Is the Neumann W495B EQ DIYable?

[radiance]

Q:Is the Neumann W495B EQ DIYable?

Here are the schematics.

I asked this question in another (neumann) thread but got no response.
My main concern is where to get the HA1-4605/4741 opamps.
I got some search results when I "googled" on "HA1-4605" but it seems that these opamps are no longer been made. Does somebody know of any replacement?

Also what transformers should I used?

More in general: what is it that gives this EQ that special sound?

 

[jensenmann]

I think the reason for not diying this eq ist that quality switches are pretty expensive. If you calculate material you will end up close to the price of a used original W495. The trannies are Haufe rk409 for Ü1 and rk310-2 for Ü2.
For more infos check kubi´s page:
http://www.kubarth.de/cgi-bin/diy/german/index
About the Op I don´t know nothing. but I´m hot for this EQ. If there´s reverseing going on, I´m shurely in for that. :green:
cheers
Jens

 

[radiance]

Thanks for the reply jensenmann.
You're right. If you have to buy these switches new it wil cost a fortune. There are 4 x 12 pos rotary switches and 2 X 3 pos needed.
I got some good deals on a couple of grayhill switches and now I want to use them.
I got them @ http://www.leedselect.com/parts-switches.html

 

[Leslie West]

[quote author="radiance"]

I asked this question in another (neumann) thread but got no response.
My main concern is where to get the HA1-4605/4741 opamps.
I got some search results when I "googled" on "HA1-4605" but it seems that these opamps are no longer been made. Does somebody know of any replacement?[/quote]

The 4741 and the 4605-5 was build by Harris. Harris was sold to intersil.

You can find the 4741 here:
http://www.intersil.com/cda/deviceinfo/0,0,HA-4741,0.html

and the HA1 4605-5 they don´t build anymore, but they have a replacement OP:

http://www.intersil.com/cda/deviceinfo/0,0,HA-5104,0.html

[quote author="radiance"]Also what transformers should I used? [/quote]

Use the numbers from "jensenmann" and buy it here:
http://www.haufe-uebertrager.de/

Regards
Leslie

 

[radiance]

Muchos gracias Leslie!

That HA1 4605-5 replacement chip is quite expensive by the way .
It lists @ farnell for 23 euro ex. VAT.

 

[jensenmann]

radiance, if you try to buy trannies at Haufe, could you please let me know whether they do sell single units. Some times ago I´ve been told that they don´t.
Thanks fo the link but I couldn´t find the 4x12. But this dealer got the bestlooking knobs :shock:
Wow :thumb: :thumb: :thumb:
Jens

 

[radiance]

Well, what I ment was that you need four 12 position rotary switches.
He sells grayhill 12 pos 2 pole (and also 1 pole) switches for only $7.25
Darn cheap compared to farnell (Europe). I think they are something like 50 euro at farnell...

I emailed Haufe asking where to buy those transformers. I will let you know what they have to say...

 

[Leslie West]

[quote author="radiance"]Muchos gracias Leslie!

That HA1 4605-5 replacement chip is quite expensive by the way .
It lists @ farnell for 23 euro ex. VAT.[/quote]

You´re wellcome...

I know, but it is a special OP for high quality active Filter designs. It has a very high Bandwith...

 

[aurt]

My main concern is where to get the HA1-4605/4741 opamps.

While I can understand the nod to authenticity, the 4741, being a quad version of the much maligned 741, is far from an ideal op amp.

# Slew Rate 1.6V/µs
# Bandwidth 3.5MHz
# Input Voltage Noise 9nV/√Hz

Spec-wise, frankly, it's crap. Much better stuff is available now. For that matter, as you're not designing for exactly the same physical compromises as Neumann was, there's not necessarily any reason to go with a quad package at all, though some decent ones are available.
That 5104 looks a bit better, but hardly a world beater. For the price... yeesh.
IMHFO you may be better off looking for a nice sounding, reasonably priced, readily available alternative. There is at least one recent thread about op amp recommendations with a bunch of good suggestions.
While some may cry "heretic" for the suggetstion, it's not entirely uncommon to modify professional gear in the field if there are better parts to use. In fact, quite a few mastering houses make a point of pooge-ing most all of their gear, and some go so far as building the whole joint from scratch.

