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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Thu Jan 02, 2014 5:46 pm
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Andree88 wrote:
wow a lot of answers!
But I'm sorry if I ask it again.. what if I put my GT 6L6S's tubes (now at 60mA) at bias 45 mA? they will die or something like this?
bluesky said that if I bias down my 6L6S I will get more headroom..
shimmilou said that 70 mA (according to plate volt) si considered 'cold bias', or have I misunderstood you? I'm sorry if I did it..

I'm a little lost..

If I buy 6L6R I'm sure of the rating but not for the harmonic sound
If I buy 6L6GC JJ I'm sure of The harmonics sound but I can fine them too early in break up..
what should I do? damn I'm in Italy.. I wish to live in USA :(

thanks a lot guys and I'm so sorry if I don't understand all The help you are givin to me..


Read what I posted earlier:

bluesky636 wrote:
Also, refer to this thread:

viewtopic.php?f=13&t=88475

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Thu Jan 02, 2014 5:49 pm
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bluesky636 wrote:
modwiz wrote:
Apologies if I seem slow. I have the multimeter see at 200 mA. Is this the correct setting? Thanks to all answering.


Repeating what I wrote earlier:

bluesky636 wrote:
There is no way that you can read mA directly on any Hot Rod amp without breaking the connection between the cathode and ground or the plate and the transformer and inserting the meter in line. If you are using the Fender test point, you are measuring across a one-ohm resistor inserted in the cathode circuit of the power tubes and the meter must be set to the lowest voltage scale. If you are reading 60 mV (the Fender spec) across the one-ohm resistor, Ohm's law says you are reading 60 mA total or 30 mA per tube.


Where is a facepalm smiley when you need one? :lol:

That would be for your use Bill. :D

Thanks.

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Thu Jan 02, 2014 5:50 pm
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shimmilou wrote:
Retroverbial wrote:
Funny thing about those "ratings"......the finest 6L6GC's ever made or ever to be made in the entire history of mankind on planet Earth had no such arbitrary grading.

(of course I'm referring to my beloved blackplate RCA's)

:mrgreen:

Arjay


Not arbitrary, there have always been specs for tubes, see the data sheet, it gives the grid voltage, Plate current, trans-conductance, etc.

Oh, the tubes varied as far as specs, but those specs were probably tighter back then. If you did get out-of-spec tubes most people wouldn't know since not many bothered to check them. Hopefully we are a bit wiser these days about biasing. I think that our memories (what's left of them) can be a bit selective about "the good old days" when everything was just peachy. :wink:

A given tube will draw X amount of Plate current at Y grid voltage with Z Plate volts. Using the same grid voltage and Plate voltage in an amp, if two tubes have two different Plate currents, that means that you would have to increase the grid voltage on one tube to match the Plate current of the two tubes, and that means that the increased grid voltage will change the way that the tube conducts when an AC signal (guitar) is applied, resulting in a different onset of breakup for one tube vs the other. So, biasing the differently rated tubes to the same Plate current and Plate voltage requires a different grid voltage for each tube, and as we know, the grid voltage is "wiggled" by the applied AC signal from the guitar.


I said arbitrary GRADING.

RCA's superb bottles had no nebulous stats written by advertising hypists and marketing clowns, most of whom wouldn't know the friggin' difference between a B+ and a B-52. Those specious ratings for contemporary wünder-tubes tossed about with all the accuracy of a casually-flicked booger are no more than a PR puff sheet.

:lol:

Arjay

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Thu Jan 02, 2014 6:00 pm
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modwiz wrote:
Where is a facepalm smiley when you need one? :lol:

That would be for your use Bill. :D

Thanks.


No need.

You're welcome.

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Thu Jan 02, 2014 6:03 pm
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Retroverbial wrote:
shimmilou wrote:
Retroverbial wrote:
Funny thing about those "ratings"......the finest 6L6GC's ever made or ever to be made in the entire history of mankind on planet Earth had no such arbitrary grading.

(of course I'm referring to my beloved blackplate RCA's)

:mrgreen:

Arjay


Not arbitrary, there have always been specs for tubes, see the data sheet, it gives the grid voltage, Plate current, trans-conductance, etc.

Oh, the tubes varied as far as specs, but those specs were probably tighter back then. If you did get out-of-spec tubes most people wouldn't know since not many bothered to check them. Hopefully we are a bit wiser these days about biasing. I think that our memories (what's left of them) can be a bit selective about "the good old days" when everything was just peachy. :wink:

A given tube will draw X amount of Plate current at Y grid voltage with Z Plate volts. Using the same grid voltage and Plate voltage in an amp, if two tubes have two different Plate currents, that means that you would have to increase the grid voltage on one tube to match the Plate current of the two tubes, and that means that the increased grid voltage will change the way that the tube conducts when an AC signal (guitar) is applied, resulting in a different onset of breakup for one tube vs the other. So, biasing the differently rated tubes to the same Plate current and Plate voltage requires a different grid voltage for each tube, and as we know, the grid voltage is "wiggled" by the applied AC signal from the guitar.


