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How can I run out of gain?


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8 minutes ago, deepthought said:

Another thought is, if you have another preamp laying around with a known amount of gain, add it into the system. Set it to max' gain then increase the gain on BHK.  If you are able to get the desired amount of SPL out of the speakers then you're looking at a system gain issue. 

I do have another preamp handy and it has a fair whack of gain. I had never thought to plug it in as you suggest but that seems like a good idea.

 

I have the Pass Labs to BHK via unbalanced and the Directstream to BHK balanced. I have some more cables on order with Bill and eventually everything will be balanced besides the phono.

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5 minutes ago, deepthought said:

And I just remembered, those figures on the BHK gain are based on the NOS 12AU7 tubes. If you are using 6V variants then you might get less gain and if you set the preamp to 6V and use 7DJ8 tubes you might even get another drop in gain.

I think it might be the other way around:

BHK from PS forum

Quote

When testing the 6922 genre tubes vs. the 12AU7 types in the actual preamp tube circuit, I remember the 12AU7s being about 1-1.5 dB less in gain. On an absolute basis this would make the actual volume numbers for a given playback volume be a little different. As others have observed, it is not all that subjectively different.

 

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Just now, deepthought said:

Oh, OK. So it's a bit higher! But the 7V might still be a tad lower in gain than a 6V??

I'll leave that for someone who knows about tubes. I don't recall noticing, but I wasn't looking for a gain difference

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9 minutes ago, deepthought said:

Bingo 

 

 

2.9ohms. Ouch.

Yeah minimum impedance is known but does it have a nasty phase angle at 50hz further complicating things? There is an impedance graph in that publication but phase is not on the graph. That's what is unknown. I should ask Nigel if I can use his DATs and do a quick measurement.

 

Edit: Looking at that graph the lowest impedance is in the 50-100hz range.

Edited by kelossus
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Just now, sakabatou said:

I'll leave that for someone who knows about tubes. I don't recall noticing, but I wasn't looking for a gain difference

I admit I wasn't listening for gain either. I was just floored by how good the Telefunken diamond 7DJ8's sounded when I put them in.......

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Just now, kelossus said:

Yeah minimum impedance is known but does it have a nasty phase angle at 50hz further complicating things? That's what is unknown.

I must be half asleep. Of course you've seen that data, you contributed to the thread. ?

DATs also gives you a phase angle sweep. If I wasn't working from home, and we weren't on lockdown I'd give you the loan of mine.

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2 minutes ago, deepthought said:

Are you here to help Chris or just prove me wrong? 

Certainly here to help , the thread is asking about "How can I run out of gain"  To understand gain one needs to know about consumer line level, as that is what is output from a CD player in every day use. It is a nominal figure of  0.310mv RMS ... which plainly is not 2V . 

 

 

Power amplifiers are always servants to their input signal. They are tested and measured with a set usually RMS input level - to deliver a wattage into a resistive load, and have ability during that test to drive a speaker cable - but rarely is a actual speaker used.  

 

So discussing gain with audio systems, knowing what our consumer equipment has on its output, with every day media playing -  is really  important.  

 

Bandied around in many forums is a gross misunderstanding that what CD players or DAC's are tested with, exampled by the Stereophile  Audio Precision audio analyzer,  has relationship to what consumers then  experience with commercial CD's ... this is  Quite wrong ... but  there is an entire forum dedicated to convincing you that what is measured by analyzers,  is output from every day devices, and those measurements correlate to music reproduction ... it is just not true.

 

Certainly you can obtain a test CD  using sine waves or the like that might have those levels, but that is a test CD ... not what you use 99.9999% of the rest of the time ( depending on how big your CD collection is ) 

 

The scenario of running out of gain cannot occur at all .... full stop where your power amps sensitivity,  matches well to consumer line level,  and is if that is not good enough, is by far IMO the best scenario for proper music.  reproduction.

 

 

 

 

 

 

 

 

 

 

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Guest Eggcup the Dafter

2.9Ohm is “ouch” but not outside the range of a 20A output.

 

it might just be worth putting the balanced cables between pre and power amps and trying the turntable again.

 

I hadn’t considered the possibility that a tube change may have reduced gain.
 

I still suspect the power amp but the evidence for another cause is mounting...

Edited by Eggcup the Dafter
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11 hours ago, kelossus said:

Outside of anecdotal accounts of the speakers being hard to drive there is no measurements to substantiate any claim

 

Nominal Impedance
Variance
4 ohms
3.0-4.5

 

and 87dB per w/m

 

ie. Very easy load.   You need an amplifier which won't misbehave at a low impedance.....  but large well-engineered solid state amplifiers like your should show no problems there.

 

Edited by davewantsmoore
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10 hours ago, kelossus said:

Yeah minimum impedance is known but does it have a nasty phase angle at 50hz further complicating things? There is an impedance graph in that publication but phase is not on the graph.

