Changing a sm op amp.

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Cressy Snr
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#16 Re: Changing a sm op amp.

Post by Cressy Snr »

You, know what Paul, you and me must be telepathic or something. Today, quite independently, I put my Beresford TC7510 Mk something or other back in the system, just to try against the Topping E30 with linear power supply.
The old Beresford sounds ridiculously good. Lovely, sweet sound but with no veiling of details. Crazy.
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Paul Barker
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#17 Re: Changing a sm op amp.

Post by Paul Barker »

Oh ballsup, it was mechanically constructed to block meddlers. Bushmaster that is. Image

So anyway, headphone volume had to be sacrificed. But I’d never use that, and could replace pot!

Image

Two surprises, op amp is a good one LMH6672 but no mention of FET input, so I’ll try a burr brown for that, but before bothering I’ll need to replace the standard elna electrolytic output caps. they’re 100 micro Farad with 33k I suppose for headphones but phono out catches them too.

I’ll have to think about this problem! I think my pot is 100k. I’ll get my capacitor spreadsheet and decide on a poly cap, but first I’ll check for offset. Might dc to amp!

No wonder bass good with 100 output cap. Why the great voicing I can’t explain except it’s a good opamp by specifications.

Any thoughts from the floor?
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#18 Re: Changing a sm op amp.

Post by Paul Barker »

Pin out of op amp same as the op amps I’ve bought.

So if the ofset is minimal can one dc via a ground connection within beresford but 100k to ground instead of the 32k Stan used so it doesn’t oscillate when not connected? Then dc to 100k amp pot and grid? So then 50k load, more than enough!
Then if ofset unacceptable I can use smaller poly output cap.

Am I on right lines?

Oh Waily Waily my best sounding dac by far injects audio through 100 ‘lyrics into my carefully thought out power amp with no coupling caps! Waily fekin Waily!

I give up, now where did I put those MOFO parts?
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#19 Re: Changing a sm op amp.

Post by Paul Barker »

Tea was drunk way too quickly, im still in shock discovering my precious powe amp was attached to big ‘lytics!
Image

AND SOUNDED BETTER BY FAR THAN SPITFIRE FFS!

I need to go to the Dr for antidepressants this has set my mental health in a spin!
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#20 Re: Changing a sm op amp.

Post by Paul Barker »

Oops itchy fingers!

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#21 Re: Changing a sm op amp.

Post by Paul Barker »

Damage limitation, if I put 100k output load resistors to ground at the dac phono out // with my 100k pot -3db is 3hz with 1 micro Farad paper in oil, I think I have some 2 micro Farad : 1.5hz. That should prevent opanps dying of current draw if an offset occurs. Maybe I can live with a pio cap.

But (you knew that Goat would be waiting somewhere didnt you?) has anyone tried dc output? I know, depends whether Stan has put an acurate ofset null circuit in and I guess all bets are off for opamp swaps. Might be easier life if I live with one cap.

This is not good for my spectrum: Capacitors! get the garlic!
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#22 Re: Changing a sm op amp.

Post by Paul Barker »

just a random thought, you know the 1 micro Farad Tants used on output of smps’s etc to mute hf ripple? Are those any good for audio?
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Nick
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#23 Re: Changing a sm op amp.

Post by Nick »

Just to say, you do realize you are denying what your ears are saying to make them fit your beliefs...
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#24 Re: Changing a sm op amp.

Post by Paul Barker »

Anyway I found two 3.3 polyprops. By my calcs -3db at 1.6 hz into the thevinine resistance of 28k. Its cool, bass remains better than Spitfire DAC. I think the bigger caps were to account for headphones, which I wouldnt have used and will have trashed anyway by damaging the pot to get pc board out. I had to look on the underside to follow the traces and be sure there wasnt a different opamp for RCA out. There wasnt! I am real cool with the no headphone situation. Top end improved bass not lacking, voicing not yet sure as the music hasnt come to voicing yet. I’ll try Eva, then Diana, and finally Nat. If they sound right, Ill find a piano piece to see if its realistic. No, lets do Patricia Barber, Cafe Blue first, WOW, that one worked. Eva next : ‘nough said, Eva is way better than Spitfire DAC Way better. Lets try over rated, but beggers cant be choosers, you have to work with people still alive aswell, Krall. OH fukc! never felt her in the room with me before, Damn thats good way more 3d imaging. Yep as it stands so far dac passes with flying colours. Lastly Nat then some piano etudes or sommat like that. Maybe Grieg conc. Please help me, has someone tricked me and sneaked some vinyl into the hose when I was asleep? Nat is at his best. Oh my god Rubenstein has snuck in with a concert Grand. But Nocturnes arent taxing, Ill try Grieg. Dee, dee dee dee, dededa dededa do do do do, doo dodo do doo! la la la, la la lee. Yep grieg is on song.

