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Old 23rd February 2003, 08:15 PM   #741
gpapag is offline gpapag  Greece
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Default "Hit me with your rythm' stick"

Dear fellows

I had claimed that i spotted dramatic differencies in sound due to resistors directionality ("This is not just another gainclone" thread, page 47, post# 698). Suggestions for repeated and reversing testing from Bobken, open doupt from MRehorst, and my own uneasiness with the subject findings, pushed me into more testing. I used various setups (one LM1875, later two LM7815 amps and special connectors for attaching the resistors), but as the testings were progressing, it became clear to me that-as Bobken and Fedde have also marked- the important think is to isolate one variance from the others. So finally, i settled for a single, fixed, compact "jury rig". A TDA7294 (more detailed sound compared to LM1875), inverted [Rin=12K, Rfb=120k,Vin+ tied to grnd. stabilised +/-15VDC, 1000uF//0.1uFper polarity], mounted on a big heatshink with all the connections to the outside world firmly attached to an aluminum angle bolted to the heatshink. No loose connections or moving cabling anymore. I started probing the feedback resistor first. I was soldering and desoldering it directly on the applicable IC pins, with listening tests in-between. Soon I found out that my listening memory is short termed, at least as some very critical details are concerned, so i had to shorten the time (approx.3 minutes) between testings. I opted for a DPDT switch for to switch btn two resistors in the feedback path. Now, time between testing was approx 3 seconds. I was more confident for my judgement now. The following resistors were under (sighted) test:

1. Single 120K 1/4W carbon film 5% resistor (two pieces, A and B).
2. Single 120K 1/2W carbon film 5% resistor (two pieces, A and B).
3. Single 120K 1/2W metal film 2% resistor (two pieces, A and B).

The test patern was as follows:
ll Test No ll Resistor in Switch Position x ll Resistor in Switch Position xx ll
ll a. ll 1A ll 1B in opposite direction of 1A ll
ll b. ll 2A ll 2B in opposite direction of 2A ll
ll c. ll 3A ll 3B in opposite direction of 3A ll
Each of the above abc tests was intended to discriminate the directional effects (if any) for each resistor type. Listening material was intentionally limited to 3 minutes sections of 2 particular musical pieces. List: Piano Concerto No1 (Boris Berezovsky, Philarmonia Orcestra, Hugh Wolff, 1995 Teldec DDD recording), and Korngold: Concerto for Violin and Orchestra in D major (Gil Shaham, London Symphony Orchestra, Andre Previn, 1994 Deutche Gramm. DDD).
Each test was comprised of 20 comparisons (switch position changes), 10 for List and 10 for Korngold.
The results did not confirm my previous claims, at least they did NOT support any dramatic directional effects. This is all that i can expect for such a test. It left me with a marginal preference for a particular direction -the same for all three resistor types-but generalisation and confirmation requires blind tests and a great number of resistors, sampled randomly from many sources at different times ect, ect.
This test gave me the chance to compare the "sound" of the three resistor types. I can say that for the particular setup, the 1/4W carbon was the least discriminating. The 1/2W metal, seems to be the most detailed. The 1/2W carbon gives the impression of having more "body", not much away from the 1/2W metal in terms of clarity.
I tried some more tests with long listening intervals and different music material, the results of which, didn't contradict the above claims.
Then i conducted some more tests:

Single 120K 1/4W carbon film 5% resistor, direction x, against
two 240K 1/4W carbon film 5% resistors in parallel, direction x. The parallel combination seems to give marginally more detailed sound. This, may be due to power sharing (douptfull, as voltage drop across resistors was approx. 3mVpp), or due to partial randomisation of the resistors properties.

Two 240K 1/4W carbon film 5% resistors in parallel, direction x,against
two 240K 1/4W carbon film 5% resistors antiparallel. No difference perceived.

These two last groups of tests (conducted following the protocol of the initial tests) were repeated for the carbon 1/2W and for the metal 1/2W. Same results, no difference.

