Hi!
My 2 1/2 years older sister is getting married this summer, and since she always admired all my DIY audio gear, and her and her husband in spe's "hifi"-equipment is actually more like "lofi", I decided to build them an integrated amplifier as my wedding present.
After some considerations (P3A, P101 from ESP, Gainclones with various chips...) I decided upon using the LM4780-Kit from Audiosector, which is already lying assembled in front of me.
Now I have to build the pre-amp part, with tone control. For this I actually decided on ESP P97 with some small mods. And now I have to figure out what OP-amps to use.
I actually narrowed it down to BB OPA2134 or OPA 2604, but cannot decide which one of them to take.
Could you give some input about the pros and cons of those OPs, or maybe even convince me of some other device (and not in the price range of the OPA627). 5€ per double OP amp is my limit (they should be double OP-amps per design).
Any help is appreciated (should I send some wedding cake?) !
Oh, and btw, I think I will use the "standard" black ALPS pot for volume control, but it would put a great strain on my budget if I used black beauty on all the pots (bass, treble and balance), so I though about normal (alps) pots for those VRs, or would you greatly advice me against that?
And always keep in mind that her other stuff (source, speakers) is not of that great quality right now (maybe I will change that too someday).
Bye,
Arndt
My 2 1/2 years older sister is getting married this summer, and since she always admired all my DIY audio gear, and her and her husband in spe's "hifi"-equipment is actually more like "lofi", I decided to build them an integrated amplifier as my wedding present.
After some considerations (P3A, P101 from ESP, Gainclones with various chips...) I decided upon using the LM4780-Kit from Audiosector, which is already lying assembled in front of me.
Now I have to build the pre-amp part, with tone control. For this I actually decided on ESP P97 with some small mods. And now I have to figure out what OP-amps to use.
I actually narrowed it down to BB OPA2134 or OPA 2604, but cannot decide which one of them to take.
Could you give some input about the pros and cons of those OPs, or maybe even convince me of some other device (and not in the price range of the OPA627). 5€ per double OP amp is my limit (they should be double OP-amps per design).
Any help is appreciated (should I send some wedding cake?) !
Oh, and btw, I think I will use the "standard" black ALPS pot for volume control, but it would put a great strain on my budget if I used black beauty on all the pots (bass, treble and balance), so I though about normal (alps) pots for those VRs, or would you greatly advice me against that?
And always keep in mind that her other stuff (source, speakers) is not of that great quality right now (maybe I will change that too someday).
Bye,
Arndt
Hi,
I think I have spelt his name correctly. He was an electronics designer, maybe 50's & 60's that developed among other things a passive tone control that was virtually flat when set so and had gentle slopes into the filter band that got steeper as the controls were advanced. Instead of a steep cut with variable F3 point that closed in towards middle frequencies as the controls were advanced.
I think I have spelt his name correctly. He was an electronics designer, maybe 50's & 60's that developed among other things a passive tone control that was virtually flat when set so and had gentle slopes into the filter band that got steeper as the controls were advanced. Instead of a steep cut with variable F3 point that closed in towards middle frequencies as the controls were advanced.
Many people seems to like LM6172.
And look at this thread: http://www.diyaudio.com/forums/showthread.php?s=&threadid=46082&highlight=
And look at this thread: http://www.diyaudio.com/forums/showthread.php?s=&threadid=46082&highlight=
To be taken with a grain of salt, but generally a good description on how various OPAs sound:
http://www.sgheadphones.net/index.php?act=ST&f=12&t=2628
http://www.tangentsoft.net/audio/opamps.html
http://www.sgheadphones.net/index.php?act=ST&f=12&t=2628
http://www.tangentsoft.net/audio/opamps.html
Peter J Baxandall
http://www.duncanamps.com/technical/tonestack.html
http://www.duncanamps.com/technical/baxandall.html
http://ampage.org/htac/garvin.tone.html
http://cidtel.inictel.gob.pe/cidtel/contenido/Publicaciones/rvargas/JBPTCN.htm
http://www.bonavolta.ch/hobby/en/audio/tone.htm
http://sound.westhost.com/dwopa2.htm
http://sound.westhost.com/project97.htm
http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/audio/part8/Page2.html
That should get you started...
dave
AndrewT said:
http://www.duncanamps.com/technical/tonestack.html
http://www.duncanamps.com/technical/baxandall.html
http://ampage.org/htac/garvin.tone.html
http://cidtel.inictel.gob.pe/cidtel/contenido/Publicaciones/rvargas/JBPTCN.htm
http://www.bonavolta.ch/hobby/en/audio/tone.htm
http://sound.westhost.com/dwopa2.htm
http://sound.westhost.com/project97.htm
http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/audio/part8/Page2.html
That should get you started...
dave
Hi!
