Ah..just one more idea..I'm doing re-cap job and have a lot of time to think..
So basically..before you put 47K inside current was to high which resulted in saturated, distorted sound....now you have resistor, current might be too small and the result is no bass...
Now there is 47K which was used in old version of Quad520, but there are 2 12V zeners used and you have 2 6v8...so maybe it is worth to try and reduce that 47K to some 24k...I would go with let's say 33k first and check......but do't go lower than some 22k
Just quick idea...
So basically..before you put 47K inside current was to high which resulted in saturated, distorted sound....now you have resistor, current might be too small and the result is no bass...
Now there is 47K which was used in old version of Quad520, but there are 2 12V zeners used and you have 2 6v8...so maybe it is worth to try and reduce that 47K to some 24k...I would go with let's say 33k first and check......but do't go lower than some 22k
Just quick idea...
R5=120k
The amp clips at 37vac into 8ohm load. That's 170Wrms. Not shabby
Scope shots as promised.
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37V...that's decent...op stage is obviously opening...
i would try that 47k to 24 k or something..and see the bass..
Otherwise I would wait till J503's arrive and than see what happens..
Ah one more thing. Have you removed 1n cap from upper side? Itmight be responsible for that crossover node.
Regards
i would try that 47k to 24 k or something..and see the bass..
Otherwise I would wait till J503's arrive and than see what happens..
Ah one more thing. Have you removed 1n cap from upper side? Itmight be responsible for that crossover node.
Regards
Yes, removed the 1n cap.
I'll wait for the J503 but I will be surprised if that changes much in the voicing of the amp. These shapes have been constant throughout my testing. The node is gone but the square wave shapes are the same. It maybe due to some of the other choices I made for transistors. I'm not knowledgeable enough to know what sets the voicing.
Blessings, Terry
I'll wait for the J503 but I will be surprised if that changes much in the voicing of the amp. These shapes have been constant throughout my testing. The node is gone but the square wave shapes are the same. It maybe due to some of the other choices I made for transistors. I'm not knowledgeable enough to know what sets the voicing.
Blessings, Terry
Aha..at least node is gone..that's great.
Well my guess is that current is too small through input stage now. Maybe for test just add another 47k in parallel with the first one. If it helps you are on right path. I assure you 606 has really good bass and it is overall really nicely balanced...
Cheers
Well my guess is that current is too small through input stage now. Maybe for test just add another 47k in parallel with the first one. If it helps you are on right path. I assure you 606 has really good bass and it is overall really nicely balanced...
Cheers
Thanks. 
I added a 47K so around 23.5k. I see 5.9v across it so that is still only .250mA so If your theory is correct, I need somewhere around 11k if the 6v holds, to see 5.6mA, though I don't know for sure that that is how the J503 works.
I may try a lower value but so far the waveform shape hasn't changed at all.
I added a 47K so around 23.5k. I see 5.9v across it so that is still only .250mA so If your theory is correct, I need somewhere around 11k if the 6v holds, to see 5.6mA, though I don't know for sure that that is how the J503 works.
I may try a lower value but so far the waveform shape hasn't changed at all.
Hey Terry
Sorry for late one.
Well probably best thing to do is to wait till J503's arrive. Especially if there is no difference in waveform or sound. If J503's won't help than problem lies somewhere else.
I assure you one more time. 606 works really well, it is not normal to be without bass.
Regards
Sorry for late one.
Well probably best thing to do is to wait till J503's arrive. Especially if there is no difference in waveform or sound. If J503's won't help than problem lies somewhere else.
I assure you one more time. 606 works really well, it is not normal to be without bass.
Regards
I tried adding a 27k resistor but the node is back. After further inspection the extra 47k resistor brought back the node. The original 47k was all that was needed.
Don't take what I have said to say that the amp has no bass. Keep in mind that I was comparing it to the Symasym which has exceptional bass. If I had no other amp to listen to I would be just fine with how this amp sounds. Did you use a scope when evaluating your amp? This amp sound good. Unfortunately, I have been involved with building a lot of stellar amps over that last couple years so this aging design has a lot of very stiff competition. I will attach a couple scope shots that I recorded today on a new amp that vzaichenko designed. You will easily see the difference.
