The discrete TC-7520(SE)(+) line output

[StanleyB]

I drew up a discrete output stage for the TC-7520 and Caiman to hear how it would sound. Leo built a prototype of it on stripboard and I did one as a 'proper' PCB. I wanted to find a solution for the low output of the passive mod and preserve the headphone output capability, but didn't want to go overboard with a complex discrete opamp type design. The gain required is only between 2X to 4X so a single ended class A design with just 10% negative feedback was all I felt that was necessary. No need to crack a nut with a sledge hammer .



It's the best I have heard my D7000 and HD800 sound to date. I managed to pick up some detail in musical passages I thought I had explored to the full.
Time for a retake on all my test tracks .

[Covenant]

I will start with the most obvious question! Will it be commercially available?

[StanleyB]

I will start with the most obvious question! Will it be commercially available?

If there is enough interest. To save cost I can perhaps just make the boards but leave the opamp socket empty. That way people can use their existing (expensive or otherwise) opamp. I have tried some non-polarized caps from Jackson, but I also fitted a couple of Rubycons I scrounged off Tirna.
Without the opamp I can try to aim for £30 plus postage. Might be a bit more or less, depending on identifying any hidden costs. Or I can perhasp do a fitting service for those who are scared to swap the PCB over by themselves.

Any suggestions on this?

By the way Leo, any words of advise for the guys on what you thought about the performance?

[leo]

By the way Leo, any words of advise for the guys on what you thought about the performance?

TBH I think the caps I used are adding more signature than the circuit which is a good thing. What I want to do is use the same caps as whats used in passive out mod.
Its definitely better than the original stock op-amp stage (IMO) . Compared to the passive mod it gives a noticeable higher output and seems more full in the mids . Reason I want to change the caps is to be sure its not those adding more in the mids

I've used it with both an active line amp and straight into a power amp using the dac as a linestage, it works well (for me ) in both locations .

[leo]

Great work Stan! its been hard keeping quiet yours looks better than my knocked up version on vero Mines basically just the transistor stage so I've not tried it with the HA op-amp yet, I'll see if I can squeeze the op-amp on there too

Simple where possible is certainly good in this case

[Puffin]

Are you going to give us the schematic?

[Puffin]

Are you going to give us the schematic?

I'll take that a "no" then

[Frizzup]

Count me in for 1 board please Stan, 30 quid seems reasonable to me.

Cheers
Frizzup

[Canetoad]

+1

[StanleyB]

I have asked my sourcing manager to get me a quote on the bill of material and the cost of a nice small foam padded box to put the finished PCB in. The PCB blanks manufacturer normally only accepts orders of 250 or more. So I'll make 250 blanks and populate 100 of those into fully working boards.
I'll know more next week, which will give me a chance to let you guys know the expected time of arrival/availability of the finished PCB and if the £30 price is about right. I am not looking to make a profit on any of my mods, which is why I give them away for free. But I have to at least cover the cost of manufacturing in this case.

In the meantime I'll PM a few people to see who might have the time to try out my PCB for a day or so in their system.