Volume Device Plans

KR500 · « **Reply #20 on:** 2 Aug 2015, 03:51 pm »

I ordered the parts except the PCB which I'll do when I finish up another vendor order tonight
I already had plans to replace my VCD I slapped together with a 50K $2.40 PE potentiometer and RCA I/O's in a Hammond ABS with a better pot .
So ,.... this is a VCD for tinkering with the 3 Sure amp boards I have.
The only thing different is adding the 4 parts and PCB that Folsom suggested .
For $20 I'll take a gamble and see how those pan out.

Folsom · « **Reply #21 on:** 2 Aug 2015, 07:37 pm »

Let us know how you like it. I think you'll appreciate what it does for the little classD.

Speedskater · « **Reply #22 on:** 3 Aug 2015, 03:19 pm »

The reason that Jensen transformers are very expensive, is because it cost's a lot to build a good audio interconnect transformer.

Folsom · « **Reply #23 on:** 3 Aug 2015, 06:45 pm »

Quote from: Speedskater on 3 Aug 2015, 03:19 pm

The reason that Jensen transformers are very expensive, is because it cost's a lot to build a good audio interconnect transformer.

They probably don't charge enough.

However I have great respect for DIY, and think a person with very novice skills should be able to build a system that truly sounds good (far too rare). For what that person will pay for in a system can be less than one commercial product at 90% the quality. We'll see how everyone likes this in a bit. It's easy to assemble one volume unit for the price of a single Jensen without any other parts, and no pot.

KR500 · « **Reply #24 on:** 6 Aug 2015, 12:45 pm »

Started receiving some of the parts I ordered and the suggested Velleman PCB has no standoff mounting holes in the corners . Maybe they're for slotted cases but not the case I have .
I'll stop by the remaining RS in town and see if they have something suitable.
The chokes from Mouser arrived and as Folsom mentioned they are fairly heavy . Plus too tall for the enclosure I had around . Time to look for another metal case.
Is there any polarity for the chokes ?
They have 4 terminals , one each corner

Folsom · « **Reply #25 on:** 6 Aug 2015, 01:58 pm »

No, they don't have poles.

Yes the velleman lacks holes. I just drill them.

KR500 · « **Reply #26 on:** 6 Aug 2015, 02:30 pm »

Thanks for that , I didn't know if the boards would crack if I tried to drill them

KR500 · « **Reply #27 on:** 14 Aug 2015, 05:17 pm »

Just received the stepped attenuator pot from Hong Kong this morning
Drilled the PCB for standoffs and then drilled holes for the RCA chassis jacks in a metal Hammond 1441 enclosure
Got to say the stepped drill bits from Hazard Fraught did a poor job , lots of messy burr on the inside of the enclosure hole . They're only good for ABS.
I went and got an Irwin stepped bit from Lowe's for drilling the additional holes in the case. Hopefully it will perform better.
I have some other things to take care, but will post when I finish the VCD and put my impressions up here, maybe in a couple of weeks.
I can compare this with my standard stereo " pot in a box ".
I know when putting together speaker crossovers I follow the standard distance/ orientation procedure for mounting coils on a base .
Are those issues in this application the same ?

Folsom · « **Reply #28 on:** 14 Aug 2015, 08:37 pm »

They're very low power so there's no need to try and seperate them greatly. Mine are an inch at most.

KR500 · « **Reply #29 on:** 17 Aug 2015, 10:00 pm »

Drilled out the hole for the stepped pot and used the Irwin stepped bit from Lowe's , a slight improvement over the HF stepped bit ones.
The cheep knob from PE doesn't fit the attenuator which is okay as I want to get a better one anyway .
I included the $2.40 stereo pot from Parts Express for size comparison along with the Sure 2X8 watt 3110 amp board . The Hammond Enclosure is the 1441 I think 4X7 inches
Pressed the chokes and resistors in . Next up soldering

Folsom · « **Reply #30 on:** 17 Aug 2015, 11:31 pm »

You're very neat and tiddy.

What is the power supply for the amp?

KR500 · « **Reply #31 on:** 17 Aug 2015, 11:44 pm »

Pyramid PSK4 13.8 Volt 4 amp power supply.
I added a 10,000 uF Nichicon capacitor to the output .
the Sure amp boards sounded so much better than the laptop 16 volt brick I was surprised.

KR500 · « **Reply #32 on:** 18 Aug 2015, 12:04 pm »

Quote

*Please notice the RCA jacks are only grounded to chassis following the ground isolator and DACT. You can simply negative the isolation rings that come with them if you sand a little bit on the enclosure so it makes contact if it's not already bare metal. The ones prior must be isolated from enclosure.

Sorry , a noob question , any tips on grounding in a metal chassis as pictured in the diagram on the first page of this post ?
Do I drill a hole , remove paint around the hole and mount a bolt nut and star washer for chassis ground ?
There are 2 different ground symbols for before DACT and after .

