So ... I finally completed my simplistic build. I'm stunned but have one unresolved issue - I have a slight channel imbalance - not gain but one channel rolled off in the highs. I've changed countries three times since getting the boards and am about to pack up again and sail. I'm 90% there and have checked both boards. No apparent differences between in terms of components values voltages bias etc - in fact when bias sing yen boards they were almost identical. I'll have to wait another couple of months while we pack & shift to have a real chance but what I will say is that this is a stunning phono stage. More life in my music then ever before.
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When having some time again to confirm what is going on, you got to measure and compare its channels for response with inverse Riaa like the one from Hagerman Audio Labs and PC software like ARTA. But before that, just swap the turntable channels at the phono inputs so to confirm that the response imbalance is not coming from the source. If it will jump to the other channel, then its not in the electronics or the speakers. Arm/cart systems can have geometrical and mechanical trimmings to sort out regarding good channel balance just as well and rather more often than response problems in the electronics. Congratulations for completing it up to this point when having to move all the time. When this issue will be resolved it will give you nicer musical focus even. We don't have audible response mismatch prior cases so to give an instant answer about some known trap in the build process but we will be happy to help with how to measure and evaluate/trace. Good luck with your travels.
I've swapped channels and also have several other phono stages so can verify its not the source. I suspect potentially the polystyrene cap in the Riaa but don't have an instrument that can measure that low. I will spend time troubleshooting and will post back as I'm sure to resolve it - should be easy with a good channel. Even with the imbalance which is pretty subtle I'm impressed. Give me a few weeks I'll be back.
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100pF off in the treble capacitors combo value is audible in this filter I have found. DER EE LCR is an affordable good investment by the way for someone who will be looking for precision in small capacitors or loudspeaker coils again in the future.
the 328 Mega test instrument is cheap and although not accurate is good for identifying devices/components as well as giving values.
A basic 328 Mega is <$10
A basic 328 Mega is <$10
Acting Upon the advice of Salas, I've been using a DER EE for a few years now. Can't say enough about the supreme accuracy. I tossed out my ancient B&K.
As for the Simplistic RIAA, I'm getting close to firing it up but have one question now and maybe a few more questions to come. Dying to get this going and spin some vinyl
*My mini kit came with 2 x 6.754K ohm, 1% resistors. R5 and R10 is showing 6.8K in the BOM. Should I place 6.754k in R5 or R10??*
Thank You.
As for the Simplistic RIAA, I'm getting close to firing it up but have one question now and maybe a few more questions to come. Dying to get this going and spin some vinyl
*My mini kit came with 2 x 6.754K ohm, 1% resistors. R5 and R10 is showing 6.8K in the BOM. Should I place 6.754k in R5 or R10??*
Thank You.
Normally there is an R6 1Meg resistor shunting the R5 6.8K resistor to make it a slightly lower value that I was after. But Tea-Bag Mike had arranged for a special order low ppm R5 with that exact value, so don't populate an R6 when you got that nice special R5.
Salas, I have been listening to this unit for several months and I am very happy with it.
Is there an easy way to add a switch to mute the outputs? I am finally going to put it into a permanent case.
Is there an easy way to add a switch to mute the outputs? I am finally going to put it into a permanent case.
Can use a relay. You want also a transient mute like a delay for when turning it on or you want it controllable with a switch only?
Just the ability to mute it with a switch, no worried about a delay when powering up.
Would it just use a relay to join the hot signal to ground or ?
Would it just use a relay to join the hot signal to ground or ?
I was using 2x150pf parallel polystyrene C2Y - on the affected channel I took one off which did make an audible difference but it's still slightly muffled and quieter. I checked bias balance between channels and both stable and identical voltages. Finally am packed for the move so radio silence from me for 2 months or so.
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Yes you can do that hard grounding because there is an output capacitor and there will be no DC over-dropping dissipation problem for R11. But do it with relay not to have the signal going around to the front panel and back through a classic switch. NEC EA2-12 NJ is a good one for signal and available in Mouser etc. Probably made by TOKIN the Japanese manufacturer that produced the legendary triode-like VFETS once.
I'm planning to put everything in two enclosures to separate the supply. I have some 18awg 5 pin connectors. What wire should I use to make a nice cable?
Any extra ideas on sheilding the supply would also be helpfull.
Any extra ideas on sheilding the supply would also be helpfull.
Have a look here Wire . There is some shielded twisted pair called M27500-22SD2T23 part way down the page, only 12 cents per foot and very high quality. Connect the pair to +V and 0V, and connect the shield to the PSU chassis only. Bundle 2 lengths in some techflex so each channel has its own shielded pair.
The mill-spec looks good but has anyone Tried BELDEN 9418?
http://www.belden.com/techdatas/metric/9418.pdf
http://www.belden.com/techdatas/metric/9418.pdf
I have used Mogami and Canare star quad because they were handy for this umbilical but the Belden or the Milspec look fine too. Its only a DC link, not very demanding.
The shield/screen is there to conduct interference to the Chassis.
The only way it can do that with a low impedance, is via a low impedance connection to the chassis.
The higher the frequencies of the interference, the more important that both ends connect to Chassis.
The only way it can do that with a low impedance, is via a low impedance connection to the chassis.
The higher the frequencies of the interference, the more important that both ends connect to Chassis.
If you build this project according to the build guide, the PSU chassis is connected to safety earth, but the 0V is isolated from that earth by a network consisting of a resistor in parallel with a pair of diodes. The amplifier chassis is connected to 0V. If you connect the screen to chassis at both ends you effectively bypass that isolating network. I don't think that is a good idea. I suppose you could connect the amplifier end of the shield to the chassis through a small capacitor to have a low impedance path for high frequencies.