I have done that aswell in the past to test with.Hi guys
My_Ref rev C, arrived last week and spent all weekend puting it together.
Boy,... the sound is amazing (CD meridian 506-20, Loudspeakers Sonus Faber).
My Wife says it,s the best sounding amp I own or owned, and I own a Jadis DA60 (Tubed Gear) and a pair of QUAD . Treble is very soft indeed althoug very present.
Transformer is a 250 VA toroid with 2x22v ac.
Thanks Russ and Brian for the good work. (Even a newbie can put it together with such a labeling).
Tanks Mauro for your idea, patience and knowlege... ( you made a lot of DIYselfers happy)
Jose Maria Martins
My_Ref rev C, arrived last week and spent all weekend puting it together.
Boy,... the sound is amazing (CD meridian 506-20, Loudspeakers Sonus Faber).
My Wife says it,s the best sounding amp I own or owned, and I own a Jadis DA60 (Tubed Gear) and a pair of QUAD . Treble is very soft indeed althoug very present.
Transformer is a 250 VA toroid with 2x22v ac.
Thanks Russ and Brian for the good work. (Even a newbie can put it together with such a labeling).
Tanks Mauro for your idea, patience and knowlege... ( you made a lot of DIYselfers happy)
Jose Maria Martins
Re: How did it do?
Well it was very informative to test this amp in another excellent system.
First of all the owner and designer of audiopax, Eduardo da Lima, who has spent the better part of his lifetime building and listening to amps had some nice things to say.
He liked it and said that there was very little of the solid state signature he usually hears on most good equipment.
In comparison to his stereo 88 amp it was a bit of an apples and oranges thing.The tube amp was really sweet and had a wonderful midrange and did not draw attention to any part of the freq range although some would find the top end too low key.The myref was much more upfront in soundstage and emphasized the upper mids.
This was something that I found slightly uncomfortable even at home and it was obvious in the audiopax system quite clearly.
The surprise of the evening , for me at least, was the new <budget> amp Eduardo recently designed with 6sn7 input stage and mosfet output stage without feedback.To me it sounded the best of the bunch as if the best of the two previous amps had been rolled into one.
So the next day I decided to tweak the myref a little bit to see whether I could cure what I perceive as a kind of peakiness in the upper mids.Trumpets would be a bit unforgiving and cymbals sounded as if they were being struck by a metal stick instead of a wooden one.
I substituted some fred diodes MUR860 for the bridges on one channel and proceeded to make some ab testing between channels.This went very well in the direction I was seeking so I fixed up the other channel as well.
Conclusion: the peakiness and slight splashiness in the treble disappeared completely to be replaced by a very natural sounding upper freq extension and slightly better soundstaging.This reminded me very much of the audiopax amps not to mention my 300b set.
To me at least it made a critical difference .Even though I have used freds before I had not expected that changing the rectifiers only was going to impact the sound so fundamentally.It really sounded like another amp.
Panelhead said:
Well it was very informative to test this amp in another excellent system.
First of all the owner and designer of audiopax, Eduardo da Lima, who has spent the better part of his lifetime building and listening to amps had some nice things to say.
He liked it and said that there was very little of the solid state signature he usually hears on most good equipment.
In comparison to his stereo 88 amp it was a bit of an apples and oranges thing.The tube amp was really sweet and had a wonderful midrange and did not draw attention to any part of the freq range although some would find the top end too low key.The myref was much more upfront in soundstage and emphasized the upper mids.
This was something that I found slightly uncomfortable even at home and it was obvious in the audiopax system quite clearly.
The surprise of the evening , for me at least, was the new <budget> amp Eduardo recently designed with 6sn7 input stage and mosfet output stage without feedback.To me it sounded the best of the bunch as if the best of the two previous amps had been rolled into one.
So the next day I decided to tweak the myref a little bit to see whether I could cure what I perceive as a kind of peakiness in the upper mids.Trumpets would be a bit unforgiving and cymbals sounded as if they were being struck by a metal stick instead of a wooden one.
I substituted some fred diodes MUR860 for the bridges on one channel and proceeded to make some ab testing between channels.This went very well in the direction I was seeking so I fixed up the other channel as well.
