Phono Stage Only?

[Brett]

Re: Why balance?

For me it is part of my pedigree. I've spent more time in broadcast and production where all interconnects are balanced. They need to be, to cope with the noisy environment.
Well, I've found benefits at home too. Home is becoming a more noisy environment as time goes on.

I agree. I worked in broadcast for a long time too. My phono stages are a couple of metres outride the RH speaker to give the TTs more isolation from the basshorns. Running balanced to the 'passive' pre (S&B TVCs and line level switching) next to the poweramps eliminated a lot of noise and garbage.

Why balance the preamp?
Unbalancing and rebalancing cause problems IMO.

Agreed again.

 

[AKSA]

OK,

In the spirit of compromise, how about balance head amp, SE RIAA mm and power amps?

I agree emphatically with CM rejection; very obviously a noise benefit at the very low levels particularly.

That do it for you Brett? Coming from a BC background, I expect you'd favour transformers for the balance/unbalanced interface? Do you have balanced in the MM pre as well? Which circuit, you own, or maybe Allen Wright's?

Cheers,

Hugh

 

[fdegrove]

Hi,

In the spirit of compromise, how about balance head amp, SE RIAA mm and power amps?

I could live with that, Hugh...you can even style it as a Ferrari...

And after all, I feel the MC stage would benefit the most...no xformer for me yet, though...
I'll take the challenge and stick to my prejudices.

Heck, come to think of it, it should be easier to opt for a balanced stage there than a SE one.

Seems I painted myself into a corner once again...Eeeek.

Cheers,

P.S. Maybe John will help us design a balanced headamp?

 

[CptTripps]

Glad to see the bickering is progressing nicely.

I finished the boards and the Power supply today. Tomorrow I'll tackle the load dial and shoudl have the case and transformers on Monday so I can dampen the chassis up and get her broken in by the time I get home Tuesday.

The kist went together REAL nicely. I had a few questions but Kevin answered them over the phone and helped me through whatever I threw at him. I'll post pics tomorrow. I'll tell you what, I was VERY aprehensive about the kit when I got all these bags of parts and instructions. After reading them through a few times, it was a snap.

ok, back to your bickering now...

 

[Brett]

In the spirit of compromise, how about balance head amp, SE RIAA mm and power amps?

As I'm building / have built it all, why would I compromise?

What you proposed seems a real hodge podge and as I've yet to hear a SET poweramp that sounded better than average, why would I take a nice clean design and put it through one of those?. System is balanced end to end (except the Decca i/p)

That do it for you Brett? Coming from a BC background, I expect you'd favour transformers for the balance/unbalanced interface?

Not always. The CM rejection of the balanced front ends is pretty good, and bunging a Tx in front of them only made it sound blurry. Perhaps one of the amorphous Lundahls, a Jensen or an S&B might be better, but I'm not spending the dough at the moment (it has to go on other things) to find out.

Do you have balanced in the MM pre as well? Which circuit, you own, or maybe Allen Wright's?

Phono 1 MC: Balanced in. Is almost verbatim RTP3C for the first stage
Phono 2 MM: Balanced in. Is inspired by the RTP but is modified enough to be called mine
Phono 3 Decca: SE in. Sort of a modification of the FVP. Decca's are surprisingly highly affected by loading capacitance.
Second stage, common to all 3 is differential, and mine, though I have a mod of the RTP5 that's pretty good to.

The power supply for the whole lot is also quite a bit larger and better developed than what VSE sells (not knocking Allen, I didn't have budget/commercial/weight! restrictions).

All the decisions I've made on what to use are based on trying them and listening.

 

[AKSA]

Hi Brett,

This caught my eye.

As I'm building / have built it all, why would I compromise?

Because you must surely realise that all machines are an exercise in the management of compromise. And I can assure you that you have not built them all. No-one possibly has that claim, and it smacks of arrogance to say it. I don't see Nelson Pass making comments like this, and if anyone has the right to make them, it is he.

