I bought the RG174 from ebay from one of your old posts - it's very delicate to work with >< I'm still not happy with how its soldered to the connectors. Doesn't seem to draw in solder very well. Oh well, case work is the worst part 😛
Hi Salas - my transformer finally arrived and I powered up the unit and set bias quite easily.
When I inject 1 khz sine and view output on my CRO I notice a gain difference (photo).
What's the best way to fix this issue?
Thanks for your help in advance Salas! 🙂
When I inject 1 khz sine and view output on my CRO I notice a gain difference (photo).
What's the best way to fix this issue?
Thanks for your help in advance Salas! 🙂
Which is due to excellent matching of active components between channels since there is no overall feedback loop in this circuit to fix the gain 😉
Hehe thanks Salas - Teabag did all the hard work 😛
I just need to case up PSU so earthing can be sorted and I’m done. Just tested with turntable then and there’s some minor hum as no connection to mains ground has been made yet. Still sounded very nice! 😛
I just need to case up PSU so earthing can be sorted and I’m done. Just tested with turntable then and there’s some minor hum as no connection to mains ground has been made yet. Still sounded very nice! 😛
Is your transformer magnetically shielded? If not, make the raw DC umbilical long enough to can place the two boxes apart in some good distance.
Nah it’s not shielded. I’ve mounted the PSU components and wired the grounding. No hum whatslever! 😉
Just to check - I originally biased with VR2 but then My rail voltages were just over 1V apart between channels. So then I used vr2 to adjust rail voltage of higher rail channel closer to about half a volt difference then used vr1 to get tp1 tp2 same as other channel. It took a lot of turns of vr1 - is this ok?
Just to check - I originally biased with VR2 but then My rail voltages were just over 1V apart between channels. So then I used vr2 to adjust rail voltage of higher rail channel closer to about half a volt difference then used vr1 to get tp1 tp2 same as other channel. It took a lot of turns of vr1 - is this ok?
VR2 is the control for the regulator's general rail output voltage and VR1 acts as fine rail adjust exclusively for the input stage if needed. So the rest of circuitry can still run on closer rail levels between channels. Thus you utilized those two trimmers properly.
It makes more sense now if you look again in the main preamp schematic as VR1 is depicted on top of the input JFET(s) current sourcing branch. Influencing that portion of the rail only. VR1//R12 is actually a small value adjustable divider working with R13. Not only a local filter with C6. R12 is also there to never lose the current path for the input JFET(s) bias just because of a wiper happened to go bad 😉
Attachments
Good voltages. Put it to work so its electrolytics gonna come up best in a couple of days, finally see about treble level from vinyl being correct in your system or adjust it with the tonearm's VTA and/or C2Y value thus you are done, and let us know how you liked it. Congrats for now, good build and setting work.
Thanks for all your effort and help Salas - it sounds fantastic. It’s also the first diy project I’ve properly cased up 😛 just waiting on umbilical cord connectors to arrive now!
Nice, don't forget to show us pics when fully done. So you think it matched your cartridge straight away? If yes no need for C2Y adjustments. What is your cart, TT, etc.?
Just for you Salas! As you can see, your amp is the only one boxed up 🙂
To do items include install 4 pole Neutrik connectors, make a longer umbilical, and spray paint the silver front panel black (I bought it many years ago but only had a purpose for it now!) - then I'll be 100% complete! This will likely be the first project I've ever properly finished with case 😛
Btw - sanding the case panels to ensure electrical conductivity was the worst activity ><
I don't know if it's perfectly matched - I don't have an accurate LCR meter and don't know how to measure. I just followed impedance as per cartridge datasheet >< It sounds good though, much much better than my old Technics mixer phono (there is no comparison).
My cart is an AT 440MLa, TT is VPI Scout, no fancy cables (BJAudio), Kevin Gilmore Dynahi Headphone amp I'm using as a preamp, Owen MPUHP 'The Wire' speaker amp.
Last edited:
When not having many test gear but the vinyl treble sounds at normal level vs other verified response sources then you needn't trim your C2Y values to others than those you installed. Good TT and interesting diy choices BTW. Congrats & enjoy. Which one KEF model is that concentric? LS50?
P.S. May I suggest one last item for your list: The Martian film poster 🙂
P.S. May I suggest one last item for your list: The Martian film poster 🙂
Hmmm I’ll have to do more critical listening to determine balance - on a related note it sounds very holographic, never felt that in my setup before.
I never planned to have all those components chained together - just happened worked out that way plus I have limited choices. I was going to build your preamp but just decided to take shortcut and wire XLR outputs to my Headphone amp 😛
Speakers are KEF LS50s - what speakers do you run/recommend? Any good DIY options?
Edit: haha re poster 😛 maybe I’ll get a blade runner one...
I never planned to have all those components chained together - just happened worked out that way plus I have limited choices. I was going to build your preamp but just decided to take shortcut and wire XLR outputs to my Headphone amp 😛
Speakers are KEF LS50s - what speakers do you run/recommend? Any good DIY options?
Edit: haha re poster 😛 maybe I’ll get a blade runner one...
I run self designed narrow towers with two 6x9 inch Tangband oval basses, a 6.5 inch PHL mid and a Celestion 1 inch exit compression driver loaded with a Faital Pro Tractrix profile aluminum horn. Those are 95dB at 2.83V 6Ω speakers. Can't have the coherence of a small concentric but I am listening at four meters away so their sound bubbles get a chance to form better. Large and sensitive enough speakers convey effortless scale nonetheless.
Maybe you could try your hand in one of those FAST type diy speakers that have a woofer and a small full ranger or an open back Nola Brio clone dual full range and a sub. Easy projects, not too big, that sound coherent. Not that the LS50 isn't good but in case you also want to experience speaker building which can be exciting.
Maybe you could try your hand in one of those FAST type diy speakers that have a woofer and a small full ranger or an open back Nola Brio clone dual full range and a sub. Easy projects, not too big, that sound coherent. Not that the LS50 isn't good but in case you also want to experience speaker building which can be exciting.