Such tests (as Steve Eddy has pointed out) can not be scientific. Even under the most strickt protocols, the only think they guarantee is that they minimise the influence of SOME variables. The conclusions are applicable to the particular setup only.
The only reason i presented them here is that i felt it as an obligation, since i have made such a claim of resistors directivity in the past. I appologise for the fuzz. The details are given for the record, and for repeatability purposes. The (due to methodology) limited conclusions are totally biased by my hearing ability, and the quality of my audio chain. This means that differencies may exist, but i am not able to detect them. In any case though, the application of two antiparallel resistors in place of a single resistor, may wipe out any real or imaginary "directivity coloration".

The whole thing took me about 50 hours. What did i gain from this ?
1. Peace of mind. I don't have to check all the resistors of my equipments. Even if differencies may exist, they are not dramatic. This is enough for me.
2. A reliable setup, which i can use in the future to A-B test other components.
3. A limited A-B testing experience.


Regards
George
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Old 23rd February 2003, 08:53 PM   #742
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Default Re: "Hit me with your rythm' stick"

Quote:
Originally posted by gpapag
The whole thing took me about 50 hours. What did i gain from this ?
1. Peace of mind. I don't have to check all the resistors of my equipments. Even if differencies may exist, they are not dramatic. This is enough for me.
2. A reliable setup, which i can use in the future to A-B test other components.
3. A limited A-B testing experience.
Great! And thanks for sharing.

Now if only every 50 hours we spent on something could yield such satisfaction in the end.

se
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Old 24th February 2003, 12:16 AM   #743
Bobken is offline Bobken  United Kingdom
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Hi George,

Thanks for sharing these details with us, and you did quite the right thing in carrying out the detailed tests like you did.

I am not really surprised at your results, as, so far, I have also not detected any directionality in resistors, although the same is not true for many capacitiors which definitely are directional.

I am glad that you are not deterred from trying out similar tests in the future, although this being your first time and the total time taken for testing so long, it must have been rather disheartening.

You have also realised that there is no point in any self-deceit in cases such as these, and that is good lesson to learn if you wish to make some real progress with sonic improvements on your audio equipment in the future.
It is all too easy to convince oneself that because you have spent a lot of time and/or money on a particular modification, that the result must be better regardless, but that is really pointless.

Ironically, several of the most difficult and expensive mods I have tried over the years have been a complete failure, but that is life, as they say, and other easy/cheap mods often unexpectedly make up for these disappointments.

As I said before, not everything that one initially thinks is a real (long-term) change, turns out to be so, but by adopting the suggestions I made, you are as absolutely certain as it is possible to be, and this is what really matters.

If I may offer some more advice for your future testing sessions, in addition to instrumentals, I always listen to vocals too and especially female ones for HF as they can be very revealing if you have some good recordings. Also, male voices cover a surprising proportion of the usual human hearing 'spectrum', and listening to a good tenor like Andrea Bocelli who has wonderful 'colour' in his voice, is always very revealing to me.

Personally, I only attend live concerts a few times each year (and live music is the only real yardstick, as this is what we are trying to replicate, of course) but we all listen to voices every day, and unusual abberations etc. are often easier to pick up this way, simply because we are more familiar with how they should sound.

If it is any consolation to you, when I first started to do these kind of listening tests maybe 30 years ago, my success rate was probably only about 60% (at a guess), but things improved over the succeeding years with practice, and I am sure the same will happen to you. It can be frustrating and may at times appear to be fruitless, but it is very rewarding when you discover some real improvements, and then it all seems worth while.

You have a very nice country, by the way, and I have had many happy holidays in the islands around your mainland.

Regards,
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Old 24th February 2003, 07:42 AM   #744
Guiness is offline Guiness  United States
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Well after reading you guyz talk about your gainclone's. I think I am sold on the idea. But me being a tube guy, I am not very familar with SS stuff. So I have a few questions regarding Peter Daniel's schematic. First off what are the capacitors rated at? 25v or 50v? The 4.7 signal cap? I am also curious if any of you have tried more expenive paper in oils or the new jupiter caps. I am very fond of them in tube gear, but maybe you do not like the tube sound.

Next the power supply is confusing me. So Peter you are using one power transformer (22-0-22 @ 400VA) for both channels, right. But I am not understanding how it is layed out. The secondaries are then led to a bridge rectifer then into a 2000uf cap? What is the rating on the power supply caps?

