you know, with my concoctions I'm able to hear even 5secs of 'Hoff and/or Kleiderman, without need to shoot speakers dead
not exactly that sole FM radio station or web radio I'm listening are putting me in that!! danger, ever
not exactly that sole FM radio station or web radio I'm listening are putting me in that!! danger, ever
An Iron Emerald?
With some encouragement, I decided to try running a pair of RJM Emerald phono stages off of the regulated rails of my Iron Pre, powered by a single 25VA transformer, and all in the same chassis. I had to puzzle awhile over the grounding scheme for the Emerald, which does have separate circuit and chassis/earth grounds. I decided there shouldn't be much harm making circuit ground common between the Emerald and the Iron Pre. I'm not yet sure that's 100% correct but troubleshooting any hum that shows up will be another day's problem.
First thing was to power up the Iron Pre alone with no additional loading. It was no problem to dial in +/- 15V and to zero out the offset across the RCA out; there was natively like only 13 or 14mV of offset as built before twiddling- testament to extremely well matched JFETs I believe (tnx to Papa). I played a bit of music this way for a couple hours in the garage through and ACA and it sounded very very good.
Next I test-wired in the Emerald boards to the Iron Pre rails, sans op-amps and with a temporary power switch on both rails, to see what would happen. Switching on the Emerald dropped the rails of the Iron Pre symmetrically by around 100mV to +/-14.9V, with no noticeable change in the sound. The Emerald's internal rails are spec'd to be a symmetrical +/-12-13V with pot adjustment for symmetry; the rails on one channel hit +/-12.25V, the other hit +/-11.56V. Not sure if this is due to Vbe differences in the shunt regs between channels, or some minor incompetence on my part, but for now I called it good and plugged in the op-amps. I have to go back and review RJM's help desk thread on this issue. The rail voltages if anything went up a bit with the op-amps in place.
Anyway, I think this is going to work! I'm still waiting on the fuse block and fuse for the Scherter power-conditioner thing, and I need to wire up the power and grounding permanently before moving it to main for phono stage listening, but this is encouraging. Deciding whether to bump the Iron Pre's rails to 15V and leave the Emerald boards permanently powered regardless of the source in use, or to make power to the Emerald switchable.
With some encouragement, I decided to try running a pair of RJM Emerald phono stages off of the regulated rails of my Iron Pre, powered by a single 25VA transformer, and all in the same chassis. I had to puzzle awhile over the grounding scheme for the Emerald, which does have separate circuit and chassis/earth grounds. I decided there shouldn't be much harm making circuit ground common between the Emerald and the Iron Pre. I'm not yet sure that's 100% correct but troubleshooting any hum that shows up will be another day's problem.
First thing was to power up the Iron Pre alone with no additional loading. It was no problem to dial in +/- 15V and to zero out the offset across the RCA out; there was natively like only 13 or 14mV of offset as built before twiddling- testament to extremely well matched JFETs I believe (tnx to Papa). I played a bit of music this way for a couple hours in the garage through and ACA and it sounded very very good.
Next I test-wired in the Emerald boards to the Iron Pre rails, sans op-amps and with a temporary power switch on both rails, to see what would happen. Switching on the Emerald dropped the rails of the Iron Pre symmetrically by around 100mV to +/-14.9V, with no noticeable change in the sound. The Emerald's internal rails are spec'd to be a symmetrical +/-12-13V with pot adjustment for symmetry; the rails on one channel hit +/-12.25V, the other hit +/-11.56V. Not sure if this is due to Vbe differences in the shunt regs between channels, or some minor incompetence on my part, but for now I called it good and plugged in the op-amps. I have to go back and review RJM's help desk thread on this issue. The rail voltages if anything went up a bit with the op-amps in place.
Anyway, I think this is going to work! I'm still waiting on the fuse block and fuse for the Scherter power-conditioner thing, and I need to wire up the power and grounding permanently before moving it to main for phono stage listening, but this is encouraging. Deciding whether to bump the Iron Pre's rails to 15V and leave the Emerald boards permanently powered regardless of the source in use, or to make power to the Emerald switchable.
Attachments
...and silly me just trying to win a range war! I am. Could I steal this? I promise I'll wear hearing protectors!
