Active Ribbon Preamp/Impedance Converter Idea - opinions?

Nice Ribbon-Zilla pics ! :thumb:

Hi Rossi,

Out of interest, what is you opinion of the Edcor ribbon transformers?

Regards,

Roddy

(Phew)..............Just finished reading through this whole thread, and the earlier ones linked to in the first page.

Good stuff.

Im a little confused though.
Is there two different generations of the RB500?
And is one better than the other? Different trannies?

I was just about to order one from Thomann, but just thought I´ll ask the ribbon experts first.

@ Roddy: The edcor tranny sounds very nice. Solid midrange, classic ribbon sound. Lundahl sounds more hifi by compariosn. But the Edcor is slightly noisier than both the Lundahl and the stock tranny. The Edcor has about the same ratio as the stock tranny.


@ Kit: The current Thomann model as well as the SM Pro Audio MC04 I dissected have a normal ratio (about 1:25). Thomann sold a different version for a while that had a 1:80 transformer, but they returned to the original version. So if you don't already own a RB-500, you can simply forget about the hot version, there's no way to buy one right now. Out of the box, the 1:25 transformer version sounds better than the 1:80 version, but the 1:80 offers a lot of modding potential and can very easily be converted to active operation.

[quote author="Rossi"]@ Kit: The current Thomann model as well as the SM Pro Audio MC04 I dissected have a normal ratio (about 1:25). Thomann sold a different version for a while that had a 1:80 transformer, but they returned to the original version. So if you don't already own a RB-500, you can simply forget about the hot version, there's no way to buy one right now. Out of the box, the 1:25 transformer version sounds better than the 1:80 version, but the 1:80 offers a lot of modding potential and can very easily be converted to active operation.[/quote]
Perhaps any indications or giveaways that indicate whether a RB-500 is the 1:25 or 1:80 ?

Since most likely I won't mod* so also don't want to open my RB-500 I was curious if it could be determined 'from outside'.
If not then I can always measure of course, comparing it with say a SM-58/57 and compare the sensitivity.

Regards,

Peter

*: which doesn't mean I'm not interested reading the articles; I'm getting me the second installment as well.

There's info & pictures on that in the 2nd installment. The only way I can tell my 1:80 RB-500 from the others without opening it is looking at the screws that hold the basket. The hot one uses slotted screws, the others Philips screws. I don't know if that's consistent with all RB-500s, though. To be sure, you have to open the mic and look at the tranny itself.

The hot RB-500, at least mine, has issues with the HF-reflector arrangement which should be corrected for optimal sound. There may be other RB-500s, MC04s and budget ribbons from other brands that suffer from wrong reflector arrangement. The reflector stuff (as well as edcor vs lundahl) was in the first installment, though.

Thanks for the info Rossi. I bought the 2nd today, some reading ahead :thumb:

Bye,

Peter

Haven't looked at specs yet, but it looks like more people found the idea of a pre-pre-amp a good one.... maybe people here have seen it already but it was new to me Rode did these:



http://www.rodemic.com/?pagename=Products&product=D-Power

Also available in barrel-style:



http://www.rodemic.com/?pagename=Products&product=D-PowerPlug



Regards,

Peter

I think we discussed the D-Plug before. If I remember correctly, the EIN figure on the Rode website is not impressive. I think someone here tried it to power a transformer-deprived SM58 or SM57 but found it too noisy. The PRR ribbon booster should be lower noise than the Rode circuit. I'm otherwise fine with Rode stuff, in fact their stuff is usually pretty amazing for the money. So no bashing involved. :wink:

[quote author="Rossi"]I think we discussed the D-Plug before. If I remember correctly, the EIN figure on the Rode website is not impressive. I think someone here tried it to power a transformer-deprived SM58 or SM57 but found it too noisy. The PRR ribbon booster should be lower noise than the Rode circuit. I'm otherwise fine with Rode stuff, in fact their stuff is usually pretty amazing for the money. So no bashing involved. :wink:[/quote]
Hi Rossi,

Oops, wasn't aware of that. And sure, its specs aren't targeted at what this thread is about. I just happened to see the Rode-plug at the Cascade-mics site, where they used it with a Fat Head ribbon-mic - the first 'commerical' in-line booster I saw.

Unsurprisingly, I guess that 8-pin SMD package of the pic above will simply be a dual opamp and we've seen that that won't meet the various demands that were on the table here in this thread.

At least I don't know of dual real-low-rbb BJTs in 8-pin SMD out there (but there's of course no reason why not).

Regards,

Peter

[quote author="clintrubber"]
At least I don't know of dual real-low-rbb BJTs in 8-pin SMD out there (but there's of course no reason why not).

Regards,

Peter[/quote]

None from Toshiba last I looked. But they take a fair amount of current to really shine and hance are challenged to give best results running from phantom power.

Even with bog-standard 30ish ohm 2SA1132GR (SOT23) or the still-smaller 1832 (?) though, you can do quite well.

Of the ones I tried in PRR's booster circuit, the Toshiba 2SC3329 and 2SC3328 as well as the Hitachi 2SC2546 were the best and noticeably lower noise than "normal" low Rbb transistors such as the 2SC1815 or 2N4401 (the latter was pretty okay, though). I tried some more, but those are the ones I remember. I didn't find any BC type transistor that was halfway decent.

The only 8-pin devices that should be okay noisewise would probably be the THAT/BB/Analog Devices preamp chips. But I suspect those would require too much power for P48.

I cannot believe the group missed this one.

Look at the Cool Audio datasheet for the 2SV888;
http://www.coolaudio.com/files/public/2SV888_DATASHEET.pdf

Look at the bottom of page 3.
Under the work "packing"
and you will find this "2SA970GR"

So there you have it folks the Cool Audio 2SV888 is really a 2SA970GR

Datasheet for 2SA970
http://www.datasheetcatalog.org/datasheet/toshiba/962.pdf

Good eye!

Noise specs are slightly better for the SV888, though.