TS808+ Build - Questions

[mydementia]

Hi Guys.
I just finished my 3rd build (the TS808 from GGG using JD's board and layout schematic http://www.generalguitargadgets.com/diagrams/ts_lo_808.gif) and really like how it sounds.  Here are my questions:

1) What's the 100uF cap (C12) for?  The GGG build notes say '(optional, use if you plan to use a power supply)' - I'm using a DC input jack...isn't a battery also a power supply?

2) What's the 4M7 resistor (R22) doing?  GGG also says optional - but not what the options are...

3) I wanted to put a symmetrical/assymetrical clipping switch into my circuit so I used an SPDT switch.  I ran a wire fom the lower D3 connection to the center pole of the switch and ran a single wire from the top pole of the switch back down to the upper D3 connection (for the jumpered cfg).  Then I ran a wire with the Diode (D3) soldered in from the bottom pole of the switch out to the wire going to the upper D3 connection.  When I flip the switch from symetrical to asymetrical, I notice a small difference in the distortion - VERY small...almost inaudible.  Should this mod have more impact on the tone?  Am I getting bleed-back when I'm trying to use the symetrical (jumpered only) config?  Maybe I put in D3 backwards...

4) I did a similar thing with the 4k7ohm-0.047uF (R6-C3) network (SPST switch as described above) using a 0.1uF cap and a 2k2ohm resistor (mod to get more gain).  When I flip the switch there is a definite difference.  My concern here is that I'm getting bleed back through the part of the circuit that's supposed to be 'off'.

5) I used the Mouser JRC4558D op-amp...is there much/any difference between this one (20 cents) and the one going for $4.50 apiece on several of the DIY/mod sites?  Can I do a 'plug and play' swap with a LM833 op amp?  Last time I used the LM833, I needed to provide -9V to pin4 - the GGG board looks like it's grounding pin4... just curious.

I just want to understand all these things before I drill my 1590BB.

This forum is awesome - it makes this hobby (addiction?) a lot of fun because we're all in pursuit of the same thing...the elusive tone!

Thanks in advance.
Mike

[ninoman123]

1) That cap is a filter cap used to help smooth out power from a wall wart. Yes batteries are power supplies but here we use the word wall wart and power supply as the same thing.

2) That helps suppress pops if you have problems with them. If you do then add it, if you dont then dont worry about it. If you wanna add it to be safe thats cool too.

3) What types of diodes are you using? This would change the affect of the distortion.

4) Not sure

5) Well thats not a JRC4558D its a NJM4558D. Its made by a different company and some believe that this change over ruined the sound of it. The ones from the DIY sites are probably real JRC4558Ds and those can be hard to come by. Hence why it costs more.

[mydementia]

1) 2) Thanks!

3) I used 1N914 diodes as shown on the GGG layout.

5) Good point about the JRC vs NJM - Maybe I'll add a real JRC to my next smallbear order to see if it makes any difference.

Mike

[johngreene]

5) Well thats not a JRC4558D its a NJM4558D. Its made by a different company and some believe that this change over ruined the sound of it. The ones from the DIY sites are probably real JRC4558Ds and those can be hard to come by. Hence why it costs more.

This is wrong. NJM4558D is NJR's part number for the JRC4558D(marking on the chip). Always has been. This crap you've been reading on the net is pure hogwash. I've seen 'vintage' JRC4558's being sold on the internet with a current date code.

People try to say that JRC became NJR when Ratheon bought them and that's when the JRC4558 became NJM4558. A little research will show that Ratheon bought JRC back in the 50's, long before the JRC4558 was even thought of.

--john

[mydementia]

From SmallBear:

IC JRC4558D
SKU: 1507
Made by the same company, New Japan Radio (NJR), that made the original chips. Most knowledgeable reviewers say that they sound identical to the NOS parts in TS clones.
PRICE:  $0.40   

I suppose I'll stick with what I've got - thanks John!

[Steben]

I used JRC4558, RC4558, KIA4558 and KA4558 and they all sounded the same, the last almost better than the first.   
My conclusion: 4558 is 4558. The number specifies the circuit.

Look at the 386 poweramp.
JRC386 exists LM386 exists NJM386 exists... What really makes difference is the suffix 1,2 or 3. they specify the maximum temperature/power achievable.

[Melanhead]

I used JRC4558, RC4558, KIA4558 and KA4558 and they all sounded the same, the last almost better than the first.   
My conclusion: 4558 is 4558. The number specifies the circuit.

Look at the 386 poweramp.
JRC386 exists LM386 exists NJM386 exists... What really makes difference is the suffix 1,2 or 3. they specify the maximum temperature/power achievable.

Good to know ... I found some KIA4558 's and couldn't find any info on 'em ...

[Steben]

"KA"4558 is Fairchild, but I don't know what KIA stands for either.

[Steben]

talking about 4558's 

http://www.diyaudio.com/forums/showthread/t-67906.html

anyone read these things?
I didn't know they still used 4558 in CD players 

[mydementia]

Interesting stuff guys - makes sense.

Any thoughts on my switching questions?  I put together the snapshot below to visually explain what I'm doing - hopefully I'm right (thus - no responses) but if I'm wrong, please tell me (with pictures) how I should be wiring in 'option' switches.  Also, how noticable should the asymetrical vs. symetrical clipping be?



Thanks.
Mike