Had a look, Nigel - sounds like the same old story to me: lack of firm bass and slightly unpleasant treble - been there a million times, when my playback is acting up ornery - a good couple of kicks in the side, and a decent squirt from the oilcan usually makes all the difference, gets it back ticking over nicely, 
...
..."... lack of firm bass and slightly unpleasant treble ..."
Blimey, I've forgotten what that's like, really. How easy it is to get spoilt.
I wonder how I'll react to Otala/Lohostroh's amp now, with speakers far superior to what I had at the time, AR5.
My run-in with the Marantz 170DC turned out really well for me, it turned out to be better than I remembered it and than I expected it to be. Perahps I'll get lucky twice.
Blimey, I've forgotten what that's like, really. How easy it is to get spoilt.
I wonder how I'll react to Otala/Lohostroh's amp now, with speakers far superior to what I had at the time, AR5.
My run-in with the Marantz 170DC turned out really well for me, it turned out to be better than I remembered it and than I expected it to be. Perahps I'll get lucky twice.
Dejan. That amp you sent me recently looks like you are in danger of exceeding the greats.
Just sent this to my local repair shop ( The Power House Kidlington Oxfordshire ). Richard is a time served engineer, he is selling a Stan Curtice design ( Moth £300 ) . Dejan. it is good reading. You know I love the Rotel RA 820.
http://www.stancurtis.com/PDFs/HiFi Critic 4.pdf
Just sent this to my local repair shop ( The Power House Kidlington Oxfordshire ). Richard is a time served engineer, he is selling a Stan Curtice design ( Moth £300 ) . Dejan. it is good reading. You know I love the Rotel RA 820.
http://www.stancurtis.com/PDFs/HiFi Critic 4.pdf
You might see previously I sent JJ a note to make a pure triode EL 34 as TR 34. I think it would please many people if she did. I chose the 34 over any other. It might need g1 slightly repositioned and sized when g2 g3 removed. It might resemble a PX25. For many it would be a drop in replacement. Dynaco comes to mind as many use triode connections. It needs to be high Mu I feel. Even most KT 88 / 6550A amps would be OK if the cathode resistors changed.
How about Dolly Parton? She certainly can sing.
I do get out quite a bit, but over the decades, I have surrounded myself mostly by people who do know what good sound is, most of them being sound professionals of one kind or another.
On Otala/Lohstroh. There are problems with originally used parts, in form of BCY dual transistors, needed for the first and second diff pair, and of the output devices.
The output devices problem is easily solved, as those BD 203/204 trannies have been replaced by updated equivalents in form of BD 801/802 or something like that, I don't have the exact designation at hand.
For the two dual trannies, no luck so far, although I am still searching, But I suspect it'll have to BC550B, or possibly BC550C if I can find them, purchasing population at least 100 (but probably 200), and a lot of time to pair them properly.
If you're willing to wait a bit, say two months worst case, I will be able to send you the files necessary to have the boards printed out at home.
In the meanwhile, Max, please do read the original text, which includes the basic schematic and BOM, courtesy of our Jan Didden, at Home.
Hah! That'll be the day!
I'm not that ambitious, Nige, I just want to make it, listen to it and think to myself - that was worthwhile, I didn't waste the time.
And if I'm happy with it, I will post it in public domain. That one I sent you and its lower power little brother, where absolute output has been reduced to favor a higher Class A to Class B crossover point.
That's what I need, the biggie for bass, and two for the mid and high range drivers, so I can triamp. Or, if I add a small elctronic crossover filter in each amp, I can do away with the passive XO altogether and turn it into a true active speaker.
Which is the way I'm haded.
BTW, I affectionately call it all "O/L Reloaded". Essentially, it is like the O/L amp, but it takes advantage of what we have today and they could only dream of. Currently, 140 mV at the input produces 28.3 V at the output into 8 and 4 Ohms (well, a wee bit more into 8 Ohms), and its THD 20-20.000 Hz is less than 0.4% at rated power open loop, over a bandwidth of just short of 130 kHz. Or less than 0.05%/0.03% into 4/8 Ohms with just short of 20 dB global NFB.
I'm not too sure about square wave performance because it is nothing short of exemplary, and honestly, I still have trouble believing it, so I test every day just to be sure.
The graet unknown are some compensation values. They work fine, but it is a simulator, and their actual value will very probably need to be changed on the real world PCB for many reasons. On the other hand, I have tremendous reserves at hand, and if they were quadrupled, which is most unlikely to be needed, I'd still be able to slew at 100 v/uS. On the version you saw, the nominal slew rate would be around 450 V/uS, as each input FET is fed by 4.5 mA of current and the compensation cap is 10 pF. What are the chances I might ever need 45 pF of Miller compensation? If I do, then I have grossly f. up somewhere.