An Iron Emerald!
It was immediately evident this thing plays records good and clean. Vocals are easy to discern, with a touch of sibilance to them and to cymbal strikes without getting obnoxiously breathy or hissy. I did some A-B'ing of the Iron Pre as a preamp alone against the B1 with a digital streaming source, and the Iron Pre is a bit fuller in the midrange, on top of the treble touches noticed playing records. Bass is a touch lacking compared to memory of a tube preamp (Schiit Freya Noval), but I think I'm okay with that. We'll see how this thing breaks in.
I'm using minimal grounding- no power toroid shield or can, just a single mount point on the bottom aluminum panel that goes directly to earth ground, with circuit ground on the Iron Pre and Emeralds passing through a thermistor on their way there. The boards are all mounted with nylon risers. There is a tiny bit of hiss on the non-phono inputs only if I crank the volume all the way and hold my ear to the drivers; this hiss changes tone and gets a tiny bit louder when the phono stage is selected as input. I'm totally fine with this. I may at some point try powering the Emerald separately to see if dynamic range improves, but probably not for a while.
I'm also not using a front panel power switch; the one on the power inlet filter is sufficient. Instead a put a blue LED in the hole which is powered directly off of the power toroid's secondaries. It's too bright with a 22k resistor and probably blinking 60 times a second, lol. We'll see how long it lasts.
Thanks so much Zen Mod for the gift of this design, and everyone at the diyAudio store who helped make this project possible. It was fun to build and sounds great too!
It was immediately evident this thing plays records good and clean. Vocals are easy to discern, with a touch of sibilance to them and to cymbal strikes without getting obnoxiously breathy or hissy. I did some A-B'ing of the Iron Pre as a preamp alone against the B1 with a digital streaming source, and the Iron Pre is a bit fuller in the midrange, on top of the treble touches noticed playing records. Bass is a touch lacking compared to memory of a tube preamp (Schiit Freya Noval), but I think I'm okay with that. We'll see how this thing breaks in.
I'm using minimal grounding- no power toroid shield or can, just a single mount point on the bottom aluminum panel that goes directly to earth ground, with circuit ground on the Iron Pre and Emeralds passing through a thermistor on their way there. The boards are all mounted with nylon risers. There is a tiny bit of hiss on the non-phono inputs only if I crank the volume all the way and hold my ear to the drivers; this hiss changes tone and gets a tiny bit louder when the phono stage is selected as input. I'm totally fine with this. I may at some point try powering the Emerald separately to see if dynamic range improves, but probably not for a while.
I'm also not using a front panel power switch; the one on the power inlet filter is sufficient. Instead a put a blue LED in the hole which is powered directly off of the power toroid's secondaries. It's too bright with a 22k resistor and probably blinking 60 times a second, lol. We'll see how long it lasts.
Thanks so much Zen Mod for the gift of this design, and everyone at the diyAudio store who helped make this project possible. It was fun to build and sounds great too!
Attachments
tidy your wiring and you'l have zero hiss
resistive attenuator is enough of evil per se, it's only logical to place it near back side, with extending shaft to front
though, not so easy when one wants everything in one case ........
resistive attenuator is enough of evil per se, it's only logical to place it near back side, with extending shaft to front
though, not so easy when one wants everything in one case ........
there is not such thing as too much Iron in signal chain
as long each of them (irons) is doing necessary work
as long each of them (irons) is doing necessary work
Yes, you got it, that's how my system is currently set up. A buffered Cinemag CMOQ-4LPC set up for 6db gain feeding a buffered Edcor 600:15k (1:5). I'm hearing less no-signal buzz, ringing, and bass attenuation with this setup than I hear using a passive preamp with a 1:8 turns ratio, based on the Electra-Print PVA-2n, for what that's worth.
thinking of impedances, all wrong
resistive attenuator combined with autoformer, buffer nowhere in sight .......
I love this thread and this preamp.. as an OG Iron Pre pre-tester—an entirely subjective SQ observation to stir the mind—F5+Iron Pre is super awesome, plenty of F5 clarity and low end... I much preferred that combo to say M2X+Iron Pre (gasp)....Totally possible that the limits of my understanding do not qualify ZM's mighty statement:
I'm sure I'll be educated.
