain all during the event, and everybody ends up wishing I were just dead or gone. I found it easier to try to get a higher percentage of amps sounding right.

I also show up at local sound checks for free, and make sure things are right if I am going to be listening so there is no charge for that when I do that.

steve f · April 22, 2003

Myles,

Assuming an amp with a quad of power tubes, outside tubes paired, inside tubes paired.

Suppose I had 4 tubes, 2 reading 40ma and 2 reading 34ma at whatever plate voltage the amp had. If I paired them 40ma+34ma inside, 40ma+34ma outside so I'd have both pairs totaling the same, 74ma in the inside and outside positions, would there be any difference in this setup compared to 4 matched tubes, each at 37ma? In other words would this be a valid method to use when biasing this 4 power tube amp?

FishWater · April 22, 2003

Looking to retube my 65 Bandmaster AB763 over a 1x15 cabinet (Weber California ceramic speaker) for playing blues/roots with a Strat. I don't hit many notes, but I torture them a lot by bending, wiggling and varying pick (and fingernail) attack. Presently, I have GT-labeled Sovtek 5881 outputs, plus EI and OS RCA preamp tubes and unbranded 12AT7 driver of unknown quality - these were inherited from other amps and have never been tested. The amp sounds very big and strong - without much character other than of the REAL CLEAN variety. I've read your primer, and am inclined to switch to Chinese coke bottle Groove Tubes rated #2 for max touch; 12ax7c9 and JJ 12ax7 preamps for inputs "normal" and "vibrato", respectively; and triode-matched 12at7 as a driver. Does this sound appropriate for a guy looking to get lots of "feel" from his rig? Should I worry about which type of tremolo circuit preamp tube I'm running?
--------------------------------------------------------------------------------

FishWater .......

Nice amp by the way.....

First off, loose the GT6L6B® tubes. Keep them as spares. These are robust tubes, but sonically, just about any other tube is nicer in your amp.

On my clients Bandmasters, I use either GT-6L6GE, Tung Sol 5881, 6L6WGB NOS, or GT-6L6S. In the GT's I use a #6 rating at 34 milliamps bias. If you want a more aggressive amp, the 6L6S is what a number of my Bandmaster, Bassman, Twin, and Showman folks use.

Wondering what "aggressive" amp would be like compared to the 6L6WGB NOS sound/feel...Can you give me a hint? I think of Fender tweed amps as aggressive; they have a midrange attack when cranked up; they overdrive and sustain. What would I lose and gain when switching 6L6WGB NOS to JJ 6L6S?

myles_rose · April 22, 2003

Originally posted by steve f:
Myles,

Assuming an amp with a quad of power tubes, outside tubes paired, inside tubes paired.

Suppose I had 4 tubes, 2 reading 40ma and 2 reading 34ma at whatever plate voltage the amp had. If I paired them 40ma+34ma inside, 40ma+34ma outside so I'd have both pairs totaling the same, 74ma in the inside and outside positions, would there be any difference in this setup compared to 4 matched tubes, each at 37ma? In other words would this be a valid method to use when biasing this 4 power tube amp?

Steve,

You don't mention whether the tubes were statically matched or dynamically matched. On dynamically matched tubes, the idle can be off by a measurable amount, but when the tubes have signal, and are in use, their curves are lined up. This is the strong advantage to dynamic matching.

In any case, take the higher tube draw, and bias for that tube.

myles_rose · April 22, 2003

Originally posted by FishWater:

Looking to retube my 65 Bandmaster AB763 over a 1x15 cabinet (Weber California ceramic speaker) for playing blues/roots with a Strat. I don't hit many notes, but I torture them a lot by bending, wiggling and varying pick (and fingernail) attack. Presently, I have GT-labeled Sovtek 5881 outputs, plus EI and OS RCA preamp tubes and unbranded 12AT7 driver of unknown quality - these were inherited from other amps and have never been tested. The amp sounds very big and strong - without much character other than of the REAL CLEAN variety. I've read your primer, and am inclined to switch to Chinese coke bottle Groove Tubes rated #2 for max touch; 12ax7c9 and JJ 12ax7 preamps for inputs "normal" and "vibrato", respectively; and triode-matched 12at7 as a driver. Does this sound appropriate for a guy looking to get lots of "feel" from his rig? Should I worry about which type of tremolo circuit preamp tube I'm running?
--------------------------------------------------------------------------------

FishWater .......

Nice amp by the way.....

First off, loose the GT6L6B® tubes. Keep them as spares. These are robust tubes, but sonically, just about any other tube is nicer in your amp.

On my clients Bandmasters, I use either GT-6L6GE, Tung Sol 5881, 6L6WGB NOS, or GT-6L6S. In the GT's I use a #6 rating at 34 milliamps bias. If you want a more aggressive amp, the 6L6S is what a number of my Bandmaster, Bassman, Twin, and Showman folks use.

