Reply with quote #1
Well, for those of you who did not get the Beasts when you could, if you could. As I said in another post, by the grace of God and a friend, a pair I built about 6 years ago came back to me. I built several pairs for fellows and every single time with just one in mono Helen would say "we NEED these". Then I remind her we can't afford even the tubes. She says "oh, I forget". Well now she has her pair and that is why I feel sorry for those of you who missed the chance to own them. They are simply amazing and I've been around the block with regard to amplifiers. Nothing and I mean nothing (except Dowdy's 30K GM70) even comes close to them. At least in my system. The system is pretty much flat from <25 to >20K and will play at insane undistorted, uncompressed volumes.
This has always been the case in my room but...they are "different". The music at 90db sounds "powerful", not loud. 105db sounds loud but not harsh or strained. Our Pass Labs X150 was similar in most regards, it too was "effortless". I had 2 of them! The Beast is different but similar.............I will never sell them. I will use them until they die or I can no longer afford to run them.....then they will rest but never go away. Ed
Reply with quote #2
I remember hearing the Beats at your house. They are definitely ahead of the rest of the other amps. I never ever heard such an effortless sound coming from your speakers (about the same as mine). I also remember you wishing for years to own a pair of Beast. Well, your wish has been granted. Congrats and enjoy. Greetings from sunny Spain
Reply with quote #3
I am absolutely thrilled that you and Helen got the Beasts, especially knowing how much you enjoyed them. Your speakers sounded fantastic at Hornfest. Musically satisfying both quiet and at rock concert levels with eight tubes per side in the Beast amps. I am still blown away with what you can pull out of a 4" driver.
Eric from Chi-congo
Reply with quote #4
Ed I am glad you finally got your Beasts. I know when I listen to my Beasts I always notice that something is missing???? The amp. it simply seems to disappear. No strain, and no coloration. As you said effortless. As we use to say years ago we just need a wire that amplifies the signal. The Beast is a close to that as I have ever heard. I have heard a lot of amps in the last 45 years and this is the best. A few very expensive amps have come close but this is the top of the heap. Bruce has promised an amp of lower power to replace it that will sound better. A very tall order indeed. For me this is as close to perfection as I will need to get. Thanks Bruce.
Reply with quote #6
Thanks, Dieter, Eric (
) and Sailor for the comments. I have one 509 that will make a sound like a firecracker and open the fuse if I really go for stupid high SPL's. I mean stupid as in excess of 105 db peaks at the couch. 110 is possible! So far the B52's, Skunkweed and the Rolling Stones (Satisfaction) have all caused that one tube to sound like it explodes! The first time is was a surprise....since no damage to anything occurred I just ignored it and continued to play the system at really insane levels! I'm not scared! I have a couple spares and have replaced that tube.............. Kevin, I suggested to Bruce a while back he should sell a version with the chassis only punched for 8 tubes. I see you have done it but I suggested he use the same xformers and leave everything the same. I sort of believe in "overkill" . He said that smaller ones could be used and it seems you have proved the concept! Good job! I will say that they have changed the way I listen to the system. My ACA's I built from scratch and they have no power switch. Neither does my line stage. I only powered it down to change or switch things. It is odd to me that I have to cut the Beasts off and on. Just not used to it and have gotten up many times at night to make sure I did, I'm running about 50/50. ed
Reply with quote #7
It's to bad you can't take the tubes to the old Radio Shack on the corner any more. But I suspect that tube may put out more power than the others and probably is dying an early death. At one time probably 10 years ago Bruce put on the board how to check the tube draw at idle of each tube. At the time it was the original SE/OTL. I think it was measuring the voltage drop across the resistor to ground on the output tubes. But I may be mistaken. The purpose is to find out how balanced the tubes are. If they all read about the same that is good. If they read very different either higher or lower it means the tubes are way different from each other. If I am incorrect I hope Bruce corrects me. Anyway it is how I found out that the spare tubes I purchased from a reputable dealer were at the 2 ends of the bell curve and my original tubes were in the dead center. That is why I always say on the board pay for tube matching or you will get the dealers impossible to match tubes at the 2 ends of the bell curve.
Reply with quote #8
I am about to get more familiar with OTL PP amps. I tried to understand what Ed could have meant with the “fire cracker” tube that blows a fuse when playing over 105dB and what that could mean practically for OTL PP amps in general regarding tube matching. I was also wondering about the tube matching process with PP pairs in this context which Sailor is mentioning.
I am referring to the SOB (p.229, Tubes & Circuits) which shows a fixed bias for the neg pair and an adjustable bias for the pos. pair of tubes. As Sailor wrote, the tubes shouldn’t be too much off (I guess regarding current at same bias settings and not regarding gain?).
My question: How can a pair of output tubes be correctly adjusted with one adjustable A-bias (+)/one fixed A-bias(-) if the tubes have not been already very closely matched (1-5mA) in the actual amp?
Buying matched pairs wouldn’t necessarily help so much as they have been matched at different voltages/bias and often we don’t even know whether they have been matched for gain or current. But of course the “bell curve” thing is a reality no matter how the matched pair performs in the actual amp.
So how can one or even more pp pair(s) of tubes be precisely matched by only adjusting for lowest DC level especially with two output tubes feeding on the same bias pot and with only one adjustable half (SOB)?
In my understanding it will only affect the DC level but the tubes’ Ip will stay pretty much exactly as it is: either very closely matched or more or less apart from each other. And if there is a tube with very high gain or very different current at the fixed bias settings in the mix it will throw off the whole balance at some volume level. It will look like a bad tube/tube failure if the tube blows but it could have been avoided by Ip reading and being able to individually adjust each tubes' bias independently from the DC level at the output.
To measure the drop across the cathode resistor gets pretty close compared to direct Ip reading but it includes also some small amount of grid current. So it’s more conservative by selecting/adjusting tubes relying on this reading which might be a good thing for long tube life.
Could somebody please explain the biasing process in OTL/PP amps in detail?
Reply with quote #9
Wolfgang, what I meant was that at levels approaching 105 db
I had a tube that would arc and pop as loud as a firecracker! It was confined to the left amp and just one tube. Last night when I shut the couch at the amp right a tube did the same thing. It then arced about a minute after powering back up. It was one tube again. I happened to see both flash. I swapped tubes around and put in a spare in that slot. Both amps bias perfectly. It is the tubes themselves. No issues since then. off I think tubes do not like being shipped, especially if they have many hours on them, and mine do, years in fact. It used seems like I remember Bruce and I talking about this. A good while ago. I got nothing for your other questions! Hope this helps. Ed