Bellari RP583 Input Tranny Specs?

Anybody got a schematic for ththe Bellari RP583? I wanna replace the input tranny, and I was looking at an ebay auction for some vintage Telefunken line input trannies. From the auction: Pri: 600 ohm in 2 sections Sec: 600 ohm in 2 sections. The model number printed on the Telefunkens is CN 157 38, but google won't cough up any details. Any help appreciated.

Nevermind, Rolls website says the input impedance is 10k balanced, 1M unbalanced. Why such a high unbalanced input impedance? Would that be for DI??? into a compressor???

Sorry for the dumb questions, all this tranny stuff is new to me.

Still looking for that schem, if anybody has it...

According to the Bellari website the RP583 has Solid State input and output buffering, NOT transformers. If you want to add tranny's you might try a "bridging" type on the input, like a 10k:10K or 15k:15k from Sowter or a vintage altec/peerless or a zillion others. Look at the METE META for transformers. VERY helpful.

Generally speaking modern equipment uses "bridging" inputs where you want your input imp to be at least 10 times higher than the output imp of the previous device. Sometimes a designer will use more or less of a difference based on the way it sounds (bless their hearts.)

A lot of older gear used "matching" imp 600 ohm in/outs.

[quote author="ciminosound"]According to the Bellari website the RP583 has Solid State input and output buffering, NOT transformers. If you want to add tranny's you might try a "bridging" type on the input, like a 10k:10K or 15k:15k from Sowter or a vintage altec/peerless or a zillion others. Look at the METE META for transformers. VERY helpful.[/quote]

According to the website, you're correct, no mention of an input tranny. However, a web search says it does, and based on that, I popped the box open, and there it was... Actually right next to the power transformer, of all places! I'll prob pop it open again this weekend to see if I can get some specs or model numbers. A web search says its a class 2 (dunno what that means yet, but I am reading that tranny meta as we speak).

I do find it interesting that the block diagram on their website makes no mention of the tranny. Maybe because its so crappy???

Thanks for that "generally speaking". Making a mental note as we speak!!! :grin:

Just as I suspected. Check this thread out...

RP583

No input tranny just two power trannys with one reversed to provide the HV for the tubes. Both are AC mains transformers. One takes the 120V from the wall and drops it to the 15V or whatever the supply uses. They wire the other one in reverse to take the 15V (or whatever) and step it back up to 117V or more likely the 220V tap for the plate voltages on the tubes. You are free ans clear to try input transformers. DON'T REPLACE EITHER EXISTING TRANSFORMER!

Sorry to waste your time, thanx for the answers...

I actually saw that thread in a search, but ignored it as it "seemed" to be about the power tranny only. I guess I deserve a b*tchslap huh...

Not a waste of time! You never find out answers if you don't ask.

Try a bridging tranny on the input and see if you like the sound. What the hell, right?

:thumb: :sam:

Yeah, can't hurt, its not like the thing sounds good as is or anything... As is, its about as muddy as the Mississippi Delta. When I bought it, I was looking for moddable budget gear, and Bellari has a rep for modding well. Actually my RP220 came out pretty darned usable with the black lion mods (and was an excellent way to get my feet wet!).

Now I'm ready for more. Which is cool because I can figure out the 583 and actually learn a bit more about circuit topology (and trannies and op amps) and reading schematics, as opposed to just following a set of directions.

After that: JLM baby animals and a G1176!

Actually i had the thought of putting trafos in this as I was sifting for this schemo today. Please let us know how this turns out or if you need more suggestions. For the o/p trafo, you are going to need something like 15k:600, I think.

Peace!
Charlie

[quote author="SonsOfThunder"]Actually i had the thought of putting trafos in this as I was sifting for this schemo today. Please let us know how this turns out or if you need more suggestions. For the o/p trafo, you are going to need something like 15k:600, I think.

Peace!
Charlie[/quote]

Could you post the schematic somewhere? 15k:600? That high of a ratio you think?

thanks again Charlie for sharing that schematic! I'm working on deciphering it right now, and quickly realizing how far I've got to go. First I'm gonna swap the op amps for something better, that way I can continue to use it while I figure out all this tranny talk.

2604s were suggested to me, but I do wanna try some other models. I've been looking at datasheets and it seems like the 2604s are in no way a match for the BA4560s in there, but then again, I'm still kinda shooting in the dark. Do either of you have a good suggestion for replacements. Also, what about the different areas, like for instance, is there a certain opamp that works well as an input/output buffer? What about in the gain stage (is it even called that in a compressor???) opamps? What specs are most important and what should I be looking out for in the datasheet?

Sorry for all the dumb questions...

Sure that ratio on the output tranny. I had the SS in/out buffering stuck in my head! We need a Homer emo for "DOOH!"

Getting schemo sent.

Thanks big time for the schematic Jonesy (and Charlie).

I am no engineer, so I am really talking out my a$$ here, but this is what I am going to try.

It seems to me that if rp220 mods sound good, alot of that could be applied to the rp583. The output stage looks the same, so the opamp swap suggested for the rp220 would probably work there. I am guessing the same opamp would work on the input stage since the original input/output ones are the same. It is probably not neccesary to change the chips that handle the gain reduction side chain stuff (Is this a good assumption? I don't know.) Swap out the output level pot with the Black Lion rp220 suggested one. Update the Caps in the signal path (maybe, I haven't looked at them yet) and swap the tubes.

Of course, one channel on mine doesn't even work, so I have to take care of that first.

Then if that all works for me, I may try the transformer mods. This looks like it would do the trick for the input stage http://www.jensen-transformers.com/as/as087.pdf (I would probably use an OEP with similiar specs) Put everything before R3 in the Jensen circuit before R5/R38 in the rp583 circuit. As far as the ouptut stage goes, I have no idea.

I am just looking for something to add a little tube/opto (/hopefully transformer) flavor for tracking into my computer.

Again... Disclaimer... I am no engineer, so I am really talking out my a$$ here...