Right so, desoldering this great opamp, adapting to dip 8 socket et al; Ive not yet talked myself into it. Im scared so far. Im only used to BIG things to solder!

To be fair to Spitfire, it also probs has big ‘lytic couplers, so I cant forsake it yet, and maybe the opamp inside isnt as good as this opamp on the ear.

So no absolutes yet! I may end up with two much better dac’s. and this im listening to is the first, even before opamps can be rolled.
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#25 Re: Changing a sm op amp.

Post by Paul Barker »

Dizzy’s New Wave album really pops out into a huge soundstage. Bugger me this Beresford DAC is pretty damn fine now.
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#26 Re: Changing a sm op amp.

Post by Paul Barker »

Humblest apologies to Ant; Little Feet “Long Distance Love” proves these speakers DO BASS……

I knew the science of the power amp was right for good bass. Now Im hearing it. Ive looked inside Spitfire DAC tinier sm stuff and I got lost tring to find output caps so fekit. Ill just sell it, because its a hopeless case anyway. No way an opamp change could make this GYNORMOUS difference!

I play with opamps on Beresford, when Ive conquered my fear of tiny solder tasks.
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Mike H
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#27 Re: Changing a sm op amp.

Post by Mike H »

Image
 
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Paul Barker
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#28 Re: Changing a sm op amp.

Post by Paul Barker »

Nick wrote: Sun May 08, 2022 10:18 am Just to say, you do realize you are denying what your ears are saying to make them fit your beliefs...
I’ll accept that. If I find differences in opamps I can at least bring those for blind auditions but without audience blindfolded, Ill change opamps behind a screen.

Ive also been watching you tube guy or two (his mate) who made smps’s for Nassa and air force. So I could do a switch of power supply’s. Paul Barker choke input black Gates compared to a lab smps. Both at same b+. Might be interesting. With the proviso judging the quality of either with the test equipment the guy’is equipment and skill so out of my capability, I couldnt tweak the smps, it appears to be highly technical. But it will be something else to assist progress. Id be delighted if smps works just fine. Getting too old for Boat Anchor power supplies. The smps at the voltage is capable of 390mA The Boatanchor 300mA. The demand: 210 mA, so the power supplies are both up to the task.

I wont bring anything else, Beresford dac has no usb just toslink and phono, bearing that in mind, ill need someone to bring a streaming source as mine is apple tv and that needs a tv and a good broadband. Maybe the broadband there is great? i could buy a smallish second hand tv with optical but if its simpler for someone with a good variety of streaming music and gadget thats less clumsy to use away from home that would make it easier for me.
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#29 Re: Changing a sm op amp.

Post by Paul Barker »

Ill mirror this or link it again when Steve starts the “what are you bringing” but as I have yet to adapt dac pads to various fitments of opamps so its not yet a thing. I have a clamp holder that expands the sm dacs to the 8pin type. The two single opamps Ill figure out a jig for those. I think there will be 5 or 6. Though if anything is pants I may not put it in the comparrison, and if later someone thinks Id like to have heard that, we can offer it. Dont have to bore everyone with too much to juggle. I will wait and see if the differences are worth it at all first. Ive only bought reasonably priced opamps, but ones liked by other audiofiles. Anyway bring youre own if you want?
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Mike H
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#30 Re: Changing a sm op amp.

Post by Mike H »

I am reminded of a magazine article some years ago, think it was for a CD player — not only a two kinds of op-amp 'shoot-out', but also involved putting blocks of sound deadening material on top of each one and they were convinced that was an improvement. There's a danger you can convince yourself of anything if you try hard enough. :D
 
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