Thanks AB, how did you arrive at 100ohms for R20?
Also you say you short R15, can you clarify?
Craigtone a Lundahl will get me 1:8, this shouldn't stress the Pearl too much should it?
DV 23R Karat with 0.2mv output sounds grand with the pearl2, ~64dB gain, with a Threshold NS10. Has about the same gain as the NS10's MM + M1 module. The Pearl2 is sweeter and more detailed on the top end and kills it on low end bass. Any Pass preamp design since 1977 should get the job done. 🙂
The LL9206/LL9226 can be set for 1:5, 1:10 or 1:20. I'd use the 1:5 setting.
Do you have any noise issues with the higher gain setting? I ran into noise problems when I tried this. What is the rest of your system? I'm running on 105dB Khorns, so they are a microscope for noise and hum.
Craigtone,
I was having noise issues with stock gain settings and raised values for input fets source resistors. After restoring it back to BOM values, revisioning my wiring and raising the gain to maximum (circa 65db) I have a slight hum, barely noticeble and less intrusive than before at lower gain settings. It's slightly more expressed on one channel than the other, which gives me hope that it can be reduced to non audible levels if screening and wiring is more carefuly revisioned.
I was having noise issues with stock gain settings and raised values for input fets source resistors. After restoring it back to BOM values, revisioning my wiring and raising the gain to maximum (circa 65db) I have a slight hum, barely noticeble and less intrusive than before at lower gain settings. It's slightly more expressed on one channel than the other, which gives me hope that it can be reduced to non audible levels if screening and wiring is more carefuly revisioned.
Just be mindful that the gain of first stage of the Pearl 2 is 40dB. This stage begins to overload ~40 to 50mV before the passive RIAA correction. Thus, if you use a 300uV cart and 1:10 step up transformer you're going to run into headroom problems above 10kHz. Cartridge velocity physics.
With an MM cartridge you can compensate somewhat by lowering the value of the input resistor from 47k, but you'll have to completely redesign the passive network.
With an MM cartridge you can compensate somewhat by lowering the value of the input resistor from 47k, but you'll have to completely redesign the passive network.
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Just wanted to post some followup to my gain adjustment for the first stage of the Pearl 2. I was experiencing overload with the stock configuration on some LPs using a 5mV MM cartridge. Increasing the source resistors from 10R to 22R reduced the jFet bias by about 20% and this has solved my overload problems. I'm not hearing distortion on any of my LPs now.
The Mezmerize is the culprit, when I used my B-1 with First Watt clones I had a similar problem. (except BA3 Complementary, which has plenty of gain) Most of the First Watt amps are 15 dB gain or so. Using the BA3 FE for preamp solved the low gain problems. Gain gives a lot more fullness in my system, even with extremely High efficiency speakers.
Try a BA3 FE as pre. It is an outstanding preamp to have around in any event, and reasonably inexpensive to build.
Russellc
100 ohm is just a standard value. I have not done any testing with different resistance values. Though I read somewere the other day that 150 ohms should be the right value for DL-103. Shorting R15 (in my case 220k) gives just the right gain when I change from MM to MC. I have R14 untouched at 1k and then in MC-mode R-16 100k. In MM-mode R-15 + R16 320k.
And Craightone, I have no noice issues. My system have speakers in +100dB sensitivity range, and I'm running the Pearl to a preamp with one tube (6N6P) and then to activ filtering with no gain. Finaly Tre poweramps per channel. One ordinary transistor 80W (-220Hz) one Pass 20W from the seventies (220-720Hz) and one tube (EL84) for the rest. / AB
And Craightone, I have no noice issues. My system have speakers in +100dB sensitivity range, and I'm running the Pearl to a preamp with one tube (6N6P) and then to activ filtering with no gain. Finaly Tre poweramps per channel. One ordinary transistor 80W (-220Hz) one Pass 20W from the seventies (220-720Hz) and one tube (EL84) for the rest. / AB
Thanks for the info ... I will try this setup and see if that helps with my 103-R!
Russellc I may have to check out the BA3 FE again...
And I thought I was nearly done building.
Ok, a quick look suggests I could just build this as an additional stage with fixed gain after the Pearl 2 boosting the output the required amount, then feed the DCB1.
Sound good?
And I thought I was nearly done building.
Ok, a quick look suggests I could just build this as an additional stage with fixed gain after the Pearl 2 boosting the output the required amount, then feed the DCB1.
Sound good?
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Budweiser did that driving F4 and used B1, ( but he wasn't using pearl) so I don't see why that wouldn't work too.
I would just put the volume pot and selector switch on BA3 and call it good, but seeing how you already have it and all,
Additional circuitry not withstanding....
Done building...that's a good one! lol
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Ha! 😀 🙁 😛 😡 😉 😱 That's exactly what I thought when I completed my a40 amp nearly 13 years ago 🙁 My equipment rack is running out of space and amps are now just laying around on the floor in my home office waiting to reach out and bite someone on the toe as they walk by 😛
My wife would call it an illness... Look at it this way, there are plenty of other activities that have far worse outcomes in life. And, at the end, you have something tangible and lasting to show for your time and money. I was never so proud of my wife as the day we were at a party/reception and she said to me "That music sounds TERRIBLE - it's all distorted!" Whether she wanted to admit it or not, she has been spoiled by nice audio equipment at home.
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Yes, I built my first project, a Paia spring reverb about 15 or so years ago and haven't stopped building valve guitar amps/bass amps/microphones/mic preamps/compressors since...
We have an overstuffed home studio/music room
DIY hifi is newer to me although my Pearl was built a couple of years ago.
It's catching 😄
LOL ... if I had a dime everytime I said that, I'd build another system! 😛
I thought I was done when I did the Pearl 2, Mez and Aleph J ... then I fixed a tube pre for someone and realized how much I missed tubes when I plugged it in to test it <sigh>
Same on the rack, going to build a custom double-width rack with PassDIY on one side and tube DIY on the other, sources on top shelf. Some of the other gear I have built/rebuilt has ended making complete systems in other rooms of the house. Always nice to have spare gear if & when something takes a dump on you.
I have also sold gear I no longer use like my RH84SE Rev2. If you build it with a pretty chassis, good parts and clean wiring, you can usually turn a little bit of a profit to put towards the "Next Best Thing". 😀
Some data. The charts are at 1kHz. The first three are inputs of 100uV, 1mV and 10mV. The fourth is THD+N% for the first stage alone, with the filter disconnected. The last chart is THD+N% for the second stage with the filter disconnected and the generator connected to the gate resistor.
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If the typical MM cartridge has 1mV/(cm/S) this is what you're looking at in terms of possible signals which the front end has to deal with:
An externally hosted image should be here but it was not working when we last tested it.
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Jack, these are interesting data points that you are sharing with us. Since I'm relatively new to the technical side of turn tables, I'm wishing I had a greater level of understanding so I could gain more knowledge from what you've shared with us.
In the set of three FFT graphs you posted above, it looks like things are pretty clean a 0.1mV and 1mV, but falling apart at the 10mV level. This seems to leave a large space between 1mV and 10mV where some observations might shed some light on what happens with a 3mV, 4mV, or 5mV output cartridge and the Pearl II.
I confess to a total lack of context for the "What signals are on records?" graph.
In the set of three FFT graphs you posted above, it looks like things are pretty clean a 0.1mV and 1mV, but falling apart at the 10mV level. This seems to leave a large space between 1mV and 10mV where some observations might shed some light on what happens with a 3mV, 4mV, or 5mV output cartridge and the Pearl II.
I confess to a total lack of context for the "What signals are on records?" graph.