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Post by Bender on Mar 6, 2018 13:36:42 GMT -6
My old Lady recently got me a new turntable for my birthday....something I've been avoiding as now I'll have a new black hole expense to contend with but I digress  .... in any case, I'm currently using the built in preamp in the turntable running RCA's into an adapter, then into my RME 802 inputs. Anyone have some leads on a decently priced Phono preamp kit? I'm open to discrete or tube but don't want to spend a ton of moolah. Anyone? |
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Post by Tbone81 on Mar 6, 2018 15:37:57 GMT -6
Radial makes a phono preamp. I haven't heard it but i willing to bet its pretty good. All of their stuff is solid.
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Post by Bender on Mar 6, 2018 17:32:06 GMT -6
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Post by Tbone81 on Mar 6, 2018 19:43:56 GMT -6
Yeah, I missed that part. Thought you were looking for something off the shelf. Don't know if any DIY but there has be something out there, right?
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Post by Deleted on Mar 7, 2018 2:07:52 GMT -6
Radial makes a phono preamp. I haven't heard it but i willing to bet its pretty good. All of their stuff is solid. I second this if you want something off the shelf (I realise you don't). I've been using the Radial J33 as my only phono pre since 2011. It sounds great and integrates well with everything in the studio (check all its outputs!) The ONLY downfall is that both times I've contacted Radial to ask about modding the unit, they have been extremely unhelpful, but I guess that's cos they don't want to deal with the fallout of many people trying to mod their gear and doing it badly. |
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Post by drc on Mar 7, 2018 15:35:31 GMT -6
I'm surprised there isn't a high quality rack mount preamp with a strong line level output available. Well at least available for people who live in a rational economic plane of existence. I say this because I use a very early Coleman switcher with passive stepped attenuator. I run my Denon CD player direct to my power amps with only that passive knob in the way. It sounds better than any high dollar high-fi unit I have ever used. I'd love to put a phono stage in that same rack with an output as robust to the same thing as I do with the Denon. Instead I'm using the phono stage in a 90's Rotel. It's ok.
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Post by Deleted on Mar 8, 2018 2:35:11 GMT -6
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Post by matt@IAA on Mar 8, 2018 9:57:02 GMT -6
I found an API 1972 catalog with this image in it: So, I presume you can do it with a simple op-amp / transformer gain stage...? Maybe see if anyone has ever seen an API 330P schematic.  Edit: ah, here you go...!  I’ll make a PCB and BOM for this if you want. 500 series or not, whatever works for you. |
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Post by matt@IAA on Mar 8, 2018 15:36:47 GMT -6
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ericn
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Post by ericn on Mar 8, 2018 19:45:42 GMT -6
There is a schematic on the John Hardy site that I’d like to build some day, first I need a turntable though!
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Post by dandeurloo on Mar 8, 2018 22:14:51 GMT -6
I have a phono pre that I designed for a client who is into studio and hifi. I have a handful of the PCB's left over if you are interested in building them. They can take pretty much any mono smt, dip or 2520's you want to use in it.
Feel free to hit me up if you are interested.
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Post by Deleted on Mar 9, 2018 14:58:54 GMT -6
Elliott Sound ProductsI'm extremely happy with this. Buy the PCB. No esoteric components but super clean phono preamp. Been using it for transfers for the last years. It's unbalanced without output gain control but I never needed You can add output transformer or electronic balanced if you want. I run mine unbalanced without issue.