I also tried both gain settings in Iron Pre and preferred 6db for what seemed to me an edge on clarity....surely system and source and taste dependent.
😛there is not such thing as too much Iron in signal chain
as long each of them (irons) is doing necessary work
I'm sure I'll be educated.
I also tried both gain settings in Iron Pre and preferred 6db for what seemed to me an edge on clarity....surely system and source and taste dependent.
trust in your own ears and brain
especially when combining things in reproduction system - final result counts and it is valued only by your own preferences
remember Papa's lectures - half of ppl are preferring dominant 2nd, other half preferring 3rd dominant
then each group again halved by preference - positive phase dominant vs. negative phase dominant
especially when combining things in reproduction system - final result counts and it is valued only by your own preferences
remember Papa's lectures - half of ppl are preferring dominant 2nd, other half preferring 3rd dominant
then each group again halved by preference - positive phase dominant vs. negative phase dominant
It just means it is a doomed design 
Or at least a design insanely dependant on source output impedance and amp input impedance, and also cables. Things that matter much less with a buffer. Then of course there is MZM’s allergy towards inhibiting signal energy with a resistive attenuator, making it doubly crap going passive.
Or at least a design insanely dependant on source output impedance and amp input impedance, and also cables. Things that matter much less with a buffer. Then of course there is MZM’s allergy towards inhibiting signal energy with a resistive attenuator, making it doubly crap going passive.
Oh, yeah I did those calculations a while ago. With a 10k pot at max volume and a 10k amp load (say an ACA), the impedance reflected back to the source across the PVA-2n's is 78 ohms 😱. Even with a 25k pot it doesn't get much better, a load of 111 ohms. Believe me I have some sources that absolutely barf when hooked up to that thing.
it is not a problem with/for source, primarily
it is a problem of pot itself being a source for autoformer, that part of the story being much more desperate
say that you have 10K pot
worst case is when said pot is at 50% of impedance/attenuation, presenting source of (5K parallel to 5K)=2K5
now, xformer (or autoformer, irrelevant) having voltage ratio of 1:8 is transforming impedance in 1:8^2
which means - even if you have 100K for amp Rin, it is transformed backward through xformer as 100K/64
meaning - your pot is presenting source with 2K5 Rout, seeing load of 1563 Ohms
whoever designed that thingie and sold it as either idea or product didn't know a squat, practically being on ZM's yesterday level of stupidity
now, I did learn something in last 24hrs ..... mostly fact that with 25K pot situation is even more hysterical
25K pot - worst case presenting source with Rout of 6K25
ACA 10K ......... fed backwards as 10K/64
meaning source of 6K25 Rout choked with 156R
anyhow, whatever value of pot is, that is going to sound somehow only if fed with small amplifier, volpot cranked to max
now, I'm going to eat my own liver all night long, why I'm incapable to those levels of selling Audiophoolery, perfect way to obtain wealth and good life
it is a problem of pot itself being a source for autoformer, that part of the story being much more desperate
say that you have 10K pot
worst case is when said pot is at 50% of impedance/attenuation, presenting source of (5K parallel to 5K)=2K5
now, xformer (or autoformer, irrelevant) having voltage ratio of 1:8 is transforming impedance in 1:8^2
which means - even if you have 100K for amp Rin, it is transformed backward through xformer as 100K/64
meaning - your pot is presenting source with 2K5 Rout, seeing load of 1563 Ohms
whoever designed that thingie and sold it as either idea or product didn't know a squat, practically being on ZM's yesterday level of stupidity
now, I did learn something in last 24hrs ..... mostly fact that with 25K pot situation is even more hysterical
25K pot - worst case presenting source with Rout of 6K25
ACA 10K ......... fed backwards as 10K/64
meaning source of 6K25 Rout choked with 156R
anyhow, whatever value of pot is, that is going to sound somehow only if fed with small amplifier, volpot cranked to max
now, I'm going to eat my own liver all night long, why I'm incapable to those levels of selling Audiophoolery, perfect way to obtain wealth and good life
math is simple, not much better, level of incompetence just notch lower
it calls for gutsy source and again there is no dynamics reaching power amp
it calls for gutsy source and again there is no dynamics reaching power amp