The first seems to be the Test Current. They run 56mA through the tube. They put a 1V change on the grid. They observe 5.1mA or 5.0mA change of current from a 1V change of grid voltage.
56mA is perhaps just convenient on their tester. It also depends on the tube. Little tubes would have to be tested at a few mA. BIG tubes might be run at 300mA, and should be tested in that area.
In professional amplifiers (with NFB), 10% and maybe 20% difference push/pull or left/right should be hardly any difference. Today the 300B is often run no-NFB, so 5.1/5.0 could be a 0.17dB left/right unbalance. Which is far less than many other stereo tolerances (especially speaker-room-listener). This match is very-good.
I have >10,000 days in, and I still have more questions than answers.
I do think you are a bit "young" (in this field) to be messing with $170 tubes. There is much joy in $20 tubes, and far less tears when something goes wrong (happens a lot).
given its SE, I wouldn't bother with matching pairs. Its likely your ears are more unmatched than a pair of randomly selected tubes from the same production batch. Without a doubt, if the equipment is in a normal room at home the placement of furniture and other surfaces (not the least your listening position) will make a bigger difference than a couple of mA/V
Thanks!
DRC mate, night and day difference
Music streamer Opt/USB > DSP > Sub/Tubes
Really hard to integrate a sub and do room correction without a DSP.
Home & Professional Audio — Dirac
In my experience, changing the driver tubes within the same model does the most effect, but it's still a very small difference. Output tubes make even a smaller difference, and for inverter tubes if there is a difference, it's so small i can't hear it.
If you change the model (not the brand but the layout), differences are way bigger. I have a Prima Luna Prologue 4 wich automaticly adapt to different pentode output tubes, and changing the stock EL-34 for KT88's did make a bigger change than when i swapped the driver 12ax7's for other 12ax7. I changed back to EL-34's because i like them more btw...
If you change the model (not the brand but the layout), differences are way bigger. I have a Prima Luna Prologue 4 wich automaticly adapt to different pentode output tubes, and changing the stock EL-34 for KT88's did make a bigger change than when i swapped the driver 12ax7's for other 12ax7. I changed back to EL-34's because i like them more btw...
Hi,
I'm a relative newcomer to building hi-fi valve amps too. I've spent the last few months designing and building a simple, single-ended amp. With several shovelfuls of advice and assistance from the good people here I'm appproaching a finished product which actually reproduces music 'properly'
It's been my experience that this forum is one of the few places online where you can find good advive from people who know what they're talking about, a lot of whom have already responded in this thread.
That said, if you're really serious about learning valve circuits, for my money the best thing you can do is read some published books on the subject.
'Valve Amplifiers' and 'Building Valve Amplifiers', by Morgan Jones are both indispensible, along with anything by Merlin Blencowe (aka 'The Valve Wizard - How to design valve guitar amplifiers - I hope his name really is Merlin
). He's a frequentt contributer here.There's also Van Valkenburgs 'Basic Electronics', over 5 volumes, which I think was the US standard text for 'tube' electronics back when transistorised guff was still a bad dream
. I'm slowly working my way through that one, although I might not have the title exactly right. There's a good sticky link at the top of this forum which will lead you there.As for tube rolling, it's already been covered here but I think the internet as a whole confuses the requirements of a valve guitar amp with the requirements of a hi-fi valve amp.
A good guitar amp promotes distortion in a way which pleases our ears. Swapping valves may well produce a change we like, but the change will be caused by moving the valves operating parameters away from the optimum (assuming it was operating there in the first place!).
Randomly swapping valves in a properly designed/implemented hi-fi amp is a step n the wrong direction, as explained already here by many who know more than I.
I've long suspected the vast majority of people who're into tube rolling are either trying to sell us something or don't know what they're talking about
.Good luck with your build. It seems what you'e setting out to do is a good deal more complicted than what I've been up to, but you have the advantage of working from proven designs. Take it steady and be careful of those voltages and I'm sure you'll be fine.
Matt.
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My original plan was to build an Elekit TU-8200, but I found the retail experience less than satisfying, and the Yaqin 300B ebay guy responded quickly and sent me the amp from HK > Syd in 3 days (order to door) for just slightly more than the Elekit TU-8200.