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Post by Bender on Mar 9, 2018 15:27:05 GMT -6
I found an API 1972 catalog with this image in it: I’ll make a PCB and BOM for this if you want. 500 series or not, whatever works for you. Yes this would be awesome! Now we're chatting! How about a 500 series version? I'm going to hit you up to dan and talk about that pcb you have as well. I knew there |
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Post by matt@IAA on Mar 11, 2018 3:02:26 GMT -6
Ok, here's a 500 series. I did it so the card can be configured with a fixed resistor or with the trim pot. And just in case you want to use a trim pot with a different footprint or locate it somewhere else there's a molex header option as well. Also, I added a 47 ohm load resistor behind the op amp. I'd consider this something you could try or not with the circuit. A lot of transformers fit in that format - you could get a CMOQ-2 from cinemag or a JT-11 or JT12X from jensen in 1:2. Really depends on how aggressive / clean / distorted you want a phono pre to sound. I'd also suggest playing with the load resistor to see if that reduces noise or finds a sweet spot depending on which transformer you use. ![]()  |
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Post by Bender on Mar 11, 2018 15:04:19 GMT -6
1st- what a master thanks so much man, and no need to worry to about it especially if you're traveling, we can hammer this out when you get back. 2nd- can't thank you enough, this will be a fun project for sure and I have the space in the rack so why not. Count me IN on the pcbs! I can't comprehend schematics to the fullest like the Real DIY/electrical engineer folks like yourself, but I certainly can read them in a signal flow/parts symbol context if that makes sense...needless to say a BOM would be comforting & way easier for my sourcing via mouser &/or digikey so I'd truly appreciate that =0) Paging jsteiger I was looking up the transformer from the 330P and I unsurprisingly gathered the Ap2157 is interchangeable with the 2623 , so that's an easy one to square away once I can figure out the color code for the litz's vs the 2157- perhaps it's more wise to go for a flat neutral/clean tone but I can get down with some coloring and experimentation with 990 opamps vs the 2520. Hey jeff maybe you could hook up some of those sweet knobs and Perhaps I could buy a couple extra metal vp26/312 card holders that are already punched to make the gain knob nice looking   ..maybe opting for a cheap one hole faceplate down the line if I wanna get fancy & make it super clean looking... Anyway as far as a gain knob that's looking really nice- but this is where I start to get confused.This single phono card is essentially mono right? I figured I'd have to make two of these for a stereo unit, is that correct? I have no clue & please correct me either way,I'm just thinking logistically when it comes to cabling that would make the most sense....because if that wasn't the case then cabling would be tricky going into a lunchbox then out into the RME... For example my cabling connection is/would be: Turntable Rca Cable L -> RCA male to Ts adapater-> Ts to xlr male ->lunchbox phono PRE 1 ->Trs -> Rme Input Turntable Rca Cable R -> RCA male to Ts adapater-> Ts to xlr male ->lunchbox phono PRE 2 ->Trs -> Rme Input Anyway assuming I need to do a pair for stereo,then the gain will have to be matched & for sake of ease wouldn't it be easier to have them stepped then for matching stereo levels? Another question, I see the output of the phono pre is +4 vs the -10 as well...not a problem in our world obviously- but being the turntable is unbalanced and presumably -10 then does that mean the modules are built for that input reference? I.e. built for unbalanced connection on input. Either case throwing in a grayhill with resistors of course will add to the price and things do add up quickly obviously but its good to have the gain option- though it might be easier just make them fixed gain to avoid all that and just control the master volume ITB with TotalmixFx... hm decisions decisions.. Anyone else care to chime in? Looks like I might have some extra Pcb's or I'll just build them out if anyone else want's to tag along/ has a lust for an api'ish phono preamp in 500 series! |
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Post by matt@IAA on Mar 11, 2018 17:33:05 GMT -6
No worries, this is fun for me.
I made up a Mouser BOM for the above, I can email it to you.
I used the footprint for a 2503 only because I think there are more options in that size. If you want the "correct" one I can change the layout to a 2623. I'm not positive if the 2623 will just drop into the same screw hole pattern - I think it might. Color designations on the pcb would be wrong - I suppose I could just label them in hi / GND, out HI / LO 1:1, 1:2, etc.
Yes, each card is be mono, so for stereo you'd need two.
For cabling, these are set up to receive an unbalanced input. You can go straight from RCA to XLR without the TS adapter. The output is balanced.
You could step them, it's a little more complicated to build and a nice stepped switch is a bit more expensive like you said.
Alternately I could put a place for a small trimmer on the card itself and you could set it and forget it. I don't think you'd want this being moved all the time, but set to receive phono level and spit out +4 into whatever amplifier or line level receiver you're going to use.
Just to clarify, the gain on this is set by the series trimmer, but this isn't like a gain knob on a 312. The total range of the trimmer is something like 2.5 dB, corresponding to 52-55 dB or so.
This is adding a lot more gain than just -10 to +4. This is adding 54 dB, phono to +4 line level. So make sure you have a way to get phono level out (truly bypass the built-in phono pre in your turntable).
