I put together the little Folsom amp.

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Cheytak.408

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Re: I put together the little Folsom amp.
« Reply #80 on: 13 Jun 2018, 05:39 am »
I did the mod that eliminates the chassis bridge between the +/- speaker outputs and have found it to be a great sounding modification.

Isn’t difficult and highly recommended!  Cool, it is:  better sound from an over-achiever!  Thanks, Jeremy!

lacro

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Re: I put together the little Folsom amp.
« Reply #81 on: 13 Jun 2018, 01:00 pm »
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.

Would you elaborate a bit more on the batteries you use? What min Ah requirement for a reasonable run time, and what are you using for a charger. I have built several of these amps using SMPS's and with Transformer/Antipole PS, but never with batteries.

S Clark

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Re: I put together the little Folsom amp.
« Reply #82 on: 13 Jun 2018, 01:56 pm »
I"m using two 18 AH batteries.  They will power the unit for a week or probably two when used an hour or so a day.  At that time I'll put in a couple of 5 AH's while charging the bigger batteries, and they'll run for than a couple of listening sessions.  I use a CTEK 12V charger. I have a switch between the 18 AH batteries.  Most times I'll simply charge one at a time when not playing, never taking out the batteries. 
I've also used a couple of 28 AH batteries that power my Dodd pre and Dodd phono stage in my main system.  I can't hear a difference in dynamics or quality between them and the 18 AH. 
These little amps are extremely efficient.  I'd bet you could use a couple of 7 AH batteries and have a dynamic system that would run for days or even a week. 

SoCalWJS

Re: I put together the little Folsom amp.
« Reply #83 on: 13 Jun 2018, 04:33 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.

Somehow, I missed this post. I am interested but have several questions after re-reading this thread and parts of a couple others.

Danny, are these chassis' still available?
I'm guessing that they are best used as mono so need 2 for a Stereo?
I read a lot about different values for the different parts. How do you determine which values will best suit your system?
Is the value dependent on your speakers, your preamp, or a combination of the 2?
What other factors should be considered?
Any final conclusion on battery vs AC SQ? (I am interested in AC - any way to maximize? I have an UberBUSS)
Would there be any way a single one would sound good on the Super V's and the LS6's? (at a lower volume).

I would probably want to have the option of limiting the output of the low frequency via the input coupling cap.

Thanks

Danny Richie

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Re: I put together the little Folsom amp.
« Reply #84 on: 13 Jun 2018, 06:00 pm »
Somehow, I missed this post. I am interested but have several questions after re-reading this thread and parts of a couple others.

Danny, are these chassis' still available?

Yes. I have a lot of them.

Quote
I'm guessing that they are best used as mono so need 2 for a Stereo?

For me it is worth the extra money to make mono-blocks out of them just to keep speaker cable lengths shorter. I can spend more on longer speaker cables than it cost to build another amp (almost). Plus the amps can be two channel amps for bi-amping or different sized coupling caps can be used to vary the low end roll off. So you can have a full range channel and a channel with a -3db at whatever you want it to be.

Quote
I read a lot about different values for the different parts. How do you determine which values will best suit your system?

Are you referring to input coupling caps? If so the value depends on how much you want to roll off the bottom end.

And spend the money of good RCA connectors, tube connectors and wire. It can really make a difference. And I stock most of that.

Quote
Is the value dependent on your speakers, your preamp, or a combination of the 2?

The input impedance of the amp and your target roll off determines the value. For this amp I think it is 25k ohms.

So a .022uF value will be -3db down at 289Hz.
A .033uF value will be -3db down at 192Hz.
A .047uF value will be -3db down at 135Hz.
A .068uF value will be -3db down at 93Hz.
A .1uF value will be -3db down at 63Hz.
A .22uF value will be -3db down at 29Hz.
A .33uF value will be -3db down at 19Hz.
A .47uF value will be -3db down at 13.5Hz.
A 1.0uF value will be -3db down at 6Hz.

Quote
What other factors should be considered?

Just a target roll off.

Quote
Any final conclusion on battery vs AC SQ? (I am interested in AC - any way to maximize? I have an UberBUSS)

I've gone back and forth quite a bit and in my system the battery sounds better. And with the power supply I used really good cables, an Uber Buss, and a Dodd Audio balanced power supply. I still preferred the battery. However, not all batteries are the same. Mine is a 100 amp hour Power Sonic.

Quote
Would there be any way a single one would sound good on the Super V's and the LS6's? (at a lower volume).

The LS-6's are going to like more power, but they will drive the Super-V's easily to good levels.

Quote
I would probably want to have the option of limiting the output of the low frequency via the input coupling cap.

Piece of cake. See above. The limiting of current demand from it will give it a little more head room too.


Folsom

Re: I put together the little Folsom amp.
« Reply #85 on: 13 Jun 2018, 06:16 pm »
I use 1.5uf, 1uf still has audible roll off even at 6hz corner. (who knows why...)

SoCalWJS

Re: I put together the little Folsom amp.
« Reply #86 on: 13 Jun 2018, 08:45 pm »
I use 1.5uf, 1uf still has audible roll off even at 6hz corner. (who knows why...)

 :scratch:
6 Hz has audible roll off? I have no speaker capable of producing anything audible at 6 Hz. Am I missing something?

