Racking Spectra Sonics 101

[clintrubber]

[quote author="JLM Audio"]

Since from what I read I got the impression that the 600 Ohm input impedance of the 101 & 110,
even when used with a 1:1 TX, give a bit too low inp.imp, correct ?
As in 'it will do just fine, but might have been a bit more'.

I usually like the sound of most mics with 600ohm loads except ribbons. [/quote]
Thanks for adding that - it's the last push to convince me to make it first as the version for which there's ample evidence around that they're nice mic-pre's. :wink:
Can always easily convert to the higher input-Z, if ever required.
So 101 or 110 it'll be, thanks,

Peter

 

[matta]

Hey David,

Any luck? Thanks Joe for the words of wisdom. I think I mentioned a while back that the DC was an issue and cap may be the answer, but what cap and what value i had NO idea.

I'm quite happy with the Variable Pad with card fixed to Max gain. but this will be cool as well.

Matt

 

[cannikin]

Hey Matta,

Nope haven't tried yet I'm still in the trenches of assembling..
Hopefully will have an answer in the couple days.

 

[guavatone]

Love those big juicey knobs!

I thought I saw someone asking about components for 101s.


The top is from a NOS comp/lim. Bottom is a card from Dotty.
The Tranies are the same but newer. The only big difference is probablt the Micas on the newer one. Maybe this is why I don't like the sound.

 

[guavatone]

dbl post

 

[cannikin]

Hey Charlie

what are the newer replacements for 2n3566 and 2n3645 that are on the NOS com/lim card??

 

[cannikin]

edit :grin:

 

[guavatone]

Ok from top to bottom looking at the component side with the edge contacts facing up. I am listing exaclty what is on the transistors.

FPN
3566
EBC

FPN
3566
EBC

N552 (the N i think is National logo with arrows on the stems of N)
PN
3645

N552 (the N i think is National logo with arrows on the stems of N)
PN
3645

MPS
3566

My mica caps say "050D03" -is that 5 pf?

 

[cannikin]

[quote author="JLM Audio"]

If someone can try the cap on a existing build and see if the clicks stop and all works fine please post on this thread your findings as I have only been able to computer simulate the cap idea at the moment.[/quote]

Hey Joe -

This Build with the 1000uf cap does not solve the clicking issue.

Would putting a cap on both ends of the switch be a potential solution?

 

[JLM Audio]

Hi David
OK the DC thumps should be gone but if a non shorting switch is used the pre will jump to huge gain in between gain steps. So if there is no clicks with no input signal but loud clicks when switching with a input signal a shorting type switch will be needed or use the toggle setup on the 110A circuit as it limits the gain jump up to 10dB. Hope that makes sense.

Let me know what you find.

 

[cannikin]

:grin: :grin:

 

[clintrubber]

[quote author="cannikin"]Hey Guys

Scanned and put in Adobe Illustrator -- not perfect but pretty good (not a illustrator master) [/quote]
Thanks ! Always handy - I've put 2 channles worth of components on Veroboard already, but no soldering yet. While the various pics around showed the traces already, your diagram will be the most convenient when wiring it.

Regards,

Peter

 

[guavatone]

I finally have hs-67j XFMRs now. What is best? on output? Will the phantom on input mess up the card without input XFMR?

 

[guavatone]

A little update on the NOS cards. I did AB to the old ones I got from Doty and so far the NOS is much "better" with more bass. I may move this to another thread and post sound files. I just recapped the 220uF caps on the old one to see if it comes close.

 

[cannikin]

GuavaT

I used the A-67J on input....

My recommendation is: Wire it 150:600 (1:2) it sounds so much better (to me).

I had 2 pair of cards One set I wired 1:1 the second I wired 1:2.

IMO The 1:2 was much fuller in sound.

Secondly I recapped the "big" caps with Sprague Atoms
Mouser Part #:

75-TVA1223 200uf 35V
75-TVA1312E 250uf 35V

The bass really came alive! Really like the sound of these they're my favorite pre right now

 

[cannikin]

Guys can you recommend a good "make before you break switch" for the feedback resistor.. the popping is the one thing that is driving me crazy!

Next "test" wiring up a newly etched board using BC560 BC550 Transistors
DO you guys know the ECB configuration for 2n3566 and 2n3645?

 

[clintrubber]

[quote author="cannikin"]Next "test" wiring up a newly etched board using BC560 BC550 Transistors
DO you guys know the ECB configuration for 2n3566 and 2n3645?[/quote]
I thought they're all EBC, just like BC5X0. But with the PCBs already in hand it's easy, just follow the traces to the other components & see what each hole needs to be, E, B or C.

Keep us posted :thumb:

Regards,

Peter

 

[cannikin]

Hey Guys...

Just curious.. I have some "make before you break" rotary switches. but they are 12 position.

I was wondering if you could add more values to the feedback resistor
Between 5.6K and 42.2K to make more gain control...

thanks

 

[matta]

It makes sense David, if you got it, do it! The issue I still have with the switches is that I got loud pop when switching, I tried MBB and BBM and both had the same results? Are you having any better luck?

Cheers

Matt

 

[cannikin]

I haven't tried a make before you break switch yet ... so I'll give that a try
and report back