I'll certainly take one board Wyn.
The combined mono / balance capability, I'll implement that with with some point to point wiring off board.
I realise it's a real edge case, but thanks for showing how it can be done.
The combined mono / balance capability, I'll implement that with with some point to point wiring off board.
I realise it's a real edge case, but thanks for showing how it can be done.
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@wynplamer2 - can I check:
I want MM and MC inputs, would like the warp filter, but don't need headphone amp and the other parts.
I would need 2 x RIAA boards and the line filter board from yourself. Then from mouser, I would need the parts for:
2 x RIAA common parts
RIAA MC parts (choose either single or parallel)
RIAA MM parts (choose either single or parallel)
line buffer parts
warp parts
SMPS filter
SMPS from mouser
along with various switches and the other parts to complete the build?
Sorry, its probably a lazy question but I'm most of the way through the first AK thread, and it'll take a while yet to work through it all!
I want MM and MC inputs, would like the warp filter, but don't need headphone amp and the other parts.
I would need 2 x RIAA boards and the line filter board from yourself. Then from mouser, I would need the parts for:
2 x RIAA common parts
RIAA MC parts (choose either single or parallel)
RIAA MM parts (choose either single or parallel)
line buffer parts
warp parts
SMPS filter
SMPS from mouser
along with various switches and the other parts to complete the build?
Sorry, its probably a lazy question but I'm most of the way through the first AK thread, and it'll take a while yet to work through it all!
The various components of the build specify WIMA 0.1uf PP capacitors, some rated 100VDC, some 63VDC.
100v SMPS-filter-parts, line-buffer-parts, phono stage kit
63v RIAA-MM-parallel-specific-parts
ATM Mouser have the 100v versions on a relatively long lead time. Will the 63V versions substitute OK? I had a look and apart from the voltage rating there didn't appear to be any difference
100v SMPS-filter-parts, line-buffer-parts, phono stage kit
63v RIAA-MM-parallel-specific-parts
ATM Mouser have the 100v versions on a relatively long lead time. Will the 63V versions substitute OK? I had a look and apart from the voltage rating there didn't appear to be any difference
In reality any voltage in excess of the rail-rail supply voltage (e.g. 35v) would be fine.
The component choices were based on the cheapest available that met the conditions for technology (e.g. polypropylene film), footprint, minimum voltage, and value. Sometimes a higher rated voltage type would be cheaper than the lower rated type. and would be chosen.
So, yes, substituting a lower voltage unit of comparable characteristics in the other ways is entirely acceptable. Also, I'm largely manufacturer agnostic for PP caps, and I view Wima, Kemet and Panasonic, for example, as being equivalent as long as the other criteria are met.
The component choices were based on the cheapest available that met the conditions for technology (e.g. polypropylene film), footprint, minimum voltage, and value. Sometimes a higher rated voltage type would be cheaper than the lower rated type. and would be chosen.
So, yes, substituting a lower voltage unit of comparable characteristics in the other ways is entirely acceptable. Also, I'm largely manufacturer agnostic for PP caps, and I view Wima, Kemet and Panasonic, for example, as being equivalent as long as the other criteria are met.
I just finished my second version of this phono section. the first used v1.0 boards and was built as MM The second is v@.0 for MC, with following options:
- LT1115 in parallel
- Warp filter
- no output buffer
It sounds excellent with the warp filter in and set for 0dB gain. but when I switch to 10dB gain, I get a lot of distortion. It seems to be much more noticeable on loud passages so I wonder if it's an overload to the second opamp in the warp filter. I could live with it in the0dB setup but would be handy with more gain. I'm testing with Denon DL103 (.25mV output) and no C1/C2. Any suggestions will be appreciated
- LT1115 in parallel
- Warp filter
- no output buffer
It sounds excellent with the warp filter in and set for 0dB gain. but when I switch to 10dB gain, I get a lot of distortion. It seems to be much more noticeable on loud passages so I wonder if it's an overload to the second opamp in the warp filter. I could live with it in the0dB setup but would be handy with more gain. I'm testing with Denon DL103 (.25mV output) and no C1/C2. Any suggestions will be appreciated
I use mine with the warp filter gain set to 10dB and a 230uv @1kHz 5cm/sec cartridge and there is no noticeable or measurable distortion.
Also, a number of people are using the v2.0 with no problems reported.
This suggests something is amiss.
Are you up for a debug?
If so, we should set up a time and do the work over PM, or some other convenient process.
However, with a 250uv cartridge and the extra 10dB gain the output should be nominally c. 72dB higher- or 1v RMS. This is many dB below clipping. Even with 12dB extra on the loudest passages it should still have c. 7dB of margin before clipping and be generating 4vRMS. What are you driving with it? Many preamps will be experiencing significant overload problems with a 4v RMS input.
Also, a number of people are using the v2.0 with no problems reported.
This suggests something is amiss.
Are you up for a debug?
If so, we should set up a time and do the work over PM, or some other convenient process.
However, with a 250uv cartridge and the extra 10dB gain the output should be nominally c. 72dB higher- or 1v RMS. This is many dB below clipping. Even with 12dB extra on the loudest passages it should still have c. 7dB of margin before clipping and be generating 4vRMS. What are you driving with it? Many preamps will be experiencing significant overload problems with a 4v RMS input.
