$175 Class D amp--120 wpc

jtwrace · « **Reply #2060 on:** 29 Sep 2010, 07:42 pm »

Quote from: raindance on 29 Sep 2010, 07:40 pm

As luck would have it I'm kind of from there too (UK by way of a colony)... I think I'll have to buy a sodding SDS series instead...

I like you more now. See this http://www.audiocircle.com/index.php?topic=86325.msg842177;topicseen#new

wushuliu · « **Reply #2061 on:** 29 Sep 2010, 07:43 pm »

Quote from: raindance on 29 Sep 2010, 07:40 pm

As luck would have it I'm kind of from there too (UK by way of a colony)... I think I'll have to buy a sodding SDS series instead...

You can also ask Tom if it's possible to increase the input impedance of your board rather than shell out for the SDS.

raindance · « **Reply #2062 on:** 29 Sep 2010, 07:48 pm »

@wushuliu - actually it is possible to increase in the input impedance, and I'm going to send the board to Tom to do that and also get the gain matched. I have heard of a gain mismatch on another board somewhere, so I'm not the first. I originally had a balance control in my design (using a stepped attenuator), but decided to get rid of it as it affected transparency.

I want gain, so the Dodd buffer won't work. Especially if I raise the input impedance, the sensitivity will go way down. Glassware appears to have great products but nobody replies to my emails.

raindance · « **Reply #2063 on:** 30 Sep 2010, 02:25 am »

I just answered my own question - the SRPP circuit I just put together should be optimal for a 5K load as-is, just needs a change of coupling cap.

grubyhalo · « **Reply #2064 on:** 1 Oct 2010, 09:47 am »

Quote from: raindance on 29 Sep 2010, 07:48 pm

... Glassware appears to have great products but nobody replies to my emails.

There's a good possibility that the emails ended up in the spam bin. Try adding the terms "tube amp" and "valve" in the subject line...

raindance · « **Reply #2065 on:** 1 Oct 2010, 10:42 am »

Thanks grubyhalo, I'll try that.

ablefire · « **Reply #2066 on:** 2 Oct 2010, 02:02 pm »

I received my SDS-254 kit today. Unfortunately they forgot to include the wired molex connectors and gain controls. I would very much like to build this amp this weekend and I wonder if actually need the gain controls. I am feeding the amp from a pre-amp. Any help to get it running this weekend would be most appreciated.

Feanor · « **Reply #2067 on:** 2 Oct 2010, 02:13 pm »

Quote from: ablefire on 2 Oct 2010, 02:02 pm

I received my SDS-254 kit today. Unfortunately they forgot to include the wired molex connectors and gain controls. I would very much like to build this amp this weekend and I wonder if actually need the gain controls. I am feeding the amp from a pre-amp. Any help to get it running this weekend would be most appreciated.

I asked Tom whether the pots could be just omitted or whether a couple of the headers could be jumped, but he insisted that the gain pots were necessary. Obviously some alternative to the supplied pots is possible but Tom offered no suggestions.

Barry_NJ · « **Reply #2068 on:** 2 Oct 2010, 02:31 pm »

Quote from: Feanor on 2 Oct 2010, 02:13 pm

I asked Tom whether the pots could be just omitted or whether a couple of the headers could be jumped, but he insisted that the gain pots were necessary. Obviously some alternative to the supplied pots is possible but Tom offered no suggestions.

Isn't a pot nothing more than a variable resistor? Couldn't a single value resistor be used in place of the pot?
The thing that confuses me though is that the pots appear to have 3 leads not just 2... Would someone please explain this...

Feanor · « **Reply #2069 on:** 2 Oct 2010, 02:41 pm »

Quote from: Barry_NJ on 2 Oct 2010, 02:31 pm

Isn't a pot nothing more than a variable resistor? Couldn't a single value resistor be used in place of the pot?
The thing that confuses me though is that the pots appear to have 3 leads not just 2... Would someone please explain this...

The leads are input, output, and ground. To put it simply, (which is the only way I know how to put it), the unit works by routing some input voltage to output while bleeding the rest to ground.

