Go Back   Home > Forums > >

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Preamp Control - Volume, input, mute, remote
Preamp Control - Volume, input, mute, remote
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools
Old 17th September 2021, 11:12 PM   #291
johnhenryharris is offline johnhenryharris  United States
diyAudio Member
 
Join Date: Nov 2012
Location: San Diego, CA
Hi Roy,
Yes a long time away. With the digitally weighted design, the first design, I would suggest using the new resistor values 20k, 10k, 5k, 2.5k, 1.25K, 625, 312, 156 ohm. That way the input resistance doesn't drop below 300 ohms.

But if you are using the preamp gain section to drive the volume resistance network it won't be a problem. With 2 cuts on the board, or 4 for balanced, you can place the gain section between the input and the volume section.

I am not wed to the volume resistance first then the gain section. I like it in my system as having the gain section low impedance output drive 20 feet of interconnect cable from the preamp on the left side of the room to the mono block amps next to the speakers in the front of the room works well.

I can make the changes to the PCB to allow input first, then either preamp or volume resistance. I would use the Rev 3 main board design. even though the discrete one-shot is a bit kludgy to an engineer it works, where as the Version 5 with the discreet one-shot is marginal in timing and the display can flicker. Hence the new design that uses an EEPROM to control the volume LEDs which is elegant but requires a programmed EEPROM, which I can supply. Also the 7-segment LEDs in though-hole went End-of-Life so I created a dual foot print LED for SMD or through-hole.

Have you checked out the new design of a constant input resistance ladder design? It has all the changes except the jumper option for gain or volume first, and is more compact, a little bit.

I did build one preamp with Pass Aleph P gain boards after the volume section and it was magic. Gave it to a friend who is really enjoying it.

So give me a laundry list of changes to the first design and I will see about updating the board.

BTW their are header pins for the input and connectors, I will look them up and give you the part numbers. I know wiring and unwiring a lot of inputs is a real pain.
  Reply With Quote
Old 18th September 2021, 01:04 AM   #292
rpafenberg is offline rpafenberg  United States
diyAudio Member
 
Join Date: Feb 2004
Location: Washington DC
Preamp Control - Volume, input, mute, remote
John,

Thank you, I really appreciate your openness to design changes that enhance flexibility. I didn't know of a header that fit your inputs but would welcome that information. In fact, it should be in the BOM as at least an option. I can't think of any other changes for the analogue board and will order it when you provide the gerbils.

Yes I am aware of your new resistance network and plan to take advantage of it. I have ordered the boards (5 each) from JLCPCB and they are very inexpensive. I will be more than happy to replace the analogue board with a new more flexible version. I will give the old ones away for postage to people who don't need the flexibility. I should have them next week

I went ahead and started ordering parts for the analogue board and found them to be painfully expensive. Only issue I found was obtaining the 6.65K resistors (6.81K part list). best I could find was the Dale CMF556K6500FHEB. Do you have a better option?

I have been working on parting the other boards and am developing a issue list on the BOM, but I will save that for another post.

Thanks again for your willingness to add enhancements!

Regards,

Roy
  Reply With Quote
Old 18th September 2021, 10:12 PM   #293
johnhenryharris is offline johnhenryharris  United States
diyAudio Member
 
Join Date: Nov 2012
Location: San Diego, CA
For the 3 Pin header the part number is 292132-3 and the matching connector is 179228-3.

For the 6.81k resistor an alternate part is RN70D6811FB14, there is 9 in stock. Any value that is close is fine so long as all four are the same so you have channel matching. I prefer the Vishay/Dale RN series large body resistors, RN65 or RN70, they have a less distortion and sound pretty good, and not as expensive as the Caddocks.

So you are using the new design volume control and want the option to insert the preamp gain section between the input selection and the volume section. That is a minor change to the Analog board. I will see if I can find some time to work on it tonight, then post gerbers.

Last edited by johnhenryharris; 18th September 2021 at 10:16 PM.
  Reply With Quote
Old 19th September 2021, 12:39 AM   #294
johnhenryharris is offline johnhenryharris  United States
diyAudio Member
 
Join Date: Nov 2012
Location: San Diego, CA
And here are the updated gerbers for the Analog board. Calling it v1.1. The difference is a break in the traces from input to volume with large via pads to solder wires to go input, gain, volume, or jumpers to go input, volume, gain section.
Attached Files
File Type: zip Main board_A_LadderV1-1_gerber.zip (64.1 KB, 12 views)
  Reply With Quote
Old 19th September 2021, 02:29 PM   #295
rpafenberg is offline rpafenberg  United States
diyAudio Member
 
Join Date: Feb 2004
Location: Washington DC
Preamp Control - Volume, input, mute, remote
John,

Thanks for your prompt response with the part numbers for the input connectors and the board changes. I ordered 5 from JLCPCB this morning and should have them in about a week. The boards were only $18 but the shipping was $30. When I bought the whole set of 4 shipping was only $36 so its much better to order as many different boards as possible a one time. In any event, I will send you one when they arrive.

I grabbed the last 9 resistors that you suggested but with 3 boards I will need 12. I guess I will need to investigate the Caddocks.

I am going to need 3 of your eproms, let me know how much they are and Iíll paypal you.

I have been going through your BOM and attempting to order parts that I canít easily move from your earlier boards. A high priority for me is the relays. They are extremely difficult to move without damage. But with 3 boards that is 90 relays which even at the 100-level pricing that still runs $170 dollars.

