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AKSA's Lender Preamp with 40Vpp Output
AKSA's Lender Preamp with 40Vpp Output
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Old 4th June 2018, 01:31 PM   #621
xrk971 is online now xrk971  United States
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AKSA's Lender Preamp with 40Vpp Output
Thanks for the reminder Twocents. I just have run a simulation then if I have you those numbers. The brain can’t remember all the sims it has performed.

Yes for Bi-amping with PLLXO, this will have plenty of oomph to drive.

If you only gave Hugh these 4 transistors, he can make anything: 2N5401, KSC1845, 2SA1837, any big N channel MOSFET.

But don’t mess with the KSC1845! It’s in every amp!
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Old 4th June 2018, 02:56 PM   #622
twocents is offline twocents  South Africa
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AKSA's Lender Preamp with 40Vpp Output
Ok X, so those values for R14 and R15 will work well then for the secondary output.

Thank you Hugh and X - the KSC1845 will stay on the bom then!
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Old 4th June 2018, 04:07 PM   #623
xrk971 is online now xrk971  United States
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AKSA's Lender Preamp with 40Vpp Output
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Originally Posted by twocents View Post
Ok X, so those values for R14 and R15 will work well then for the secondary output.

Thank you Hugh and X - the KSC1845 will stay on the bom then!
I should ask you what your PLLXO input impedance is? Itís parts of the design so you can spec it. I would suggest no lower than 4k7.
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Old 4th June 2018, 04:23 PM   #624
twocents is offline twocents  South Africa
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AKSA's Lender Preamp with 40Vpp Output
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Originally Posted by xrk971 View Post
I should ask you what your PLLXO input impedance is? Itís parts of the design so you can spec it. I would suggest no lower than 4k7.
I am nowhere near that part yet X, but according to the PLLXO calculator it will probably be between 5k and 10k - so I should be ok.
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Old 16th June 2018, 11:57 PM   #625
vlv81 is offline vlv81  New Zealand
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Hi X, hi all

Just ordered the boards and curious to the value you used for R11 when using the AKSA Lender pre with the Aleph J you built? Reading the thread it appears altering R10 isn't the correct thing to do, but changing R11 to something around 2K would be suitable?
Secondly I see twocents has mentioned the option of two "pre outs". I was also considering this for bi-amp purposes. Here is the newbie question sorry: what would the procedure be if the input impedence to the second amplifier was different than that of the main amplifier? Reason for asking is that I am considering adding a sub with its own amp for reinforcemnt below 60Hz maybe 80Hz or so. Stereo only, not home theatre. I recently moved and the room is a different shape. It seems I have lost a small amount of low level.

Looking forward to building this. Just ordered the boards on the 14th and made other parts orders yesterday.

Thanks
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Old 19th June 2018, 08:41 PM   #626
jwjarch is offline jwjarch  United States
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Quote:
Originally Posted by vlv81 View Post
Hi X, hi all

Just ordered the boards and curious to the value you used for R11 when using the AKSA Lender pre with the Aleph J you built? Reading the thread it appears altering R10 isn't the correct thing to do, but changing R11 to something around 2K would be suitable?

Thanks
vlv81, I have a similar question regarding R10/R11. I currently have a 3.9k in for R10. Twocents posted about staying with 10k at R10 and using a 2k2 at R11 to reduce gain. Would this be the way to go if I'm using the 2SA1837's with R15 at 22 Ohms and R14 at 4.7 Ohms? I am using this with my ALPHA 20 at the moment. Could I also use this as an HPA without any modifications?
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Old 20th June 2018, 12:05 AM   #627
xrk971 is online now xrk971  United States
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AKSA's Lender Preamp with 40Vpp Output
Click the image to open in full size.

Changing R11 to 2k2 is a good way to reduce gain while keeping the amount of feedback low to preserve sound stage and spatiality.

For a HPA the recommended resistor settings are here and don’t forgot to reduce Vcc to 24v:
Click the image to open in full size.

Qnty 2 x 22R for R15 (11R) and 2.2R for R14 and use 2SA1837 (mounting on backside since pins reversed). It will work fine as HPA and preamp for Alpha 20 or Alpha B.B. with lower gain as described above.
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Last edited by xrk971; 20th June 2018 at 12:08 AM.
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Old 25th June 2018, 05:56 PM   #628
GASCo is offline GASCo  United States
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AKSA's Lender Preamp with 40Vpp Output
Considering to build this preamp to feed a Pass ACA, but potentially feed others in the future as well (F5 and MoFo for example), so I have a few questions. Sorry, they are basic questions:

1- R10, R15, R11: Wouldn't be easier to use trim pots instead of changing resistors? Why?

2- SMD vs TH Daughter Board: Any other differences other than physical?

3- The BOM AKSA-LENDER-X-MB_PL_04_01_2018 has a few lines defined as option. If you don't take that option, you just leave the space unpopulated? Any more details on what changes with that option? As example lines 15, 16, and 17. All of them are Caps that are marked option but are not shown anywhere else (as if there was a basic option and these would be the premium option)

4- Does the BOM contain the components for the on/off switch, filter and RCA selector as well?
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Old 25th June 2018, 07:43 PM   #629
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AKSA's Lender Preamp with 40Vpp Output
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Originally Posted by GASCo View Post
Considering to build this preamp to feed a Pass ACA, but potentially feed others in the future as well (F5 and MoFo for example), so I have a few questions. Sorry, they are basic questions:

1- R10, R15, R11: Wouldn't be easier to use trim pots instead of changing resistors? Why?

These are critical audio path resistors and need to be high quality fixed metal thin film or carbon thin film in order to reduce distortion and not introduce unwanted third order distortion.

2- SMD vs TH Daughter Board: Any other differences other than physical?

SMD boards can sometimes achieve slightly lower distortion, but really neglible. The through hole board is needed if you wante to make it a HPA since larger 2SA1837 can be used and external heatsink can be fitted.

3- The BOM AKSA-LENDER-X-MB_PL_04_01_2018 has a few lines defined as option. If you don't take that option, you just leave the space unpopulated? Any more details on what changes with that option? As example lines 15, 16, and 17. All of them are Caps that are marked option but are not shown anywhere else (as if there was a basic option and these would be the premium option)

The options are for large film caps. If your cap does not need all the room, thatís ok, just leave it unpopulated.

4- Does the BOM contain the components for the on/off switch, filter and RCA selector as well?
Yes, but the RCA jacks are rather expensive $10/set and you need 5. Also, interconnect 8pin ribbon cable/jack has wrong solder pad on BOM. It needs to be through hole version.
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Old 25th June 2018, 08:28 PM   #630
GASCo is offline GASCo  United States
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AKSA's Lender Preamp with 40Vpp Output
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Originally Posted by xrk971 View Post
The options are for large film caps. If your cap does not need all the room, thatís ok, just leave it unpopulated.
.
I'm sorry X, what do you mean by "if your cap does not need all the room"? As a beginner I understand this might be a dumb question, my apologies.
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