Batty can you try the head amp on a battery? I have built both without success. The power supplies seem ok, but no luck with two builds of the amplifier.
Salas what is the 220k resistor doing?
Salas what is the 220k resistor doing?
Gives local reference to gnd. Can work without, it may give the odd ''pop'' from cout, but no big deal. To check the build properly, provide a sub mV sine wave from a divider, watch on a scope for output. See that you got no DC on input, check all your component connections against the schematic.
Thanks Salas you really are a gem.
I will have to borrow my scope back, it has been with someone for a long time.
I will have to borrow my scope back, it has been with someone for a long time.
As I mentioned before look in the simplistic Riaa thread for smpkje's 63dB build, he had successfully used your pre-pre and the HighMC main Riaa pre directly from the pdf instructions and input sensitivity selection DIP switching. He had shown some layout details, maybe comparing it can help your debugging.
Attachments
Thanks for putting this circuit out there for us. I have the Denon 103R; it has .29mV output. My MC pre requires more gain.
Vince
Vince
Thanks Batty & Salas, great that more people build this, it's really sounds good 🙂, worth all the effort.
here are my updates, last time I still have hum and transparency problem on the mid-high side. Also I like to try bypassing the 1000uF caps.
On transparency I know it must be very good referring to my TDA1541 sk170 DAC I/V (ECdesign), so problem must lies elsewhere
bypassing all 7809 and BC550's 1000uF caps with 0.1uF wima I got better mid & silky highs
Changing azur540 Cout from prev, mod 100uF black cerafine to 10uF silmic2 is surprising , silmic gives better transparency and bass...silmic will stay until I can find small sized 10uF MKP 🙂
Hum largely gone after tidying up litz wire leads, too bad I still use bad-hot transformer.. I'm happy now & starting enjoying records maybe for 6 months 🙂 then build the complete RIAA, Thanks Salas !
regards
TeguhPS
here are my updates, last time I still have hum and transparency problem on the mid-high side. Also I like to try bypassing the 1000uF caps.
On transparency I know it must be very good referring to my TDA1541 sk170 DAC I/V (ECdesign), so problem must lies elsewhere
bypassing all 7809 and BC550's 1000uF caps with 0.1uF wima I got better mid & silky highs
Changing azur540 Cout from prev, mod 100uF black cerafine to 10uF silmic2 is surprising , silmic gives better transparency and bass...silmic will stay until I can find small sized 10uF MKP 🙂
Hum largely gone after tidying up litz wire leads, too bad I still use bad-hot transformer.. I'm happy now & starting enjoying records maybe for 6 months 🙂 then build the complete RIAA, Thanks Salas !
regards
TeguhPS
Attachments
Nice progress. Maybe you can find 5mm pitch 63V Wima 1uF and 0.1uF MKP1837 Vishay to step bypass your 10uF Silmic since space is a problem.
Thanks for your tip, I'll look for small 1uF wima MKP and 0.1uF 1837 to replace 0.01uF orange drop, the silmic's are still on long leads, I plan to try another electrolytic caps ha ha, but no need..
regards
TeguhPS
regards
TeguhPS
😀😀 Today I have some success. I missed a couple of links to connect the earth. It is sounding sweet but a little light on the bass compared with the battery version.
Maybe it needs some time to burn in. The components are basic. What are suggested types for the caps to make it really sing.
I will start on valve itch soon.
By the way I have nearly 0.5v difference from the power supply between the two channels as measured from the transistor, voltage in is the same for both. Is this due to different gain from the transistors?
Thanks for the circuit salas.
Maybe it needs some time to burn in. The components are basic. What are suggested types for the caps to make it really sing.
I will start on valve itch soon.
By the way I have nearly 0.5v difference from the power supply between the two channels as measured from the transistor, voltage in is the same for both. Is this due to different gain from the transistors?
Thanks for the circuit salas.
Its due to slightly different combined IDSS. Small DC difference, no worries. The total Yfs times the load counts. I.e. having balance between channels for gain. The 1000uF electrolytics can play a role to bassy tone or else, Nichicon Muse tend to gravitate there. The value and type of your load resistor can affect tonality also, cheapest test. For the 0.47uF I suggest Teflon, NOS USSR are attractive in price. See if you need more gain also if it never will fill up. Increasing the load resistor in conservative steps will be upping the gain.
Hi Salas,
As an update I haven't yet upgraded the caps, but the sound has improved. The frequency range has extended with the bass filling out.
Interestingly I have a incorporated switchable cart loading, i selected the values too close as there isn't much difference in sound. I used 90,100,120,220 and 560 ohm.My cart has recommended loading 120R.
As an update I haven't yet upgraded the caps, but the sound has improved. The frequency range has extended with the bass filling out.
Interestingly I have a incorporated switchable cart loading, i selected the values too close as there isn't much difference in sound. I used 90,100,120,220 and 560 ohm.My cart has recommended loading 120R.
Dear Salas,
Unfortunately i can't found 2SK170BL, but i found only 25K170GR with Idss about 5mA .
Can it works to the Low MC prep-pre circuit with the 25K170GR or it needs conversion the element? e.t.c resistors, caps....
THANKS
STERGIOS
Unfortunately i can't found 2SK170BL, but i found only 25K170GR with Idss about 5mA .
Can it works to the Low MC prep-pre circuit with the 25K170GR or it needs conversion the element? e.t.c resistors, caps....
THANKS
STERGIOS
Use a 500R trimmer instead of R1, match 4 K170GR, use 2 per channel as in the schematic, turn the trimmer until 1/2V+ on the drains, then substitute a good quality resistor for the value you will find on the trimmer.
I made the MC step-up also and it wasn't just a voltage step-up 🙂
I used 2 LT1086CT in serie in their best config.
FT3 teflon is very honest, pure & great for instruments but I needed a more juicy sound so I used Clarity Cap DACT with MKP1837.
My cart is an Ortofon Rondo red.
Thanks again Salas !
I used 2 LT1086CT in serie in their best config.
FT3 teflon is very honest, pure & great for instruments but I needed a more juicy sound so I used Clarity Cap DACT with MKP1837.
My cart is an Ortofon Rondo red.
Thanks again Salas !
Attachments
ANOTHER approach at the mc- pre. This time with a BiB shunt, the power an open sound it gave made me go back to the FT-3 teflon cap. I had some issues to tackle hum, put the mc-stages in metal boxes and installed some RC filters in front of the BiB.
Maybe it's premature when I say that this is my final setup of Salas his MC stage,
because you never know, but it's good !
Maybe it's premature when I say that this is my final setup of Salas his MC stage,
because you never know, but it's good !
Attachments
