Gainclone heaven ?

[nik.d]

Here comes another "Gainclone". Seen on the photo are basic building blocks of bridged LM3886 amp.
Interesting (domestic) project using 'External Feedback' like it is used in any (serious) measurement instrument.
With this concept, speaker cable influence on sound is diminished. Another advantage would be using such an amp
with servo controlled woofer(s) - there are few on the market today.

[listening]

After trying out a lot of things with 0.9z-9b and Windows 8 the system seems to be very stable and the time has come to ban the input capacitor. For the case of accidents it's easily connected again. Additionally I connected in parallel with the buffering capacitor a styroflex capacitor on the amp board which works beautifully for the heights.

Georg

[PeterSt]

For the case of accidents it's easily connected again.

That's true. But did you calculate-in the FACT that when accidents happen all your GC chips will have been smoked and that you need to replace a couple of speaker drivers ?

NOT ADVISED.

Peter

[Nick]

After trying out a lot of things with 0.9z-9b and Windows 8 the system seems to be very stable and the time has come to ban the input capacitor. For the case of accidents it's easily connected again. Additionally I connected in parallel with the buffering capacitor a styroflex capacitor on the amp board which works beautifully for the heights.

Georg

Georg hi,

I tend to agree with Peter. In addition I find the sound tends to get better with input caps. Without is very pure but with seems to improve balance of the sound. I prefer with.

Paul and I are using blackgate n types. In my case I use type nx in 47uf size. There is a guy selling them on ebay from japan at the moment. They are expensive but very very good on the input of gainclones.

Cheers,

Nick.

[Nick]

Nik.d hi,

Interesting looking boards, how is your build coming along ?

Regards,

Nick.

[listening]

Thanks Peter, thanks Nick,

it's easily switchable. So I can try a new hardware config or software version with input capacitor at first  . I found the Blackgate seller in Japan and another source in Europe and will order a pair.

Georg

[Scroobius]

Hi Georg - as the unfortunate owner of a couple of "smoked" drive units I would not go without caps now. The BGN's are superb and they have very little impact on SQ. Best of luck with your project.

Paul

[nik.d]

Nik.d hi,
Interesting looking boards, how is your build coming along ?
Regards,
Nick.

Hi Nick

Sorry for late reply, spent 'long weekend' on Danube river with friends. A nice one. I'm a bit slow, actually wanted somewhat better basic components and ordered
(and finally received) Bayschlag 0.1% resistors and some Roederstein elcos. Transformers are ready. Need only good 4.7 uF polyprop cap and final decision: to build
separate cases or one as dual mono. This because I already use two sub (plate) amps. Adding separates near mid/hi section would eliminate long speaker cables.
Old dilemma: long spkr cables or long IC's... Esp. when amp is constructed to minimize (spkr) cable influence

Brgds,
George

[Nick]

George hi,

That is a chestnut, long interconnects v speaker cables.

I found that having transformers in the same case as the amp modules really hit sound quality. My current design is two box but to split is amps in one box and transformers in the other. The amp performs much better like this.

If the 4.7uf caps you are looking for are for input decoupling it might be worth hunting out some 22uf or 47uf Black gate nx types (see earlier post). Paul and later Myself have had very nice results with them. I preferred them to mondorf silver gold oil caps, wish I had known earlier !

Cheers,

Nick.

[nik.d]

Nick hi,

Yes, am looking for good input cap. Reading nice things on ClarityCap MR series PP's but guess what: seems I'l be able to get few
BG-NX 22uF/6,3V caps as well. Seems my old friend (passed away last Summer) left behind him some good audio parts, not only
couple of unfinished GM70 power amps. His book was (still is) nice reading on tube audio gear.

Brgds,
George

[Nick]

That is sad to hear about your friend George.
GM70s look like a serious tube, 1000v b+, your friend must really have known his way around valves. What book did he write your?

Regards,

Nick.

