The stock is years old predates any of the blather here. I would think excess noise would worry the resistor makers more but what would I know. We bought a small thick film maker in the 60's to get their wizard. He knew how to formulate TiW thin film targets for exact TC and make contacts with some secret sauce so there is no excess noise.
Our in-amps (especially the AD621, humble me) that use all internal thin film gain networks don't show any of these effects even at micro-volt levels. The feedback network is 2X 25K and ~500 Ohms at a gain of 100.
OK, I stand corrected. Don't use any thick film resistors unless they are special magic stocks made by a real wizard of resistors and now no longer obtainable.
As to the blather here it not only showed how to make precise measurements without the use of references it also used a bridge to allow the use of off the shelf oscillators by nulling the signal source. Prior to that method was the one developed in the '60s as used in the Radiometer Copenhagen units to use a very, very low distortion current source to drive the resistor under test and then look at the resulting third harmonic distortion. Prior to that you used an oven and precise method of measuring resistance change.
Now as to thin film resistors used in instrumentation amplifiers, I have never had any issue with these. If the gain setting resistors change values by just varying length then temperature coefficient should have no effect. They also as far as I know are on a common substrate and ratiometricaly well matched. But that is your area of expertise not mine.
Finally if you do try measuring the distortion of a 100 ohm metal film resistor at .005 volts I suspect you will find that the second order harmonic distortion does change when you reverse directions! (There is a nice rational reason why.)
Last edited:
I don't mean to be mean, but I'll wait to see if someone else tries it and confirms the results. It is an issue that may affect other tests.
Yup that's the one. ............ pension it off for a rebuild as and when Chris finds some time.
I take pride in owning not one but two power amps that got bad reviews from stereophile
Ricardo lent me one on trial.....it was back in his house inside 24 hours!! Probably the most bland amp I had ever heard. WHY even contemplate a re-build? [I also considered a Moscode......Ricardo - again - obliged and that too was returned pretty damn quick! At that time ended up rebuilding a HK Citation 1&11.....the pre was too laid back, but the power amp was a beaut. (it came from Olympic Studios (RIP) at the time it was sold to Virgin and was reputed to have been used for the bass in 'Sticky Fingers".....[Down Jacco............we know that you have one which is in bad health at the moment (hope it is healing well)]
Last edited:
...........The third of the unfortunate trio at that time was the Robertson/Robinson...(not a hybrid).
You could always get better sound by putting a gain clone in that case!
Did you ever try the BE YAM resistors which Be YAmamura specified? The final brief was delivered at my kitchen table in SW London to the boss at Vishay (in Norfolk) who had them made by Sfernice as they had the most suitable stuff to make them. In most applications they were superb but they did produce a definite sound change from the usual film types. [ I have a PA and pre (with stepped H-pad attenuators which use these throughout). They need a complete rebuild though due to a very bad power surge taking the output devices down.
You could always get better sound by putting a gain clone in that case!
Did you ever try the BE YAM resistors which Be YAmamura specified? The final brief was delivered at my kitchen table in SW London to the boss at Vishay (in Norfolk) who had them made by Sfernice as they had the most suitable stuff to make them. In most applications they were superb but they did produce a definite sound change from the usual film types. [ I have a PA and pre (with stepped H-pad attenuators which use these throughout). They need a complete rebuild though due to a very bad power surge taking the output devices down.
Last edited:
Hi brianco,
I don't think you would have been in a rush to send this amplifier back. Maybe you wouldn't care for it too much in the long haul, but it might have lasted a week or more at your place.
-Chris
Yup, that's about right. The THD numbers of the original SA-100 and SA-12 stink. You can really hear the problems. I said problems because it is a circus of engineering blunders.
Because. I was authorized warranty for Counterpoint for a while and felt really badly for their customers and the unrepairable products they were sold. It was also a challenge from a good customer who was heavily invested in all kinds of Counterpoint equipment. Once I examined the Counterpoint products in detail, many things became evident. The changes made to the SA-100 corrected technical problems that cleaned up the sound quality quite a bit. There are a couple things I have yet to look after, but the results were well worth the effort I put in. As a side benefit, the amp became much easier to find parts for and repair. The prototype has now been in the field for many years with purposely mismatched components in one channel, the other side matched and On Semi parts. No failures and the owner is extremely pleased with the results. I am too, but it can do better still. Through all the changes, I was able to keep the signature "Counterpoint sound" as well. These days it is a much more pleasant amplifier to listen to.
I don't think you would have been in a rush to send this amplifier back. Maybe you wouldn't care for it too much in the long haul, but it might have lasted a week or more at your place.
-Chris
Perhaps my system is unusual, but there are far more resistors in it than transducers. I keep trying to get rid of the little boogers, but they resist.
Bin the vertical MOSFETs and get yourself a couple of (Exicon) lateral TO-3s.