Barry_NJ · « **Reply #2070 on:** 2 Oct 2010, 02:54 pm »

Quote from: Feanor on 2 Oct 2010, 02:41 pm

The leads are input, output, and ground. To put it simply, (which is the only way I know how to put it), the unit works by routing some input voltage to output while bleeding the rest to ground.

So it's like 2 variable resistors, in parallel, that are the inverse of each-other(?)

jtsnead · « **Reply #2071 on:** 2 Oct 2010, 04:30 pm »

The following is a quote from Tom, I was looking for a fixed gain option, this is what he said

"You can put a resistor instead of the pots for fixed gain. It might be best to first run the amp with your other equipment and set the gain to the best match for your preamp and other equipment, and then take a measurement of resistance from the two pins (two pins on the left of side of the MOLEX connector… yellow and black wire). What the measurement is, you can just put a resistor of that value between the yellow and black wire and remove the pot"

roymail · « **Reply #2072 on:** 2 Oct 2010, 05:20 pm »

Quote from: wushuliu on 29 Sep 2010, 07:43 pm

You can also ask Tom if it's possible to increase the input impedance of your board rather than shell out for the SDS.

Does anyone know if Tom can increase the input impedance of a CDA board to 47K or higher? Thanks

HT cOz · « **Reply #2073 on:** 2 Oct 2010, 06:24 pm »

Can someone with the SDS boards comment on switching between balanced and single ended inputs? Is it easy?

ablefire · « **Reply #2074 on:** 2 Oct 2010, 06:28 pm »

Quote from: ablefire on 2 Oct 2010, 02:02 pm

I received my SDS-254 kit today. Unfortunately they forgot to include the wired molex connectors and gain controls. I would very much like to build this amp this weekend and I wonder if actually need the gain controls. I am feeding the amp from a pre-amp. Any help to get it running this weekend would be most appreciated.

I received a reply from Tom:
> It is possible to get sound by putting a 10 ohm resistor in place of the gain controls temporarily.

Feanor · « **Reply #2075 on:** 2 Oct 2010, 06:37 pm »

Quote from: HT cOz on 2 Oct 2010, 06:24 pm

Can someone with the SDS boards comment on switching between balanced and single ended inputs? Is it easy?

There is a header for each channel comprised of three pins. Remove the supplied jumpers for balanced operation, (or leave them for single-ended). I supposed it would be possible to have an external switch that would open/close the circuits if you wanted to switch between the two modes.

jtsnead · « **Reply #2076 on:** 2 Oct 2010, 06:40 pm »

Quote from: ablefire on 2 Oct 2010, 06:28 pm

I received a reply from Tom:
> It is possible to get sound by putting a 10 ohm resistor in place of the gain controls temporarily.

quote from Tom

"When bridged, you only use the left channel, change the jumper from Stereo to Bridged, and only use the right speaker + out and the left + speaker out"

ablefire · « **Reply #2077 on:** 2 Oct 2010, 10:37 pm »

Quote from: jtsnead on 2 Oct 2010, 06:40 pm

quote from Tom

"When bridged, you only use the left channel, change the jumper from Stereo to Bridged, and only use the right speaker + out and the left + speaker out"

jtsnead: Is this relevant to my temporary fix with the 10 ohm resistor?

Also, the male molex connector for the gain has 3 pins. Which pins should I connect the resistor to?

Barry_NJ · « **Reply #2078 on:** 2 Oct 2010, 11:24 pm »

Quote from: ablefire on 2 Oct 2010, 10:37 pm

jtsnead: Is this relevant to my temporary fix with the 10 ohm resistor?

Also, the male molex connector for the gain has 3 pins. Which pins should I connect the resistor to?

I think he meant to quote the message above yours, which I've put below...

Quote from: HT cOz on 2 Oct 2010, 06:24 pm

Can someone with the SDS boards comment on switching between balanced and single ended inputs? Is it easy?

SCM · « **Reply #2079 on:** 7 Oct 2010, 04:25 pm »

Greetings Gents...I`ve been reading along with great interest !

I`d like to use an Adcom 555 MK II that i`ve had for years as a platform for an SDS-258 build.
I know the 555 it has an 800va torodial for a power supply.

I have a question...What all can I reuse/salvage from the 555 while building this project ?