I can figure out schematics, but I'm not a proficient reader and nowhere near a designer. So I would have preferred to build something, but I can't build something as pretty as the Yaqin... it sounds pretty good too.
So I'm at the stage of just understanding and next maybe to reverse engineer... the schematic I posted on the previous page is similar but they've done some revisions and changed parts.
If there are any full kits with a "pretty" looking case, I'm all ears. Sourcing transformers, caps, shells is a bit too involved... I spent months building/adapting the shell for my nixie clock (still has issues), and a day when it came with an acrylic shell.
HiFi amp tube rollers are just as passionate as the musicians when it comes to describing the changes... I have no experience so I really can't comment at this stage, just gathering intel.
I have waiting to be read:
Morgan Jones; Building Valve Amplifiers
John Linsley Hood; Valve and Transistor Audio Amplifiers
I can figure out schematics, but I'm not a proficient reader and nowhere near a designer. So I would have preferred to build something, but I can't build something as pretty as the Yaqin... it sounds pretty good too.
So I'm at the stage of just understanding and next maybe to reverse engineer... the schematic I posted on the previous page is similar but they've done some revisions and changed parts.
If there are any full kits with a "pretty" looking case, I'm all ears. Sourcing transformers, caps, shells is a bit too involved... I spent months building/adapting the shell for my nixie clock (still has issues), and a day when it came with an acrylic shell.
HiFi amp tube rollers are just as passionate as the musicians when it comes to describing the changes... I have no experience so I really can't comment at this stage, just gathering intel.
I have waiting to be read:
Morgan Jones; Building Valve Amplifiers
John Linsley Hood; Valve and Transistor Audio Amplifiers
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I think that if you're looking to build from a kit, you just need to find the right kit for your needs and build it verbatim.
If you'e looking to swap out any parts or make changes to the circuit as a whole you'll need to bite the bullet and do enough reading to know which changes you might want to make and why.
I've been tinkering with valve amps for a long time (admittedly from a guitarists perspective), but all I've really been doing is arbitrarily swapping one part for another, on the strength of what the internet tellls me sounds 'better'.
A couple of years ago it finally dawned on me that what I was doing was largely pointless, and I resolved to teach myself as how to do things properly.
It's been a long road and I'm far from a final destination but I'm slowly getting a handle on the differences between some of the perceieved 'wisdom' about valve circuit design and it's realities, especially concerning valve hi-fi.
Hi-fi tube rollers may be every bit as passionate about things as guitarists/musicians/etc, but as your signature ably notes, opinions are as common as the people espousing them, and generally no more valid.
I can only speak for myself, but the time I've invested learning the basics has paid dividends I still don't properly understand a tenth of what's discussed here, but each new concept I get my head around broadens my understanding of something else that was previously a mystery. It's a fascinating and enlightning journey and I can't recommend it enough...
.Re your books, Morgan Jones 'Building Valve Amplifiers' focuses on the practical concerns of assembling a valve amp - in great detail. Follow his advice and you can't go wrong. His other book, 'Valve Amplifiers' teaches you how to design them. For the beginner, the two should be read as a pair.
As a final note (my apologies, I take a long time to say very little
), the aesthetics of an amp should probably be your final concern.Mine currently looks like this:
I suspect most people here have dedicated test rigs for prototyping, I built mine from what I had lying around my worshop. When I finalise the circuit, I'll build it a new home. Ultimately, it's being integrated in to an old music centre I inherited from my wife's grandad, which is a handsome piece of furniture but utterly uselesss from an audio perspective.
Again, good luck with the build.
Matt.
Whoops...
Just realised, I've conflated (is that a word?) two threads I've been following and you're not the guy who's building a KT88 amp.
Apologies for that, my 'advice' was intended for him, and while I stand by it, such as it is, it may not be entirley relevant here.
They don't call me the lefthandfool for nothing...
Matt.
Just realised, I've conflated (is that a word?) two threads I've been following and you're not the guy who's building a KT88 amp.
Apologies for that, my 'advice' was intended for him, and while I stand by it, such as it is, it may not be entirley relevant here.
They don't call me the lefthandfool for nothing...
Matt.
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Matt,Just realised, I've conflated (is that a word?) two threads I've been following and you're not the guy who's building a KT88 amp.
