Yay! New toy

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Nick
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#16 Re: Yay! New toy

Post by Nick »

Thats right I sort of remember now :-)
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Greg
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#17 Re: Yay! New toy

Post by Greg »

Tony Moore wrote: Sun Jan 10, 2021 1:10 pm By the way, does anyone know if Leo from Nottingham is on this forum or where I might get in touch with him? It was Leo who got me into the 1541 chip and Pedja's DAC implementation. I have an email address for him and pinged it but no response yet,

Cheers,
Tony
Hi Tony
I’d give Richard on the WAD Forum a shout. I bet he still has contact info for Leo.
Tony Moore
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#18 Re: Yay! New toy

Post by Tony Moore »

Hi Greg,

Thanks, good idea, I'll give him a shout.

How are you keeping? What are you up to these days?

Cheers,
Tony
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#19 Re: Yay! New toy

Post by Tony Moore »

Right, well....moving on with the Transporter... :x

I looked up a few circuits around that I could try in place of the stock output stage in the Transporter and came across the FET-ishator. :lol:

This is a Lampizator derived idea that is based on a FET as the principle device rather than a tube. I thought I've give it a try and had some boards made up with a slightly modified version of the cct. The originally specified FET has been obsolete for a few years and even the ones meant to be equivalent are also obsolete so I went with a surface mount device, BF861C. The circuit has a MOSFET follower and that's it really. As simple as it gets. Today, after messing around with the resistor values I hooked it into the Transporter and into my HD83 and Senheiser phones.

Wow. :shock:

I am gobsmacked. I had to switch back to the stock outputs just to make sure I wasn't imaging things. Nope, with the stock output the sound is muddled and tizzy and although it's perfectly acceptable I guess it bears no resemblance to the output using the simple FET/MOSFET circuit. Here the space has opened up around my head, I'm hearing things in 3d that I've not heard before. It's wonderfully detailed but not at all tizzy.

So all in all it was a very well worth it experiment and I'll be drilling the case and adding a pair of phonos to the back for the permanent installation. Don't get me wrong, this is not perfect of course as I'm not using the differential outputs that the DAC can provide plus I don't have a low pass filter (yet) so all sorts of HF junk will be getting out, however the headphone amp will no doubt help here! I would not dream of connecting this to a SS amp in this form though!

In my opinion the TDA1541 still sounds better but this has significantly closed the gap.

ps. Still not managed to get in touch with Leo. Richard has not heard from him for years either. :(
Tony Moore
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#20 Re: Yay! New toy

Post by Tony Moore »

Well, I'll keep on rambling along to myself... :)

I have now tried 2 more "experiments" on the output stage of the Transporter. The first is the example circuit in the AK4396 datasheet which uses a single 5534 op-amp per channel to subtract the balanced outputs of the DAC to convert to unbalanced for my headphone line input. This circuit is simpler due to the fact that it is not also trying to output balanced signals too. As mentioned, the Transporter uses the second example circuit in the datasheet which has 100uF electrolytics in both +/- signal paths. Yuk. I think it was probably these caps that were initially sounding so horrible after being stored for 10 years+. The sound through the stock outputs _has_ certainly improved with use although still not as good as with the single op-amp with no need for the DC blocking caps. (and better component qualities)

The next thing I tried was some cheap (£2 each) line transformers from Ali Express. Well, that was a bit of a revelation. :shock:

I wasn't expecting too much, given the price but they really show what's possible. Vocals and piano are just so much better. So now I'm really tempted to splash out on some Lundahls.

btw, I did hear back from Leo!

Cheers,
Tony
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pre65
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#21 Re: Yay! New toy

Post by pre65 »

Tony Moore wrote: Sun Mar 07, 2021 1:25 pm
Well, I'll keep on rambling along to myself... :)
Well, I'm reading, and find it interesting. :)
Life is what happens to you while you're busy making other plans. John Lennon

G-Popz THE easy listening connoisseur. (Philip)
Tony Moore
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#22 Re: Yay! New toy

Post by Tony Moore »

Thanks Phil! I'll keep on then.

I'll report back when I've had chance to try some Lundahls.

Also, I'm probably going to build a SS class A headphone amp to see how it would compare against the WAD HD83. All this is more of a trip down memory lane, playing with scopes and bread-boarding than any real need but there you go...there's always for more to learn!

And who knows, maybe I'll have something to bring along to Owston 2025? :lol:

Cheers,
Tony
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#23 Re: Yay! New toy

Post by steve s »

Tony Moore wrote: Thu Mar 11, 2021 10:05 am

And who knows, maybe I'll have something to bring along to Owston 2025? :lol:

Cheers,
Tony
Hopefully before then Tony but who knows. My plan is to see how next winter goes, if alls OK maybe next year.. but I'll put it out to everyone 1st

I must admit to being a little laid back about dac's I've used a 16 chip (1543) valab dac for quite a few years, made a point of comparing it to alot of other dac's, where it at least held its own in my view.

Then i bought an older technics cd player in a job lot, that after very extended listening equalled my dac. The dacs now are in the unused pile of gear. Along with the a spare technics I bought.
The tube manual is quite like a telephone book. The number of it perfect. It is useful to make it possible to speak with a girl. But we can't see her beautiful face from the telephone number
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#24 Re: Yay! New toy

Post by Tony Moore »

Well, to carry on the story...

I ordered a pair of Lundahl transformers around 4 weeks ago so hopefully anytime now I might get the email saying they are ready. In the meantime I thought I'd see if I could improve on the HD83 headphone amp.

I looked at a few SS designs on the web and settled on this one:

http://www.pavouk.org/hw/dynalo/en_index.html

The only issue are the jFETs which are now obsolete. So Ali Express it was and buying some possibly dodgy/fake 2SK170/2SJ74s. Since I didn't have Eagle I used this as a way to get practice with KiCad and so I captured the schematic and laid out the PCB myself and got them made at this place:

https://jlcpcb.com/

This is the result so far:

https://photos.app.goo.gl/kZbhFPUrAsXWuLsA8

It certainly sounds amazing, bass especially good in comparison with the HD83. I took at lot of time matching the jFETs, out of the 50 of each type I bought I managed to find 8 that matched, which is what I needed. The specs seem to match the datasheet ranges so if these are fake then I don't really care since it works and sounds great.

Now to the power supplies and fitting in into the case I got for a tenner from China which just arrived today.
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