Wondering what "aggressive" amp would be like compared to the 6L6WGB NOS sound/feel...Can you give me a hint? I think of Fender tweed amps as aggressive; they have a midrange attack when cranked up; they overdrive and sustain. What would I lose and gain when switching 6L6WGB NOS to JJ 6L6S?

Fishwater ........

Tweed amps, to my thinking, are not agressive, being cathode biased in some cases, and even the A/B amps had 12AY7's in the front end.

A Marshall with a cathode follower tone stage, to me, is agressive and also SS rectified, making it more crisp.

The 6L6S will be more agressive, due to it's rise time and coloration, but I would refrain from using these in a tweed amp personally.

PBBPaul · April 22, 2003

Originally posted by myles111:

Originally posted by PBBPaul:
Myles,

As I'm contemplating doing the recap job on my Bandmaster, it occurred to me, what's the best solder to use for max conductivity? I should know this from all the hours I've spent with a soldering iron in my hands but I don't. Is silver solder better than the tin/lead?

Thanks again,

Paul
Paul,

What the amp was done with originally, was conventional everyday solder as you find in most electronics stores.

I'd steer clear of silver solder, sure it is great, but required higher temperatures to work, and this can damage other components nearby.

Good enough, thank you. I have some of each kicking around.

It's my understanding that the caps don't have to be quite exact replacements. Below is what is in the amp currently and what I can find for replacements. Can you tell me if this will work OK? Should I replace the molded caps as well as the electrolytics?

Power supply filters (under the cover):

Current:

20uF @ 525VDC X 3

70uF @ 350VDC X 2

Replacement?

20uF @ 500 Volts, Sprague # TVA1906

80uF @ 450 Volts, Sprague # TVA1716

On the board:

Current Electrolytics:

25uF & 25uF @ 25VDC X 2

25uF @ 25VDC X 1

Replacement?

25 uF @ 50 Volts, Sprague # TVA1306 X 5

Onthe board:

Current molded:

.1uF 400VDC X 3

.1uF 200VDC X 1

.047uF 400VDC X 3

.1uF 600VDC X 2 (These are not original)

Replacement? (Orange Spragues)

.1uF @ 600 Volts, Sprague # 715P10496L

.1uF @ 200 Volts, Sprague # 715P10492L

.047uF @ 600 Volts, Sprague # 715P47396L

.1uF @ 600 Volts, Sprague # 715P10496L

By the way, I was pleasantly surprised to discover some unused GT6L6S' in my tube box the other night. They sound great in this Bandmaster (except for that bad distortion when cranked).

Thank you again, Myles.

myles_rose · April 23, 2003

Originally posted by PBBPaul:

Originally posted by myles111:

Originally posted by PBBPaul:
Myles,

As I'm contemplating doing the recap job on my Bandmaster, it occurred to me, what's the best solder to use for max conductivity? I should know this from all the hours I've spent with a soldering iron in my hands but I don't. Is silver solder better than the tin/lead?

Thanks again,

Paul
Paul,

What the amp was done with originally, was conventional everyday solder as you find in most electronics stores.

I'd steer clear of silver solder, sure it is great, but required higher temperatures to work, and this can damage other components nearby.
Good enough, thank you. I have some of each kicking around.

It's my understanding that the caps don't have to be quite exact replacements. Below is what is in the amp currently and what I can find for replacements. Can you tell me if this will work OK? Should I replace the molded caps as well as the electrolytics?

Power supply filters (under the cover):
Current:
20uF @ 525VDC X 3
70uF @ 350VDC X 2

Replacement?
20uF @ 500 Volts, Sprague # TVA1906
80uF @ 450 Volts, Sprague # TVA1716

On the board:
Current Electrolytics:
25uF & 25uF @ 25VDC X 2
25uF @ 25VDC X 1

Replacement?
25 uF @ 50 Volts, Sprague # TVA1306 X 5

Onthe board:
Current molded:
.1uF 400VDC X 3
.1uF 200VDC X 1
.047uF 400VDC X 3
.1uF 600VDC X 2 (These are not original)

Replacement? (Orange Spragues)
.1uF @ 600 Volts, Sprague # 715P10496L
.1uF @ 200 Volts, Sprague # 715P10492L
.047uF @ 600 Volts, Sprague # 715P47396L
.1uF @ 600 Volts, Sprague # 715P10496L

By the way, I was pleasantly surprised to discover some unused GT6L6S' in my tube box the other night. They sound great in this Bandmaster (except for that bad distortion when cranked).

Thank you again, Myles.

Paul,

These will all work fine and dandy.

Vantage · April 23, 2003

Reposted from original.

"Hi All.....

I am new to your fine looking forum. I tinker up amps for people. My name is James.

On to the meat of the post.....

I am trying to put together an amp similar to the Hughes and Kettner © Tri-Amp. I am looking for a few differant ideas as to what sounds I should be going for and what the channel setup should be. I am not a very good player myself and have never giged as a guitarist. With that said I have a pretty good grasp on sound and would likke some advice from people who do gig regularly.

First,

assuming 3 distinct PreAmps, what 3 sounds would you like to have in one amp???

