Got it. I think Davey was a little over-dramatic. I don't know how you would blow up your "tester" and I assume he means your DVM. However, I don't want to play down the hazard with adjusting the bias the way the manual states to perform it. The last Quicksilver Audio amp I owned was a pair of the V4s. I could set the bias on all four output tubes on each amp in about oh, one minute per amp.
Tube gear obsolete??
- Thread starter DaveyF
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Got it. I think Davey was a little over-dramatic. I don't know how you would blow up your "tester" and I assume he means your DVM. However, I don't want to play down the hazard with adjusting the bias the way the manual states to perform it. The last Quicksilver Audio amp I owned was a pair of the V4s. I could set the bias on all four output tubes on each amp in about oh, one minute per amp.
Micro, I am going to give you an idea as to what the ARC manual says regarding the biasing scheme for this amp....which I suspect you may have forgotten about. There are three(3) stages for biasing the amp..1) The output tube idle current, 2) the DC balance and 3) the AC balance. A DVM has to be connected to TP1, TP3 on the V8 tube TP 5 and TP 7 on the V10 tube ( which according to my tech, IF you are not VERY careful can lead to touching a high voltage part that will not result in anything that great) then on the 2nd channel, TP2 and TP 4 on tube V9, and lastly TP6 and TP8 on tube v11....Minor detail here.....According to the manual,the adjustment points are NOT indicated on the circuit board ( Even IF they were, wouldn't help most hobbyists like myself, LOL)
I won't even go into the DC voltage adjustment as it was just way over my head. Something to do with minimum second order harmonic and distortion measuring equipment ( Please do not tell me that you have that gear handy in your home, Micro
)So, I say again, IF you think this biasing scheme is acceptable...
I used to own a Melos tube amp, could bias the KT88's in about two minutes, had a easily accessible screw to turn the bias and a LED light to tell you when it was correct. Simple and effective.The D70Mk2 KILLS that amp, BUT I truly cannot see how anyone can argue that the biasing scheme on the D70Mk2 is anything but insane for the consumer...maybe great for ARC tech's.
Micro, I am going to give you an idea as to what the ARC manual says regarding the biasing scheme for this amp....which I suspect you may have forgotten about. There are three(3) stages for biasing the amp..1) The output tube idle current, 2) the DC balance and 3) the AC balance. A DVM has to be connected to TP1, TP3 on the V8 tube TP 5 and TP 7 on the V10 tube ( which according to my tech, IF you are not VERY careful can lead to touching a high voltage part that will not result in anything that great) then on the 2nd channel, TP2 and TP 4 on tube V9, and lastly TP6 and TP8 on tube v11....Minor detail here.....According to the manual,the adjustment points are NOT indicated on the circuit board ( Even IF they were, wouldn't help most hobbyists like myself, LOL)
I won't even go into the DC voltage adjustment as it was just way over my head. Something to do with minimum second order harmonic and distortion measuring equipment ( Please do not tell me that you have that gear handy in your home, Micro
So, I say again, IF you think this biasing scheme is acceptable...
I used to own a Melos tube amp, could bias the KT88's in about two minutes, had a easily accessible screw to turn the bias and a LED light to tell you when it was correct. Simple and effective.The D70Mk2 KILLS that amp, BUT I truly cannot see how anyone can argue that the biasing scheme on the D70Mk2 is anything but insane for the consumer...maybe great for ARC tech's.
DaveyF,
The adjustements referred in 2) and 3) should not be carried by users! They are set at factory and can be fine tuned, but as you say you need to have expertise to make them and instruments - that I surely have (you can also have it for free if you have a good soundcard and a PC) . How do you thing I check all my tube equipment and select tubes?
Many amplifiers have very crude and approximate biasing systems, accepting that small current unbalances in the push pull transformer do not affect performance. ARC considers that it is better to use a more accurate and less convenient system. And yes, I also biased my D70 in less than two minutes (after a five minute mandatory warm-up ...)
Micro, the manual states as follows in regards to the DC balance...IF input tubes V2 or V3 are changed the DC balance has to be adjusted. It then goes on to say:" If any tubes are changed the AC balance should be checked" and adjusted if necessary. I guess in ARC's defense they do say in the manual: " The following internal procedures ( here they are referring to the biasing) should not be attempted by the owner unless he is TECHNICALLY QUALIFIED. There are high voltages and currents within this unit which can be lethal under certain conditions. All internal adjustments should be accomplished by a qualified individual." So, I guess all the info on biasing is NOT meant for the typical hobbyist to attempt, OTOH...I think this is NOT that acceptable in a tube amp that will obviously need re-biasing as a) the tubes age and b) the tubes need to be replaced.