 

[Samuel Groner]

if you try to buy trannies at Haufe, could you please let me know whether they do sell single units.

I just bought a single power transformer with static and magnetic shield, so at least for power stuff they sell single units.

Samuel

 

[Leslie West]

[quote author="aurt"]
Spec-wise, frankly, it's crap. Much better stuff is available now.

IMHFO you may be better off looking for a nice sounding, reasonably priced, readily available alternative. [/quote]

perhaps you are right.... When you want to rebuild it you can use other OP´s. But why not use the originals, when you like the sound of this EQ....

 

[radiance]

I realy don't know much about op amps so I try to stick to the original parts where possible.
OK, I just read the "OPAMPs EASY EXPLAINED" section on Franks webside and also a couple of data sheets so I know a little.
Looking at the w495b schematics I noticed that these HA1-4605/4741 op amps are powered with 24V (pin 4) and 0V (pin 11).
I thought that all op amps needed a +V and a - V power suply or are this different op amps?

 

[radiance]

Got a reply from Haufe:

transformer RK 409 and RK 310/2 you can buy from us. Now our offer:

input audio-transformer RK 409 with magnetic shielding, article-no. 050019

1 - 10 pcs. ....................... a' Euro 75,00
11 pcs. ....................... a' Euro 64,50
21 pcs. ....................... a' Euro 56,80
50 pcs. ....................... a' Euro 52,50

output audio-transformer RK 310/2 with magnetic shielding, article-no. 050093

1 - 10 pcs. ....................... a' Euro 84,50
11 pcs. ....................... a' Euro 72,00
21 pcs. ....................... a' Euro 63,50
50 pcs. ....................... a' Euro 58,90


delivery-terms: ex works, excl. packing
payment-terms: payment in advance
delivery-time: 3 - 4 weeks


Best regards

i. A. Katrin Fach
Werkstätte für Studio - Technik
Dipl.-Ing. H.Haufe GmbH&Co.KG

 

[rafafredd]

Haufe is strange. Sometimes they are cheap, other times they are really expensive.... I would say that this time they are really expensive.

 

[radiance]

So I'm paying 319 euro (for a stereo unit) for in/output transformers alone.
I guess I'm better of buying a second hand stereo (w495bst) unit on ebay...
There is one for sale right now for 699 euro.

Can someone explain to me why this HA1-4605/4741 op amp is powered (see w495b schemo) with 24V and 0V ?

 

[aurt]

I don't think those are exactly crappy specs.

I figured I'd get roasted on that. I just mean that a 5534 handily beats those by a long shot. A TL07x is about twice the noise, perils of fet inputs, but otherwise quite a bit faster. The OPA604 is a touch noisier (11nV/Hz E-2), also fet input, but is twice as fast as the TL07x. I'm having a hard time finding a spec on the 2520, but the 990s are certainly better looking than a 741. Something like an AD797, has a tenth the Voltage noise, -20dB, and is quite a bit faster than anything reasonable audio demands.
That said, yes, if you especially like a piece of gear, and want to recreate it exactly, then it is a fine idea to try to source all the original parts. If using a 741 imparts a "tone" pleasing to the ear, by all means use 'em. I just haven't had the best of luck with them. The 5534 was a considerable improvement and people moan about it being bad, though I'm pretty comfortable with them.
Seeing a how there are TL07xs in a lot of perfectly useable gear, the noise spec isn't, in every case, the most important thing. Also, in this application, where these are not providing enormous amounts of gain, The GBW and slew rate don't really need to be quite as spectacular. But hey, if you can...