GreenStreet Audio
I'd think Counterpoint hybrids are perfect for a conversion, but certainly not a rebuild of a design by folks who were the most ignorant about MOSFETs I've encountered to date.
(http://www.diyaudio.com/forums/solid-state/204919-counterpoint-sa12-mosfets-rfm10p12-rfm10n12.html)
A typical audio system has two transducers (microphone and speaker) or four if it uses vinyl. It may use a hundred resistors. Assuming resistor distortion adds up (it might not be that bad) that means that we would want resistor distortion to be at least 50 (or 25) times better than transducer distortion. Good news! Resistor distortion is much better than that so in almost all situations we can ignore it.Pano said:
Are you confirming that metal oxide with a 300ppm/C tempco is good enough?
Given that the inherent noise and distortion in microphones are orders of magnitude greater than those in good modern resistors, you would appear to be a victim of your misapprehensions and spinning your wheels.
That said a high percentage of modern mics are capacitor mics, and many have one fairly special resistor in them that applies bias to the diaphragm.
Wow those greenstreet guys are channeling the spirit of the original designers 'upgrade' packages.
"[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular] All of the resistors in the signal path are replaced with PRPs and the coupling capacitor is changed from a 20 year old Wonder Cap to a far better sounding Auri-Cap. Next, we perform one of the most critical steps: The big blue Sprague power supply filter caps next to the transformerwe are replaced with the very best, Nichicon KG series capacitors. These are very expensive and worth every penny. Finally, we install ceramic tube sockets with gold plated contacts and rewire everything with high purity copper 12ga wire."[/FONT]
Hi jacco,
Hi billshurv,
-Chris
How could I disagree with that statement? There might be a battle for the most ignorant about Mosfets title though. They are out there.
Hi billshurv,
They recognized Michael's business model, that's all. They are getting just as bad as Micheal too. It drives me nuts when some folks dive into the magic component end of the pool. They do improve an SA-100, but nowhere near the limits you could reach by actually designing the changes. I had hoped we would see a clean upgrade, instead we get more internet hacking.
-Chris
After ordering a handgun from a magazine at age 8 in exchange for all my worldly possessions, to discover it wasn't even a flare gun, I instantly turned blind for ads.
(at age 11, I stumbled on an entire hidden arsenal plus ammo in a huge old leather factory, which regained my faith in the dark lord)
It's mad isn't it,
Complete rubbish..sound change with resistors..
You would think this applied:
Kiwame= rolled off treble.
Takman MF= smooth bright treble<<good bass clear mid.
Takman CF= warmer less treble but darker sound. Can create hiss in high gain placement.
Tantalum Non magnetic= smooth treble slightly dark sound reduced sparkle.
Tantalum magnetic= brighter sound with smooth treble but not as bright sounding as Takman MF.
Carbon film warmer sound less splash than cheap MF.
Metal film warm with high treble.
Cheap and nasty MF splashy treble ear piercing highs with smear in the mid range..
But then there is the solder used to connect..
You must be joking..
Then magnetic components seem to sound brighter than non-magnetic..but that is just NUTs...I don't believe any of this rubbish..
Lead out..hummm nawww..its all rubbish..
Mills..sound dependant on placement..dull mid with sparkle in the highs..Good bass <<you must be joking...
Then you would think resistors could smear midrange..a bit like Carbon film..
But give a warm sound with smooth treble..
And CC could sound absolute pants...but they would warm up over time..
What a load of rubbish..Like putting non magnetic tantalum in everything and having a clod of an amp with dark mid and distorted bass..LMAO
Regards
M. Gregg
Complete rubbish..sound change with resistors..
You would think this applied:
Kiwame= rolled off treble.
Takman MF= smooth bright treble<<good bass clear mid.
Takman CF= warmer less treble but darker sound. Can create hiss in high gain placement.
Tantalum Non magnetic= smooth treble slightly dark sound reduced sparkle.
Tantalum magnetic= brighter sound with smooth treble but not as bright sounding as Takman MF.
Carbon film warmer sound less splash than cheap MF.
Metal film warm with high treble.
Cheap and nasty MF splashy treble ear piercing highs with smear in the mid range..
But then there is the solder used to connect..
You must be joking..
Then magnetic components seem to sound brighter than non-magnetic..but that is just NUTs...I don't believe any of this rubbish..
Lead out..hummm nawww..its all rubbish..
Mills..sound dependant on placement..dull mid with sparkle in the highs..Good bass <<you must be joking...
Then you would think resistors could smear midrange..a bit like Carbon film..
But give a warm sound with smooth treble..
And CC could sound absolute pants...but they would warm up over time..
What a load of rubbish..Like putting non magnetic tantalum in everything and having a clod of an amp with dark mid and distorted bass..LMAO
Regards
M. Gregg
Last edited:
- Status
- Not open for further replies.