B'ASS Current Amplifier

[manisandher]

Using the parallelled outputs is not optimal, but people do it more often (without me knowing). It is not really forbidden anyway.

Thanks Peter. I think I'll give it a go.

Actually, I think it is a 'simple' attenuator...

Well, apparently not a simple attenuator. I've just received the following info from the designer of the Einstein poweramp in question: "It's an attenuator, but not a simple one. It's  acting as a shunt and not in the signal path. So there is no loss in quality compared to a standard attenuator."

Sounds good to me  

Mani.

[manisandher]

black

Noooooo 

Mani.

[acg]

Actually, I think it is a 'simple' attenuator...

Well, apparently not a simple attenuator. I've just received the following info from the designer of the Einstein poweramp in question: "It's an attenuator, but not a simple one. It's  acting as a shunt and not in the signal path. So there is no loss in quality compared to a standard attenuator."

Sounds good to me  

Mani.

Hi Mani,

Which Einstein Amp do you have?  Is it OTL? 

If the amp varies gain as a method of attenuation then it probably uses some form of variable cathode shunt.  In every schematic that I have seen the current in the signal path must flow in a loop that passes through the cathode, so if that is the case then the attenuator really is in the signal path even though it is not in the "direct" signal path that you would expect unless you marked the current flow loops. 

Semantics I know, sorry.  The new PSAudio preamp does something similar with its attenuation by varying the gain of the input tube with use of (I assume) a variable cathode shunt.  This may be the very least damaging form of volume attenuation currently available, but not many are doing it and it is not that easy to develop as far as I can tell.

Sorry for the off-topic Peter, but it is only a little off-topic because we are talking about volume attenuation.

Cheers,

Anthony

[manisandher]

Hey Anthony, it's the OTL... in my dreams! Actually even in my dreams, I'm not sure I'd want such an amp for an office system. A totally gorgeous piece of kit though.

No, I bought a used Einstein 'Light in the Dark Mk II'. I didn't need it - I've already got a couple of really nice amps sitting around (the nicest probably being Bert's BD30-SPR monos, which I currently use to drive my K-1000 headphones). I sold my Berning Siegfried amp a couple of years and I think I just miss having a component with valves in it! (Actually my Thöress phono stage has valves, but that doesn't count.)

I think the attenuator is simpler than you're suggesting. The recommendation is to use the amp's XLR inputs because it's a truly balanced amp design. The amp also has two sets of RCA inputs per channel - one in +ve phase and one in -ve phase (so essentially connected directly to pins 2 and 3 of the XLR inputs respectively). So if you're using these inputs, you can change the phase by using one or the other input. Now, these RCA inputs can also be used as line-level outputs for multi-amping. If you do this, then the attenuator control will attenuate these outputs too, as well as the XLR input.

So it seems like a more straight forward setup than the one you suggested.

Mani.

[PeterSt]

No, not off topic at all. I take it for granted that the Attenuation will degrade anyway, unless indeed it is voltage regulating. But that needs a completely different design and is out of the question.

So it sure *is* a matter of obtaining ideas. And anyway, my first (and last ?) idea is on its way - due next week - so I can try it for measurement results. But really, I have not *any* hopes at all, plus that it isn't necessary for anything (it's necessary for nothing). And the headphone people ? they are used to it already. Soooo .... buuuut ... it is a matter of doing it the best possible way with the super clear advice that the digital attenuation of XXHighEnd should be used BUT that the volume should (and easily can) be used for TV etc. input. That looks harmless to me. Right ?

Peter

[acg]

Hey Anthony, it's the OTL... in my dreams! Actually even in my dreams, I'm not sure I'd want such an amp for an office system. A totally gorgeous piece of kit though.

No, I bought a used Einstein 'Light in the Dark Mk II'. I didn't need it - I've already got a couple of really nice amps sitting around (the nicest probably being Bert's BD30-SPR monos, which I currently use to drive my K-1000 headphones). I sold my Berning Siegfried amp a couple of years and I think I just miss having a component with valves in it! (Actually my Thöress phono stage has valves, but that doesn't count.)

I think the attenuator is simpler than you're suggesting. The recommendation is to use the amp's XLR inputs because it's a truly balanced amp design. The amp also has two sets of RCA inputs per channel - one in +ve phase and one in -ve phase (so essentially connected directly to pins 2 and 3 of the XLR inputs respectively). So if you're using these inputs, you can change the phase by using one or the other input. Now, these RCA inputs can also be used as line-level outputs for multi-amping. If you do this, then the attenuator control will attenuate these outputs too, as well as the XLR input.

So it seems like a more straight forward setup than the one you suggested.

Mani.

Actually, with what you have just said I am more sure that I am right.  Clever design by the sound of it!

[acg]

No, not off topic at all. I take it for granted that the Attenuation will degrade anyway, unless indeed it is voltage regulating. But that needs a completely different design and is out of the question.