HAL

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Re: I put together the little Folsom amp.
« Reply #87 on: 13 Jun 2018, 09:04 pm »
For a single pole filter, a -3dB down point at 6Hz means that it is -0.1dB down at 60Hz. 

SoCalWJS

Re: I put together the little Folsom amp.
« Reply #88 on: 13 Jun 2018, 09:26 pm »
For a single pole filter, a -3dB down point at 6Hz means that it is -0.1dB down at 60Hz.
Thanks Rich. I'm guessing that would be tough for me to notice.

SoCalWJS

Re: I put together the little Folsom amp.
« Reply #89 on: 13 Jun 2018, 09:36 pm »
Yes. I have a lot of them.

For me it is worth the extra money to make mono-blocks out of them just to keep speaker cable lengths shorter. I can spend more on longer speaker cables than it cost to build another amp (almost). Plus the amps can be two channel amps for bi-amping or different sized coupling caps can be used to vary the low end roll off. So you can have a full range channel and a channel with a -3db at whatever you want it to be.

Are you referring to input coupling caps? If so the value depends on how much you want to roll off the bottom end.

And spend the money of good RCA connectors, tube connectors and wire. It can really make a difference. And I stock most of that.

The input impedance of the amp and your target roll off determines the value. For this amp I think it is 25k ohms.

So a .022uF value will be -3db down at 289Hz.
A .033uF value will be -3db down at 192Hz.
A .047uF value will be -3db down at 135Hz.
A .068uF value will be -3db down at 93Hz.
A .1uF value will be -3db down at 63Hz.
A .22uF value will be -3db down at 29Hz.
A .33uF value will be -3db down at 19Hz.
A .47uF value will be -3db down at 13.5Hz.
A 1.0uF value will be -3db down at 6Hz.

Just a target roll off.

I've gone back and forth quite a bit and in my system the battery sounds better. And with the power supply I used really good cables, an Uber Buss, and a Dodd Audio balanced power supply. I still preferred the battery. However, not all batteries are the same. Mine is a 100 amp hour Power Sonic.

The LS-6's are going to like more power, but they will drive the Super-V's easily to good levels.

Piece of cake. See above. The limiting of current demand from it will give it a little more head room too.
If I understand everything correctly, I would be looking at somewhere between .1 & .15 uF (I'm currently using the Fmods at 50 Hz when running the LS6s).

What else would I need besides the Chassis and the Chip boards to build out 2 Mono blocks? Separate boxes for the PS and all of the other electronics for the PS and the Amp box?
Trying to figure out if I can swing this with good RCA's, tube connectors and Wire - what's the total cost to get 2 channels of amplification?
 (and how much my soldering skills and ability to read a circuit diagram would be taxed  :green:)

Folsom

Re: I put together the little Folsom amp.
« Reply #90 on: 14 Jun 2018, 02:22 am »
Ryan from Vapor could hear the roll off with 1uf. So it was not just me.

The amp may exaggerate it a little, especially since it has a -3db at 20hz.

But all you have to do is add a little more capacitance and all is good.

limits

Re: I put together the little Folsom amp.
« Reply #91 on: 14 Jun 2018, 02:26 pm »
Ryan from Vapor could hear the roll off with 1uf. So it was not just me.

The amp may exaggerate it a little, especially since it has a -3db at 20hz.

But all you have to do is add a little more capacitance and all is good.

...This seemed to work for me... :thumb:





Plund

Re: I put together the little Folsom amp.
« Reply #92 on: 20 Jun 2018, 10:33 am »
In building the Folsom amp, I understand quality of results vary considerably with the choice of caps used.  What caps would some of you recommend I order/use?  I lean more towards the "cheap and cheerful" approach as opposed to "no holds barred" .  Let me say my caps budget, for the amp and the anti-pole, is $50.

Pete

lacro

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Re: I put together the little Folsom amp.
« Reply #93 on: 20 Jun 2018, 12:43 pm »
In building the Folsom amp, I understand quality of results vary considerably with the choice of caps used.  What caps would some of you recommend I order/use?  I lean more towards the "cheap and cheerful" approach as opposed to "no holds barred" .  Let me say my caps budget, for the amp and the anti-pole, is $50.

Pete

I am happy with Clarity ESA caps.
https://www.partsconnexion.com/CLARITY-74834.html




Danny Richie

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Re: I put together the little Folsom amp.
« Reply #94 on: 20 Jun 2018, 03:37 pm »
I did the mod that eliminates the chassis bridge between the +/- speaker outputs and have found it to be a great sounding modification.

Isn’t difficult and highly recommended!  Cool, it is:  better sound from an over-achiever!  Thanks, Jeremy!

More on this Mod?

Danny Richie

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Re: I put together the little Folsom amp.
« Reply #95 on: 20 Jun 2018, 03:40 pm »
In building the Folsom amp, I understand quality of results vary considerably with the choice of caps used.  What caps would some of you recommend I order/use?  I lean more towards the "cheap and cheerful" approach as opposed to "no holds barred" .  Let me say my caps budget, for the amp and the anti-pole, is $50.

Pete

Since the value needed is quite small, it is worth spending a little more to get high quality caps.

I like the Jupiter caps and Sonicap Platinum's myself.