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Post by mattyt on Mar 12, 2018 12:49:46 GMT -6
I have been working at this for a few years now. I have used the Radial J33 which definitely gets the job done, but then I got bit by the DIY bug. Ive built the KA project which is quite nice and works pretty darn well, however it doesnt give you the flexibility to use DOA such as the 2520. This project does come together really easily and I do like the way it sounds. Ive built the John Hardy schematic using some of his 990s and it was pretty nice, but I got a pretty high noise floor probably since im not skilled enough to add stuff like filtering circuitry or beefy psu other than using a standard five fish Then I talked to Dan D about this project. He came up with a really nifty pcb that lets you use either a surface mount, through hole or DOA opamp in the 2520 footprint. There is a tone of filtering involved as well on the power. I built it up, sent it back to Dan who tested the RIAA curve and it was as close to perfect as you can get. Using a five fish psu the noise floor is really low. All of the builds were pretty fun, but for flexibility of opamps I would definitely go with Dan's. What more, he can sell you a case to go with it! Attachments:
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Post by maq3396 on Mar 13, 2018 17:34:39 GMT -6
These two fellows have designed a number of high end preamps, amps and phono amps based on tubes. Their products receive high praise in the hifi world Havent built any of the projects yet but have a SP14 preamp on order and am about to order a pair of the M125 mono blocks Both reply to their emails within 30 minutes www.tubes4hifi.com/pre11.htmCheers Mac |
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Post by Bender on Mar 13, 2018 19:15:55 GMT -6
Thanks ya'll love to see there are some other options...having the extra spaces on the rack and not having to deal with build a PSU makes the 500 series route all the better. Just sent payment for the boards. I'll post updates once I get this project built and going....now hopefully it sounds good!!!! |
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Post by rocinante on Mar 18, 2018 4:43:53 GMT -6
I'll echo Elliot Sound as he has great stuff with an entire book full of articles on projects and info about them. Dude knows his stuff and has variety mixed with simplicity plus stability.
Pete Millet is a good source too and yeah he has an eBay store but he designs top notch well respected pcb's and circuits. From the pretty simple to the overly complicated.
You could also check out Glassware Audio and the Aikida line.
AMB is just great but it's more dac orientated but has phono stuff too.
Transcendental is considered to have some top end kits.
Dynakits are pretty famous for having kits and parts for building 50's style stereo amps like Dynaco.
DiyAudio is really the spot for that stuff. I could go on. I've built several hi end tube and solid state amps. Using several of the aforementioned companies. I've thrown arduinos in there and made a monitor controller with a rPi dac with its own amp that I was pretty proud of.
Or go API.
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Post by Bender on Mar 22, 2018 19:17:26 GMT -6
Cards and all the parts have arrived, let the building begin! matt@IAA the color layout on the card is for the standard 2503 provided by capi...which is the same color code as the api i believe.... if that's the case then I can just use the color "de-coder" provided on the litz transformers page. Thanks again! |
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Post by matt@IAA on Mar 22, 2018 19:53:02 GMT -6
Yes, it’s color coded for the standard CAPI. May want to double check anyway.  |
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Post by Bender on Mar 23, 2018 22:31:59 GMT -6
As previously mentioned everything has arrived.Have a little spare time before a big CAPI build and with a new turntable on the way I figured lets get building... so here's the pair! Thanks again for all the help matt@IAA the pcbs do the job nicely! they don't perfectly line up with the default CAPI metal cards in the corners but I can live with just popping em the lunchbox and putting a faceplate in front of them and calling it a day! I'm burning em in tomorrow and will get the full audio experience going tuesday when the table arrives- beer and smoke time now so the electronic fun will have to wait until then. Audio clips to follow for fun perhaps? I'm going to try them out with the 1731's 1st and experiment from there. |
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Post by Bender on Mar 23, 2018 23:00:41 GMT -6
There is a schematic on the John Hardy site that I’d like to build some day, first I need a turntable though! These guys are pretty awesome and where mine was ordered from, they offer a built in preamp or external, but DIY was more fun . The turntable snobs will highlight how it doesn't have anti-skate or auto return but you can easily add on a kickback/q up www.thequp.com/ which shoots the arm back once it reaches the end of a side. Anyway check out the tables, made in the ol USA uturnaudio.com/ |
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Post by matt@IAA on Mar 24, 2018 4:36:23 GMT -6
Sweet, enjoy em!
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.... in any case, I'm currently using the built in preamp in the turntable running RCA's into an adapter, then into my RME 802 inputs. Anyone have some leads on a decently priced Phono preamp kit?
