[Barry_NJ]

How many Watts do these resistors need to be rated for: 1, 1/2, 1/4, or will 1/8th Watt resistors do?

Thanks, Barry

[guest1632]

How many Watts do these resistors need to be rated for: 1, 1/2, 1/4, or will 1/8th Watt resistors do?

Thanks, Barry

Hi Barry,

I would think no more than a half watt resistor. An 8th watt might be hard to handle. a quarter watt might be just fine. Just make sure they are say 1% or at most 5% difference in value between each other. I'd probably get tweaky, and get 1% values. But, that's just me.

Ray

[Barry_NJ]

Thanks Ray, as far as % variation goes, I'd likely get a hand full and measure to get a matched pair


One more question...

Would a simple jumper with no resistance cause problems?

[guest1632]

Thanks Ray, as far as % variation goes, I'd likely get a hand full and measure to get a matched pair


One more question...

Would a simple jumper with no resistance cause problems?

You would be at max gain, and probably it would be as if you turned the pots all the way up. Nothing gained there. no puns intended. lol.

[jtsnead]

so if I wanted max volume/gain I could disconnect the pot and solder together the yellow and black wires and that would be ok?

I guess the red wire does not need to be attached to the pot?

I use a tube buffer so max gain is fine.

[Barry_NJ]

You would be at max gain, and probably it would be as if you turned the pots all the way up. Nothing gained there. no puns intended. lol.

Don't you mean nothing lost

[guest1632]

Don't you mean nothing lost

Yep, there's always one in every crowd. Actually, yeah, nothing lost. What I should have said, nothing gained sonically. It might be interesting though to try a 5K in there as a fixed resistor. I suppose if he just wanted to have the amp gain at max, he could just run some solder between the two points, or just have a piece of wire soldered between the two solder points on the board. Then all you'd have to do is to just cut the wire to restore it back to the original factory specs.

Ray

[earflappin]

For all of you using a balanced input on your SDS amps be sure you pull the J1/J2 jumper (it's located close to the stereo/bridge jumper).  With this jumper in place you are running the amp single-ended. 

My set-up is balanced and I was unwittingly running the amp in single-ended mode and I can tell you that when I removed the jumper I got a very audible improvement in resolution and soundstage width/depth.

I wonder if this means that balanced users should be using two fixed resistors per channel in place of the gain pots - one across the yellow/black pins (input/output) and one across the red/black pins (red is chassis ground).  Anyone?  Tom has been too busy selling amps to give me a definitive answer on this.

Also, when you go from SE to balanced you will pick up 3-6db.

[poseidonsvoice]

For all of you using a balanced input on your SDS amps be sure you pull the J1/J2 jumper (it's located close to the stereo/bridge jumper).  With this jumper in place you are running the amp single-ended. 

My set-up is balanced and I was unwittingly running the amp in single-ended mode and I can tell you that when I removed the jumper I got a very audible improvement in resolution and soundstage width/depth.

I wonder if this means that balanced users should be using two fixed resistors per channel in place of the gain pots - one across the yellow/black pins (input/output) and one across the red/black pins (red is chassis ground).  Anyone?  Tom has been too busy selling amps to give me a definitive answer on this.

Also, when you go from SE to balanced you will pick up 3-6db.

Thanks for the heads up. FWIW, this amp was designed with balanced inputs in mind. Running it single ended is compromising its performance. So even those fellas who have their entire system running with RCA's/unbalanced I would encourage you to build or buy a differential/balanced preamp or source so you can hear this unit in all its glory.

Best,

Anand.

[toxteth ogrady]

FWIW, this amp was designed with balanced inputs in mind.

Anand,
Is this coming from Tom? I asked him about this when I bought my kit and seem to recall from our conversation that going balanced offered no real sonic improvements over single ended.

[poseidonsvoice]

No, its purely subjective, and with some objectivity thrown in! The differential input stage is designed for excellent common mode rejection (as he states on his website), and as such can benefit single ended inputs as well. When I auditioned the SDS 254 that jtwrace had lent me, I had two Belden cables, one unbalanced and the other balanced. I then set the levels to be the same as the balanced input had as much as a 6 dB increase in gain. The balanced input sounded better, although the RCA was no slouch. From a purely subjective standpoint, I found the balanced connection to sound *cleaner* and imaging was sharper if that makes any sense. If you are going to try it, I wouldn't splurge on some fancy balanced cable just yet. Use something cheap and well designed (like Belden) and borrow a balanced preamp.

