Finally. Music!!!

G · 11th March 2003, 03:53 PM

Hi All,

It's been a long time coming but I finally built my amp. If someone wants to host the images I'll send them to you. I haven't been able to get them small enough to post them. It's a SE 7189 amp with a 5687 in the gain stage and a 5AR4 in the PSU. I ran both cathodes to one resistor and one bypass cap in the output stage ala Zen amp and I think I need to change the biasing. Instead of getting 7 volts on the cathodes I'm getting 9 volts. I didn't take into account that I would be biasing two tubes with one resistor. I'm getting 60 mA with a voltage drop of nine volts across the resistor which gives me approximately 30 mA per 7189. I need to decrease the resistance to 75 ohms 0r so to get the 7 volts 48mA per 7189 that I'm looking for. As a result of this oversight the liitle guy runs out of gas and starts clipping at about 11 o' clock on the Parasound PHP850 that I'm using as a preamp. I'm using Klipsch KSB 3.1's which are somewhere close to 94dB/1 watt 1 meter. I think the little fellow should have more uhmph than it does. It sound nice though. Dead quiet.

G

G · 11th March 2003, 04:57 PM

A picture of the amp can be found here:

http://www.sighost.us/members/gkh6/Image001.jpg

fdegrove · 11th March 2003, 05:09 PM

Hi Gavin,

Well done...that are really big OPTs you have there.

I resized the pic you have on the website and can try to post it here if you like.

Cheers,

G · 11th March 2003, 05:18 PM

Please do Frank. For some reason I couldn't get it to work so I found some free image hosting. I had the output transformers from another aborted project. They are from Handwound transformers. You know. The guy on Ebay. Well They are 4800 ohms on the primary. Not optimal but they get the job done. Thanks.

G

Elkaid · 11th March 2003, 05:21 PM

Very nice looking

I never heard SE 7189 but if it sounds as good as it looks, it must be pretty nice !

Btw, where did you get your chassis ?

Great job !

fdegrove · 11th March 2003, 05:23 PM

Cheers,

G · 11th March 2003, 05:23 PM

It's a hammond 12 x 10. I painted it my self. Thanks. I still can't believe I finally did it! No Hum and only a minor biasing problem. I'm loving life.

G

Bas Horneman · 11th March 2003, 06:57 PM

Wow..congrats on your amp...looks great..

Photo resized again ..closeup.. I just love tube porn!

G · 11th March 2003, 07:02 PM

Thanks BAS. I finding though that it does not, contrary to what Steve Deckert would have you believe, Have enough power to give satisfying listening levels in triode mode. I think that I need to connect the screend directly to B+ and run it in pentode mode. I'm still thrilled to have built it and have it work immediately with no hum. Thank you again for the complement. It is still a work in progress though.

G

Bas Horneman · 11th March 2003, 07:08 PM

Quote:

I finding though that it does not, contrary to what Steve Deckert would have you believe, Have enough power to give satisfying listening levels in triode mode.

Yes I'm suprised about that...especially since your speakers are 94db ?

I once had a single sv83 amp well actually 3*sv83 but pulled out the other 2 just to see..and was suprised that my 90db speakers had sufficient power for my needs...(Enough to get into problems with my neighbours...(Dutch house ..)

I suppose the Klipsh does not have a complicated crossover network??

Cheers,
Bas

11th March 2003, 03:53 PM	#1
G diyAudio Member Join Date: Apr 2002 Location: Belleville, IL.	Finally. Music!!! Hi All, It's been a long time coming but I finally built my amp. If someone wants to host the images I'll send them to you. I haven't been able to get them small enough to post them. It's a SE 7189 amp with a 5687 in the gain stage and a 5AR4 in the PSU. I ran both cathodes to one resistor and one bypass cap in the output stage ala Zen amp and I think I need to change the biasing. Instead of getting 7 volts on the cathodes I'm getting 9 volts. I didn't take into account that I would be biasing two tubes with one resistor. I'm getting 60 mA with a voltage drop of nine volts across the resistor which gives me approximately 30 mA per 7189. I need to decrease the resistance to 75 ohms 0r so to get the 7 volts 48mA per 7189 that I'm looking for. As a result of this oversight the liitle guy runs out of gas and starts clipping at about 11 o' clock on the Parasound PHP850 that I'm using as a preamp. I'm using Klipsch KSB 3.1's which are somewhere close to 94dB/1 watt 1 meter. I think the little fellow should have more uhmph than it does. It sound nice though. Dead quiet. G __________________ Gavin

11th March 2003, 04:57 PM	#2
G diyAudio Member Join Date: Apr 2002 Location: Belleville, IL.	A picture of the amp can be found here: http://www.sighost.us/members/gkh6/Image001.jpg __________________ Gavin

11th March 2003, 05:09 PM	#3
fdegrove diyAudio Senior Member Join Date: Aug 2002 Location: Belgium	7189A Hi Gavin, Well done...that are really big OPTs you have there. I resized the pic you have on the website and can try to post it here if you like. Cheers, __________________ Frank

11th March 2003, 05:18 PM	#4
G diyAudio Member Join Date: Apr 2002 Location: Belleville, IL.	Please do Frank. For some reason I couldn't get it to work so I found some free image hosting. I had the output transformers from another aborted project. They are from Handwound transformers. You know. The guy on Ebay. Well They are 4800 ohms on the primary. Not optimal but they get the job done. Thanks. G __________________ Gavin

11th March 2003, 05:23 PM	#7
G diyAudio Member Join Date: Apr 2002 Location: Belleville, IL.	It's a hammond 12 x 10. I painted it my self. Thanks. I still can't believe I finally did it! No Hum and only a minor biasing problem. I'm loving life. G __________________ Gavin

11th March 2003, 05:21 PM	#5
Elkaid diyAudio Member Join Date: Jan 2003 Location: Canada	Very nice looking I never heard SE 7189 but if it sounds as good as it looks, it must be pretty nice ! Btw, where did you get your chassis ? Great job !

11th March 2003, 07:02 PM	#9
G diyAudio Member Join Date: Apr 2002 Location: Belleville, IL.	Thanks BAS. I finding though that it does not, contrary to what Steve Deckert would have you believe, Have enough power to give satisfying listening levels in triode mode. I think that I need to connect the screend directly to B+ and run it in pentode mode. I'm still thrilled to have built it and have it work immediately with no hum. Thank you again for the complement. It is still a work in progress though. G __________________ Gavin

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