Zachary,
If you are trying to implement input transformers for balanced inputs there are many options including Jensen, Lundahl, etc...
However...I am going to try Tom Christiansen's Neurochrome THAT Receiver
The measurements are compelling along with a very competitive CMRR of 85-90dB rivaling transformers. The THAT Receiver is a direct and astute application of the THAT 1200 IC. Do consider it.
Best,
Anand.
I bought a bag of qnty 40 x 2SK170's on a whim from Aliexpress for $7 thinking they probably would be fake or not work. Turns out they work very well. So not hard to find for cheap. You can get genuine ones from Linear Systems in the US for about $1ea so not expensive if only need a few.
You can also get genuine Vishay IRFP240's from Ali for about $1ea. The ZTX450 can be substituted with a BC550 I think. So this amp ends up being very accessible and economical to make.
You can also get genuine Vishay IRFP240's from Ali for about $1ea. The ZTX450 can be substituted with a BC550 I think. So this amp ends up being very accessible and economical to make.
It is only 14dB overall gain Mike! Typical solid state amps are 26-30 dB!! So there is a 12-16dB difference in gain compared to most solid state amps.
5 watts is about 6.32V RMS assuming an 8 ohm load. Knowing the gain is 14 dB, means the input sensitivity is about 1.5V RMS.
Best,
Anand.
5 watts is about 6.32V RMS assuming an 8 ohm load. Knowing the gain is 14 dB, means the input sensitivity is about 1.5V RMS.
Best,
Anand.
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Yes I do have the 2.2k resistor mod. The current kits include this resistor and the boards have an R15 spot for it.
I just checked and the amp I normally use in this system (PrimaLuna Prologue 4) has 29dB of gain. Instead of a preamp I use a zero gain tube buffer in combination with the power amp. The 13dB gain difference between the PL and the ACA is certainly significant and explains why I have to run the pot on the tube buffer at 1 o'clock instead of 9 o'clock.
Thanks,
Mike
Anand,
The Prologue 4 is an EL34 based tube amp but still has 29dB of gain.
There is also a big difference in the input sensitivity between the P4 and the ACA. The ACA has 1.5V for 5 watts while the P4 has 600mV for 35 watts. Which explains why I have to open the buffer up a lot more with the ACAs.
By the way, I have the ACAs driving 94dB sensitive open baffle speakers that are 10ft from the listening position right now.
I would characterize the sound from the ACAs and subdued, closed off, constrained. I think this is because I just fired them up for the first time this evening. I expect them to open up over the next week or so as they accumulate some playing time.
To clarify, I have no intention of the ACAs replacing the Prologue 4 in this system. I built the ACA kit because I have never built an amp before and they looked like something I could handle. Later on I might try them in my desktop system. In the desktop system the ACAs would be connected to an iFi micro iDSD DAC/headphone amp.
Thanks,
Mike
What d'ya think of the sound Mike?
Best,
Anand.
Looks like we were both typing at the same time
Mike
Update:
My earlier description of the sound of the ACAs as being subdued, closed off, constrained is way off base. This sound profile is what I got from not supplying the ACAs with enough voltage to fully drive them.
Since I use a passive tube buffer (0 gain) in this system instead of an active preamp the DAC supplies all the voltage to the power amp. The DAC in this system outputs 2V (that's for both channels). When used with the PrimaLuna, which is a stereo amp with an input sensitivity of 600mV, this 2V output is more than three times what is needed to drive it to full power. Therefore, additional gain from a preamp is unnecessary so the 0 gain buffer works fine.
The ACAs have an input sensitivity of 1.5V each (3V total). In this case the 2V output from the DAC is only 2/3 of what is needed to drive the ACAs to full power. This means a 0 gain buffer is not appropriate and is why the ACAs sounded subdued, closed off and constrained.
Today I took a preamp out of another system that has a maximum output of 7V and an additional 10dB of gain. Guess what? the ACAs no longer sound thin, closed off, constrained or any other such descriptor. They can now put out over 100dB at the listening position and sound full. I look forward to spending more time listening to these.
I can't evaluate bass response with these speakers because they roll off at 200Hz. Later on I'll see what they sound like in the office desktop system which plays down to ~65-70Hz and with the MTM transmission line speakers in the living room (40Hz).
I built the kit stock except I used Cardas RCA jacks and binding posts instead of the ones that came with the kit.
Overall I like what I am hearing at this point.
Mike
My earlier description of the sound of the ACAs as being subdued, closed off, constrained is way off base. This sound profile is what I got from not supplying the ACAs with enough voltage to fully drive them.