My little study wasn't double blinded so my results could be completely biased, I will admit that.

YMMV,

Anand.

[toxteth ogrady]

Cool. Are you still building the dc coupled B1 to pair with the ClassD? If you are, I'd like to see how you put a balanced version together...maybe post in the thread Wushuliu started a few weeks back.

[earflappin]

Hey Anand, thanks for the update the other day on your multi-sub set-up.  I hope I can take advantage of your learning when I do the final set-up on my three subs which I hope to complete in the next month.

In my current set-up I run balanced from my Metric Halo LIO-8 DAC/Pre to the SDS-224.  I had been listening to it for 2 weeks (since I put it in my system) effectively in single-ended mode with a 5kohm resistor across the yellow/black pins (replacing the standard gain pot).  So I had a very established baseline for comparison.  Pulling the J1/J2 jumpers, as Anand described, yielded a "cleaner", more resolute presentation - in comparison to single-ended mode the sound seems just a bit "smeared".  The difference was immediately audible in my system.  I had to dial the gain down in my pre by 6db to restore the balance.

There is no question in my mind that this amp is at its best in balanced mode.

 

[praedet]

No, its purely subjective, and with some objectivity thrown in! The differential input stage is designed for excellent common mode rejection (as he states on his website), and as such can benefit single ended inputs as well. When I auditioned the SDS 254 that jtwrace had lent me, I had two Belden cables, one unbalanced and the other balanced. I then set the levels to be the same as the balanced input had as much as a 6 dB increase in gain. The balanced input sounded better, although the RCA was no slouch. From a purely subjective standpoint, I found the balanced connection to sound *cleaner* and imaging was sharper if that makes any sense. If you are going to try it, I wouldn't splurge on some fancy balanced cable just yet. Use something cheap and well designed (like Belden) and borrow a balanced preamp.

My little study wasn't double blinded so my results could be completely biased, I will admit that.

YMMV,

Anand.

So, what about building the amp balanced and using balanced (XLR) to RCA cables?  Would that be more beneficial than using RCAs out of the amp?

[poseidonsvoice]

So, what about building the amp balanced and using balanced (XLR) to RCA cables?  Would that be more beneficial than using RCAs out of the amp?

You mean RCA's into the amp. I haven't tried it so I can't tell.

For my *main* speakers, everything that runs it is designed to be balanced and runs with balanced cables only. In other words, I don't look for diy projects or designs that convert RCA to balanced or vice versa without the supporting circuitry, be it tubed or solid state.

Anand.

[poseidonsvoice]

Cool. Are you still building the dc coupled B1 to pair with the ClassD? If you are, I'd like to see how you put a balanced version together...maybe post in the thread Wushuliu started a few weeks back.

I am currently half way through the build on the circuit boards, taking my time. I still have to design the chassis, and get the encapsulated toroidal transformers. I will be building the 600mA hot rod version for those who are curious (that's 600mA per board or 1.2A for the entire unit!). Each toroid is 80-100VA, probably Plitron. I already have the remote for the volume control which is a K&K balanced attenuator. All the series resistors in the main part of the circuit are TX2575 type.

I want to build this buffer once and not tweak afterwards.

Anand.

[praedet]

Yeah, sorry, I was thinking about the pre-amp as I was talking...

Balanced in from an RCA preamp (DODD Buffer)

You mean RCA's into the amp. I haven't tried it so I can't tell.

For my *main* speakers, everything that runs it is designed to be balanced and runs with balanced cables only. In other words, I don't look for diy projects or designs that convert RCA to balanced or vice versa without the supporting circuitry, be it tubed or solid state.

Anand.

[toxteth ogrady]

For anyone interested in buying a kit, there's a guy on head-fi selling a new sds-258 kit and he's willing to hear offers.

[wushuliu]

The TX2575 resistors finally arrived. Smaller than I thought, kind of fragile. They sound very, very good.

I have also finished an Optical Volume Control pre based on the Lightspeed circuit. It is also VERY good. They go well together. Music is Pure.

[Nick77]

Wush can you give us some details, you replaced your gain pots with fixed naked Vishays?

Pics??