If you have time can you draw up the power supply for both channels. Help out a beginner in the middle of all this information. Thanks
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Old 24th February 2003, 09:13 AM   #745
JDeV is offline JDeV  South Africa
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Quote:
Originally posted by Guiness
Next the power supply is confusing me. So Peter you are using one power transformer (22-0-22 @ 400VA) for both channels, right. But I am not understanding how it is layed out. The secondaries are then led to a bridge rectifer then into a 2000uf cap? What is the rating on the power supply caps?


Hi Guiness

Here are some more good links on the Gainclone.
http://www.geocities.com/rjm003.geo...dio/diy_gc.html
http://home.student.utwente.nl/f.s....o/thor-amp.html
http://www.euronet.nl/~mgw/diy/amps/uk_geenkloon_1.html
http://www.diyaudio.com/forums/show...p?threadid=9112
http://diyaudio.com/forums/showthread.php?threadid=9270

Here is basic PSU connectio, option 1:
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Old 24th February 2003, 09:18 AM   #746
JDeV is offline JDeV  South Africa
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PSU option 2:
Supply caps can be 50V.
For this option you can put 1 IC on one bridge and the other IC on the other bridge - (for stereo version)
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Old 24th February 2003, 09:28 AM   #747
JDeV is offline JDeV  South Africa
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Same as option 1 , but better to take separate leads to IC's.
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Old 24th February 2003, 03:59 PM   #748
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Hey, you forgot PS option no. 3.

<center>
<img src="http://www.q-audio.com/images/bipolar.jpg">
</center>

se
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Old 24th February 2003, 04:42 PM   #749
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Default grrrrrrrrrr

I have a question for all. What am I doing wrong WRT grounding ... I know that is to open ended.

I have build several p3a's and hummmmmmmmmmmm

I thought I would try something easier and build a couple of gainclones and hummmmmmmmm

The hum only is there when I have a stereo amp with a signal on both channels from the same source. For example from a stereo cd player. There does not have to be and music playing but the cd player must be on. I have also tried my Pre Pro and same thing. It is a perfect 60cycle repeat on my scope.

I have the ground going back to the long leds of the powersupply caps. So it is a star as all ground meet there. I have both amps with it's own starground. They meet back at the transformer.

One channel works great by itself. No hum or noise at all. Only when I connect it through an external source do I get a hum.

Can anyone give me any help. I am getting desprete to make somthing work after all this time (about 4 months) and money (abouit $800 total) invested.


Thanks a lot allll

Ted Polzin
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Old 24th February 2003, 04:49 PM   #750
fedde is offline fedde  Netherlands
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Quote:
Originally posted by Peter Daniel


If you use the schematic below: 50k log pot at the input, 4.7BG N coupling cap, standard BG caps for PS filtering (4,000u in total), 400VA toroid (double 22v secondaries) with 8 discreet hexfred diodes (separate bridge per rail, both channels share rails, separate wires from PS to amp, 8 total), no bypas, no filtering in PS. Resistors - Riken 1W for 10K input and 220k, 0.5W Holco for feedback (Holco worked well here, Riken might be good too, but I didn't check it yet). Chassis should be solidly built as well. Check my example here: This is not just another gainclone

If you built the amp with those parts, I can almost guarantee that it will equal or better most other commercial offerings, regardless of price. How's that?

Respect!

Unfortunately, there's a lot you can do wrong in building your amp. (this is also from my own experience ). I made so many changes to my equipment in the last months, and the sound changed very much too. Things as grounding, topology, shielding, wiring, soldering etc. are also very important besides component quality, condition & treatment. I hope to update my Thor-amp (and dac!) page soon about some of my findings and new knowledge acquired from this and other forums!

And also the matching with other components is important (especially speakers !)

Quote:
As to the sound, here's a quote from an e-mail I received recently (not my amp):

The sound keeps getting better, and keeps getting 'meatier' and smoother. You are correct in saying that this is an incredible sounding amp, I am in love with it. It has such a 'grab you' factor, that I really have never heard before, and the soundstage is UNBELIEVABLE.

That's the best I can do for you.
Enough for me :-)

Yeah, soundstaging is good. And the amp is quite addictive IMHO !

Fedde
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