Racking Spectra Sonics 101

[87w]

Bump,

Log, Linear, Anyone?

Sam

 

[matta]

Hey Sam,

I'm not sure, best drop Joe an e-mail and post back. I didn't use the variable pad, I just have a Lorlin switching the resistors in the Feedback path, which is not so cool as I'm getting pops when switching.

I know Ray used a REV pot in the Feedback loop, he said this in an e-mail/PM

----
A 50k audio or log taper pot wired in reverse with a 5.5k resistor hanging off the ground side (used as a variable resistor, NOT a shunt to ground) in the feedback loop makes a really nice and smooth gain control
----

I dropped him and e-mail to get more details, I'll report back if I hear anything.

Cheers

Matt

 

[JLM Audio]

The pot for the variable pad should be a dual 1k log or audio taper pot.

 

[raysolinski]

I used a 50k audio taper in the feedback loop with a 5 k in series so the minimum is 5k and the max 55k..a little over spec but you can watch your gain for distortion etc...Since it is in a dc feedback loop it is a little noisey when you turn it...probably better to set it at 50 db with a resistor and control the output, or with an input pad. Not very much gain with these guys..probably best suited as intended, as a line amp, or maybe strap 2 together set at 40 db and control it with some type volume pot?

Ray

 

[cannikin]

Hey Matta,

I'm starting to dive into this project and I was wonder what PSU you used.
I got 2 101 cards :grin:

I was thinking of getting one of JLMs PSU boards and the go between (of coarse). Also, What is Power trannie Rated.

In Addition, I have a 103 card - What Could I use it for?? a DI?

thanks

 

[matta]

Hey Cannikin,

I can't praise Joe's kits enough. I wired all my FETboy's off board, took about and hour or more, and alot of caution, and still managed to mess up the pad... I bought some of Joe's kits for the Spectra Sonics, had them built in 20 minutes and since it is all on one board as long as you don't mess up resistors (which is kind of hard to do) you will be up and running in no time.

RE PSU I used a converted Peter C Green Pre PSU board as I had a few lying around. But I would suggest using Joe's if you are going to order the switch kits. They 2 are easy to use and will allow you to trim down/up the rails.

I would suggest you heed Joe's advise on using a Variable input pot. Ray tried a pot, and is is scratchy because it is in DC feedback path, and I used a Lorlin which pops and not as easily tweaked.

I'm going to be fixing my gain at say 50dB's and using a 20dB variable pad on input.

RE the 103's, I'm not familiar with them so can't comment on their use. If you wanted to add a DI I would suggest adding in Joe's DI kit which combined with the 'Go Between' will be a great combo.

Cheers

Matt

 

[Twist Turner]

I have a pair of these to rack as well. Matt I really like the red knobs. Where did you get them???

 

[cannikin]

Hey guys could I Use the sowter 9145 Neve Mic/Line Input
300/1k2 to 1k2/4k8. Ratio 1+1:2+2. For the input??

Got a couple on the shelf collecting dust... :?

 

[matta]

Hi Guys,

Twist, the knobs are from Small Bear Electronics (http://www.smallbearelec.com/home.html)

Cannikin, not sure the tranos will work. The board was designed to see 600R on input. So a good 1:1 at 600:600 is what you should be looking for.

I have mine wired 150:600, which seems to work well.

Cheers

Matt

 

[cannikin]

thanks Matta


I'm just going to use the triad HS-66 on input and a Cinemag 1:1 on the output

Cheers

 

[Twist Turner]

Got a quick question for you guys. I've got 2 Sowter 3603 600ohm to 600 ohm transformers and also a pair of Triad HS-66's coming. Which would you use on the input, which on the output and why? I was thinking to use the Triads on the input using the 150ohm to 600 taps, and the sowter on the output, what do you think?

Oh, thanks for the knob link Matt, those Cream colored ones they have look pretty nice.

 

[cannikin]

Hey Matta,

I have a couple questions about racking the 101. I'm a little baffled on a few things.
Imagine this was a block diagram:

XLR in --
JLM go Between --
input level Pot (Have a couple DAVEN 600 Ohm) --
input transformer (triad HS66) --
101 card --
Output transformer (Cinemag 1:1) --
XLR out

Also I could do without the Input Level Pot and just use the 3way Switch to attenuate within 10dB ... Correct?

