I have been driving Apogee Stages (4 ohms or less) for some time on classical music. The 50 watts is a bit marginal when it gets really loud.
ray
ray
Thank you very much for replying so quickly. 🙂
So it's safe to run 4 ohm speakers with this amp in a normal hifi configuration. That's good news.
So it's safe to run 4 ohm speakers with this amp in a normal hifi configuration. That's good news.
My golly, Ratbagp, the Apogees get down to 1.8R, IIRC. I wouldn't have expected a single pair of lateral FETS would driving these very difficult loudspeakers, but, hey, the FetZilla seems to be OK!! Maybe this is a welterweight prizefighter, huh?
Thanks for the leap of faith, and for passing the revelation to us.....
Cheers,
Hugh
Thanks for the leap of faith, and for passing the revelation to us.....
Cheers,
Hugh
As I seem to remember, the larger Apogee models were the ones that got down that low in impedance. The Stages are reasonably flat in the 3 - 4 ohm range with a rise about 500hz due to the crossover. The curves can be seen in this reprint of the old Stereophile review (see figures 5 & 6).
Stage Stereophile review
It still is impressive that it works. Remember most of the time I play classical music and not to earsplitting volumes.
ray
Stage Stereophile review
It still is impressive that it works. Remember most of the time I play classical music and not to earsplitting volumes.
ray
I am driving 6 ohm speakers and they can get as low as 3 ohm at some frequencies. No problems here. It has been one year since I built this amp and I really like it.
George
George
Before I connect speakers...
Hello All,
I am almost there... I have done biasing etc. as described in the building guide. One channel dials into 37 mV just fine. The other gets to 38.1 mV and then I run out of travel on the potentiometer. On both channels, everything else adjusted as prescribed.
a. Is there a need to be concerned about the 38 mV channel?
b. I neglected (forgot) to ground the inputs when I set the bias. Should I go back and redo it?
Can't wait to get this baby going and see what it sounds like. I will post some pictures if there is any interest. I've put this in the new DIYAudio 4U chassis.
Thanks!
Ryan
Hello All,
I am almost there... I have done biasing etc. as described in the building guide. One channel dials into 37 mV just fine. The other gets to 38.1 mV and then I run out of travel on the potentiometer. On both channels, everything else adjusted as prescribed.
a. Is there a need to be concerned about the 38 mV channel?
b. I neglected (forgot) to ground the inputs when I set the bias. Should I go back and redo it?
Can't wait to get this baby going and see what it sounds like. I will post some pictures if there is any interest. I've put this in the new DIYAudio 4U chassis.
Thanks!
Ryan
Thanks Guys for the replies.
I will button it up and have a go ASAP. I have a little bit of tidying up to do with wiring and the chassis assembly.
More to come ...
Cheers,
Ryan
I will button it up and have a go ASAP. I have a little bit of tidying up to do with wiring and the chassis assembly.
More to come ...
Cheers,
Ryan
Hi Ryan,
37mV, 38mV, not a problem!
Being unable to set it higher is just fine. That is a design limit to prevent excessive quiescent at switch on. Never much of a problem of latfets, but a high issue with mosfets, and dangerous, explosive settings for bipolar output stages.
We look forward to your listening test!
Cheers,
Hugh
37mV, 38mV, not a problem!
Being unable to set it higher is just fine. That is a design limit to prevent excessive quiescent at switch on. Never much of a problem of latfets, but a high issue with mosfets, and dangerous, explosive settings for bipolar output stages.
We look forward to your listening test!
Cheers,
Hugh
It lives !!
Just a quick update. Where to begin? How about the eye candy first:
Here is my version residing in the DIYAudio Standard 4U Chassis. 2 Antek 25 x 2 @ 400VA transformers. I was too anxious to get it going to bother with any fancy lights on that gorgeous front panel. On-off switch resides on the IEC inlet on back.
Post 1 of 2 or so ....
Just a quick update. Where to begin? How about the eye candy first:
Here is my version residing in the DIYAudio Standard 4U Chassis. 2 Antek 25 x 2 @ 400VA transformers. I was too anxious to get it going to bother with any fancy lights on that gorgeous front panel. On-off switch resides on the IEC inlet on back.
Post 1 of 2 or so ....
Attachments
Continued ...
Dang, just lost my post due to a touchy mouse.
When I put everything in the chassis, I rechecked the bias and offset. Now both sitting nicely at 37 (and change) mV. I had to re-zero the offset a bit. I'm running 1uF Mundorf MKP in the input spot. The recommended Auricaps were out of stock when I was collecting parts.
Current set up:
SB Touch serving flac -> CA Dac Magic -> DCB1 (Mesmerize) -> Fetzilla -> MJK Open Baffles (~93 dB/watt efficient)
Initial impressions ...