So that gives me a fast Japanese amp, a la Sansui or Kenwood at the heigth of Slew Rate Wars in the late 70ies. Now, the big question is - that's nice for the input part of the amp, but how about the amp as a whole? It seems that the full power bandwidth into 8 Ohms comfortably exceeds 500 kHz, where O/L were happy with 200 kHz, but they had the BD trannies, and I'm throwing about MJL 3281/1302 about, and according to their data sheets, in the region within which I would use them, both should have a bandwidth exceeding 40 MHz, and there are four series/parallel pairs on line.
But here's the best part of it. I repeated the whole battery of tests using Toshiba's 2SC5200/2SA1943 trannies, which are easily obtained and are cheap. Not surprisingly, since they are the middle brother of the same family the Motorolas are from, aside from needing to change just one resistor value in the protection circuit - no difference. Same results overall. Now, that is approaching my dream, a good sounding amp using standard parts, no esoteria!
Just one thing for those protection circuit naysayers - the protection will not act for 50 mS, not 20 mS as demanded by IEC standards, and the single slope curve has been worjed out according to not standard continuous, but 100 mS power dissipation capabilities of the output stage. This should hopefully mean that large impuske current capabilities should be just fine, but with no neghative effects during normal operation. I checked - disconnect the protection scheme, and NOTHING changes until the load drops below 3 Ohms steady state. And if the argument comes up that under tremednous power dissipation conditions the amp will start to seriously heat up, which is true, my first advice is get bigger heat sinks, standard Euro form, avaialable in several heigths, and my second advice is think, what do you think I put that overheat protection function in for?
No, impossible, Dolly Parton is a much more productive artist, otherwise it is a matter of taste.
I've tried a few BR recordings but found the recording quality lacking, to be nice.
Jan
Or work with low cost components. Higher quality items have many things in place already, may only need some relatively minor tidying up - cheaper audio gear has had all sorts of corners cut, in an effort to minimise final price ... the interesting exercise is to see if satisfactory subjective sound is possible if enough tweaking is thrown at it. Along those lines, we have 2 Aldi TVs, the older, bigger unit can acquit itself well; the newer, small one, for the bedroom is just not worth playing with, the raw sound has too many issues, and is too limited in SPLs - a line has to be drawn somewhere.
Haa, haa ... just got me another "wife in the kitchen" anecdote: someone we know just popped in, a music lover, to discuss something regarding the house. At the front door he said to my wife, "Ahhh, Frank's playing the piano, is he!?" I had turned on the Yamaha keyboard, playing MIDI files - the quality was well down on what it could be, for a variety of reasons - yet the impression of the real thing was coming through ...
Have you heard her "Nick of Time" album? I think it's good sonically and outstanding musically, although she is one singer i would listen to with 25% distortion, if that was my only choice - like the very early Staple Singers.
I love the comment under this Austin City Limits performance of "Pride And Joy":
https://www.youtube.com/watch?v=6Mylo0piAgc&feature=youtu.be
The comment is "I saw her live when i was about 12. My voice dropped 3 octaves that night."
It's never too late to learn. BBC radio 4 is responsible for maintaining the high degree of eccentricity in this country. Today a program about plastic trumpets for schools at 1/6 th the usual price. The musician says they are virtually identical. In 1983 I visited Tournai in Belgium and met an organ specialist. He was rebuilding the organ at St Lazare. His special feature was gas pipe to replace lead. The sort that goes under the road and high grade plastic. I truly heard no difference except to say the organ and church sounded great. He was very pleased as that was the point. As he said a pipe should be a pure sine wave. It struck me the trumpet might be exactly the same. Thus it is the shape and the strength that matters.