Thank you all for your input. Considering price range, I think I will stick to OPA 2134. OPA 2107 definitely is interesting as mell, but maybe as a later upgrade, since it costs about eight times as much as the 2134... Still better that OPA627.
Those AD devices I do not like because of a) their price tag and b) more often than not only available as SMD devices...
What I am pondering right now is whether to add some "real" capacitance to the amplifier (not only the 2* 1500 uF directly on the chip), like 2*10000 uF per channel.
I have never done this in a GC before, I think I will simply try it out (have some 10000 uF BHC SlitFoils lying around
)...
Another topic, does anyone have an adress where to get mono alps pots (the good quality kind) in Germany / Europe? Schuro and its likes only carry stereo versions...?
Bye,
Arndt
Thank you all for your input. Considering price range, I think I will stick to OPA 2134. OPA 2107 definitely is interesting as mell, but maybe as a later upgrade, since it costs about eight times as much as the 2134... Still better that OPA627.
Those AD devices I do not like because of a) their price tag and b) more often than not only available as SMD devices...
What I am pondering right now is whether to add some "real" capacitance to the amplifier (not only the 2* 1500 uF directly on the chip), like 2*10000 uF per channel.
I have never done this in a GC before, I think I will simply try it out (have some 10000 uF BHC SlitFoils lying around
)...Another topic, does anyone have an adress where to get mono alps pots (the good quality kind) in Germany / Europe? Schuro and its likes only carry stereo versions...?
Bye,
Arndt
Hi!
Well, here comes the price comparison between Farnell and Reichelt:
OP 249 at Farnell (401195): 6.25 €
OP 249 at Reichelt ( OP 249 GP ): 3.65
While I do use Farnell (Reichelt doesn't have such a variety of brands, and doesn't deliver as quick as Farnell), I would like to know how such a price difference is justified.
I think I will order OP 249, and compare them to BB OPA 2134 (of which I have three pcs lying around).
Thanks so far,
Arndt
Well, here comes the price comparison between Farnell and Reichelt:
OP 249 at Farnell (401195): 6.25 €
OP 249 at Reichelt ( OP 249 GP ): 3.65
While I do use Farnell (Reichelt doesn't have such a variety of brands, and doesn't deliver as quick as Farnell), I would like to know how such a price difference is justified.
I think I will order OP 249, and compare them to BB OPA 2134 (of which I have three pcs lying around).
Thanks so far,
Arndt
The gap gets even wider toward the low end. For example, a TI NE5532P is more than five times as expensive at Farnell than at Reichelt: 1,30 euros vs. 0,23 euros. My theory is that warehouse space is really cheap in Friesland and that Reichelt has hyper-active, hyper-efficient employees from the huge volumes of tea they drink in those parts.
One thing you have to accept when ordering from Reichelt is that you can't count on always getting what you expect. They have, however, always let me return things for a refund if what they sent turned out to be a great deal different from what you would suppose from the catalog or from what they sent last time.
If you need something quickly from Reichelt, order by phone. They have an unpublicized, internal rule to automatically hold an order for two business days if a line item is out of stalk. They just did this to me on an order I placed through their website on the 21st. They are shipping all but one item today (the 25th) and will ship the remaining item after it comes in – which is also today. I don't understand this.
One thing you have to accept when ordering from Reichelt is that you can't count on always getting what you expect. They have, however, always let me return things for a refund if what they sent turned out to be a great deal different from what you would suppose from the catalog or from what they sent last time.
If you need something quickly from Reichelt, order by phone. They have an unpublicized, internal rule to automatically hold an order for two business days if a line item is out of stalk. They just did this to me on an order I placed through their website on the 21st. They are shipping all but one item today (the 25th) and will ship the remaining item after it comes in – which is also today. I don't understand this.
That's bureaucracy!
They want to serve the customers well and probably didn't realize thay they should receive the missing item.
I only can second the Reichelt phoning option. They can tell you instantly if the parts are on stock. And if yes, Reichelt is very fast!
Also the shipping cost was just 3,50, if I remember well. Wasn't Farnell sth. like 7,50 (Euro) - I am still holding back my Farnell order because I always fear that I'd forget to order something and then would have to pay those 7,50 again!
Cheers
Dominique
They want to serve the customers well and probably didn't realize thay they should receive the missing item.
I only can second the Reichelt phoning option. They can tell you instantly if the parts are on stock. And if yes, Reichelt is very fast!
Also the shipping cost was just 3,50, if I remember well. Wasn't Farnell sth. like 7,50 (Euro) - I am still holding back my Farnell order because I always fear that I'd forget to order something and then would have to pay those 7,50 again!
Cheers
Dominique
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