On the Triad HS66 anyone know off hand which Pin is Ground?

Thanks

 

[matta]

Hey Cannikin,

Your sequence looks pretty dead on. You could indeed do away with the level pot. Something to be aware of is that when you change the level you are switching the gain resistor in the feedback path, which has some DC and I tried this with both MBB and BBM switches and still got a 'pop' doing it (not sure if it was because of the DC, just thinking aloud) so I FIXED the gain at 50dB's and then used Joe's Input Pad instead of a level pot.

So it now goes JLM, Variable Pad Pot and then transformer, and then 101 card.

This has provided the best result for my needs, it is wired so that as you turn the pot CW the pad decreases the pad till it is off when fully CW.

I'm not sure on the Triad as I used an OEP trano as my input.

Cheers

Matt

 

[jamesfei]

If you're mostly using the 101 as a mic pre, it's better to put the Daven (probably a Ladder or T?) on the output, before the transformer, and keep the input path as clean as possible. If the JLM has a 20db pad it'll keep the card from clipping, along with the gain adjustment switch, and the output attenuator will let you set levels precisely. Off hand I don't think the Triad has a ground pin, just ground the case via the mounting screws.

Best,

James


[quote author="cannikin"]Hey Matta,

I have a couple questions about racking the 101. I'm a little baffled on a few things.
Imagine this was a block diagram:

XLR in --
JLM go Between --
input level Pot (Have a couple DAVEN 600 Ohm) --
input transformer (triad HS66) --
101 card --
Output transformer (Cinemag 1:1) --
XLR out

Also I could do without the Input Level Pot and just use the 3way Switch to attenuate within 10dB ... Correct?

On the Triad HS66 anyone know off hand which Pin is Ground?

Thanks[/quote]

 

[cannikin]

Thanks Guys

Much appreciated...

 

[cannikin]

Hey Guys,

I'm having some difficulties -- I'm stumped :roll:

First of all Let me tell you what I have and what I'm trying to do...

JLM ac/dc (+/- 24Vdc)

Here's My Signal Chain:

XLR In
JLM Go Between (NO DI) using Jumpers
Triad A-67j Input (Wired 1:1 600 Ohm)
101 Card
HS-66 Output ( 1:1 600 Ohm)
XLR out

Feedback Using Grayhill Switch with Resistors (10K 20K 42K) for DC Signal Ouput Gain Adjust

I'm using the layout supplied by JLM

THE ISSUE: NO Signal

I noticed that -24V (B-) is really not connected to anything on the card... Correct? ON the Layout connection C

Next I thought Maybe I have the Transformers wired incorrectly :?

Go Between to transformer Input Primaries - Secondaries to 101 ( D which is + and E which is Minus)

101 Card output (H -- signal output + and F -- Signal Output MInus) to Secondaries of the HS66 Primaries to XLR

I can't figure it out.......

 

[matta]

Hey David,

The 101 is single ended, only needing a +24V rail, so you are right there is no -24V rail.

Let try break it down to the simplest form.

Your connections sound right on the front end, to just check things lets do a basic processes of elimination.

Can you remove your switch and for now just hard wire a 10K resistor between tab K+L.

Then run the card unbalanced out, removing the output trano, so tab H to Pin2, tab F to Pin 1 on the Output XLR, and join pin3 to pin 1.

Now we concern ourselves with the basics, which should be.

XLR In - Go Between
Go Between - Input trafo primaries
Input trafo secondaries - 101
101 - XLR Out

Just try that configuration and report back with results.

Cheers

Matt

 

[cannikin]

Thanks Matta..

Ok Your suggestion worked....

Getting Sound (although output is really low)

Next... ??

 

[matta]

Getting Sound (although output is really low)

Hi David,

Good to hear. Just clarify the sound you are getting. Is it clear, just low output, any distortion, muffled in anyway?

Try replacing the 10K with a 42K, this should bring the volume up, and also make sure you tie Pin 1 and Pin 3 together on the Output XLR, otherwise you will loose some volume there as well.

Once done, report back.

Cheers

Matt

 

[cannikin]

The sound is Pretty Dirty ... Definitely not clear..

I haven't Grounded the circuit like your recommended and have not replaced the caps Yet.