well, there is a possibility, real, that your reference is already on high level
if you had proper impedances in system ( low Rout of sources, highish Rin of amp) and adequately lowish attenuator impedance ("passive pre"), with not so long and benign cables ......... then you're already in good place
nobody can say that you must like flavor which autoformer is bringing to game
anyhow, give it day-2-3, and then draw conclusions
just in case, pic or two could be informative
btw. when I was writing about differences between various attenuator arrangements - differences in sound quality are small, when things done properly, at least when speaking of normal voltage levels
so, splittin' da hair, as I said
if you had proper impedances in system ( low Rout of sources, highish Rin of amp) and adequately lowish attenuator impedance ("passive pre"), with not so long and benign cables ......... then you're already in good place
nobody can say that you must like flavor which autoformer is bringing to game
anyhow, give it day-2-3, and then draw conclusions
just in case, pic or two could be informative
btw. when I was writing about differences between various attenuator arrangements - differences in sound quality are small, when things done properly, at least when speaking of normal voltage levels
so, splittin' da hair, as I said
^ Also, some basic, but crude and quick math led me to a system gain of about 40X (20 from amp and 2 from IP) into a likely minimum sensitivity for speakers of ~91dB / 2.83V using a modern source.
So... lotsa lotsa lotsa attenuation.
I find almost any solution attenuating that much lacking some detail at low listening levels .... even the mighty turtle, which is the best I've personally used. My Pumpkin is set to 0dB gain even with a 10X gain amplifier in most situations. My exception is the rare situation of an old tape deck source with really low sensitivity speakers and the F4s or when I really want to invite the neighbors over to party without calling.
Edited to add - Tonight may be just the night... hmmmmm... and to fix dodo doubling of already doubled gain... 🙂
So... lotsa lotsa lotsa attenuation.
I find almost any solution attenuating that much lacking some detail at low listening levels .... even the mighty turtle, which is the best I've personally used. My Pumpkin is set to 0dB gain even with a 10X gain amplifier in most situations. My exception is the rare situation of an old tape deck source with really low sensitivity speakers and the F4s or when I really want to invite the neighbors over to party without calling.
Edited to add - Tonight may be just the night... hmmmmm... and to fix dodo doubling of already doubled gain... 🙂
Pics as promised. All I/O:s soldered. SQ has not changed. Will have to listen more still.
Wishing everyone a Happy New Year 2025! 🙂
Wishing everyone a Happy New Year 2025! 🙂
Can't see anything wrong, except some nitpicky - input signal wires too thick for my liking, but not a game changer
anyhow, as I wrote :
anyhow, as I wrote :
I didn’t have much time over the holidays to work on my IP, but I am back at it now. I just wired the Goldpoint step attenuator and now I am second guessing my wiring. I followed the wiring in Patrick’s post #3783 below. Then after I soldered it all in, I searched to see how others have wired the SE outputs to the Bal outputs and came across ZM’s post #3673 which says In goes to the Wiper. Which post works with the Goldpoint?
CCW on board goes to EARTH on POT
Wiper on board goes to Out on POT
CW on board goes to In on POT
Thanks,
Glen
CCW on board goes to EARTH on POT
Wiper on board goes to Out on POT
CW on board goes to In on POT
Thanks,
Glen
I am on step 3 of the Quick and Dirty Startup Process and I am happy to report another Iron Pre is singing happy tunes!
Startup was quick and easy, with all of the adjustments turning right into place. I didn’t experience drift with any of the settings - very gratifying.
Following are my notes and impressions so far. I hope my insights are inline with other’s who have completed their builds, and useful to anyone contemplating this build. Overall, this build is not complicated. There are a lot of closely placed parts, so solid soldering skills are a must.
System Setup and Listening Impressions
I have the Iron Pre (IP) going into my XA252 mono blocks (I tried Bal and SE inputs), and I also listened with my SissySIT mono blocks, which are SE-only. Both amps were attached (at different times, of course) to a pair of Troels Gravesen designed SBA-761s I built. Digital source is an Odroid C2 based streamer (running Volumio) into a Denafrips Ares II DAC with balanced connections into the IP. Analog source is a Schiit Sol/AT VM540ML into a Pete Millet LR phono pre with RCA connections into the IP.
Starting with the digital side of my setup using the balanced input and Bal output to the XA252s, the Ares II had no problem with the Goldpoint V24-4-10k step attenuator I chose for the level control on the IP. High volume settings are loud. Louder than I would ever need them to be in my room. Going SE into the XA252s, the volume knob spent more time in the 11:00 to 2:00 position at normal listening volumes in my room. Further to the full clockwise position, volume was loud to uncomfortable. SE into the SissySIT required a bit more of a clockwise advancement to between 12:00 and 3:00 at normal levels in my room. I could easily go “full throttle” on the volume knob comfortably without it being “loud”.