I am having several part issues. On the Analogue Board you have a new relay driving transistor and have changed the design to only use 9 rather than 18 as before. The problem is its availability. The 2N3904BU is out of stock at Mouser and Digi-key and Octopart didnít show inventory at any of the other major distributors. Do you have a viable substitute?

On the power supply board, I will have no problem moving the parts over from the old main board. However, new buyers will have problems with the switch. It seems to be out of stock everywhere until at least November.

The Display Boardís BOM still has the part number for the obsolete LED display parts. You have indicated that the board will now take those or the newer surface mount versions but there is no part number for them. I donít think I will have a problem moving mine but that will not help new buyers.

I believe the remotes I have now should still work. Never did get the second version board you set to work but I am sure itís a surface mount chip issue which I will address when necessary.

Regards,

Roy
  Reply With Quote
Old 19th September 2021, 07:24 PM   #296
johnhenryharris is offline johnhenryharris  United States
diyAudio Member
 
Join Date: Nov 2012
Location: San Diego, CA
EEPROMs are $5 but with shipping in and out makes it around $10 each.

For the relays, I have a Metcal solder station and I have tips for most chips so I can heat all legs at once and the part drops out. If you wanted to send me the 3 boards I can desolder the relays and ship all back, with the EEPROMs, for the cost of shipping.\

On the 2N3904, it is just an NPN transistor being used as an analog switch so any small signal transistor should work. The BC549 works well and it cheap and in stock.

For the AC selection switch, it is nice to have but you can just use jumpers in place of the switch until it is available. I had to do that on some power supply boards for the preamp.

The Through Hole LED is available in Green and Red and maybe some other colors but
blue seems to be the most wanted so you can use ACSC56-41QBWA/D-F01.
On desoldering the through-hole LEDs be careful the pins are connected to a circuit board inside the LED housing and can be pulled out too easily. If you can do all pins at once and quickly it isn't a problem. If you send relay board to unsolder you can include the display board and I can remove the LEDs also, not hard for me with the Metcal.

I will update the BOM and repost. If you have any thing else for the BOM let me know.

Thanks,
John
  Reply With Quote
Old 19th September 2021, 08:55 PM   #297
johnhenryharris is offline johnhenryharris  United States
diyAudio Member
 
Join Date: Nov 2012
Location: San Diego, CA
Looking for the resistor values I see Mouser has 71-CCF60-6.81K-E3 in stock, you would be stepping from a Mil spec part to a Industrial spec part. They are less expensive and you can give them a listen and let us know how they compare sonically, probably too close to hear any difference.
  Reply With Quote
Old 20th September 2021, 04:58 PM   #298
rpafenberg is offline rpafenberg  United States
diyAudio Member
 
Join Date: Feb 2004
Location: Washington DC
Preamp Control - Volume, input, mute, remote
John,

I will take you up on your fine offer to remove the components from my boards. To bring the weight down I will remove the power supply sections from the main boards before I ship them.

Your choice of a CCF60 for a substitute is interesting. I have heard it said that there was very little difference in "Dell" resistors between military and industrial besides the specs. For grins I worked out a comparison chart on values and pricing. The BOD is made up of 10 RN65 and 5 RN70 resistors. This is how values compare with the available CCF60 resistors.

I assume the determination of where to use 65 vs 70 resisters was made based on closeness to nominal value. If the difference in sound quality is minimal and we would like to match the nominal value as closely as possible and obtain the best pricing then purchasing mostly CCF60 with the exception of the 3 farther out of tolerance values makes the most sense.

Regards,

Roy
Attached Files
File Type: pdf Balanced Resisters.pdf (99.3 KB, 17 views)
  Reply With Quote
Old 20th September 2021, 05:21 PM   #299
johnhenryharris is offline johnhenryharris  United States
diyAudio Member
 
Join Date: Nov 2012
Location: San Diego, CA
BTW, I placed an order for a small quantity of EEPROMs last night so they should be here in a few days.
  Reply With Quote
Old 20th September 2021, 08:31 PM   #300
rpafenberg is offline rpafenberg  United States
diyAudio Member
 
Join Date: Feb 2004
Location: Washington DC
Preamp Control - Volume, input, mute, remote
John,

I received 5 sets of your V3.0 boards today and was dry fitting the stacking of the analogue and digital boards and was puzzled by the placement of the digital board over the connectors. Looking at the tracing and the ample space on the board I see no reason why the two center holes couldnít be moved back on the analogue board to have the digital board sit in the ďfrontĒ of the stack and not impede access to the input connections. The same is true of the power connectors. It would also make the digital-to-display connectors shorter. I assume that the 1 by 12 pin J1 to J5 connection must be the showstopper in that regard. It must not have been easy to move J1 to the front of the board. It looks like it might be possible by reversing the connections but that might require a change in board size. Am I correct?

Regards,

Roy
  Reply With Quote

Reply


Preamp Control - Volume, input, mute, remoteHide this!Advertise here!
Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Building a complete Preamp with an Arduino, remote, volume and input control maxw Analog Line Level 183 4th October 2021 09:23 AM
Quad II passive preamp - remote volume control tzurby Tubes / Valves 5 19th October 2017 01:36 PM
Remote volume control knob for old preamp elsewhere Parts 12 23rd February 2016 11:02 PM
Analog Matrix-mixer with MIDI remote Audio Volume Control/mute Mix44 Analog Line Level 6 22nd November 2015 02:49 PM
Remote 23-steps volume control (need to add TVC or resistors), optional 6 pairs input DIY Hifi Supply DIY HiFi Supply 3 31st March 2015 02:59 PM


New To Site? Need Help?

All times are GMT. The time now is 08:18 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 13.64%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Copyright ©1999-2021 diyAudio
Wiki