Conclusion: the peakiness and slight splashiness in the treble disappeared completely to be replaced by a very natural sounding upper freq extension and slightly better soundstaging.This reminded me very much of the audiopax amps not to mention my 300b set.
To me at least it made a critical difference .Even though I have used freds before I had not expected that changing the rectifiers only was going to impact the sound so fundamentally.It really sounded like another amp.
Cool idea, think I'm going to bend the pins on my old PSU's bridges to make it fit the kits, as I liked what came out of that amp more, ok, only a teeny little bit. ok?
Then maybe give those diodes of yours a shot...
unfortunatly I got some nasty ceramic 1ufd input capacitors and some 24 year old foil 220pf caps.. so it could symply be those coponents holding me back, will get nicer ones after Monday.
Then maybe give those diodes of yours a shot...
unfortunatly I got some nasty ceramic 1ufd input capacitors and some 24 year old foil 220pf caps.. so it could symply be those coponents holding me back, will get nicer ones after Monday.
Hi Nordic
use the MKS 1uf caps that i supplied to you (i think it is a panasonic) on the input and use the 220pf ceramic supplied for the HF cut-off , not the best and you can replace that at a later stage. unless you have some polystyrene or multi layer ceramic caps for the 220pf
the MKS is a filler at this stage. and you really need to use a MKP cap there. a Wima is a safe cheap bet. but very difficult to get here in that size. i have access to larger ones.
if you aren't using a preamp but a passive then you can bypass the cap all together, there is no harm in that.
use the MKS 1uf caps that i supplied to you (i think it is a panasonic) on the input and use the 220pf ceramic supplied for the HF cut-off , not the best and you can replace that at a later stage. unless you have some polystyrene or multi layer ceramic caps for the 220pf
the MKS is a filler at this stage. and you really need to use a MKP cap there. a Wima is a safe cheap bet. but very difficult to get here in that size. i have access to larger ones.
if you aren't using a preamp but a passive then you can bypass the cap all together, there is no harm in that.
Russ / Mauro
Is there any way to "roll off" the low end of this amp using the components on board? Any slope and freq below 400Hz.
I will be ordering one to use on the top end of a bi-amped speaker and don't want to put another device in the signal chain.
The low end I don't mind, but the crucial top end I would like to keep as direct as possible.
Is there any way to "roll off" the low end of this amp using the components on board? Any slope and freq below 400Hz.
I will be ordering one to use on the top end of a bi-amped speaker and don't want to put another device in the signal chain.
The low end I don't mind, but the crucial top end I would like to keep as direct as possible.
I was hoping to "filter" the feedback or manipulate the opamp to invoke a HP function so as to not need another device in the chain...
Marchand makes some very good cross-overs if I "HAVE" to go that route, but I would prefer to try not to.
EDIT:
The 12 db unit in Mr Erath's feedback controller network does work, but again, I would prefer NOT to add it to the top end.
Marchand makes some very good cross-overs if I "HAVE" to go that route, but I would prefer to try not to.
EDIT:
The 12 db unit in Mr Erath's feedback controller network does work, but again, I would prefer NOT to add it to the top end.
rudi said:
You can still DC offset with a passive pre so you would need to check for zero DC volts. ( at full volume )
I have a transformer volume control and with this I can report that removing the i/p cap brought the o/p offset voltage down from 9mV average to 2mV average.
It also improved clarity...
... ....so I would agree that if you have to use a cap then it should be good quality.
mike
Low pass filter
Troy,
I see two easy ways to roll off the highs. Try a 0.22 ufd input cap. This will roll off the lowend in the area of a sub.
A better way is to replace the 220 ufd cap in the feedback loop with a 50 or 47 ufd. This should shelve off the bottom fine.
Try both ways and see which works better in your system.
George
Troy,
I see two easy ways to roll off the highs. Try a 0.22 ufd input cap. This will roll off the lowend in the area of a sub.
A better way is to replace the 220 ufd cap in the feedback loop with a 50 or 47 ufd. This should shelve off the bottom fine.
Try both ways and see which works better in your system.
George