 

The phase can be inferred from the magnitude (the change of the magnitude)

 

10 hours ago, kelossus said:

that publication

 

OK, I hadn't seen that before posting above.

 

That is a remakably flat imedance curve.... they have obviously left out the lowest resonance in their 3.5-4.5 (or whaetever) range.... which is fair enough.

 

This speaker is about as "easy" load as it gets for such a speaker (ie. there's very little out of phase current and voltage, and "wasted" power)

 

 

48 minutes ago, Eggcup the Dafter said:

2.9Ohm is “ouch” but not outside the range of a 20A output.

 

It's hard to say.... it depends totally on how loud he's listening as to whether the current is "clipping".

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10 hours ago, deepthought said:

DATs also gives you a phase angle sweep.

The electrical impedance is a minimum phase system..... so the phase of the imedpance can be inferred from the magnitude.

 

Where the impedance changes, the phase angle deviates from zero.

 

The impedance doesn't change a lot.... so the phase angle is quite flat  (relatively, to most other speakers, that is)

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10 hours ago, stereo coffee said:

output from a CD player in every day use. It is a nominal figure of  0.310mv RMS ... which plainly is not 2V

????

 

All of my CD players over the years have been said to output 2v or thereabouts single-ended.  With no amount of mathematics can I turn 310mv into 2v.  Isn't the relationship between peak v and RMS v about 0.7 (or 1/0.7 = 1.4)?   What am I missing?

 

[~300mv was the number used for tape-in, tape-out, tuner and aux amp inputs on amps in the olden days]

[Sorry, a bit OT but has been raised already]

 

 

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Guest Eggcup the Dafter
53 minutes ago, Jack Goff said:

Paper values on ohms and watts do not apply.

?

Yes.... they do (assuming what is written on paper, is actually correct).

 

That doesn't mean people for some reason don't like to drive them with a powerful amplifier ..... but this doesn't mean that the laws of physics don't apply.

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14 minutes ago, aechmea said:

????

 

It's confusing  :) 

 

Hint:  In this calculator:  http://www.sengpielaudio.com/calculator-db-volt.htm

 

 

To find "consumer level"  

Enter -10 in "Level Lv" click calcuate, Answer = 0.316V RMS

 

To find unloaded peak level.   Enter 0 in "Level Lu" click calculate.

Answer=  -2.218487499 dBV

 

Enter -2.218487499 in "Level Lv" click calculate

Answer = 2.2V P-P

 

 

... at the end of the day, it is not so important..... as long as we have appropriate gain structure in the system  (which is what Stereo Coffee is essentially going on about).

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5 minutes ago, Jack Goff said:


The part you left out. 
You have to have lived with the speakers. What seems like good matches on paper (the written specs of the Sovereigns) don’t seem to translate when amp matching. 

 

Cool... so there's a different reason for that, in addition to the electrical load (which is easy).

 

5 minutes ago, Jack Goff said:

It’s a shame people like @kab and others with actual experience of these speakers left the forum because of know it all’s with no actual experience with the said equipment. 

 

I'm not saying he, or you, or anyone else is "wrong" about what you expereinced ......  except in where you say "the ohms and watts don't apply".....  They do apply.... there's just a different reason for what you have expereinced.

 

 

Here's an analogy:

 

I had 3 cups of coffee and went for a run this morning.   I got my best time, and I felt like my feet were hardly touching the ground.   It's becasue the laws of gravity don't apply to me like it does to everyone else.

 

Nonesense, right?!

 

As far as electrical impedance goes, and electrical-accoustic efficiency goes..... these speakers are a relatively benign load.

 

 

That being said..... these speaker have high power handling, and can play loud levels with low distortion (won't sound "loud") .... so people are probably choosing to put a substantial amount of power through them.....  but again, that doesn't mean that the electical specs don't tell you what you need to know.

 

You would need a solidly engineered 100w or more (coindidentally exactly what is says on the spec sheet).   It's easy to find 100w which is not well engineered.... so sometimes (often) than can be sidestepped by moving to an amp which is much larger  (as if it makes it to ~500w, then the first couple hundred watts are quite well behaved - or similar).

 

 

Back to the topic at hand.  The PassLabs amp in question is well engineered.   I'd be looking elsewhere than at it in general.

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Is it not  amazing in the year 2021 where we know so much, that we are now on 3 pages of comments where nobody has really provided an answer - warning - sarcastic comment.

 

I think we have here a case of what a lot of us have been saying: that is everything in a system matters. There are just so many variables that nothingon paper / in theory could be believed untill put in practice.

 

I unfortunately do not have the answer, but maybe the answer is:

  • listening to @Jack Goff
  • contacting Simon at VAF as he worked for Duntech and may just be able to sell/source you the right amp and or advise re pre or both
  • contact Kiat that also worked at Duntech and are now selling a new Duntech range
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