What you proposed seems a real hodge podge and as I've yet to hear a SET poweramp that sounded better than average, why would I take a nice clean design and put it through one of those?. System is balanced end to end (except the Decca i/p)

It's not a hodge podge. It is called a hybrid, and might even (gasp!) use tubes and SS devices. And there are many people around the world disagree categorically with you about SET power amps; I personally think they sound wonderful, properly done.

Not always. The CM rejection of the balanced front ends is pretty good, and bunging a Tx in front of them only made it sound blurry. Perhaps one of the amorphous Lundahls, a Jensen or an S&B might be better, but I'm not spending the dough at the moment (it has to go on other things) to find out.

I find myself agreeing with this comment.

Cheers,

Hugh

 

[Brett]

Because you must surely realise that all machines are an exercise in the management of compromise.

I've been an engineer a long time Hugh.

And I can assure you that you have not built them all. No-one possibly has that claim, and it smacks of arrogance to say it.

I meant I've built all of my system not every possible topology. You and I have both been posting here long enough that I feel that was an awfully long jump. I also thought it was pretty clear from context.
Now, down off the horse.

It's not a hodge podge. It is called a hybrid, and might even (gasp!) use tubes and SS devices.

To balance/unbalance a system unneccessarily (in my mind) is a hodge podge. If the rest of the system post MM input was SE, then a step up Tx, to keep it balanced all the way to the start of the active stages for improvrd CMR would probably be my approach.

As for the use of sand, I use it all over the place where it works to some benefit; CCS, shuntregs to name two. I'm not sandophobic, but generally I would prefer it not to be the active devices as I've yet to hear anything better than tubes for that, properly implemented.

And there are many people around the world disagree categorically with you about SET power amps; I personally think they sound wonderful, properly done.

And there are many who don't. Hell, there are people who like to listen to AV receivers so I don't see the point of the comment. I never said I had the absolute taste or alternative paths were incorrect/lesser, just that I don't like those I've heard. What I actually said was "...as I've yet to hear a SET poweramp that sounded better than average...". Notice the "I've"?

Because an amp is a SET it is not automatically inherently better. I think I can hear what people like about some of the ones I've heard but they didn't juice my lizard, and in the same manner as the quote below, I don't feel the need to spend a heap on iron to try it out (no point doing it half arsed eh?)

And I doubt you've heard that many PP's the ways I've done them. Not everything PP is a Williamson/Mullard, which are almost invariably people's references when making the comparison.

Not always. The CM rejection of the balanced front ends is pretty good, and bunging a Tx in front of them only made it sound blurry. Perhaps one of the amorphous Lundahls, a Jensen or an S&B might be better, but I'm not spending the dough at the moment (it has to go on other things) to find out.

I find myself agreeing with this comment.

Good we agree on something.

Cheerio

 

[AKSA]

Brett,

Thank you for your measured, direct reply.

I appreciate the explanation; but one thing I've learned, don't ever try to reverse someone else's beliefs. Never works.

Now, to work. My preferred arrangement is this:

Balanced MC head amp (SS) to SE conversion block then SE MM preamp (hybrid) - SE input/VAS power amp with push pull output stage (SS). Like you, I'd prefer to avoid use of transformers to convert from balanced to SE. To be honest, it might be just as effective to have the entire preamp process balanced, with either option available at the output for subsequent power amplification.

I'm not in favour of MC transformers because of the granular nature of the Barkhausen effect; the quantum behaviour of the magnetic domains at very low amplitudes. I believe this robs resolution. My first preference would always be SS for this task.

I'm interested that you have built both SE and fully balanced MM preamps and found the latter to sound better. I am particularly interested because you say you've done this by listening tests; this is unusual for an engineer (ahem!), and I respect the approach.

Brett, were the circuit blocks pretty much the same?

My notion is this: balanced circuitry processes opposing waveforms with identical circuitry, thus introducing very low distortion because the amplitudes of the signal in both circuit blocks will be half that of a single ended circuit, but the distortion is symmetrical, thus odd order. If identical, the two halves will thus cancel any even order, thus skewing the distortion into the odd order. With no feedback, this will be low order, so not really discordant, but the impression will be that it is sharper, and a little strident. Have you noted this over the single ended version?

