I suddenly like youI live in west central New Hampshire, about 500 yards from Vermont. With my 40W Blues Deluxe, I can play along with bands playing on the other side of the river, and be heard. Luckily, they haven't tracked me down yet
Took long enoughI suddenly like you
I like that track! Well done.I suddenly like you
I am not in the LEAST surprised! That Blues DL is a very different beast from the 30 watt AC30 type amplifier (which itself is 'king loud!) It runs two 6L6 OP valves at over 400 volts in "fixed bias". Thus the 40W rating is almost certainly its "clean" power output and distortion would be well under 10%. Pushed hard I would expect that amp to put out close to 100 watts.I live in west central New Hampshire, about 500 yards from Vermont. With my 40W Blues Deluxe, I can play along with bands playing on the other side of the river, and be heard. Luckily, they haven't tracked me down yet
I remember reading that the Blues DL is the same circuitry that was in the old Bassman 100W amps. I have not verified it, but I would believe it.Pushed hard I would expect that amp to put out close to 100 watts.
It is my understanding that Groove Tube valves are good quality components that are selected into bias 'batches'. Therefore the set in your BDL will have been chosen to give optimum results, probably a bias current of 25-30mA per valve.I remember reading that the Blues DL is the same circuitry that was in the old Bassman 100W amps. I have not verified it, but I would believe it.
Interestingly, the amp came with 2 GT 6L6-R output tubes. One died. For my use I couldn't justify the $$$ for a matched pair of GLs. so I put a matched pair of JJ 6L6s. I was blown away by the reduction in the output with the JJs vs the GTs. It was immediately noticeable. For my use, it works, but if your gigging? Go with the GTs.
Its not really a tube brand more than finding ones with a certain gain characteristic. Which is always been the downside to a non-adjustable fixed bias circuit. Just like Mesa Boogie amps. They market a set of tubes for them they selected so that they would work with that bias voltage. So when they sold that amp they engineered it so no tubes but their own that they sell work correctly unless you go through trail and error on your own with different tube sets.remember reading that the Blues DL is the same circuitry that was in the old Bassman 100W amps. I have not verified it, but I would believe it.
Interestingly, the amp came with 2 GT 6L6-R output tubes. One died. For my use I couldn't justify the $$$ for a matched pair of GLs. so I put a matched pair of JJ 6L6s. I was blown away by the reduction in the output with the JJs vs the GTs. It was immediately noticeable. For my use, it works, but if your gigging? Go with the GTs
honestly how long do your valves last? Years..Or stay in spec? I kinda like the modded bias tones you can get playing around with it.Pretty much d', the world and his wife hates paying for service people and GT built their business on the idea that you did not need to go amp-in-hand to a technician just to change and bias your OP valves. You do pay over the odds for GT valves however!
Yeah, Ok ..Once adjusted sure. New.But yes, one 6L6 is exactly the same as any other 6L6 (or it should not be called a 6l6!) except that there is a range of grid voltages for any given anode current (at a specified anode and G2 voltage) Once biased to that point the valve will perform to the data sheet spec'.
My EL34 has new EHX tubes and it biased out nice and proper. Power amp kicks ass on everything.I found at least one 100W EL34 amp where I had to mod the bias circuit to get more range to get some samples of OP valve to the specified 25mA.
I don't know details on Marshall amps, only what I can glean from online schematics and they rarely show traff taps!Dave, I got a marshall EL 84 20/20 , with a UK transformer. Is there a cross-reference part that is US wall voltage you might know of? It is a 5 wire transformer.
So I dont need that step up converter box.
But this has 84's. UK gets the goods this time. They are so sweet..use a tiny 6 or 8" celestion or orange speakers..put it in your bedroom..not go deaf..I actually agree with the design practice. That is to supply amplifiers with the correct transformer for their market country.
I thank you, sincerely, for that information. You sent me back to my books. I'm an analog guy, but not a tube person per se.My guess is that the JJs you fitted needed a lower bias voltage and were running very 'cold'. Unfortunately the schematic I find for that amp shows no means of bias adjustment. Should not be an expensive job to have done though.
Ah, that opens a whole new can of worms! The schematic I found is probably an older one, perhaps they put bias pots in the later models. Giving you a value for the bias current is the easy bit. I biased all EL34S, 6L6, KT88 at 25mA. Some folks like to go hotter but you need to watch the anode dissipation, 25W for the 6L6 so for an anode supply of say 430 V 25mA will give you 0.025X 430= 10.75W . Some folks say biasing hotter makes the amp sound "better" but I have never seen any evidence for that. Wasting power and reducing efficiency offends my engineering sensibilities! In any case, amps get hot ENOUGH and heat is the enemy of all components. Hobby horse stabled.I thank you, sincerely, for that information. You sent me back to my books. I'm an analog guy, but not a tube person per se.
I had a Dynaco ST 70. I had replaced the original RCA unmatched tubes with a quad set of Mallards. Part of the installation was adjusting the bias. Never thought that this would be an issue with this amp, but after digging in, I realize that a bias adjustment *should* be in order. I had completely forgotten that the grid bias need be adjusted for each tube set.
Until I actually open the amp up again I won't know for certain. But the videos show that there is a pot for adjusting the grid bias.
That said, how do I know, or find out, what the correct voltage(current) is for the JJs?
Thanks in advance
PS: On my Dynaco, It specified what the bias voltage should be: 1.342V. And that measurement was across a resistor. (I think 1 ohm, but that seems like a lot of current)
That is my first rule of life. 30kV DC was my worst bite. I still have the scar. Your advice is sound, and well taken.You need to be sure you can work safely on high voltage circuits. If so I can give you chapter and verse on setting the bias. A schematic of that actual amp would be a great start but a really good gutshot the next best thing.
What I've read today with regard to the grid being hot or cold, In a "passive" context, a cold grid would be analogous to "a limiter", i.e., resisting the flow of electrons from the cathode to the anode, and vice versa. The hotter the grid, the higher the gain/output.Some folks say biasing hotter makes the amp sound "better" but I have never seen any evidence for that.
That was the number that I've seen floating around for the 6L6.I biased all EL34S, 6L6, KT88 at 25mA.
You are very welcome but I am not sure? Do you want to go ahead and re bias the amp? If so PM me then we can communicate via email. I do not post potentially lethal methodologies on an open forum...some daft ***er will have a go and die!That is my first rule of life. 30kV DC was my worst bite. I still have the scar. Your advice is sound, and well taken.
What I've read today with regard to the grid being hot or cold, In a "passive" context, a cold grid would be analogous to "a limiter", i.e., resisting the flow of electrons from the cathode to the anode, and vice versa. The hotter the grid, the higher the gain/output.
That was the number that I've seen floating around for the 6L6.
I really appreciate your responses, and digging in. I am much obliged. I come from an analogue background, but op-aps and transistors. So, I appreciate the lessons on tubes.