BTW, I know this sounds like I am ****ing on ARC, BUT in actuality I think that this amp is so great that the crazy biasing scheme is NOT that much of a factor to me..plus, i would say the same about ANY manufacturer who did the same thing to their tube amp consumer.
I don't think changing tubes in most tube amps is an annual occurrence...at least it shouldn't be. I know Sam may not agree...But
Thought you'd slip that by me...huh, Davey?
Well, truth be told, I derive irrational pleasure from characterizing tubes -- LOL
In fact, I'm contemplating a rig where I can characterize a tube's noise vs frequency content
Thought you'd slip that by me...huh, Davey?
Well, truth be told, I derive irrational pleasure from characterizing tubes -- LOL
In fact, I'm contemplating a rig where I can characterize a tube's noise vs frequency content
Sam, you are one sick pup, LOL
I thought I was bad with this tube stuff
Thought you'd slip that by me...huh, Davey?
Well, truth be told, I derive irrational pleasure from characterizing tubes -- LOL
In fact, I'm contemplating a rig where I can characterize a tube's noise vs frequency content
Well, I have done it since long. It is also very useful to check microphonic tubes. It also helps to explain why some tubes sound better after burn-in.
DaveyF,
Sorry for my insistence, but I fail so see why the adjustments you refer are "crazy". Adjusting DC points to 90V is a simple adjustment. And the AC balance is just tweaking a pot looking for a distortion meter needle. The amplifier will perform excellently even without them. Also if you used ARC sourced and closed matched tubes these adjustments would not be needed - they were included as a convenience for users who wanted to have their amplifiers re-tubed using non specially selected tubes.
A pity your technician is afraid of the D70.
You should ask him to suppress the triode inverter at the input and connect the D70 with a XLR using the fully balanced cross coupled mode with a balanced source. It sounds really fantastic, better than in single-ended mode.Micro, I don't think my tecb is afraid of the amp, he's just commenting on how crazy it is to expect the "non-technically" inclined to handle these adjustments.
I have noticed that all of the new ARC gear ONLY runs in balanced mode ( or at least with balanced connections only). Like Mark said, my CAT only has single ended inputs and outputs. Since you are using a REF150, and I presume that you did do the conversion on your D70Mk2 to balanced, could you give us an idea as to how that amp would compare today with your Ref 150. Any thoughts on the comparo between the Ref 75 ( If you have heard it) and your amp or the D70mk2 ?
I have noticed that all of the new ARC gear ONLY runs in balanced mode ( or at least with balanced connections only). Like Mark said, my CAT only has single ended inputs and outputs. Since you are using a REF150, and I presume that you did do the conversion on your D70Mk2 to balanced, could you give us an idea as to how that amp would compare today with your Ref 150. Any thoughts on the comparo between the Ref 75 ( If you have heard it) and your amp or the D70mk2 ?
Sam, you are one sick pup, LOL
I thought I was bad with this tube stuff
Haha, Davey
I've got this cool lab gear that I thought I could incorporate into the afflict -- no, um, avocation...yeah, that's it (channeling Jon Lovitz)
The main question when making this type of adjustments is using adequate tools. If you do not use the appropriate insulated tools and clips and a good pair gloves to protect your hands you risk burning yourself and damaging the amplifier. Thin leather gloves are mandatory.
I did not have the D70 anymore by the time I got the REF 150, a direct comparison was not possible. But, when used with the appropriate ancillaries the REF150 is a much more complete and extended amplifier than the D70. IMHO, even the old VT150's monoblocks bettered the D70 by a reasonable margin. One often forgotten great preamplifier of ARC is the LS5 mk3. Although the original and the mk2 were not my cup of tea, the mk3 was a great unit and was a great match with the D70 or the VT150. BTW, the major improvement in the balanced D70 was the bass control. The conversion is very simple and can be easily reverted later if desired.
Hi micro,
Very cool
A noise tester, similar to this, is being constructed for me: http://www.youtube.com/watch?v=tx0G_ObVwn4&list=UUIGQDUXm67v44o6E7wXUGkQ
By any chance, would you have any familiarity with the HP 35665A Dynamic Signal Analyzer?
Hi micro,
Very cool
A noise tester, similar to this, is being constructed for me: http://www.youtube.com/watch?v=tx0G_ObVwn4&list=UUIGQDUXm67v44o6E7wXUGkQ
By any chance, would you have any familiarity with the HP 35665A Dynamic Signal Analyzer?
Sam,
Looking only on the oscilloscope can be misleading and will only give limited information. If you connect a spectral analyzer to the output of the tester you will be able to see the amplitude, frequency band and mainly decay time of the noise.
Tapped with an hard pencil most good tubes will show some microphony in the spectra - it can even be used to identify different brands. However a poor tube usually has a wider bandwidth and the ringing has a different decay time - you see a delayed component in some frequencies.
