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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Fri Jan 03, 2014 12:03 am
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" 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. "


Now that is a first for me. Hey! At least they are both output tubes! :lol:

My bet is, in the 1950's a "matched" pair of tubes = a couple of fried 5881's from an out-of-control B-58 Hustler that augered into the earth.


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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Fri Jan 03, 2014 1:37 am
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Retroverbial wrote:
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:

Arjay



While rolling a cigarette.....in a high wind :lol: :lol: :lol: :lol:

Jerry

Sorry :roll: I couldn't help myself. :mrgreen:

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Fri Jan 03, 2014 5:00 am
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Guys I've set the bias to 50 mA.. 40 mA.. Nothing. The break up of my 6L6S is always at 2,5/3. I think I will buy 6L6R.. At least i have 'rating 8' than try a pair of JJ 6L6GC that maybe breaks up at 2,5 level like my actual tube (waste of money) :(
I hate what italians say to me 'impossible to know rating of JJ, Tung Sol etc...'

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Fri Jan 03, 2014 8:08 am
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Do these suppliers offer "Matched Pairs" or "Matched Quads" of tubes? If so, I would ask how in the he!! they match them without measuring the current, and if they do measure the current, please tell you WTF they don't put the number on the box.

The tubes rating is simply a current draw and sometimes a Gm (transconductance), it is very simple, nothing mysterious or arbitrary, and nothing to do with hype. Every supplier of tubes from which I've ever bought puts some type of rating on the tube or box, and yes even NOS tubes will have some kind of rating.

Makes me wonder why Leo put balance pots, and then bias adjust pots on his amps during the magical age of perfect tubes. :wink:

Andree88 wrote:
Guys I've set the bias to 50 mA.. 40 mA.. Nothing...


Yeah, you will definitely get earlier breakup when setting the bias that low, try going higher, like 85 mA. But likely, due to the low tube rating, you will still get early breakup, proving the point that I made about the tube's rating affecting the breakup point.

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Fri Jan 03, 2014 8:15 am
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Andree88 wrote:
Guys I've set the bias to 50 mA.. 40 mA.. Nothing. The break up of my 6L6S is always at 2,5/3. I think I will buy 6L6R.. At least i have 'rating 8' than try a pair of JJ 6L6GC that maybe breaks up at 2,5 level like my actual tube (waste of money) :(
I hate what italians say to me 'impossible to know rating of JJ, Tung Sol etc...'


If you are measuring 40 to 50 millivolts at the Fender test point, you may have the tubes biased so cold that they are into crossover distortion which sounds like crap.

Have you tried lower gain tubes in V1/2/3? I have a Blues Deluxe Reissue which is similar to the HRD with JJ 6L6GC power tubes biased at about 68% max plate dissipation (I have no idea what the rating is, nor do I care). But I also use either a NOS 12AY7 or NOS 5751 in V1. I have no problem getting a clean tone out of the amp at higher settings than you seem to be using.

I'm not sure what you are expecting or what you are actually hearing when you say you want a clean tone but that the amp is breaking up too early. That amp is perfectly capable of running clean and reasonably loud, but it is not going to be as loud as the amp can be when it is cranked. If you want clean and LOUD, you probably have the wrong amp and need to look at something like a Twin Reverb Reissue. Your ears will be bleeding before that amp ever breaks up.

By the way, without measuring plate voltage, as was explained in the thread that I referred to (twice) in this thread, you have no idea where your tubes are really biased at and if the amp is even capable of being biased properly. You are only getting half the story. Saying your tubes are biased at "50 mA" means absolutely nothing without knowing the plate voltage that is measured at that cathode current.

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Last edited by bluesky636 on Fri Jan 03, 2014 8:23 am, edited 1 time in total.

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Fri Jan 03, 2014 8:22 am
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bluesky636 wrote:
... That amp is perfectly capable of running clean and reasonably loud....


Use higher rated output tubes and likely it will. Even better with the lower gain preamp tubes that I recommended at the beginning of the thread.

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Fri Jan 03, 2014 8:37 am
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I just looked at my little box of tubes. I have one matched pair of JJ 6L6GCs rated at Ip = 45 mA, one matched pair of JJ 6L6GCs rated at Ip = 60 mA; two unmatched JJ 6V6Ss rated at Ip = 25 mA and 26 mA, a matched pair of JJ 6V6Ss rated at Ip = 28 mA, and a matched pair of EH 6V6GTs rated at Ip = 33 mA. I don't know what the E34Ls in my Wrecking Ball are rated at as I no longer have the boxes. In all cases I have biased these tubes at about 68 to 70% of maximum plate dissipation. I set all of my amps to get a clean tone with the guitar volume at about "6" (the amps all end up around "5" or "6") and ride the guitar volume to get "clean to mean" sounds. I have no problem getting a clean sound at lower levels or a nice, creamy breakup (to raging overdrive in the Wrecking Ball :lol: ) at higher levels.