I don't fully agree that any reduction of distortion makes the sound better; rather I'd qualify it even more and say that any improvement in linearity always results in better sound. I believe this covers all forms of distortion, particularly intermodulation. Splitting hairs, but probably a worthwhile distinction.

Lastly, Brett, are you in Queensland? A pity if so; I'd like to discuss these weighty issues over good coffee.........

Cheers,

Hugh

 

[fdegrove]

Hi,

Well,well..

Glad to see somebody knows something about xformers...I always had the impression I'd be banned for mentioning Barkhausen and/or Kirchoff in one sentence...but there you go.

Just to not make anyone worry, I squarely disagree with most of what follows....not that you didn't know that already.

Balanced MC head amp (SS) to SE conversion block then SE MM preamp (hybrid) - SE input/VAS power amp with push pull output stage (SS).

I'll ignore the SS for the time being and go balanced from source to amp....using valves, bien sur.

Why use that travesty you suggest? If you choose balanced, at least go as far as you can, won't you agree?

What about if one of us opens a thread on the ultimately capable, brass balls, well balanced MC capable, without barking hauses preamp?

I volunteer...,

 

[AKSA]

Frank,

Your offer is wildly accepted; please proceed.

Steam is mandatory. NO turbines; large pistons and cylinders only. Feedback is not permitted; your tender will be filled both with adequate coal and water. Sand for the steep slopes is verbotten.

Oh, and no bloody nine pins. You must use octals, preferably 6SN7 and 6SL7. No 5842/417As, either. Everyone uses them. Boring.

Balanced throughout, and what will you use to convert to SE for the power amp? It must be tres elegant, Monsieur.

Cheers,

Hugh

 

[EC8010]

OK, no 9-pins, and steam only.

Input differential pair: 3A/167M (Loctal), or EC1000 (B8D/F).
Coupling: DC coupled (must avoid dielectric absorption - capacitor equivalent of Barkhausen).
Succeeding stages: 14N7, 12SN7, 76, 37, or whatever. (6SN7 is too boring.)
Output stage capable of driving cable from turntable to remote power amplifiers: Transformer-loaded cathode followers with floating secondary.
Constant current sinks: Pentode, courtesy of C3m (Loctal).

 

[fdegrove]

Hi,

Balanced throughout, and what will you use to convert to SE for the power amp? It must be tres elegant, Monsieur.

As long as the preamp doesn't have to be able to speak French, I think we can concoct something...

As for conversion to single ended, I was think about a circuit John Broskie ( what would be without that good soul) has presented but anything's welcome.

BTW, I'd like the summing done at the amps' input as it allows for long cable drive but I'm not strict here.

So, I'll start the thread for the fun of it hoping nobody's mad at me?

Cheers,

 

[fdegrove]

Hi,

Gents, the seed of joy has been planted here:

Balancing act.

Cheers,

 

[Brett]

Brett,

Thank you for your measured, direct reply.

Thanks for reading it that way. When I looked back on it the first time, I read it as bitchy, but it wasn't intended to be, more wryly amused and typically blunt.

I appreciate the explanation; but one thing I've learned, don't ever try to reverse someone else's beliefs. Never works.

Agree 100% and I seldom try to do that. Just when I see an "orthodoxy" I disagree with, I state my contrary view.

Balanced MC head amp (SS) to SE conversion block then SE MM preamp (hybrid) - SE input/VAS power amp with push pull output stage (SS). Like you, I'd prefer to avoid use of transformers to convert from balanced to SE. To be honest, it might be just as effective to have the entire preamp process balanced, with either option available at the output for subsequent power amplification.

I think I see your logic, but you have to phase split again later and that brings it's own problems. Transformers are my fave approach. Actually, my passive pre is a set of S&B TVC's, and the unbalanced sources like the DVD run through a SE tube stage with a parafeed TX to balance, before the TVCs.

I'm not in favour of MC transformers because of the granular nature of the Barkhausen effect; the quantum behaviour of the magnetic domains at very low amplitudes. I believe this robs resolution. My first preference would always be SS for this task.

