Ariamella
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Posts posted by Ariamella
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Ah sorry, I mean, which transistors should I match? Is it all of them?
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Apologies, this is probably a silly question, but what's the most important components to match? (And for the GRLV too...) I'm still a little new to this side of DIYing...
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Also, is matching a must for this amplifier?
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Ah, am I blind or is there not actually a 10k on the silk?
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On 7/4/2018 at 10:22 PM, Pars said:
Documentation? heh
Which amp? This is a confusing thread because there are at least 3 amps discussed here, maybe more (Kevin or others, correct me if I am wrong):
- CFA2 (CFP) - current feedback amp. Each board does 1 channel SE, so 2 for stereo SE, 4 for stereo balanced. Kevin later did a mod to this adding current mirrors feeding the servo. People who had built the original noticed that the servo was audible as to quality of opamp. The schematic in Kevin's archive is the older version.
- CFA3 - current feedback amp for balanced. Not sure if anyone ran boards for this one. Basically a pair of CFA2 amps and ubal-bal board on one pcb. Schematic does not show the current mirror mod as in 1 above
- uberamp - seems to be a power amp; I've never quite figured this one out
Here are the schematics for the CFA2 (current mirror version), and the CFA3. I also attached my BOM for a CFA2. Amp quantity shown is for stereo SE. If going balanced, double it. It should reflect the later current mirror version. You'll also need some GRLVs or other power supplies, etc.
EDIT: I also ran across another schematic on Kevin's site which I hadn't seen before: currentsourceamp2.PDF. This seems very similar to the cfa2cmirror schematic, but is described as a transconductance amp.
Your BOM has 1k specified but I can't find that anywhere in the schematic. Is the 1k necessary?
Edit: here's the mouser BoMs for the CFA2 and GRLV I created:
I think they're both correct but if there are any mistakes please let me know...
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Alright, I'll think I'll use a 100VA traffo and keep it at 35V for 10uF and 25V for 47uF for the tants then. Thank you for the help!
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Holy crap, it takes that much power?
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Thanks my dude. Also, I'm aware that 28-30vac is a good range for the traffo for 30vdc but if I want to power a CFA2, what va is recommended?
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Apart from the big caps (using 50v ones) and r8/r9 to 3kR, do I need to change any other parts assuming a 30v output? I assume the tants too, but would 50v for the 10uF and 35 for the 47uF ones be fine?
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On 12/19/2017 at 4:15 PM, luvdunhill said:
Just Vf - it’s a voltage reference.
Ok, thank you very much! Would wirewound trimpots be ok to use instead of the cermet ones specified? Happen to have some lying around.
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Do the other specs of the LED matter or is it only the forward voltage (1.7V) that is important?
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14 hours ago, Pars said:
Matching never hurts... not sure that they need to be though.
Sent from my iPhone using TapatalkI'm pretty certain they don't but I want to ask just in case!
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3 minutes ago, PretentiousFood said:
This is the hFE chart on the datasheet of the KSA992 (and should be identical to the grading system on the KSC1845).
@kevin gilmore, do the 2SA1145/2SC2705 on the ss dynahi boards I have need to be matched?
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1 hour ago, PretentiousFood said:
I think I have about 100 of each (ksa992/c1845) that I'll never use if anyone needs. Can check tonight.
What grade are they? I'd love some if you can spare them!
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5 hours ago, justin said:
2sa1201 / 2sc2881 is what i use..you could probably stand them up in TO-92 holes just watch the power
They appear to be discontinued, sadly enough.
Urg getting through-hole sand is incredibly difficult it seems...
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Do you have any other suggestions for 2SA1145/2SC2705 replacements?
EDIT: Just checked the pin outs for everything else and they're a match!
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I was wondering about the transistors used on one of the older versions of the susy dynahi boards being obsolete, and after searching online I think I've found replacements for all of them that seem to be drop in. I'm just wondering if these are fine or if I need to find something else or try and source NOS or used parts.
- 2SA1358/2SC3421: KSA1220AYS/KSC2690AYS
- 2SA1145/2SC2705: MMBT5551/MMBT5401LT1G
- 2SA1349/2SC3381: matched pairs of KSA992/KSC1845
- Matched pairs of 2SJ74/2SK170: matched pairs of LSJ689/LSK489 or LSK74/LSJ170 (both seem to be rare/expensive!!)
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5 hours ago, gepardcv said:
Yeah, those are the numbers from the Gerbers I used for my boards. SMT and MJE output sand. No idea about sizes for any older revisions, but if you get me the Gerber for it, I could try to figure it out for you.
Ok, thank you anyways! The older revisions are probably close enough that the case I plan to use can fit them all...
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2 hours ago, gepardcv said:
@Ariamella: I pulled the following numbers from the Gerbers, and I think they match the produced boards:
- ssdynahibalsmtm.zip: 215.9×115.3mm
- goldenreference6.zip: 93.3×109.9mm
Thank you very much! Is that the newest SMT version of the dynahi? Sorry to be a bother but do you happen to know what the dimensions are for the V1 Susy Dynahi boards are?
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Maybe I'm blind...but I can't seem to find the dimensions for the offboard ss dynahi PCB. Does anyone happen to know them?
EDIT: And maybe the GRLV too. I'm currently doing a layout plan on google sketchup so it would help to have those dimensions handy!
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49 minutes ago, MASantos said:
I remember Salas saying how having the reg on the same board as the phono was a big influence on the great sound of the FSP. You could use the GRLV before the shunt, some people used a jung super reg as a "pre regulator" for the integrated shunt.
Hm that could work at some point, but I doubt I'd be able to afford both of them at the moment...:p
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37 minutes ago, mwl168 said:
I would not recommend using 25 vac trafo for 30VDC output. The drop voltage will also vary a bit depending on current draw.
Yeah, that's what I figured. 30VAC it is!
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Ok, crunch time, time to decide which PSU to use! I've settled for either the GRLV or the Salas SSLV1.1/BIB. Both of them seem to cost about the same amount of money to make, so I'm having difficulty deciding which one to go for...
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24 minutes ago, Pars said:
A 2x30Vac SumR is what I am using on mine. The Antek transformers seem to work well also, and much cheaper.
Alright, thank you. Thinking of something like these:
and now for something completely different part 3
in Do It Yourself
Posted · Edited by Ariamella
Gotcha, thank you very much! Do you mean opposing transistors as in complimentary transistors? Google wasn't very helpful in that regard...
Reading through the thread is a little overwhelming x)