[12796]

Did you try loading resistors or comp caps in the f/b loop at all? cap drive seems to be important for the treble and bass.

 

[PinkFloyd]

Quote:

Originally Posted by FritzS Has anyone tested other output transistors in place of BD138/139? Toshiba's 2SC2238 / 2SA968 have a higher ft - about 100 MHz

Hi Fritz,

The transistors are BD139 / 140 I haven't tried the tosh varieties but maybe someone else here has? I tend to stick with the stock kit parts and only really experiment with alternative opamps and caps etc. Have you got your kit as yet Fritz?

Quote:

Originally Posted by FritzS What case use you? I search for a little bit greater - for place for a headphone protection circuit kit.

The enclosure I use is the bog standard Hammond 1455N1602 which measures 160 x 103 x 43mm Part number N77AL available from Maplins You will certainly need a slightly larger enclosure if you're contemplating incorporating a headphone protection circuit... then again, you may have enough room in a 1455N1602 to piggyback the head protection circuit onto the amp PCB dependant on the size of the protection circuit etc.

 

[PinkFloyd]

Quote:

Originally Posted by biovizier Did you try loading resistors or comp caps in the f/b loop at all? cap drive seems to be important for the treble and bass.

I must confess I didn't Nick..... plug and played it and all sounded fine with OP caps in place.. will try without OP caps and report back.

As I type this AD744 is in the circuit (brand new virgin) and sounding exceptionally good, very spacious with superb three dimensional soundstage but the mids are ever so slightly recessed (laid back) with the treble and bass dominating the proceedings..... even so, this is one pretty nice sounding opamp and I am taking notes

truckloads of space around instruments though.... a very thrilling, roller coaster ride of a listen indeed..... will let it burn in for a few hours. Dunno why I haven't rolled this puppy in before now

 

[12796]

I havent tried that one yet - I have heard good things about it though.

Did you try ad847 yet? Try that one without caps too.

I will send you two ad8067 - PM me your address.

I am still interested in the composite pcbs - I sugggest ad8067 coupled with ad847 will be stellar.

I suggest we try out a few more opamps (ad843-847-8065-8067 et al). Then concentrate on tweaking the best one as we did with the lm6171. I bet some of these chips have a lot more to give to given the spec sheet notes.

 

[PinkFloyd]

To be honest Nick..... this 744 is a lot better than the 843, just did a very quick hot swap and the 843 sounds thin and veiled compared to the 744 which is now in again.... must get David to have a listen to this one.

PS: my new opamp "puller" is superb I can remove and refit 2 opamps in 12 seconds flat now

Mike.

 

[12796]

Where did you get the puller?

I would remove the caps before reaching a final judgement

 

[PinkFloyd]

Quote:

Originally Posted by biovizier Where did you get the puller?

It's actually the trim remover for my cars alloy wheels (to gain access to the nuts) It's a perfect fit and slots under the opamp.... you then simply lift up and out she pops

Quote:

Originally Posted by biovizier I would remove the caps before reaching a final judgement

To be honest Nick..... removing the output caps is the same as going from an opa134 to a LM6171... they stifle the sound something horrible, I would NEVER go back to using output caps....... NEVER.... they are like putting a mattress between your ears and the signal..... awful!

 

[12796]

I have removed the input caps too. No caps at all now! Works with the ad8065 a treat.

 

[PinkFloyd]

Nick,

There is a chip I'm trying at the moment and I'm not going to tell you what it is until next week (I'll give it a good listen all weekend) I can say that it is seriously "by far" streets ahead of all of the others I have tried and it gives new meaning to the term "spaciousness".

Sounds are coming from all directions..... directions I didn't even know existed! No Bull, to my ears the search is well and truly over (for me) Nick..... as I say, I'll give it a damned good listen over the weekend and if things remain the same or get better I'll divulge on Monday.... I want to be absolutely certain about this before saying any more........

Mike.

 

[12796]

you little tease! lets see how it stacks up against the ad8067 without any caps.

 

[PinkFloyd]

Quote:

Originally Posted by biovizier you little tease! lets see how it stacks up against the ad8067 without any caps.

Let's just say I find it so good that I'm off out to increase the gain a tad right now! A clue for you, It's not an AD chip and neither is it considered a "high end" chip

 

[StevieDvd]

Is it one of the NE/SA/SE5534 per chance?

Give me more soundstage pleeeeeeeeeeeaaaaaaaaaaaasssssse

Will I need to learn how to trim my WNA to opamp swap soon

 

[12796]

Yeah the ne5534 I bet. Or an lt1028.

 

[PinkFloyd]

Quote:

Originally Posted by biovizier Yeah the ne5534 I bet. Or an lt1028.

Not even warm

not NE or LT you'll probably piss yourself laughing when I tell you what it is and call me the antichrist which is why I wanna be "absolutely" sure that what I'm hearing isn't a freak of nature / hallucination or an otex overdose before I say what it is!

Quote:

Originally Posted by StevieDvd Will I need to learn how to trim my WNA to opamp swap soon

No. all you have to do is pee about with the trimpots Steve until the offset is zero on both channels (with a screwdriver) piece of cake..... in fact, with this particular opamp you don't need trimpots, input caps or output caps

Edit: your amp is output cap free with trimpots isn't it Steve?

 

[StevieDvd]

Quote:

Originally Posted by PinkFloyd Not even warm not NE or LT you'll probably piss yourself laughing when I tell you what it is and call me the antichrist which is why I wanna be "absolutely" sure that what I'm hearing isn't a freak of nature / hallucination or an otex overdose before I say what it is!

It's not a 3amp fuse is it?

Quote:

Originally Posted by PinkFloyd No. all you have to do is pee about with the trimpots Steve until the offset is zero on both channels (with a screwdriver) piece of cake..... in fact, with this particular opamp you don't need trimpots, input caps or output caps

Where do you measure it though?

Quote:

Originally Posted by PinkFloyd Edit: your amp is output cap free with trimpots isn't it Steve?

Yep, that's the one.