Talking to Mark Baker of Origin Live I was very surprised to hear that the Conqueror arm is multi layer carbon fibre. Mark was totally unwilling to say what the other layers were. The fact it looks like metal means Mark is not into the carbon fibre look. One thing to say. Frank Schroeder made a carbon fibre arm that I didn't like. I was quite prepared to leave it at that and reinforce my prejudice. Unhappy to be so unscientific I added mass to the arm. It was totally transformed. Sadly ignoring the typical mass and thinking a lower mass can only be good is so obviously wrong. Carbon fibre was mostly wrong in being untypical. The LF resonance of a PU is critical. If you have a strong low mass arm you will be able to fine tune it. SME 3 comes to mind as no one rates them. If too high you will not. The blu-tak is good because it damps as well as adding mass. It looks horrible as the downside. Tracy Chapman truly was magical once tuned in. The noticeable quality was complete freedom from spittiness and expansive warmth. The SME 12 inch of old sounds dramatically better than the 9 inch. On taking them apart they are identical. Some say it is the geometry. That is nonsense as most of us can not see well enough to get the alignment better than 1/4 mm. Also at some point the 9 inch error will be zero. I suspect on the 12 inch SME gave in and built a better arm for no more money and forgot low mass. The 9 inch is 60% as good as lets say the Mark Baker arm. The 12 inch is in the same category. This proves the supposedly rubbish SME bearing is OK and in fact rather good. The SME bottom bearing is usually badly set. If you loosen/ tighten it and do the blowing test at 0 g it can be optimized. It will take you about one hour. Like motorcycle or bike head race it needs to be the point between tight and loose. Usually I take it back slightly more than it needs towards loose. On a Garrard this should slightly reduce the effects of rumble and give dynamics. SME seem to have it loose and use gravity to hold it firm. In my opinion this is a big improvement to get it right. There is an Allen key set screw and threaded part to do the setting. The 10 inch is a great arm. It goes for less money and will fit in the standard 9 inch slot on most turntables. 222 and 210 mm centre to pivot distance I seem to remember. I usually set the hole to 215 mm to suit both. The mass of the 10 inch seems to pay off. Again the " better geometry " is the stated reason. If the slot is set at 45 degrees that is ideal . Sometimes space will not allow it. Some say the slot is wrong and compromises the geometry. I will not say what I think of that. The older arms had fibre rawl plugs inside ( resin plus rope ). That will do a very good job. I think the metal changed also over time. If rewiring leave the arm tube as it is, if not you will be in for plenty of work. Do not scrap the socket in favour of RCA as it is of very high quality.
One thing most ignore is the bass enhancement the LF resonance adds. This is said to compensate for the cutting roll off. This is observation rather than fact. Myself I feel it is a mild loudness effect and most welcome.
Going back to the Mark Baker arm. It has a dual pivot much like uni-pivots. The sound is both powerful and sweet. Sweet and carbon fibre are not to my ears the usual bed fellows. Uni-pivots often are delicate but lack bass dynamics. Nice to be wrong. Who knows I might hear a carbon fibre speaker I like. The one I did like was very cheap and was a freebee in a Sansui system. Wood is the ultimate carbon fibre. It is slightly superior in having relaxed fibres. Wood comes in types so should offer anything you want. Mostly the glue rescues carbon fibre. If one uses wood or carbon fibre it is very likely it is the glue that is the bigger deal in the sound. Sadly the buyer sees the carbon fibre and thinks racing cars. I went on an Airbus A380. They chose glass fibre plus aluminium composite as it offered the better outcomes. I am told hemp exceeds carbon fibre if processed properly. Hemp clothing looks great. Also it produces good quality paper. Carbon fibre started as nylon burnt in a vacuum. That sounds a bit too easy to me .
The SME slot might not be ideal if having setting tools. A slotted head shell might help if it is compatible ( ears ). Then the SME slot and head shell slots can super tune the position. This is what people mean about the SME being wrong. You will need high power binocular lenses to see this alignment. If so it is true. Then anti skating comes into it. I could believe if the bottom bearing was optimum some pick ups would suit zero bias if the 12 inch. Grado comes to mind.