Second,

assuming each preamp has 2 channels, would you want 2 distinct channels, one dirtier than the other. Or would you prefer two identicle channels with a seperate gain for each?

Thanks guys. I am "tabulating" these results with others before wrking out my design.

James Ashton"

I was told to "Ask Myles"

myles_rose · April 23, 2003

Originally posted by Vantage:
Reposted from original.

"Hi All.....
I am new to your fine looking forum. I tinker up amps for people. My name is James.

On to the meat of the post.....

I am trying to put together an amp similar to the Hughes and Kettner © Tri-Amp. I am looking for a few differant ideas as to what sounds I should be going for and what the channel setup should be. I am not a very good player myself and have never giged as a guitarist. With that said I have a pretty good grasp on sound and would likke some advice from people who do gig regularly.

First,
assuming 3 distinct PreAmps, what 3 sounds would you like to have in one amp???

Second,
assuming each preamp has 2 channels, would you want 2 distinct channels, one dirtier than the other. Or would you prefer two identicle channels with a seperate gain for each?

Thanks guys. I am "tabulating" these results with others before wrking out my design.

James Ashton"

I was told to "Ask Myles"

James ..........

Best wishes on your "new amp" when it comes out ... keep us all posted.

Chipotle · April 24, 2003

Myles, I'm attempting to make a homemade JTM45 and have decided to do a DC filament supply for the 12AX7's. I'm using a couple extra diodes for voltage dropping. Anyway my question is that loaded with 3 12ax7's the filament voltage is 6.3 volts DC when the AC current is around 115-116 volts, at 120 volts the DC volts rise to around 6.6 volts. Do you think that's within an acceptable range (+ 5%)?

myles_rose · April 24, 2003

Originally posted by Chipotle:
Myles, I'm attempting to make a homemade JTM45 and have decided to do a DC filament supply for the 12AX7's. I'm using a couple extra diodes for voltage dropping. Anyway my question is that loaded with 3 12ax7's the filament voltage is 6.3 volts DC when the AC current is around 115-116 volts, at 120 volts the DC volts rise to around 6.6 volts. Do you think that's within an acceptable range (+ 5%)?

Your range is fine, you can be +/- 20% or more and be fine actually.

Chipotle · April 24, 2003

Originally posted by myles111:
[QBYour range is fine, you can be +/- 20% or more and be fine actually.[/QB]

Thanks, Myles. I appreciate your help.

myles_rose · April 24, 2003

Originally posted by Chipotle:

Originally posted by myles111:
[QBYour range is fine, you can be +/- 20% or more and be fine actually.
Thanks, Myles. I appreciate your help.[/QB]

Chipotle........

You are more than welcome.

Chipotle · April 25, 2003

Myles, I read your review of the Ruby Tubes EL34B-STR and thought I might try either a pair of those or a pair of the GTKT66 HP's in this JTM45 type thing. I was thinking a #4 rating for the KT66's, but how does one specify an equivalent power rating for the Ruby tubes? I was planning on buying from Antique Electronic Supply who do some type of matching for $1 per tube.

myles_rose · April 25, 2003

Originally posted by Chipotle:
Myles, I read your review of the Ruby Tubes EL34B-STR and thought I might try either a pair of those or a pair of the GTKT66 HP's in this JTM45 type thing. I was thinking a #4 rating for the KT66's, but how does one specify an equivalent power rating for the Ruby tubes? I was planning on buying from Antique Electronic Supply who do some type of matching for $1 per tube.

Chipotle .............

In a JTM-45, to my thinking, the KT66HP is the only way to go. It was the original tube.

If your amp has about 400 B+ and a GZ34 rectifier, get these in a #6, and bias at 36mA (some may say bias higher, but then the amp gets a bit harsh at some settings). Make sure V1-V3 are ECC83 and not 12AX7 or 7025 tubes (ECC83's were original and do sound different), and make sure V3 is a matched phase inverter, and not just matched for gain, but matched for rise time also, as in these amps, it is one piece of the magic.

Brambles · April 25, 2003

Myles, I really appreciate you spending so much time sharing your expertise.

I was wondering if you know of a pedal I have in mind: I want to take two inputs of same signal level and blend them into one output of the same signal level. Kind of like a pan pedal, only in reverse. I tried the Ernie Ball volume/pan pedal but it only wanted to pan between the two outputs.

Do you know of such a pedal, or will I need to design one with an electronics wiz?

Thanks again -

myles_rose · April 28, 2003

Originally posted by Brambles:
Myles, I really appreciate you spending so much time sharing your expertise.

I was wondering if you know of a pedal I have in mind: I want to take two inputs of same signal level and blend them into one output of the same signal level. Kind of like a pan pedal, only in reverse. I tried the Ernie Ball volume/pan pedal but it only wanted to pan between the two outputs.

Do you know of such a pedal, or will I need to design one with an electronics wiz?

Thanks again -

Brambles.............

I don't know off the top of my head, but this may be available, and if not, would not be hard to make.

Feel free to ask Myles

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