So it sure *is* a matter of obtaining ideas. And anyway, my first (and last ?) idea is on its way - due next week - so I can try it for measurement results. But really, I have not *any* hopes at all, plus that it isn't necessary for anything (it's necessary for nothing). And the headphone people ? they are used to it already. Soooo .... buuuut ... it is a matter of doing it the best possible way with the super clear advice that the digital attenuation of XXHighEnd should be used BUT that the volume should (and easily can) be used for TV etc. input. That looks harmless to me. Right ?

Peter

Looking forward to what you have concocted.

[PeterSt]

Hi all,

What you see below is the case as I intend it now.
We really tried to make it look beautiful with the idea that cost is no object (hopefully some will agree).

Outside footprint is 23 x 23cm / 9.2 x 9.2". Height is 7.4 cm / 3".
The case is all 6mm aluminium, except for the back plate which is 2mm.
Cooling is provided by means of heatsinks at the sides and a large vent in the cover.

This is not all decoration since it is also a headphone amp. So of course there are a few outputs at the front (4 pin balanced + 6.5mm jack).
The switches are for attaching more of the internal amplifiers. One switch can attach one additional level of "amp" :
- with SE amplification for the Left and Right channel at the same time (a total of 4 additional amp levels possible);
- with differential amplification (balanced) for Plus and Minus at the same time for one channel (a total of 2 additional amp levels possible).

The back presents two hybrid XLR outputs (normal XLR + 6.5mm jack - thus Left / Right balanced).

There are also Inputs and Outputs for RCA and Inputs and Outputs for 75 Ohm BNC.

A rough description :

One of the inputs will connect directly to an output of choice (but is amplified for current under way); the remainder of the inputs can be input selected and is subject to volume control. This is the lesser path, but say for the convenience of connecting a TV or radio for input. Input sensitivity is not really arranged for, but the volume control can be set to memorize the level for the separate input channels.

Questions ?

[Arjan]

Hi Peter,

About the volume control, is it remote controlled?
The input - output selection is manual?

About the input - output selection I am not so sure what it means. I my case the NOS1a output will be on the BNC inputs.
From there I can select or the BNC outputs (on the back) to the amplifiers or headphone 6.5 mm jack (on the front) for my headphone.
So I can switch between those two outputs, and both will to use the higher path for best SQ? Or just one of them?

Next I could also connect via RCA my TV and switch again to the amplifiers or headphone but via the lesser path with volume control.

Is that how it will work?

The design looks great!

About the title, is it still the cheapest upgrade?

Regards, Arjan

[PeterSt]

Hi there Arjan,

Cheapest upgrade ? well, what to say. Maybe not anymore. But hopefully the best looking one ?

About the volume control, is it remote controlled?

Yes. But maybe one of those knobs is able to turn as well.
The stupid thing is, the gear I need for this - ordered the 24th of April - still did not arrive from China. DHL tracking number does not exist, so I just can't test things.

The input - output selection is manual?

No, although it can be.
(same story)

I my case the NOS1a output will be on the BNC inputs.
From there I can select or the BNC outputs (on the back) to the amplifiers or headphone 6.5 mm jack (on the front) for my headphone.

Arjan, this is as vague as can be;

Let's first observe that this was designed as what we just as well can call a buffer. In your case BNC in and BNC out - done.
Then I was so smart (maybe not) to see that there can also be a headphone output. So for fun I "designed" that in. This really went without much thought about the exact how, but the least we can do is switch off the normal amplifiers and stick in that headphone jack. Right ?

Well, not so right, once you start to think about the other options surfacing, like inputs and also outputs. I mean, if I for the life of me couldn't let sound the BNC output good when it was there in parallel with e.g. RCA (and which is logic because the output impedance is molested again) then how should all this work ? Well, one thing for sure :

There is one output only. Thus, it is not so that the outputs can be selected. Thus your situation again : BNC in and BNC out and that's it. This means that all the other connectors are for inputs ...

Sure ?
No, of course not, because the dreaded headphone outputS are there as well. Mind you, three of them (4 pin XLR, Stereo Jack, and L/R XLR+Jack).

So what is this now ? A headphone amp ??

Although I know it can be done, I can not envision exactly how because I don't have that input selection stuff or anything. And, nothing would be the matter for 100% sure, IF that BNC connection did not exist. But it does - and actually most of us have precisely that.
So what needs to be done is that this needs to sound as good as without the other stuff (the headphone outputs). But say that I make an additional switch do detach the headpone outputs. Thus yes, that will be the lesser part now. That switch can also be in the normal output (say for those who don't even use speakers).

But I need the lot in my hands or otherwise I am blind ...

Thank you for the good questions.
Regards,
Peter

[doublelife]

Peter,

Could this B'ASS be used to feed into an electrostatic (headphone) amp?

Paul

[PeterSt]

Hi there Paul - I'm afraid not.

Peter

[doublelife]

Thanks, I suspected not.
Paul

[PeterSt]

[Gerard]

Leave it like this for me  ...... No paint......