Apologies for that, my 'advice' was intended for him, and while I stand by it, such as it is, it may not be entirley relevant here.
They don't call me the lefthandfool for nothing...
Matt.
1 - conflated is a word.
2 - some very good advice in your longer posts. Taking time to study and learn is always the better approach. I applaud your efforts.
Often both in equal measure...
It's a fascinating and enlightning journey and I can't recommend it enough...
Very true. Everyone on these forums takes a different approach. Some build multiple amplifiers a year. Others take many years over each one; I'm one of the latter. It doesn't matter. What matters is the pleasure and satisfaction that we each gain from the process.
Well guess what; I bought some Genalex GL 300B's and did some A<>B testing with PSVANE.
The Genalex look almost identical bar some perforation in the plates.
The Genalex also have fluctuating bias; so my amp requires 0.8v; and the Genalex are constantly moving around 0.789~0.816v the fluctuations were worst when 1st installed. The PSVANE stay at 0.800~0.801v.
Genalex on time with me ~18hrs.
So most importantly how do they sound? Well I am unable to discern any difference whatsoever. I can hear a clear difference between Input 1 and 2 (darker) of the amp, but changing the tubes NADA. There is a slight delay between tube changes, but I can't tell any difference, just like you all said.
So these HIFi tube rollers are tripping, new tubes has been the biggest waste of audio money since buying expensive speaker cables... and my only hope of getting some benefit is if one set of tubes stop working.
The Genalex look almost identical bar some perforation in the plates.
The Genalex also have fluctuating bias; so my amp requires 0.8v; and the Genalex are constantly moving around 0.789~0.816v the fluctuations were worst when 1st installed. The PSVANE stay at 0.800~0.801v.
Genalex on time with me ~18hrs.
So most importantly how do they sound? Well I am unable to discern any difference whatsoever. I can hear a clear difference between Input 1 and 2 (darker) of the amp, but changing the tubes NADA. There is a slight delay between tube changes, but I can't tell any difference, just like you all said.
So these HIFi tube rollers are tripping, new tubes has been the biggest waste of audio money since buying expensive speaker cables... and my only hope of getting some benefit is if one set of tubes stop working.
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Hi Raybies, I don't think tube rollers are tripping, after all, tubes are the engine of the amplifiers, the ancestor of the transistors, a steam engine to a gas engine.
If you do tube rolling you might like some more than others for the wrong reasons. With the premise that you want to improve the sound, there is only one way, through better matching, better distortions and better linearity of the amplifier curves and stability.
Only a precise measure of distortion and inter-modulations can help you choose better tubes. Guessing by ear will be only guessing, but very fun!
I tube rolled 5751 to replace a similar 12at7 in a Chinese SET input. Bought like 20 GE, 7 Sylvanas and 2 or 3 others ! I found by trial and error the ones I liked the most.
The 6sn7 is not going to make a(any?) difference as a "follower" but trust me in 20db feedback amps when I switch the input 6sn7 from a premium tung-sol to a NOS (ken rad or rca or any premium matched dark) it totally TRANSFORM the amp into something more liquid, clear and detailed with a measurable 5-8db improvement in distortions! from one gain stage!
Tube rolling the 300b will be very expensive...
If you do tube rolling you might like some more than others for the wrong reasons. With the premise that you want to improve the sound, there is only one way, through better matching, better distortions and better linearity of the amplifier curves and stability.
Only a precise measure of distortion and inter-modulations can help you choose better tubes. Guessing by ear will be only guessing, but very fun!
I tube rolled 5751 to replace a similar 12at7 in a Chinese SET input. Bought like 20 GE, 7 Sylvanas and 2 or 3 others ! I found by trial and error the ones I liked the most.
The 6sn7 is not going to make a(any?) difference as a "follower" but trust me in 20db feedback amps when I switch the input 6sn7 from a premium tung-sol to a NOS (ken rad or rca or any premium matched dark) it totally TRANSFORM the amp into something more liquid, clear and detailed with a measurable 5-8db improvement in distortions! from one gain stage!
Tube rolling the 300b will be very expensive...
I did it by ear... but I can also pullout my measuring gear, maybe this weekend.
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