Here It Is: The All Singing All Dancing HTMCPS
- Thread starter HypnoToad
- Start date
Or just take the supply from one of the RJM X-Regs.
MartinG
Active Member
Question about resistor calculation
I'm getting ready to put in an order for parts. I want to get the proper resistors to run the HTMCPS with my DL103R or my buddy's DL103. The specs for the 103R list output impedance as 14 Ohms and the output as .25mv. That gets me 14 Ohms and 420 Ohms in the calculator. That's fine but for the DL103 the specs list output impedance (40 Ohms) and load impedance (100 Ohms). Should I use 40 or 100 in the calculator? I'm thinking 40 but I want to be sure.
I'm getting ready to put in an order for parts. I want to get the proper resistors to run the HTMCPS with my DL103R or my buddy's DL103. The specs for the 103R list output impedance as 14 Ohms and the output as .25mv. That gets me 14 Ohms and 420 Ohms in the calculator. That's fine but for the DL103 the specs list output impedance (40 Ohms) and load impedance (100 Ohms). Should I use 40 or 100 in the calculator? I'm thinking 40 but I want to be sure.
You're correct, you want to use 40.
Thanks to Sachin (Sachu888) for getting me more PCB's made for the HTMCPS. They will be on there way tomorrow via India Speed Post.
I have included at his request an optional terminal block for the power supply/battery inputs and there have a been a couple of component value adjustments.
There is a new BOM to reflect these.
PLEASE NOTE: There is no buying or selling allowed in these threads so don't ask to purchase these boards.
I have included at his request an optional terminal block for the power supply/battery inputs and there have a been a couple of component value adjustments.
There is a new BOM to reflect these.
PLEASE NOTE: There is no buying or selling allowed in these threads so don't ask to purchase these boards.
Can I get some troubleshooting advice?
I finally got around to building my HTMCPS, and attempted a smoke test this morning with an AT33PTG II. I only got sound out of one channel. Inspection of that channel revealed that one leg of R1 wasn't firmly seated in the terminal sockets. But when I addressed that, I still got sound out of only one channel.
When I disconnected my batteries, I noticed one of them running VERY hot.
I made sure my turntable interconnects were fine (both channels played through an MM cart/pre)
I tested the AT33PTG with the MC side of my CA640p, and only one channel came through. Thinking I may have fried the cart, I checked the coils with my DMM and I get continuity at the pins. I didn't check for a resistance number though (should I? Afraid to fry some coils!). Didn't check my headshell leads, but I will do so when I get home. Would a loose R1 fry a cart?
My solder connections on the pcb look ok.
Is it possible that I fried my opamp? I have some extra OP Amps that I could sub to see if that fixes things.
Any thoughts would be welcome!
I finally got around to building my HTMCPS, and attempted a smoke test this morning with an AT33PTG II. I only got sound out of one channel. Inspection of that channel revealed that one leg of R1 wasn't firmly seated in the terminal sockets. But when I addressed that, I still got sound out of only one channel.
When I disconnected my batteries, I noticed one of them running VERY hot.
I made sure my turntable interconnects were fine (both channels played through an MM cart/pre)
I tested the AT33PTG with the MC side of my CA640p, and only one channel came through. Thinking I may have fried the cart, I checked the coils with my DMM and I get continuity at the pins. I didn't check for a resistance number though (should I? Afraid to fry some coils!). Didn't check my headshell leads, but I will do so when I get home. Would a loose R1 fry a cart?
My solder connections on the pcb look ok.
Is it possible that I fried my opamp? I have some extra OP Amps that I could sub to see if that fixes things.
Any thoughts would be welcome!
Kappaholic
Active Member
Thanks to Sachin (Sachu888) for getting me more PCB's made for the HTMCPS. They will be on there way tomorrow via India Speed Post.
I have included at his request an optional terminal block for the power supply/battery inputs and there have a been a couple of component value adjustments.
There is a new BOM to reflect these.
PLEASE NOTE: There is no buying or selling allowed in these threads so don't ask to purchase these boards.
Thanks for the update, I see that R3,4,11 &12 have been updated from 390 to 470 ohm registers, from your prior recommendations.
Would this change impact the calculations for the input/output resistors for the cartridge?
Thanks again for the update.
Kappaholic
Active Member
Fried opamps make no sound and usually fries both channels, this can happen by putting them backwards in a socket. I've fried a pair myself.
Recheck for the polarity of the audio wires and make sure there is no short.
Not worth worrying about, I always thought it had a little too much gain in the second stage, the resistor calculator is correct though and nothing else needs to be changed.
GreatTone
Super Member
I'm just about to order my parts ... would you recommend that I make this change as well? thx
Good advice, also make sure the batteries are wired correctly, also make sure your you don't have any dry joints, they tend to be dull gray in color not shiny.
Failing that take a pic of both sides and post it on here.
Never check the resistance of a moving coil cart with a DMM as it can burn them out.
I would also check the DC offset on all preamps before connecting them just to make sure. On the HTMCPS it should be zero at the outputs and inputs.
Last edited:
If you have the old PCB and earlier BOM use 200k resistors instead of the 75k, 2.2uf caps instead of the 1.5ufs this gives improved bass extension and 470ohm resistors instead of the 390ohms which gives a "little" less gain in the second stage.
Kappaholic
Active Member
Thanks HypnoToad!
Thanks for the suggestions Kappa and HypnoToad.
The lost channel was due to a bad headshell lead, thankfully! Whew.
However, checking DC offset I saw 0.4mV on one channel and -0.4mV on the other, even when swapping out opamps to two different pieces. Outputs showed zero DC. Any guidance there?
And -- how the heck do you avoid mangling the legs when pulling out opamps? Yes, I'm a noob diy'er.
The lost channel was due to a bad headshell lead, thankfully! Whew.
However, checking DC offset I saw 0.4mV on one channel and -0.4mV on the other, even when swapping out opamps to two different pieces. Outputs showed zero DC. Any guidance there?
And -- how the heck do you avoid mangling the legs when pulling out opamps? Yes, I'm a noob diy'er.
Thanks for the suggestions Kappa and HypnoToad.
The lost channel was due to a bad headshell lead, thankfully! Whew.
However, checking DC offset I saw 0.4mV on one channel and -0.4mV on the other, even when swapping out opamps to two different pieces. Outputs showed zero DC. Any guidance there?
And -- how the heck do you avoid mangling the legs when pulling out opamps? Yes, I'm a noob diy'er.
0.4mv is negligible, which is 0.0004 of a volt, no problems there at all.
Removing op amps is best done with a very fine blade screwdriver, like those ones for eye glasses. You can gently lever up one corner a little at a time or if you have enough room slide in the end and lift up one end at a time.
Did you work out why the battery was getting hot?
Let us know how it sounds after a bit of break in, those Wima's really open up after some use.
Kappaholic
Active Member
And -- how the heck do you avoid mangling the legs when pulling out opamps? Yes, I'm a noob diy'er.
Straight edge micro screw driver works well to pry the chip and lift up. When I am rolling opamps for testing, I use another bracket on top of the soldered bracket and this allows better grip and lift the whole bracket with ease. It takes less than 5 sec to replace both opamps.
kardus
New Member
Anyone try this with a DL-110 HOMC yet? Deciding between this and the CNC build. See what I mean here: http://www.audiokarma.org/forums/showthread.php?t=256704 (specifically http://www.audiokarma.org/forums/showpost.php?p=3101877&postcount=7). Originally only wanted to build one but maybe I need to build both to see for myself?!
Last edited: