I put together the little Folsom amp.

Folsom · « **Reply #60 on:** 9 Mar 2018, 12:40 am »

If you plug yours into the other output on the preamp, do you get different volume than the 3.3uf? The different preamp outputs are the only thing that make any real sense. Putting a second capacitor between the chips isn't an attenuation device in itself. The chip is internally set for gain.

The battery will provide a little more RF in order to enhance some high frequency character. (more air = the most common benefit of some RF)

The TL431 regulator can be swapped for one from Fairchild to dirty up the supply a little, which will give a little more enhanced character from RF. But it will maintain filtration of mostly lower frequency stuff that makes the amp not sound as good. "warmer" might be the best description.

Danny Richie · « **Reply #61 on:** 9 Mar 2018, 12:48 am »

Quote from: Folsom on 9 Mar 2018, 12:40 am

If you plug yours into the other output on the preamp, do you get different volume than the 3.3uf? The different preamp outputs are the only thing that make any real sense. Putting a second capacitor between the chips isn't an attenuation device in itself. The chip is internally set for gain.

Mine won't play plugged into the the output with the 3.3uF output caps unless I plug in a filter cap right at the amp. I keep a .022uF, a .033uF, and .047uF inline filter handy for different speakers.

There is clearly an output difference. I don't know why.

I just listened to to Vienna Teng recorded live, using the your amp. I went back and forth several times using the A/C power supply and the battery again. Her voice is slightly more chesty and with a little more body with the A/C power supply and slightly more open and airy with the battery.

I wish everyone here could hear this system right now. Unbelievable!

drmike · « **Reply #62 on:** 9 Mar 2018, 12:02 pm »

hey danny.
do you have any of those cases for sale?
what are the dimensions?
thanks,
drmike

Danny Richie · « **Reply #63 on:** 9 Mar 2018, 02:17 pm »

Quote from: drmike on 9 Mar 2018, 12:02 pm

hey danny.
do you have any of those cases for sale?
what are the dimensions?
thanks,
drmike

Yeah, I have a lot of them. I'll make some deal on them.

dBe · « **Reply #64 on:** 10 Mar 2018, 02:59 am »

Quote from: Danny Richie on 9 Mar 2018, 02:17 pm

Yeah, I have a lot of them. I'll make some deal on them.

Danny, shoot me a cost for 4. Thanks. It'll be good just to have a GD design on hand other than my pre and amp.

I loved that man. He was an inspiration in chasing battery power and just a hoot to hang out with talking audio. I miss him muchly.

S Clark · « **Reply #65 on:** 10 Mar 2018, 03:20 am »

When you shoot Dave a PM, send me one too. I could use a couple of those as well.

gmurray618 · « **Reply #66 on:** 10 Mar 2018, 06:34 am »

+1
Me too please.

mlundy57 · « **Reply #67 on:** 10 Mar 2018, 07:34 pm »

Danny,

You can add me to the case list also.

Mike

jparkhur · « **Reply #68 on:** 10 Mar 2018, 08:02 pm »

Quote from: Danny Richie on 9 Mar 2018, 02:17 pm

Yeah, I have a lot of them. I'll make some deal on them.

I need 2 please.

Odal3 · « **Reply #69 on:** 11 Mar 2018, 03:03 am »

Fun to see the Folsom amp still gets the attention and great reviews it deserves!

Nice build!

nrenter · « **Reply #70 on:** 11 Mar 2018, 10:49 pm »

Any thoughts on integrating these amps INTO the crossover of your 2-way models? I could see a single chip amp "bi-amping" one of your speakers (one channel for the tweeter, one channel for the woofer). The speaker binding posts (or tube connectors) would be replaced with a single RCA connector and an input for power.

Danny Richie · « **Reply #71 on:** 11 Mar 2018, 11:12 pm »

Quote from: nrenter on 11 Mar 2018, 10:49 pm

Any thoughts on integrating these amps INTO the crossover of your 2-way models? I could see a single chip amp "bi-amping" one of your speakers (one channel for the tweeter, one channel for the woofer). The speaker binding posts (or tube connectors) would be replaced with a single RCA connector and an input for power.

It would be real easy to make that happen on just about any model we offer.

Early B. · « **Reply #72 on:** 11 Mar 2018, 11:43 pm »

Quote from: Danny Richie on 11 Mar 2018, 11:12 pm

It would be real easy to make that happen on just about any model we offer.

Why stop there? Throw in a "do no harm" volume control and you've got a true audiophile integrated speaker system. Just plug in a source via a long pair of XLR cables to the speakers, and press, "play."

Jonathon Janusz · « **Reply #73 on:** 12 Mar 2018, 03:24 am »

Next thing all y'all are going to tell Danny to design line level crossovers for all his kits and sell kit-form true active systems...

Danny Richie · « **Reply #74 on:** 12 Mar 2018, 02:49 pm »

Quote from: Folsom on 7 Mar 2018, 12:32 am

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.

Keep me informed as to how development of this goes.

Danny Richie · « **Reply #75 on:** 12 Mar 2018, 03:03 pm »

Okay, for you guys asking about these chassis's.

I looked up the all the cost that I have in these. There was raw Aluminum, CNC machining, and engraving. The front baffles say Commemorative Designs in honor of Gary Dodd as he designed these.

I have $115 in each chassis.
I can throw in the Cardas RCA's for $10 each. That's less than the retail for.
The Neutrik connectors are $15 a set (male and female).
And the tube connectors are $59 a set.

These little chassis are perfect for the Folsom amps.

I also have a bunch of the TDA7850 chip sets and circuit boards. These are what the chassis's were designed for. It's a similar chip set, but will output 50 watts per channel into four channels. You can vary the input coupling cap value to allow one set of outputs to be full range and the other can have reduced low frequency (filtered lows). That's what Gary was going to do with them.

http://html.alldatasheet.com/html-pdf/233387/STMICROELECTRONICS/TDA7850/1944/1/TDA7850.html

I can throw in these chip sets and boards for another $20.

Oh yeah, the internal space is 6" by 5" and 2.375" tall.

dBe · « **Reply #76 on:** 13 Mar 2018, 05:38 am »

Gentlemen, I have once again been disinvited to post on Audio Circle by your Imperious Leader JohnR. If anyone needs or would like help with the Folsom 7297 amp, please PM Danny and he can give you my email address.

This amp is an overachiever at its price point and a great overall performer at any price.

Kudos, Jeremy!

Bye, ya'll.

rockdrummer · « **Reply #77 on:** 13 Jun 2018, 04:01 am »

Hi, I am interested in these, and I have come to the conclusion that I'm a little lost. I know it needs a chassis, but I'm lost on the rest. Jeremy sends a parts list, directions and a psu board and the amp board. I can follow directions and solder, but outside of that, noob. After ordering the mouser parts list, will I need anything else to plug it in and go? I read several of you use batteries and don't know how to do that.

I have built 4 gr kits and a bottlehead amp by watching and learning. What else do I need to know before I order one of these?
Thanks for any help.
Ben

Folsom · « **Reply #78 on:** 13 Jun 2018, 04:39 am »

The BOM does not include the connectors. It has a few suggestions. You also need a heatsink, which I mention can be got at heatsinkusa if you want something specific cut to size.

You also have to buy wire.

You may find this topic useful. https://www.audiocircle.com/index.php?topic=138229.0

S Clark · « **Reply #79 on:** 13 Jun 2018, 04:41 am »

Don't know about several of us using batteries, but I am. Simply take two 12V SLA batteries and connect in series to up the voltage to 24V and connect to the power input on the board.
Don't get in a hurry and you should have no problems. The board is well marked.