A wee bit of turn on thump. Background noise is black as night. I couldn't hear a thing. Playing Krauss/Plant at very low levels (the family is in bed). Sound stage is noticeably better than the amp it replaced (for this set up). Detail is extraordinary. Did I say the detail is extraordinary?
I don't write/haven't written much about listening impressions on any of my diy Amps. I lack the words and experience. I'm not here to pit one of my projects against another. My basic 'call' is do I like it or not. I really like what I hear in the Fetzilla. Definitely a keeper😀
This was really a fun build. For me, it's the journey, not just the destination The board layout is great. The parts count is relatively low. Construction was quick. Dialing in the bias etc. was a snap. The availability of the awesome diyAudio chassis was fortuitous timing. I really like it when a plan comes together.
I cannot wait to put the amp through its paces when I can turn it up a bit and listen with more intention. But... after all of 25 minutes powered up, it is great. Really great.
Cheers to Hugh for making the boards available and the support of this thread! As I wrap this up... currently playing Anne Akiko Meyer's Air, (violin conerto) just lovely. 🙂
Ryan
Dang, just lost my post due to a touchy mouse.
When I put everything in the chassis, I rechecked the bias and offset. Now both sitting nicely at 37 (and change) mV. I had to re-zero the offset a bit. I'm running 1uF Mundorf MKP in the input spot. The recommended Auricaps were out of stock when I was collecting parts.
Current set up:
SB Touch serving flac -> CA Dac Magic -> DCB1 (Mesmerize) -> Fetzilla -> MJK Open Baffles (~93 dB/watt efficient)
Initial impressions ...
A wee bit of turn on thump. Background noise is black as night. I couldn't hear a thing. Playing Krauss/Plant at very low levels (the family is in bed). Sound stage is noticeably better than the amp it replaced (for this set up). Detail is extraordinary. Did I say the detail is extraordinary?
I don't write/haven't written much about listening impressions on any of my diy Amps. I lack the words and experience. I'm not here to pit one of my projects against another. My basic 'call' is do I like it or not. I really like what I hear in the Fetzilla. Definitely a keeper😀
This was really a fun build. For me, it's the journey, not just the destination The board layout is great. The parts count is relatively low. Construction was quick. Dialing in the bias etc. was a snap. The availability of the awesome diyAudio chassis was fortuitous timing. I really like it when a plan comes together.
I cannot wait to put the amp through its paces when I can turn it up a bit and listen with more intention. But... after all of 25 minutes powered up, it is great. Really great.
Cheers to Hugh for making the boards available and the support of this thread!
As I wrap this up... currently playing Anne Akiko Meyer's Air, (violin conerto) just lovely. 🙂Ryan
Hi Ryan,
You know, since my daughter is living in NYC, when I get well I'm hoping to go to the US again. I would like to visit you in CO, I love that state passionately.
Your build is wonderful, very elegantly and carefully assembled. No wonder it makes no noise! I'm delighted it sounds good, Kudos to Greg, Mike, and Paul - and yeah, I liked the pcb layout too!
Cheers,
Hugh
You know, since my daughter is living in NYC, when I get well I'm hoping to go to the US again. I would like to visit you in CO, I love that state passionately.
Your build is wonderful, very elegantly and carefully assembled. No wonder it makes no noise! I'm delighted it sounds good, Kudos to Greg, Mike, and Paul - and yeah, I liked the pcb layout too!
Cheers,
Hugh
Speedy recovery
Hugh et al.,
Thank you all for the compliments on the build. I neglected to thank the others: Greg, Mike, and Paul. Well done fellows. After I signed off last night, I continued to listen for another hour. The amp continued to surprise me and I caught myself smiling, even giggling out loud. It is really that good.
Hugh, I wish you a speedy recovery and will welcome you to Colorado when you are able. We have a lot to show you and plenty of local brew that is well worth tasting if you are inclined and able.
Too bad I have to go to work today ... I can think of another, far better way to spend my day. 🙂
Cheers,
Ryan
Hugh et al.,
Thank you all for the compliments on the build. I neglected to thank the others: Greg, Mike, and Paul. Well done fellows. After I signed off last night, I continued to listen for another hour. The amp continued to surprise me and I caught myself smiling, even giggling out loud. It is really that good.
Hugh, I wish you a speedy recovery and will welcome you to Colorado when you are able. We have a lot to show you and plenty of local brew that is well worth tasting if you are inclined and able.
Too bad I have to go to work today ... I can think of another, far better way to spend my day. 🙂
Cheers,
Ryan
Hello Hugh
If you go to NYC one day, I could try to meet you there if it's possible for me.
Bye
Gaetan
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