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I definitely agree that something is amiss.
I wondered about overdriving the preamp. Currently I'm using a DIY preamp based on boards from AMB Labs. With the phono section set on 0dB, I need to set the preamp to -4dB to get reasonable sound. (i.e. almost the max volume setting). For point of reference, the 1.0 version of your phono section is plenty loud at -30dB with 1:10 SUT and the same cartridge.
I'd love to arrange a debug session but am fairly tied up until Sunday. I have a decent set of test gear so perhaps there's some things I can look at in the interim?
I wondered about overdriving the preamp. Currently I'm using a DIY preamp based on boards from AMB Labs. With the phono section set on 0dB, I need to set the preamp to -4dB to get reasonable sound. (i.e. almost the max volume setting). For point of reference, the 1.0 version of your phono section is plenty loud at -30dB with 1:10 SUT and the same cartridge.
I'd love to arrange a debug session but am fairly tied up until Sunday. I have a decent set of test gear so perhaps there's some things I can look at in the interim?
The easiest things to do are to check the DC output voltages and the AC gains at the various stages- for example at the output of the phono stage and at the output of the warp filter stage.
Also, the voltages across the 10 ohm decoupling resistors in series with the power supplies and the absolute value of the supply rails (+/-15v).
To test the gain I recommend using a generator and loading the inputs enough to pull the input voltage down to a reasonable value. i would also turn off the warp function itself as this could confuse the AC measurements.
For example if the generator has a 50 ohm source impedance load a single input with 1ohms across and use the generator to provide 100mv p-p at 1kHz.
Short both inputs together- signal to signal- and remove the load R from the second one, or keep it if it's 100 ohm or greater. If the generator output has a non 50 ohm impedance the input signal should be scaled proportionally.
This will provide c. 2mv peak-peak at the input and the outputs from the phono stage will be about 2.5v p-p, and from the warp stage 2.5v p-p in the 0dB gain mode and c. 6.6v in the 10db gain mode. The outputs should be near zero offset in all cases, and this can be checked with the 1ohm in place and no generator applied as the generator tends to introduce its own offsets.
Generally this is enough to expose the problems.
The few problems with the warp stage found so far consist of improperly soldered opamps or incorrect wiring/components and have been easy to find.
Also, the voltages across the 10 ohm decoupling resistors in series with the power supplies and the absolute value of the supply rails (+/-15v).
To test the gain I recommend using a generator and loading the inputs enough to pull the input voltage down to a reasonable value. i would also turn off the warp function itself as this could confuse the AC measurements.
For example if the generator has a 50 ohm source impedance load a single input with 1ohms across and use the generator to provide 100mv p-p at 1kHz.
Short both inputs together- signal to signal- and remove the load R from the second one, or keep it if it's 100 ohm or greater. If the generator output has a non 50 ohm impedance the input signal should be scaled proportionally.
This will provide c. 2mv peak-peak at the input and the outputs from the phono stage will be about 2.5v p-p, and from the warp stage 2.5v p-p in the 0dB gain mode and c. 6.6v in the 10db gain mode. The outputs should be near zero offset in all cases, and this can be checked with the 1ohm in place and no generator applied as the generator tends to introduce its own offsets.
Generally this is enough to expose the problems.
The few problems with the warp stage found so far consist of improperly soldered opamps or incorrect wiring/components and have been easy to find.
By the way, the line stage on the version 2.0 is exceptional as far as distortion. noise, load drive capability etc. is concerned. Now that a balance/mono capability and output relay protection/turn on delay/mute and a superb headphone amp have been added it's starting to approximate a real preamp, albeit without remote.
Well, I might have to add the components to the output stage and make this into a full-blown preamp...
OK, It was an easy problem to solve. The decoupling resistors for the power supply to the warp filter opamps were missing. I'd run out when building and forgot to install these after I received the parts.
I have plenty of gain without needing the extra 10dB from the warp filter. The sound is excellent. I think I like it slightly better than the v1.0 with SUT. It's extremely quiet.
I have plenty of gain without needing the extra 10dB from the warp filter. The sound is excellent. I think I like it slightly better than the v1.0 with SUT. It's extremely quiet.
I'd be interested in an output relay board that delays the output turn on by c. 2s if they become available
best
t
best
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The boards exist and are verified. A single resistor can be changed to increase the turn on delay. The relays control four signal channels. so it can support record and line stereo outs if you wish.
However, only three test boards were fabricated by OSHpark in the US and all have been assigned. No other requests have been made, which is why so few were made, but I can arrange to make the Gerber files available if you want to go that way, or if you have some other suggestion it will be considered.
However, only three test boards were fabricated by OSHpark in the US and all have been assigned. No other requests have been made, which is why so few were made, but I can arrange to make the Gerber files available if you want to go that way, or if you have some other suggestion it will be considered.
There is a v3.0 version of the board available. It includes all of the previously added functions- MC or MM phono, balance, mono, "elliptic" warp filter, additional switchable 10dB gain, line buffer, line output amp, output turn on delay/supply detect/headphone switch relay section.
Same cost as prior v2.0 board. Identical specs and design philosophy.
Same cost as prior v2.0 board. Identical specs and design philosophy.
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