Don't take what I have said to say that the amp has no bass. Keep in mind that I was comparing it to the Symasym which has exceptional bass. If I had no other amp to listen to I would be just fine with how this amp sounds. Did you use a scope when evaluating your amp? This amp sound good. Unfortunately, I have been involved with building a lot of stellar amps over that last couple years so this aging design has a lot of very stiff competition. I will attach a couple scope shots that I recorded today on a new amp that vzaichenko designed. You will easily see the difference.
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Ha...great...
It seems you are getting somewhere. I understand, and I know you have built many amps haha....you are probably the most active diy member here I don't write much here around but I'm reading a lot. You know late hours, last thing every day..haha..
I hope things will improve further with J503.
I've used scope of course, and I listened it a lot. I have few diy speakers and also few nice vintage ones. I love my AR10pi
And also I've build many amps, clones and other designs. I've repaired many too, maybe too many There are some 40 amps lying here around. Most of those for my rental company but still nice collection of diy and vintage. And because of all that I must say 606 is really decent amp. I've done mine little different. Since I'm lazy to do excessive mechanical work mine has all transistors ''in line'' All plastic. I used MJL21194 outputs....but still soundwise I don't think it will make any really big difference. I would be really interested if you manage to build one. There was a lot of talking about this amp but not many completed it. It was always nasty oscillations and even how to make proper coils etc...bty I like yours..haha..
Stay in touch. I'm really interested in your progress. I was starting to believe that only I was ''lucky'' enough to clone one.
Cheers
It seems you are getting somewhere. I understand, and I know you have built many amps haha....you are probably the most active diy member here
I don't write much here around but I'm reading a lot. You know late hours, last thing every day..haha..I hope things will improve further with J503.
I've used scope of course, and I listened it a lot. I have few diy speakers and also few nice vintage ones. I love my AR10pi
And also I've build many amps, clones and other designs. I've repaired many too, maybe too many
There are some 40 amps lying here around. Most of those for my rental company but still nice collection of diy and vintage. And because of all that I must say 606 is really decent amp. I've done mine little different. Since I'm lazy to do excessive mechanical work mine has all transistors ''in line'' All plastic. I used MJL21194 outputs....but still soundwise I don't think it will make any really big difference. I would be really interested if you manage to build one. There was a lot of talking about this amp but not many completed it. It was always nasty oscillations and even how to make proper coils etc...bty I like yours..haha..Stay in touch. I'm really interested in your progress. I was starting to believe that only I was ''lucky'' enough to clone one.
Cheers
you could hold a small stock of jFETs. BF244 are cheap.
They are available as A grade Idss 2mA to 6.5mA, B grade Idss 6mA to 15mA, C grade Idss 12mA to 25mA
There are hundreds of other N jFETs of lowish gm with useful Idss. Just find the cheapest in your area and buy a stock.
To create a CRD (Current Regulator Diode) just connect gate to source and it becomes a 2 terminal device.
If you can't get an Idss to exactly suit, you can adjust the current to a lower value by inserting a source resistor. It is still a 2 terminal device.
Any N or P channel jFET can be used as a CRD, or as an amplifier.
When you have passed the tests, you should connect the amp direct on line.
When output current becomes significant, say more than 500mApk any increase in the mains source impedance will corrupt your results.
Prove your wiring is OK via the Bulb Tester. Then bypass the tester for subsequent measuring.
BTW, a slipped probe with the Bulb Tester in line will still blow up the amplifier due to the energy stored in the smoothing capacitors discharging through the shorted device/s.
hey Terry I found a mod from a Quad site
The specifications of the 909 transformer are: 2x 80,5 Volt 500VA
well I guess is better to wait for CR2 J503 to arrive
http://quadrevisionspot.blogspot.com/2010/08/improving-new-quad-
909.html
Best Regards
Juan
- (2x) R29 (in the bridge) is replaced with 10R 1/2W 1% Metalfilm
- (2x) R30 (in the bridge) is replaced with 47R 1/2W 1% Metalfilm
- (2x) C1, C4 and C6 (6 in total) are replaced with 330pF Silvered Mica
- (2x) C7 is replaced with 100µF 63V Nichicon
- (2x) C9 and C11 (4 in total) are replaced with 470µF 63V Nichicon
The specifications of the 909 transformer are: 2x 80,5 Volt 500VA
well I guess is better to wait for CR2 J503 to arrive
http://quadrevisionspot.blogspot.com/2010/08/improving-new-quad-
909.html
Best Regards
Juan
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