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Fri Jan 03, 2014 9:03 am
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Yeah, it seems odd that the tube suppliers in Italy don't have some sort of rating on their tubes. Maybe they do and the OP didn't ask the right question?

Love the "raging overdrive" in my B* also. Image

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Fri Jan 03, 2014 9:12 am
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shimmilou wrote:
Yeah, it seems odd that the tube suppliers in Italy don't have some sort of rating on their tubes. Maybe they do and the OP didn't ask the right question?

Love the "raging overdrive" in my B* also. Image


But my point is, I have never asked for tubes with a specific "rating" or "grade". I buy all of my JJs from Eurotubes (incidently, the two 6L6GCs rated at Ip = 45 mA were the two cryo tubes you sent me). They send me matched pairs (within 3 mA or less). I bias them where I want them. End of story.

nI no other forum I regularly participate in does tube grade or rating enter into a biasing discussion. We are usually arguing over biasing via plate voltage/cathode current measuring or using an o-scope to stay out of crossover distortion. :lol: :lol: :lol:

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Fri Jan 03, 2014 9:16 am
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Well you're knee deep in a discussion now. :lol: First time for everything. :wink:

I am obviously not doing a good job of explaining the ratings, but non-the-less the info is there for your consideration.

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Fri Jan 03, 2014 9:49 am
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shimmilou wrote:
Well you're knee deep in a discussion now. :lol: First time for everything. :wink:

I am obviously not doing a good job of explaining the ratings, but non-the-less the info is there for your consideration.


Sorry, I still maintain (as I said earlier) that tube "grade" is only of concern with non-adjustable fixed bias amps. Take a look at the tube kits for different amps on the Eurotubes website. The only time tube grade is mentioned (they just say hot/warm/cool) is for amps that are non-adjustable fixed bias, i.e.; Mesa, Pro/Blues Jr, and similar amps. For all other kits they provide matched pairs that you then bias to taste. Groove Tubes even implies that you can install the same grade tube in your adjustable fixed biased amp and make no adjustments to the bias setting!

If you have never read it, you should read Randall Smith's article on tube biasing. This article is brought up often on TGP after which a bar room brawl usually erupts. :lol: :lol: :lol:

http://www.mesaboogie.com/US/Smith/biasadjust.html

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Fri Jan 03, 2014 9:54 am
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Hey guys.. Finally I've found someone that said to me the rating of tubes.. 6L6GC STR Tung-Sol with lp 40.. Are them 'hard' (or 'high' like GT says) with the max headroom, right??

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Fri Jan 03, 2014 10:08 am
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Who knows. Groove Tubes is the only tube dealer (they are not a manufacturer) that applies grades like that.

I really think you are wasting your time (I know shimmilou will disagree with me). You should ignore these so-called "grades" and buy a good pair of closely matched tubes and bias them PROPERLY as I have described twice already in this thread. Couple those power tubes with a low gain 12AY7 or 5751 in V1. I firmly believe that will get you where you want to be.

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Fri Jan 03, 2014 10:29 am
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Andree88 wrote:
Hey guys.. Finally I've found someone that said to me the rating of tubes.. 6L6GC STR Tung-Sol with lp 40.. Are them 'hard' (or 'high' like GT says) with the max headroom, right??


Based on my experience with many amps, and the HRDlx in particular, 40 is actually the number that I think will be perfect, just on the hard side but not so much as to be too "stiff". :D

For maximum benefit, try those lower gain preamp tubes while you are swapping tubes, and be sure to bias the output tubes properly.

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Post subject: Re: Tubes for Hot Rod Deluxe III for max headroom?
Posted: Fri Jan 03, 2014 10:38 am
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bluesky636 wrote:
...If you have never read it, you should read Randall Smith's article on tube biasing...


Yes, read it many times, and he does an excellent job of explaining the ratings. Maybe you're over thinking it, it is quite simple. It is absolutely true that when using tubes of the same rating, such as GT or Mesa does, you can install the new tubes of the same rating as the old with no adjustment needed for the bias. Notice that when you put in tubes with a different rating, even the same brand, you have to adjust the bias. This is because, as I've tried to explain, a different grid voltage is required to achieve the same Plate current between the two different grades. It's math, not voodoo. 8)

BTW, as you pointed out, your dealer put ratings on the tubes also. So, it is not just GT or MB that puts ratings on the tubes. Every place that I buy tubes from puts a rating number on nearly every output tube that I buy, and I don't even have to ask for it, it's standard procedure. They have to measure something in order to match the tubes, otherwise they would have to be great guessers. :)

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