I said arbitrary GRADING.

RCA's superb bottles had no nebulous stats written by advertising hypists and marketing clowns, most of whom wouldn't know the friggin' difference between a B+ and a B-52. Those specious ratings for contemporary wünder-tubes tossed about with all the accuracy of a casually-flicked booger are no more than a PR puff sheet.

:lol:

Arjay


I stand by what I responded earlier to shimmilou:

bluesky636 wrote:
Not sure that I agree (though I'm not sure how to prove it).

You are only considering plate current, but what is the plate voltage at that current rating? Seems to me that the percentage of max plate dissipation that the two example tubes are biased at is the determining factor of when they break up. If the lower rated tube is biased at 70% and the higher rated tube is biased at 70%, both plate current and plate voltage will be different, but both tubes will still be putting out about 21 watts at idle (for a 6L6GC). I think the rating is only a concern for non-adjustable fixed bias amps like early Blues Deluxes/Devilles (I think the Hot Rods were always adjustable, right?) and Mesas.

Like I said, I have never ordered tube based on their ratings. I just bias them up to about 70% and wail! :lol: :lol: :lol:

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Thu Jan 02, 2014 7:01 pm
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Walked a half mile throught he snow to go to my mailbox and get my tubes. Instead of two 5881's I got a 5881 and a 6v6. :shock: They are a matched pair. I am hesitant to put these separate tube types in together. Am I just ignorant?

I know you can use certain 6v6 in this 6l6 amp, but mixing and matching? :?:

Sent an email but will not get a reply until tomorrow.

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Thu Jan 02, 2014 7:04 pm
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Quote:
RCA's superb bottles had no nebulous stats written by advertising hypists and marketing clowns, most of whom wouldn't know the friggin' difference between a B+ and a B-52. Those specious ratings for contemporary wünder-tubes tossed about with all the accuracy of a casually-flicked booger are no more than a PR puff sheet.

:lol:

Arjay


This is metaphor heaven. :D

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Thu Jan 02, 2014 7:36 pm
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I wouldn't mix a 5881 and a 6V6. :shock: What brands?

Can't be a matched pair if two different types. :wink:

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Thu Jan 02, 2014 7:39 pm
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Retroverbial wrote:
...the accuracy of a casually-flicked booger...


Or worse yet, the casualty from an accurately flicked booger........eeewww!

:lol:

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Thu Jan 02, 2014 7:44 pm
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shimmilou wrote:
I wouldn't mix a 5881 and a 6V6. :shock: What brands?

Can't be a matched pair if two different types. :wink:


They are both TS tubes. They are a matched pair with the number 26 on them. According to the tube store this number indicates the plate current that they measured. This comes with the little booklet they send with the tubes.

This is more than my newbie tech brain can handle. :lol:

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Thu Jan 02, 2014 8:11 pm
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modwiz wrote:
shimmilou wrote:
I wouldn't mix a 5881 and a 6V6. :shock: What brands?

Can't be a matched pair if two different types. :wink:


They are both TS tubes. They are a matched pair with the number 26 on them. According to the tube store this number indicates the plate current that they measured. This comes with the little booklet they send with the tubes.

This is more than my newbie tech brain can handle. :lol:


No, they are not a matched pair. A 5881 is a 25 watt tube (or 30 if it is really a 6L6GC in disguise) and a 6V6 is either a 12 or 14 watt tube depending on the version.

They are from the Tube Store? That is really lame. :roll:

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Thu Jan 02, 2014 8:13 pm
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bluesky636 wrote:
They are from the Tube Store? That is really lame. :roll:


+1

At best, very unusual. It's not even Super Bowl weekend.

:lol:

Arjay

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Thu Jan 02, 2014 8:31 pm
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To say I am displeased at this tubestore situation would be an understatement. I look forward to their email reply tomorrow.

I think. :roll:

I am perplexed. I'll hold off on disgust until I get some answers.



I walked a half mile through 6 inches of snow for this? :lol:

I'll go see which my 12at7's sound better in V3. I'll also look for a VDC setting on the multimeter. Might try one in V1 too. The 5751 is working well but perhaps the at7 will make it all George Bensony. :wink:

Thanks to all.

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Thu Jan 02, 2014 9:29 pm
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modwiz wrote:
I walked a half mile through 6 inches of snow for this? :lol:


Uphill both ways, I bet too! :lol: :lol: :lol: :lol:

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Thu Jan 02, 2014 10:25 pm
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bluesky636 wrote:
modwiz wrote:
I walked a half mile through 6 inches of snow for this? :lol:


Uphill both ways, I bet too! :lol: :lol: :lol: :lol:


Barefoot......

:wink:

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