BTW , the ebay seller started shipping a "new and improved" version of the stepped potentiometer after July 15 . Green in color instead of black

Folsom · « **Reply #33 on:** 18 Aug 2015, 03:07 pm »

In this case you could just leave off the insulating ring on the inside of the output RCA jacks, and scrape the paint around them. The input RCA's must be isolated, you don't see anything, and no drilling.

The symbol before the DACT is not connect, and is crossed off, indicating not to do it...

KR500 · « **Reply #34 on:** 19 Aug 2015, 11:59 pm »

Got the VCD finished tonight and tried it with a Sure 2X8 , 2X25 and SureTDA7492.
All sound very bright and revealing , harsh and not too smooth
All 3 boards cut in/out stutter after turning up to 65 -70 %
Took the VCD out of the chain and went back to the $2.40 Parts Express 50K stereo pot in a ABS case.
Nice and smooth , not super but listenable
Did the previous posters on page one get theirs finished ?
If so I'm curious what their impressions are

Folsom · « **Reply #35 on:** 20 Aug 2015, 12:20 am »

Let's see pictures. It sounds like something is incorrectly wired. Also it would need a little burn in time.

Burn in time won't fix cutting out. Cutting out tells me there's a problem.

In fact looking at your first pics, it looks like the CMC would be wired right if it was turned 90°. You may be incidentally using them like a transformer atm.

KR500 · « **Reply #36 on:** 20 Aug 2015, 12:14 pm »

Thanks for your post FA
Will take the PCB out and rotate the wiring to the coil 90 degrees and re-solder
I can't remember if I rotated them after taking the pictures as at that time they were just pushed in place
Sorry , a little fuzzy , had outpatient surgery Tuesday so a little slower than usual

KR500 · « **Reply #37 on:** 21 Aug 2015, 08:56 pm »

Just re-soldered the choke coils with the proper orientation. I should have asked first about the orientation when I initially asked about polarity for the 4 unmarked terminals of the coils.
The rapid on/off power issue at 3/4 volume and up is gone, except for the 3110 and 3116 boards at the full volume step of the pot
I'm using a Marantz Cd player and Overnight Sensation speakers . Still bright and thinnish sounding but not as harsh as before.
Maybe it's the Cd of Good Vibrations recording itself ? so I put in a CD of Perfidia by Hank Marvin and The Shadows . a bit smoother.
Next up is to move the VCD and Sure amp boards to where I have a pair of large Klipsch MTM towers and a pair of Amethyst small 2 ways to do some listening in there

Folsom · « **Reply #38 on:** 21 Aug 2015, 09:21 pm »

It may take a few hours of playing before it sounds as good as it can. That volume device is pretty accurate, so it won't mask recordings or add 2nd harmonic distortion to overly smooth and increase bass artificially.

KR500 · « **Reply #39 on:** 25 Aug 2015, 07:41 pm »

okay , I moved the VCD to an exercise room and hooked things up to contrast and compare
First I picked out 3 well re-recorded pieces of music and sampled a minute and a half of each
Nigel North - Linn Records - the Baroque Lute
Kings X - Atlantic Records - Not Just for the Dead
Neko Case- Margaret Vs. Pauline - Fox Confessor
First I played music through an Audio Source Amp 100 which is a hundred dollar amp that sounds way better with $45 worth of mods
( per Tyger 23 on the PETT ) , not great but decent. Then disconnected the Amp 100 and switched to the VCD and Sure amp boards
Source is a Marantz CDP and Musical fidelity V-DAC with Radio Shack power supply , not the OEM wall wart.
I usually use a Little Dot Mk 2 preamp as it warms things up nicely, but left it off for this session for simplicity. Then
Klipsch MTM speakers in 1.5 ft. cabinets with two 6.5 inch metal woofers and the tractrix horn per .
Always takes my ears a minute to get used to these horns . I usually listen to a Seas full ranger and SET amp , so.... quite different.
I then switched from klipsch to the Amethyst speakers , a good small affordable 2-way monitor with TB polyprop cone and neo tweeter ,and a smoother presentation than the horn . Both are 4 ohm speaker cabinets.
In a quick and dirty comparison with the "pot in a box " the VCD has a wider sound stage and a more accurate presentation , the box with the $2.40 stereo pot sounded narrow and wooley in comparison to the VCD, but a bit more "body" , maybe also known as distortion ?
I'm using a Pyramid Mk 4 power supply for the Sure 3110 amp boards .
Still getting power on/off fluttering at the very loudest setting with Sure board, fine everywhere else though.
This week I'll spend some more time with this but wanted to post a quick impression. I plan on trying the Sure boards with a 16 volt laptop brick too although last time in my initial test it just didn't sound as good as the Pyramid. I'm thinking maybe of using the Sure and VCD for the Amethsts and I have an SCS power amp I might use for a sub for low end . the Sures have a nice clear middle and top end but not much low end .