[nik.d]

Book was collection of ideas & examples on building tube audio pre/power amplifiers, with god examples of various 'schools'.
One of rare books well written in local language. His 6L6 integrated was positively reviewed by Jean Hiraga in (think) 'Revue
Du Son'. Had cooperation w/ 'Teresonic' as well. And above all, loved motorboats and Danube river.
Some pic from his book presentation

[Scroobius]

Hello fellow noise hunters. I thought I would post on my continuing quest to get noise in my system to absolutely the minimum possible.

As described elsewhere I got a very significant reduction in noise resulting in improved sound quality by separately connecting the cases of my amp, PC and NOS1 back to the earth rod in the garden. NOS1 and amp cases are NOT connected to electronic ground. I have to say I was very surprised at the level of improvement this brought about (but see below as this may be related to the problem found below).

But still although noise levels were now low there was still some noise I could hear with ear next to speaker cone albeit at a fairly low level.

My amp layout is shown here http://www.phasure.com/index.php?topic=1575.msg26709#msg26709    there was some discussion at the time about moving the transformer box away from the amp to potentially reduce noise. So this weekend I spend many hours doing just that. I moved the transformer box 2 feet away from the amp box and guess what no difference at all in the noise levels. Ah well something learnt.

Later that night I was lying in bed thinking that I must have missed something. And I had !! - because then I thought that whilst I was listening to the speaker cones I was missing the point  that actually I was hearing more noise from the actual transformer box in the conservatory than from the speaker. Surely the transformers should not hum that loudly!!.  This thought was exemplified by the fact that the character of the sound I was hearing from the speaker cone was exactly the same as I was hearing from the transformers.

Mmmmm so there was only one conclusion the transformers were louder than they should be because they were next to each other in the box and their EM was interacting. So I removed one transformer from the box yesterday morning and hey presto the noise from the transformers AND the speakers lowered.

So then I removed both transformers from the box (and well away from each other say 2 feet) and the noise level went UP slightly. So I tried them in all sorts of positions (including stacked Peter) and the noise level changed each time.

But then the really strange thing was that putting both transformers back in the box but in a different position resulted in the lowest noise of all!!!.

So then I spent hours rebuilding the amp to end up with exactly the same amp setup that I originally had BUT with the transformers diagonally opposite each other in the box but with very low hum levels and lower than in any other configuration (including 2 feet apart on the carpet). But then it gets better because putting the lids back on and back in the final setup on the hi-fi stand lowered the noise even further. In fact I really struggle to hear any noise at all from the speakers (OK I know they are only 92db sensitivity) even with my ear right on the cone and I mean right on the soft dome in the centre of the speaker oh and also with a very quiet house.

This is all basic stuff which really I knew before but had overlooked in my enthusiasm to build the amp. The moral of the story is when building the amp in the first place check all positions for the transformers to find where they hum the least it is really really important to do that especially with the big transformers I now have. And make sure you only use high quality quiet transformers.

I have been listening to strings and opera and I have never heard this level of clarity - stress free crystal clear clarity - in my system before.

A lot of work this weekend but well worth it. I cannot imagine what else I could do now to get noise levels lower but I would always be open to suggestions.

And also having got the noise levels so low I can now really appreciate just how good this bridged bi amped gainclone amp is.

Paul

[PeterSt]

Congratulations Paul !

And since you're asking anyway ...
I am fairly confident I am overlooking something now, but why do you use two trafo's in the first place ?
I forgot a bit, but looking at your picture again, did you put two (differential) channels in there ?
If so, mono's would be the solution ...
I don't think you'd gain on anything but a cabinet and a power inlet plus switch and fuse. Or ?

And if you have a wire connected to the shield of the trafo's, just don't connect it to anything (for trials).

Regards,
Peter

[PeterSt]

And Paul, one more other thing I wanted to tell you, but forgot :

I don't think any torodial transformer should acoustically hum in the first place.

Unless you have DC offset on your mains.

Yea, now what. Another can of worms ?

And I dare to add : when your transformer hums because of DC Offset, you will have a very hard time in discerning the same noise from the speaker (which really is there - watch it !).

Assuming you have a sort of isolated situation of your audio chain, hence not all that many devices can imply the DC offset, investigate your PC's PSU ...
(hence switch off the PC and and listen again).

HTH,
Peter