I thought that all op amps needed a +V and a - V power suply or are this different op amps?

There are specific "single supply" op amps, but these aren't them. It looks like they're "floating" the ground, deriving it with IC2d, R110 and R111. "Ground", for the op amps, is at +12V relative to 0V. This gives them effective +/- 12V supplies.

 

[jensenmann]

o.k.
Switches are the first reason and trannies the second not to do it. But now we have cheaper switches maybe we can substitute those trannies. Does anybody know more about them (windings, impedances,...)?
Alright, I found the infos (sorry in german)
http://www.kubarth.de/cgi-bin/diy/german/getfile?f=%3B%2C3%24P.%238X%2C%23%2CX%2CE%5DT%3CF%25F%3BW%2CO%3CFLT%2C%23DN%3C%261F%0A
http://www.kubarth.de/cgi-bin/diy/german/getfile?f=%3D%2C3%24P.%238X%2C%23%2CX%2CE%5DT%3CF%25F%3BW%2CO%3CFLS%2C3%60M%2CBYP9%268%60%0A

Any suggestions for substitutes?
Jens

 

[radiance]

@ jensenmann: the link displays this "Sorry, can't find the file you're looking for or your session just timed out, please reload the index file
" when clikced.......

 

[Leslie West]

[quote author="jensenmann"]o.k.
Switches are the first reason and trannies the second not to do it. But now we have cheaper switches maybe we can substitute those trannies. Does anybody know more about them (windings, impedances,...)?
[/quote]

You can find the data here:

http://www.kubarth.de/cgi-bin/diy/german/index

Input is 0,25+0,25:1 and Output is 1:1

 

[PRR]

> the 4741, being a quad version of the much maligned 741, is far from an ideal op amp.

Compared to the 741, it is 3 times faster and specifically claims low crossover distortion. It is in the "super 741" class that NJR now dominates. Despite being 35 years old, the 101/741 topology IS a good design for audio. Original-spec/process 741s were limited by the silicon technology of the day. A 3X faster 741 has been "simple" for 25 years, though sexier designs get the headlines. Also mass-produced chips can be careless with output stage biasing because only audio-heads care about that (and it can conflict with low power demands which all other users care about). This 4741 and the NJR "super-741"s do control output bias current and crossover distortion.

It is a fine medium-performance chip.

> it is a special OP for high quality active Filter designs. It has a very high Bandwith...

Well, a $0.19 TL074 has better bandwidth (but more noise). This 4741 was good, not great, back in 1990. Its special virtues are audio-crossover claims, and perhaps special reliability certification, and perhaps it was already pre-qualified for German broadcast use (they had an ample supply of high-quality parts both from the factory and in repair depots). $25 each is steep, but not a killer cost if "authenticity" is a goal. Frankly, I suspect 5532 would work as well, a trace better, and a lot cheaper, but may not have that German Radio sound. A study of NJR's super-741 chips might turn up something with essentially the same specs AND topology, under a buck each, but their site is hard to study, and NJR sells production quantities, not twos and threes.

> I noticed that these HA1-4605/4741 op amps are powered with 24V and 0V. I thought that all op amps needed a +V and a - V power suply

The op-amp does not care where ground is.

If you need DC response and output swing on both sides of ground (+ and -), then yes you need a dual-polarity supply.

In audio we do NOT want DC response. We can pass audio through capacitors, independent of DC levels. If you look close, the amp inputs return to a bias voltage about half of the 24V supply (R110 and R111 buffered by IC2, R94, C33 and running all over the board). Each opamp output idles at +12V, swings up to about +22V and down to about +2V. The output capacitor blocks the 12V DC, and passes audio swinging +10V to -10V.

The +24V supply scheme is seen in big BBC and German broadcast systems and a few other places. It keeps power supply requirements simple and standard. It also makes it possible to float a battery on the power bus so when the lights go out the broadcast can go on, vital to radio's emergency communications mission.