My analog equipment also had no problem with the 10k Goldpoint. Gain is more than adequate with the Bal output to the XA252s. The volume knob with the SE output to either amp needed a lot more twist to the right. The SissySIT in particular needed to be between 3:00 to 4:00 for a “normal” listening experience in my room, with the “full throttle” position being at the top end of ”normal” volume levels in my room. I have a Salas UltraFSP phono pre I need to try as it might be a better match overall with the IP.
At any volume and with either output to either amplifier, the IP provides a spacious sound stage, articulate presentation, and an inky black, noise-free background - quiet passages are quiet, crescendos impress as they should, and the preamp gets out of the way of the music. Functionally, I used the rotary switch which works well. I especially appreciate the first “muted input” position provided. I have been using that position to “park” the preamp before I turn it on or off.
Thanks ZM for another great piece of stereo gear. And my thanks to Patrick and everyone else who made this project possible.
Startup was quick and easy, with all of the adjustments turning right into place. I didn’t experience drift with any of the settings - very gratifying.
Following are my notes and impressions so far. I hope my insights are inline with other’s who have completed their builds, and useful to anyone contemplating this build. Overall, this build is not complicated. There are a lot of closely placed parts, so solid soldering skills are a must.
System Setup and Listening Impressions
I have the Iron Pre (IP) going into my XA252 mono blocks (I tried Bal and SE inputs), and I also listened with my SissySIT mono blocks, which are SE-only. Both amps were attached (at different times, of course) to a pair of Troels Gravesen designed SBA-761s I built. Digital source is an Odroid C2 based streamer (running Volumio) into a Denafrips Ares II DAC with balanced connections into the IP. Analog source is a Schiit Sol/AT VM540ML into a Pete Millet LR phono pre with RCA connections into the IP.
Starting with the digital side of my setup using the balanced input and Bal output to the XA252s, the Ares II had no problem with the Goldpoint V24-4-10k step attenuator I chose for the level control on the IP. High volume settings are loud. Louder than I would ever need them to be in my room. Going SE into the XA252s, the volume knob spent more time in the 11:00 to 2:00 position at normal listening volumes in my room. Further to the full clockwise position, volume was loud to uncomfortable. SE into the SissySIT required a bit more of a clockwise advancement to between 12:00 and 3:00 at normal levels in my room. I could easily go “full throttle” on the volume knob comfortably without it being “loud”.
My analog equipment also had no problem with the 10k Goldpoint. Gain is more than adequate with the Bal output to the XA252s. The volume knob with the SE output to either amp needed a lot more twist to the right. The SissySIT in particular needed to be between 3:00 to 4:00 for a “normal” listening experience in my room, with the “full throttle” position being at the top end of ”normal” volume levels in my room. I have a Salas UltraFSP phono pre I need to try as it might be a better match overall with the IP.
At any volume and with either output to either amplifier, the IP provides a spacious sound stage, articulate presentation, and an inky black, noise-free background - quiet passages are quiet, crescendos impress as they should, and the preamp gets out of the way of the music. Functionally, I used the rotary switch which works well. I especially appreciate the first “muted input” position provided. I have been using that position to “park” the preamp before I turn it on or off.
Thanks ZM for another great piece of stereo gear. And my thanks to Patrick and everyone else who made this project possible.
Attachments
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I’d like to have a full parts list, I know folks have all done them different. If someone could give me a full parts list including all connectors , I can’t remember the name of the place in the us I used to buy the toroidal transformer. Antec maybe. Any help would be greatly appreciated.
thank you
I am doing single ended
thank you
I am doing single ended
See Post #1. If there's anything you can't find from there, let us know, but it should all be there (or links to it).
that bridge/whatever block in between two channel pcbs is redundant
you have 8-10mm Dia 10R NTC on each channel, with reason
I installed the NTCs supplied onto the boards. I added the ground lift as a measure of protection against live mains hitting the chassis in whatever freak accident might cause that to happen. I have a stack of those boards, so I’m using them.
Troubleshooting question for you folks. I am having trouble with my balanced iron pre I finished building a week or two ago. I took advantage of the ZM's suggestion to use Edcor 600:15K at the output for a high gain and low gain output. With the high gain output hooked up to my power amp, the volume pots work and while there is bleed through between all inputs, when the correct input is selected it is far louder.
My problem is the low gain (without the Edcor) output. Using that, when i turn the volume pots there is no impact on volume and sound output is the same regardless of which input is selected. Any idea what might be going on here?
My problem is the low gain (without the Edcor) output. Using that, when i turn the volume pots there is no impact on volume and sound output is the same regardless of which input is selected. Any idea what might be going on here?
How, exactly, is this wired…? 
I've got an Iron Pre 2021 SE too on the kitchen tab.. ehm.. on the bench, fingers crossed 🤞
Probably not critical but I will be using an external circuit to handle the input relais.. what is actually the voltage output of M3 transistor for 12v relais?
Probably not critical but I will be using an external circuit to handle the input relais.. what is actually the voltage output of M3 transistor for 12v relais?