Since I use a passive tube buffer (0 gain) in this system instead of an active preamp the DAC supplies all the voltage to the power amp. The DAC in this system outputs 2V (that's for both channels). When used with the PrimaLuna, which is a stereo amp with an input sensitivity of 600mV, this 2V output is more than three times what is needed to drive it to full power. Therefore, additional gain from a preamp is unnecessary so the 0 gain buffer works fine.
The ACAs have an input sensitivity of 1.5V each (3V total). In this case the 2V output from the DAC is only 2/3 of what is needed to drive the ACAs to full power. This means a 0 gain buffer is not appropriate and is why the ACAs sounded subdued, closed off and constrained.
Today I took a preamp out of another system that has a maximum output of 7V and an additional 10dB of gain. Guess what? the ACAs no longer sound thin, closed off, constrained or any other such descriptor. They can now put out over 100dB at the listening position and sound full. I look forward to spending more time listening to these.
I can't evaluate bass response with these speakers because they roll off at 200Hz. Later on I'll see what they sound like in the office desktop system which plays down to ~65-70Hz and with the MTM transmission line speakers in the living room (40Hz).
I built the kit stock except I used Cardas RCA jacks and binding posts instead of the ones that came with the kit.
Overall I like what I am hearing at this point.
Mike
Mike,
Nice update. Gotta love DIY! Thankfully my DAC output is 4V RMS.
Pics or it didn't happen!
Best,
Anand.
Anand,
Here you go
The first two pics are of the build in progress and getting close to the end.
The third is a shot of the Cardas RCA connectors and binding posts. These required reaming the binding post holes out to just over 1/2".
Next is the first time I powered them up. All magic smoke stayed inside where it belonged.
The 5th pic is the ACA occupying the space where the Prologue 4 usually sits. The wood front piece on the second shelf is the Dodd Audio tube buffer I normally use for source switching and volume control.
Next is a shot of the system. The Xeon based computer in the lower right is the source. You can't really see the DAC because it is black and sits on top of the Dodd tube buffer. The DAC is an LH Labs Pulse X-Infinity. The speakers are open baffle DIY kits (I built and finished the cabinets) from GR-Research. The ACAs are powering the top sections which play from 200Hz-20kHz. The subs (20Hz - 200Hz) are powered by the plate amps on the floor between them. When fed through the Dodd the ACAs sounded anemic. This is because the Dodd tube buffer does not have any gain.
The last picture is of the ACAs on top of a Jolida JD-5T preamp which I borrowed out of another of my systems. When fed through the Jolida the ACAs came alive due to the 10dB of added gain and 7V output of the JD-5T.
Mike
Attachments
I've used the iFi with my ACAs and some 90db Eton symphony S7s I built, and found the iFi works really well with the ACAs. Of course, this is in my study which is a fairly small room. I now use a Marantz SA-8005 as both an SACD player and a DAC (will do DoP DSD), with an old but well maintained Kenwood L-07II preamp. That combination also works very well in my study. In addition, I have a Nottingham turntable with a Rega RB303 tonearm and Ortofon 2M Black cartridge as a source in that system. I have yet to consider putting it in my main system, where my 94db MTM speakers (Scan Speak 7" carbon fiber drivers with Raven R2 tweeters) could probably make them sing.
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The speakers in the system with the iFi DAC only have an efficiency of 85dB. However, they are in my office, flank my computer monitor and are only 3ft from my ears. Additionally, music played on this system is intended to be soft background music while I work. Which means they only draw a fraction of a watt.
The ACA's actually have to work a lot harder where they are at right now even though the speakers are 10dB more efficient than the ones in my office.
I may get a wild hair and move the 85dB speakers from my office upstairs to the bigger system in the larger room just to see what they sound like with the ACA's.
Mike
If in your main system you are positioned ~ 10 ft away (for example) from your speakers that are 95 dB efficient, then 1 watt of power will give you roughly 85 dB SPL peaks. And at 10 watts you'll get 95 dB peaks. 6 watts is probably around 91dB peaks.
And that's just 1 speaker.
Food for thought.
But I can't wait to hear what you think of the ACA with your 85dB efficient speakers.
Efficiency is a beautiful thing
Best,
Anand.
I'm using a pair of 6 ohm 86db/w/m old school 3-way wharfdales. With a 2v output from a DAC I get more than enough volume. A little less from a phono stage with a high output MC, but its acceptable.
Will probably kill me with the 110db horn system they'll be driving before long
Given their use in the desk system, you're right, they're not working very hard. While I think tonality will be fine if you move the 85db speakers to the main system running ACAs, my guess is that dynamic range and transients are going to suffer mightily. Who knows, though, it might still be engaging.