I have found that the choice of the tapping stick is critical for these tests - it should not induce glass ringing, but should not also be too soft. My tests were mainly carried with the 6H30, soon I will test some octal double triodes. What type of tubes are you going to test?
I have no experience with the HP 35665A.
Micro, I'm curious to know what ancillary gear you were using when you owned your D70.
Some good points, here, micro :b
My intent is to employ the HP 35665A in spectrum analysis duty.
I have a motherlode of 6H30P-DR's that I want to test along with about 30 Melz 1578's (6SN7).
There are other tubes, too. The idea is to have the capacity to test tubes found in the BAT REX, VK-150SE, and Atma-Sphere MP-1 Mk. 3.2.
Dear DaveyF: I read it your posts and other gentlemans posts on the thread's subject and I wonder why we music lovers are questioning if the SS technology could sometime " sound better or equal to what tube amps " or the other way around because we can ask for it too ( why not? ).
IMHO what have to define about " better " sound is what is right or wrong in what we are hearing, I repeat: what's right or wrong, not what we like it but what's right or wrong. Seems to me that for almost all of you the " reference " is tube's sound instead LIVE MUSIC that btw is my " reference ": not tube sound or SS sound.
I support that what makes the difference in between different audio systems is the distortions ( any kind and any where. ) level on each one audio system. We all are accustom not only to some kind of distortions but to differente distortion levels.
Distortions that comes in different ways: colorations, frequency deviations, room relationship, noises, electrical pollulation, speaker feedback, wrong match between cartridge/toneaqrm, etc, etc. When I talk of distortions I'm saying that.
I think that today SS makes right " things " a lot better than tubes that IMHO makes wrong " things " in higher grade than SS.
There are several areas where tubes fail to fulfill the music reproduction home audio systems needs and the first and main one is about synergy/matching all over the audio chain. Let me explain a little here:
first I 'm not talking of the wrong kind of synergy when we use a bright amp for my speakers that are to dull/warm, this kind of synergy is wrong because we want to compensate an speaker wrong design with an amp that's a wrong design too: we try to compensate an " error " adding other " error". No, I'm not talking of this wrong kind of synergy but true synergy.
Fortunatelly or unfortunatelly an audio system first main target is to match it electrically, this means firat than all that we have to take care matching electrical impedances in between electronics/speakers. Ohms's Law is very specific about and we can't avoid it.
Any audio system needs that the preamp output impedance can match with the amplifier input impedance. If this is not accomplished provoque distortions/colorations and one of them is frequency deviations.
The ones of you that like are LP advocates knows very well the critical importance to match the cartridge internal impedance with the phono stage impedance, if that impedance " match " is not the right one then we have here distortions/colorations coming from ferquency deviations.
But the main tube technology failure comes when we try to match the tube amp output impedance with the speakers electrical impedance/phase curve, you can take any Stereophile speaker reviews and look at the speaker real mesurements and in the graphic that shows the speaker impedance/phase you can see that electrical curve over the frequency spectrum/range.
Well for any amplifier ( SS or tube one. ) can handle can match that speaker impedance/phase curve with out any single frequency deviation that amp must has a very low output impedance, 0.1 ohm or lower is desired. Tube amps has very high output impedance .
No one tube amp can do it and it's not because amp design failures but because a tube technology failure/drawbacks. So what are we listening trhough our speakers that are runned by a tube amp ( any )?: heavy and higher distortions with high frequency deviations. Frequency deviations and distortions that are not on the LP or in the CD. Yes all the tube advocates are accustom and like those high distortions but unfortunatelly even that you like it what you are hearing is wrong and can't honor the LP/CD what's in the recording.
SS technology provide low output impedance on amps and phonolinestage preamps with no frequency deviations/colorations. Yes, there are other SS advantages too.
That " tube magic " that you like does not exist, what exist are very high distortions that you like it/you are accustom but IMHO are plain wrong and certainly can't honor the LIVE MUSIC Reference.
I can " dissect " several other tube drawbacks but this one is enough at the moment.
Today has no sense to me that some speakers that have a complex and very hard to handle impedance/phase curve as Wilson/YGA/TAD been running through tube amps and that the owners and the owner's friends be satisfied with those very high distortions and trumpeted that " lovely experience ".
No one of us has the culprit that all those still today is happening and that we are " suffering " that. Problem is that we audio customers are ignorant about because no one informed us: no one of the audio dealers, no one of the profesional audio reviewers and almost no one audio manufacturer.
IMHO all them are the responsables that we stay with our " eyes closed ". The pity and sad subject is that IMHO all of them has a main responsability with we customers and this responsability MEANS to mantain informed, with the true and hidden nothing, to we all audio customers and they did not
Regards and enjoy the music,
R.
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