I put together the little Folsom amp.

Danny Richie · « **on:** 6 Mar 2018, 08:52 pm »

Dave Elledge sent me populated boards and told me I had to build these out and listen to them. I've learned from experience if Dave says to listen to something then there is something special going on. I've learned a lot form Dave and one of those things is to trust him when he likes something.

I built a pair of amps as mono-blocks a few years ago using these same chips and the results were exceptional. I like the off the grid systems for the zero noise floor and for the fact that they will sound the same no matter where I take them (Audio shows...). Here is a link to that thread: http://www.audiocircle.com/index.php?topic=124981.msg1317309#msg1317309

I think that the Folsom version takes them up several levels by design of the boards much better and with support of assembly. It will be interesting to compare this version to the pair that I made. The power supply is really nice, but I have an expensive power cables on it, plus a balanced power supply from Dodd Audio, and an Uber Buss from Dave Elledge. So three of four thousand dollars worth of conditioning verse a $200 100 amp hour Power Sonic battery. Which will I like better? I don't know.

I mounted the amp part in an Aluminum chassis that Gary Dodd designed before he passed away. I have a lot of them.

Somewhere I have a box of on/off switches that fit the front baffle of the chassis. The on/off switch lights up when turned on too. At some point I'll find them and replace what I used with what belongs there.

I used a Neutrik connector for the DC power in. I used Caradas RCA inputs, and tube connectors of coarse. There was no way I'd ruin it with binding posts.

The input wire is Vampire's continuous caste Copper. The input coupling caps are Sonicap Platinum's. The speaker wire is our internal wire that is solid core Copper in polyethylene. The power wire is OFC Copper in 12 gauge.

I have interconnects from High Fidelity Cables. http://www.highfidelitycables.com/ It's there entry level $1,600 a meter pair version. And the speaker cables are from Electra Cable, B6 model. http://www.electracable.com/speakercables.htm I made the DC cable using a braided 6 wire configuration of Silver Coated Copper.

I put the power supply in a separate chassis.

I put the power input on one side and the DC output on the other side. And I put a power switch on the input side.

Dave populated the boards before sending them to me and there is no telling what extra's he did to them.

I turned them on a little bit ago and they are up and playing with no issues. They sound great immediately. Now to let them burn in for a while. Those Sonicap Platinum's are going to take a while....

So more on this after some play time.

lacro · « **Reply #1 on:** 6 Mar 2018, 09:40 pm »

Danny, glad to see your positive review of the Folsom amp. I have built several of them, and I am really impressed with Jeremy's creation. Paired with my X-LS Encores, it's one sweet system for cheap! Hope to hear your observations when the caps break in.

Hirst · « **Reply #2 on:** 6 Mar 2018, 11:36 pm »

I have mine (thank you Danny for recommending it to me) hooked up to a pair of X-LS as well and I am stunned at how good the combination sounds. I am really looking forward to trying it with the wedgies (...ahem, Danny).
I believe that Jeremy has come out with another amp with a lot more power. Going to build that one and compare it to the Folsom.

Paul

Danny Richie · « **Reply #3 on:** 6 Mar 2018, 11:49 pm »

Quote

I am really looking forward to trying it with the wedgies (...ahem, Danny).

We are working on it.

SoCalWJS · « **Reply #4 on:** 6 Mar 2018, 11:59 pm »

Looks very nice! Anybody ever take some measurents on these? Do they produce enough power to drive speakers to fill a good sized room?

Folsom · « **Reply #5 on:** 7 Mar 2018, 12:11 am »

It depends on the efficiency of the speakers.

The amp can actually do 24w peaks, even though it's rated at 15w.

FullRangeMan · « **Reply #6 on:** 7 Mar 2018, 12:15 am »

What exactly is this amp?
Its J-fet or chip amp?
It can be biased in Class A?

ctviggen · « **Reply #7 on:** 7 Mar 2018, 12:18 am »

Quote from: SoCalWJS on 6 Mar 2018, 11:59 pm

Looks very nice! Anybody ever take some measurents on these? Do they produce enough power to drive speakers to fill a good sized room?

Although if they're that cheap, you could bi-amp or tri-amp.

Do they have a version with turn on based on a trigger (from receiver, for instance)?

Folsom · « **Reply #8 on:** 7 Mar 2018, 12:32 am »

It's AB.

Technically it's a chipamp, but it doesn't sound like any basic chipamp you've heard before (3875, 3886, 7293 etc). It has balanced outputs, which is unlike all of those.

My newer amp uses the 7293 to get some more serious power, but it doesn't sound like the 7293 because it has specialized feedback that is error correcting. It's sensitive enough to compare the incoming and outgoing signal, for voltage tracking, but not when it's own self power is moving. That's why it is battery/solar powered feedback.

Folsom · « **Reply #9 on:** 7 Mar 2018, 12:40 am »

Quote from: ctviggen on 7 Mar 2018, 12:18 am

Although if they're that cheap, you could bi-amp or tri-amp.

Do they have a version with turn on based on a trigger (from receiver, for instance)?

I have not made one. The idle current is so low that it isn't really necessary.

FullRangeMan · « **Reply #10 on:** 7 Mar 2018, 12:45 am »

Nice, thanks bro.

BRN · « **Reply #11 on:** 7 Mar 2018, 01:14 am »

I really like the two chassis design. You could build a battery supply and switch between the two.

Folsom · « **Reply #12 on:** 7 Mar 2018, 01:21 am »

SClark runs 24v battery power on his unit. It can be done fairly easy. I'm not saying it's better or anything, as I usually prefer AC powered gear, but it works well with the design of the amplifier and keeps the voltage regulation section active - which is also a major filter.

HAL · « **Reply #13 on:** 7 Mar 2018, 01:24 am »

Does the new amp have the capability for balanced inputs?

Folsom · « **Reply #14 on:** 7 Mar 2018, 01:47 am »

Not yet. It requires a lot more work due to the way the feedback works. Maybe I'll have a solution for a possibility with an additional PCB board you'd need to run along with it, but I don't suspect the demand for that too soon.

HAL · « **Reply #15 on:** 7 Mar 2018, 01:52 am »

Thanks for the feedback.

corndog71 · « **Reply #16 on:** 7 Mar 2018, 04:30 am »

Looks like a fun project. If only there was a kit available.

Folsom · « **Reply #17 on:** 7 Mar 2018, 04:40 am »

What would a kit need to entail for you? When someone orders I include an uploadable BOM to mouser for all the parts that go on the PCB boards, and the transformer.

Danny Richie · « **Reply #18 on:** 7 Mar 2018, 04:40 am »

Quote from: BRN on 7 Mar 2018, 01:14 am

I really like the two chassis design. You could build a battery supply and switch between the two.

I just happen to have a large 100 amp hour battery with a power cable that has the same plug on it. So I can swap between the two.

Folsom · « **Reply #19 on:** 7 Mar 2018, 04:52 am »

Is the battery 24v? If it's not you'd want to add another in series. The regulator filter, KMR, doesn't fully activate with under voltage. The problem with that is it'll reduce current from an infinite capacitor to like a 1500uf cap (sorta).