As others have said (and rudely stolen all my dog jokes), I'm not sure this is a big deal, but it might be. All the MC tx's I've used to date just sounded a bit fuzzy to me. Maybe the Lundahls / S&B's would be better......

I'm interested that you have built both SE and fully balanced MM preamps and found the latter to sound better. I am particularly interested because you say you've done this by listening tests; this is unusual for an engineer (ahem!), and I respect the approach.

I built Allen's design based upon respect for his gear I'd heard in the past, and found it exceptional. Playing with some other designs on the interim using the RTP as reference have all left me cold. Interested to explore some of the supposed harmonic spectrum advantages of SE, I also built his FVP5 phono stage, and find it great too, but just slightly less so and I could live with this one happily. It only took a few hours to build one night when I was bored, and I used the same PSU, so it was easy to plug the cart through both. I'm not good at describing what I hear in words so I can't give a flowery description.

The last comment I find sort of funny. As the purpose of an audio amp is to be a conduit to reproducing recorded music, how else would you finally test it but listening? I learned this principle the hard way when playing with hi-po motors and esp bikes. A Yamaha R1 is a weapon of a bike with awesome technical specs, but on our typically crap rural (or wet!!) roads it's frightening. I rode a Suzuki GSX1400 on the same day, and the B grade racer I was with couldn't get away from me on the R1 on the tight roads we were riding. I had the biggest grin afterwards, and my friends will tell you I still giggle every time I talked about it because it was so much fun. Now you can measure the enjoyment I had that day in my face, but I was on the technically inferior bike*.

Brett, were the circuit blocks pretty much the same?

The circuit for the bal MC is Allen's RTP3C, but he phono section only, with no VC, but still loaded into 50k. This goes to a selector switch.
The Bal MM is an all tube cascode of my design, and I'm keeping that one under my hat for the moment, but it is reminiscent of some of the VSE circuits. Loads into the same 50k (for convenience) and selector switch.
The SE Decca is currently the FVP5 phono section, first stage. because I need so little gain the second 6922 has been replaced with a 6h30 and the load and RIAA tweaked to suit.
After the selector it goes to a differential mu line stage or I can plug in an RTP5 'line' stage, also tweaked.

All use a common PS tx, damper diode rectification, LCLC with oil caps then a pair of CCS/shunt regs. Each stage is only powered up as I use it to cheapen/simplify the PS a bit, and save the life of the tubes in the stages that aren't used. I typically only use one of the TTs in a session, and may simplify the lot into the P77 and Decca stages. Currently being rebuilt into a big case to sit beside the TT's.

My notion is this: balanced circuitry processes opposing waveforms with identical circuitry, thus introducing very low distortion because the amplitudes of the signal in both circuit blocks will be half that of a single ended circuit, but the distortion is symmetrical, thus odd order. If identical, the two halves will thus cancel any even order, thus skewing the distortion into the odd order. With no feedback, this will be low order, so not really discordant, but the impression will be that it is sharper, and a little strident. Have you noted this over the single ended version?

No. I think that with a linear enough circuit with enough headroom (this is *very* important esp with hi o/p carts), the distortion will be so low as to be insignificant. Similar to pentodes, the load R determines the harmonic structure of the cascodes. If you can give up the gain, low loading can be benficial.
I couldn't easily measure the MC stage when I last tried.

I don't fully agree that any reduction of distortion makes the sound better; rather I'd qualify it even more and say that any improvement in linearity always results in better sound. I believe this covers all forms of distortion, particularly intermodulation. Splitting hairs, but probably a worthwhile distinction.

This would accurately describe my feelings too. Lots of low order HD is usually accompanied by a lot of IMD too, and this is a lot bigger sonic problem than 2H.

Lastly, Brett, are you in Queensland? A pity if so; I'd like to discuss these weighty issues over good coffee.........

No, not a bananabender, but not far from there. I'd like to sit and discuss this and other topics with you face to face sometime. Unfortunately I'm not that far south very often, and I may have a new job to keep me busy soon. Raincheck and some day we might get to meet I hope.

Regards




* for the bikers who read this, I want one of these motors transplanted into an early GSXR chassis with a Hindle 4-2-1 playing the music. Woohoo!