[walkern]

My system includes a Sain Smart tube preamp (still amazes me for how cheap it is, although I have a Aikido buffer build in progress), Zen Wave ICs and SCs, an Oppo 103 used as a transport except when playing SACDs (as well as an Asus laptop for hi rez files), and an SMSL M8 DAC.  The speakers are Dennis Murphy MB27s on 28" Paradigm stands, and a GR-Research servo 12" subwoofer. My listening room is modestly sized (our spare bedroom), however it has a sloping ceiling (up to 14 feet). It has no special acoustic properties and is filled with full bookcases, has wall-to-wall carpet and a nice queen sized bed in there in addition to my recliner.

Amps I have used for comparison (that I still have around) include a Chip Amp dot com LM3875 and LM3886 (built from kits), a modded (Fulsom suggestions) Chinese 7297 amp, a Class D Audio Amp (that's the brand name) SDS 120 (slightly modded and using an SMPS power supply), and a TPA 3116 (again Chinese) amp.  Amps I've owned in the past and remember fairly well include a Nakamichi PA 7 (Threshold era Pass design), Golden Tube Audio 300B monos, RAM Labs RM 100s (I think that was the model number), and an Oddyssey Stratos... and I'm sure there are others that are not coming to mind right now. I used to work as a salesman in a brick and mortar Hi Fi shop, so I got access to lots of nicer products at dealer cost, or cool stuff that was traded in.

I listen to and enjoy a wide range of music... much of it classical.  I also enjoy some pop, some jazz, and occasionally a little folk and country.  I'm really impressed by how 'listenable' the Folsom 7297 makes some of my older (1980's era) CDs (Al Jarreau, James Taylor, Rikkie Lee Jones, Julia Fordham, the Rippingtons, Pink Floyd, lots of older Telarc discs, etc.).  The amp doesn't hide the flaws, it just doesn't emphasize them, and it allows the music to shine through in spite of them. Modern hi rez downloads can sound absolutely fantastic, but most of my music has been collected over many many years, and I have very eclectic taste.

[Dmason]

Anyone gearing up to build some?  The anecdotes, and inpouring of talent is too much... I now need one.

[S Clark]

Anyone gearing up to build some?  The anecdotes, and inpouring of talent is too much... I now need one.

I'm in the process of repairing mine.  When done, I'm looking to sell it and upgrade. 

[poseidonsvoice]

Thanks Walkern for the details, very useful to put your review in context.

Best,
Anand.

[mlundy57]

Would 2.0uF input caps work and/or what would be the expected result?

I'm going to build the first one with the 1.5uF caps speced in the BOM but am looking at doing some upgrades for the second build.   The caps I'm considering are:

1.5uF, 400VDC Clarity Cap MR,
1.5uF, 600VDC Jupiter Copper Foil & Wax, or
2.0uF, 300VDC Sonicraft Platinum

Mike

[Folsom]

1.5 or larger are fine.

I've been itching to try Lefson caps. You could ask Dave at PI what he likes, he was saying it was a huge upgrade whatever he is using.

[mlundy57]

1.5 or larger are fine.

I've been itching to try Lefson caps. You could ask Dave at PI what he likes, he was saying it was a huge upgrade whatever he is using.

I'll check, thanks.

The reason I asked about the 2.0 is because apparently the Sonicap Platinums are not available in 1.5uF

Mike

[Folsom]

The cap size determines the corner frequency, and when bass begins to roll off. Under 1.5uf sounds like attenuated bass, anything over will not. You could use 10uf and it should work fine, but it'll cost a lot more for no gain in performance.

[wushuliu]

What about transformers like Jensen or cinemag instead of input caps?

[Folsom]

That should be tested, the grounding on the 7297 is sensitive to anything interrupting it, but may not be an issue.

[Captainhemo]

I'll check, thanks.

The reason I asked about the 2.0 is because apparently the Sonicap Platinums are not available in 1.5uF

Mike

Mike, I'm assuming you'll be driving your Wedgies with the    amp, if you only want it to play flat down to the  180-200 hz  the Wedgies are capable of,  ther ei s no reason to even go with 1.5uF caps, if you do the math  you'll find you'll get away with a  smaller value and save some  $, and a  bit of workload on the amp..    If you are  wantting to run the amp with the MTM's,  or even at full range with other speakers, you'll want  it to play lower  and use the   at least the 1.5 uf caps recommeneded or do the math to  determine what you need to reach the roll off point you   desire.
IIRC,  a 1.0 uF cap on the standard 7297  resulted in a  -3db at around 20 Hz
The above being said, I also believe you could  go the other way, your Dodd buffer runs  output caps so i don't think you  even require input caps  on the amp....  this would limit  what you could play the amp behind but  remove a cap(s) from the cirucit. 

jay

[Folsom]

1uf -3db was around 10hz or so, it still caused low bass.

Ya, it's weird, but that's how it works. Many designers shoot for 7hz, some say 4hz...

[Captainhemo]

Jeremy,
Have you by chance calculated the  roll of points of different  valued caps for the amp ?
Can't recall the input impedence off hand.... 

jay

[Folsom]

I have in the past. My point is that roll off has negative consequences in ranges you're not trying to meddle with.

Turns out 1uf was closers to 6hz. Input impedance is 25-30kohm.

http://www.muzique.com/schem/filter.htm

[lacro]

Hey Jeremy,
I know you said the 15V Antek 200VA Toroidal transformer would work with the Antipole, but would the 15V 100VA 3.3A Transformer also work? http://www.antekinc.com/as-1215/. Antek states:  "this transformer can be output 20% more power from its rating at 60Hz power source without any problem" I know you have mentioned earlier that the transformer should have at least an 80VA power rating.

[Folsom]

Yes that'll be fine ; it needs higher voltage. Just wire the outputs in parallel for enough current.

[mlundy57]

Would the damping layer from a piece of NoRez work for isolating the transformer from the case?

I could get rubber washers but I have quite a few various size pieces of NoRez left over from speaker builds. I was thinking of using a piece a little larger than the base of the transformer, removing the foam, then sticking the NoRez damping layer to the case under the transformer.

Mike

[Folsom]

You tell me

[walkern]

I tried a variety of damping choices before settling on rubber washers (including rubber bands, and a piece of rubberized foam) and I'm pretty sure that damping layer (without the foam) should work well.  I ended up using something like that between the top of my transformer and the top of the case, and it works there.  My only concern would be that it's thickness may extend the transformer up high enough to make the top of it come into contact with the top of the chassis, at which time the top of the chassis will hum and buzz no matter how well damped the under side of the transformer is.  Then you'll need to figure out something to put between the top of the transformer and the top of the chassis (maybe another piece of the same stuff?).

Give it a shot!

[lacro]

I have used, and really like these anti vibration pads: http://www.supplyhouse.com/DiversiTech-MP-3E-EVA-Anti-Vibration-Pad-3-x-3-x-7-8 These are probably too thick for the Hammond Transformer, as it would raise it too much, but probably could be sliced thinner with a fine cut hand saw of sharp knife.