Solid State Pultec Idea (Fabio/Gyraf/RogerFoote/JLM hybrid)

I ahve quite a few building blocks and spare parts hanging around so I thought I would come up with one of my own "hybrid" ideas
Be patient with me please .. it's my first project by myself..

Looking at what others have done (all hail Radiance and Steffen)
I thought I might have a go at this project

Basically what it does is the following..
1 x +24volts provided by a JLM PSU (Neve Out Board)
1 x +12volts provided by a JLM PSU (Rogers Bypass Relays)

XLR IN --------->
Roger Footes Bypass boards (24v relays)--------->
Stripboard with LL5402 and 10k resistor --------->
Gyraf (Gustavs boards) Pot Board with inductors/caps ------>
Fabios Neve Out Board (with a 10k log pot at the front) ------>
Stripboard LL5402 with 2K2 resistor -------->
XLR OUT

Questions:
1. Do I use the 2K2 of the gyraf schematic after output transformers to XLR or do I go back to Fabios boar forthe 620R, 1K5 and 10n

(oops just realised 620R + 1k5 nearly equals 2K2 - coincidence?)

2. Other Options for LL5402 in and out

3. Neve Out input pot is 10K - Steffans schematic is 50K


Schematics
Bypass Boards
http://www.groupdiy.com/index.php?topic=13870&highlight=bypass
Pot Boards for Pultec
http://www.gyraf.dk/gy_pd/pultec/gy_pd_sch.gif
http://www.gyraf.dk/gy_pd/pultec/gy_pd.pdf
Neve Out Board
http://www.thediypill.phx.com.br/forumfiles/neveout_sch.pdf
Pultec Solid State (Steffen)
http://www.diygallery.de/DIYsites/eq/Pultecschemo.gif

You will have a hard time making this Lundahl work as the output for this circuit. You need a NEVE type LO-1166 or similar, GAPPED output transformer for the outputs.

UNLESS,

You use a T1310 load inductor. Then you could use your Lundahl as the outputs for the neve circuit. But these T1310 are hard to find...

Just so happens I have a Carnhill LO1166 lying around (thanks to the valve man, Mr Flinn)
Thanks rafa
Okay...
LL5402 on the input
LO1166 on the output

[quote author="rafafredd"]You will have a hard time making this Lundahl work as the output for this circuit. You need a NEVE type LO-1166 or similar, GAPPED output transformer for the outputs.

UNLESS,

You use a T1310 load inductor. Then you could use your Lundahl as the outputs for the neve circuit. But these T1310 are hard to find...[/quote]

Dan Alexander has some 1310's for a good price.

A 10K pot wil also work. On Steffen webside it sais: "gain pot changed to 50K (found out the high boost sounds sweeter when the EQ-network is less loaded)".

Maybe with a 10K pot it was a bit to sweet I guess.Just try both and listen,.... and tell us which one you like best :grin:

What I did was build al separate parts, test if they work on their own, and then connect them all together. Connecting all parts took me some time and experiementing but this way you'll learn a lot.

What about wireing the LL5402 in a 2:1 (step down) way? I read somewhere that it might sound different.....

[quote author="rafafredd"]... You need a NEVE type LO-1166 or similar, GAPPED output transformer for the outputs.[/quote]
Joe's Gapped/API will do the trick
and for us down under is a good price
his Hybrid amp should be cool ... with or without an output trafo

I have a similar project in mind. I have some line amps lying around and want to turn them into EQs using the Pultec filter set.
Here's the line amp:



Looking at the schemo, where would you think is the best place to insert the filters?

that line amp looks like it is a balanced input and then a differential into the op-amp

just out of interest ... what is Q1 ?

the basic 325 amp card the transformer unbalances the signal and that is feed into the DOA
... it is at this point that things are convenient for the Pultec style EQ section

I don't see a fast solution to the attached without some re-thinking and perhaps a track cut or two
:roll:
perhaps it's too early in the morning to think
need coffeeeee

Hey Kev,
The Q1 on this board is an old style metal cap roundy one. (I am not home at the moment to read them)
But I have others which are designed a little differently than this.
On the thread below I have posted the schematics for the other ones too:
http://www.groupdiy.com/index.php?topic=4613

one of those circuit diagrams looks like it could suit
and one of the other guys may have a better idea or suggestion as to how to go about modding your units for the job

but
now I'm confused as to which you have
LA1600
LA1603

and the A4000 does look like a differential inpout

Oh, I have both units.

Funny you mention this as Ive just finished 2 pultec type eqs for mastering similar to what you describe.

They use JLM pultec boards that we no longer make and a dual 99V MB PCB with two JLM Hybrid opamps to provide electronically balanced in and quasi balanced out. We did some rewiring and used the PAD relay to bypass the eq. I chose the Hybrid opamp to drive the eq circuit because it stays very linear with unchanged THD into any load down to 50 ohms, so it can easily cope with the low and changing impedances of the pultec circuit no matter what the settings. I was going to use a 99V for the output amp but tried some Hybrids to start and loved the sound so Ive left them in.


M

yes there are a few cool project ideas coming from JLM in the next few months

just to clarify what Matt said about his Pultec Project

EQ section was made with OLD JLM stock (others can use the Gyraf front board)
1 x 99V mother board
2 x Hybrid .. (one for input buffer and one for output drive)

a few cut tracks and a few jumpers and the one of the relays was recycled to be an EQ Bypass

Matt,
you didn't mention if you went with transformers or not ... which ones did you use ?

by the way
GET OFF YOUR BUM and take a few pictures
document the 99VMB changes
and do a bit of text
and we can post the project at the DIY Factory for others to have a go
I may be inspried to do a version with the Gyraf front panel and add that to your page
:grin:

Don't overlook Lang PEQ = Solid State Pultec.

I got those darn Freed In and Outs, but don't have the time.
Sound familiar?

[quote author="CJ"]Don't overlook Lang PEQ = Solid State Pultec.[/quote]
correct
is this the right thread ?
http://www.groupdiy.com/index.php?topic=76417&sid=378ab80ff7cd59a4816e383f58aa29b1

[quote author="Mundox"]Hey Kev,
The Q1 on this board is an old style metal cap roundy one. (I am not home at the moment to read them)
But I have others which are designed a little differently than this.
On the thread below I have posted the schematics for the other ones too:
http://www.groupdiy.com/index.php?topic=4613[/quote]
Cyril Jones read this thread and had a few comments:
Ref your discussion groups, I had a peep ealier, the Q1 IC you were unsure of will alomst certainly be a NE5534 or substitute.
For the period of the design I would imagine NE5534 or under the first type number TBA1034 (Philips No.) pre the current Jedec ref. There was no other IV around at the time which required a compensation cap between pins 5 and 8.
RE the transformer. A gapped transformer is required to raise the reluctance of the transformer to prevent saturation by the DC current passing through the primary windin.