Talking to Mark Baker of Origin Live I was very surprised to hear that the Conqueror arm is multi layer carbon fibre. Mark was totally unwilling to say what the other layers were. The fact it looks like metal means Mark is not into the carbon fibre look. One thing to say. Frank Schroeder made a carbon fibre arm that I didn't like. I was quite prepared to leave it at that and reinforce my prejudice. Unhappy to be so unscientific I added mass to the arm. It was totally transformed. Sadly ignoring the typical mass and thinking a lower mass can only be good is so obviously wrong. Carbon fibre was mostly wrong in being untypical. The LF resonance of a PU is critical. If you have a strong low mass arm you will be able to fine tune it. SME 3 comes to mind as no one rates them. If too high you will not. The blu-tak is good because it damps as well as adding mass. It looks horrible as the downside. Tracy Chapman truly was magical once tuned in. The noticeable quality was complete freedom from spittiness and expansive warmth. The SME 12 inch of old sounds dramatically better than the 9 inch. On taking them apart they are identical. Some say it is the geometry. That is nonsense as most of us can not see well enough to get the alignment better than 1/4 mm. Also at some point the 9 inch error will be zero. I suspect on the 12 inch SME gave in and built a better arm for no more money and forgot low mass. The 9 inch is 60% as good as lets say the Mark Baker arm. The 12 inch is in the same category. This proves the supposedly rubbish SME bearing is OK and in fact rather good. The SME bottom bearing is usually badly set. If you loosen/ tighten it and do the blowing test at 0 g it can be optimized. It will take you about one hour. Like motorcycle or bike head race it needs to be the point between tight and loose. Usually I take it back slightly more than it needs towards loose. On a Garrard this should slightly reduce the effects of rumble and give dynamics. SME seem to have it loose and use gravity to hold it firm. In my opinion this is a big improvement to get it right. There is an Allen key set screw and threaded part to do the setting. The 10 inch is a great arm. It goes for less money and will fit in the standard 9 inch slot on most turntables. 222 and 210 mm centre to pivot distance I seem to remember. I usually set the hole to 215 mm to suit both. The mass of the 10 inch seems to pay off. Again the " better geometry " is the stated reason. If the slot is set at 45 degrees that is ideal . Sometimes space will not allow it. Some say the slot is wrong and compromises the geometry. I will not say what I think of that. The older arms had fibre rawl plugs inside ( resin plus rope ). That will do a very good job. I think the metal changed also over time. If rewiring leave the arm tube as it is, if not you will be in for plenty of work. Do not scrap the socket in favour of RCA as it is of very high quality.
One thing most ignore is the bass enhancement the LF resonance adds. This is said to compensate for the cutting roll off. This is observation rather than fact. Myself I feel it is a mild loudness effect and most welcome.
Going back to the Mark Baker arm. It has a dual pivot much like uni-pivots. The sound is both powerful and sweet. Sweet and carbon fibre are not to my ears the usual bed fellows. Uni-pivots often are delicate but lack bass dynamics. Nice to be wrong. Who knows I might hear a carbon fibre speaker I like. The one I did like was very cheap and was a freebee in a Sansui system. Wood is the ultimate carbon fibre. It is slightly superior in having relaxed fibres. Wood comes in types so should offer anything you want. Mostly the glue rescues carbon fibre. If one uses wood or carbon fibre it is very likely it is the glue that is the bigger deal in the sound. Sadly the buyer sees the carbon fibre and thinks racing cars. I went on an Airbus A380. They chose glass fibre plus aluminium composite as it offered the better outcomes. I am told hemp exceeds carbon fibre if processed properly. Hemp clothing looks great. Also it produces good quality paper. Carbon fibre started as nylon burnt in a vacuum. That sounds a bit too easy to me .
The SME slot might not be ideal if having setting tools. A slotted head shell might help if it is compatible ( ears ). Then the SME slot and head shell slots can super tune the position. This is what people mean about the SME being wrong. You will need high power binocular lenses to see this alignment. If so it is true. Then anti skating comes into it. I could believe if the bottom bearing was optimum some pick ups would suit zero bias if the 12 inch. Grado comes to mind.
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Agreed on learning from BBC.
Look back and you'll find that as long as the Brtisih speaker industry offered BBC based designs, they were doing well.
This is not to say that only BBC knows speakers, of course there are some very knowledgeable people out there, but it seems obvious to, with the benefit of hindsight, that BBC's knolwedge of crssover networks was unique at that time. mostly throughout the 70ies, and is I believe still very rare today.
I base this on the experience accummulated from a friend who makes a living out fo correcting designers' booboos. You bring an otherwise so-so speaker to him, he analyzes it and redesigns usually a totally different crossover for them, turning unpromising speakers to rather good speakers, and on occasion, if good drivers were used, or the owner accepts a change of the drivers, into excellent speakers. He also designs his own speakers, without the problems built in. A mechanical engineer by formal trade.
I'm willing to bet that if one could get the BBC to design a few speakers, we'd have something well above the norm to talk about.
Look back and you'll find that as long as the Brtisih speaker industry offered BBC based designs, they were doing well.
This is not to say that only BBC knows speakers, of course there are some very knowledgeable people out there, but it seems obvious to, with the benefit of hindsight, that BBC's knolwedge of crssover networks was unique at that time. mostly throughout the 70ies, and is I believe still very rare today.
I base this on the experience accummulated from a friend who makes a living out fo correcting designers' booboos. You bring an otherwise so-so speaker to him, he analyzes it and redesigns usually a totally different crossover for them, turning unpromising speakers to rather good speakers, and on occasion, if good drivers were used, or the owner accepts a change of the drivers, into excellent speakers. He also designs his own speakers, without the problems built in. A mechanical engineer by formal trade.
I'm willing to bet that if one could get the BBC to design a few speakers, we'd have something well above the norm to talk about.
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