Author Topic: How to Build a killer Amp  (Read 45257 times)

Offline stevenvalve

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Re: How to Build a killer Amp
« Reply #140 on: September 15, 2017, 07:01:09 PM »
This circuit is for my 50 Amplifier. You guys can thank Pixelplay for drawing this. Zenelectro is also responsible for some of the circuit, it''s the best soundíng amp i have heard, Magical indeed, but it is more than just the circuit, it's the wire, choice of parts, and then years of tuning. I do not run 400V into the rectifier, mine is around 300v at the Valve. I dont push the UX250 valves to run hard. Mine has about 2 to 2/5 watts, but with 450 volts you can get 4.6 watts. If you plush them they will not last as long, and can sound stressed, The circuit picture was not right, i will resubmit the correct revised picture soon
« Last Edit: September 20, 2017, 04:51:28 PM by stevenvalve »

Offline stevenvalve

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Re: How to Build a killer Amp
« Reply #141 on: September 15, 2017, 07:13:42 PM »
Some pictures of the amplifiers being made. The wood is Australian Cedar. Second amp has a copper top. The 5692 RCAs are replaced with ECC32 Mullard.
« Last Edit: September 15, 2017, 07:28:52 PM by stevenvalve »

Offline stevenvalve

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Re: How to Build a killer Amp
« Reply #142 on: September 15, 2017, 07:33:40 PM »
Here is a picture of the 50 amp underneath. I have made changes since this picture, i will take a new picture soon.
« Last Edit: September 15, 2017, 07:55:06 PM by stevenvalve »

Offline rab

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Re: How to Build a killer Amp
« Reply #143 on: September 24, 2017, 10:37:51 PM »
Curse you guys! Just when i thought i was nearly at the end game, I hear Pixelplay's incarnation of this damn amp -- not even tuned -- and can't stop thinking about it. 

Offline Pixelplay

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Re: How to Build a killer Amp
« Reply #144 on: September 25, 2017, 12:19:26 AM »
Ha ha Rab, it is a fun journey. Perhaps we will have to build you one!
Steve has been such a great help, let alone a treasure trove of useful information.
I have updated the schematic and will post some images of the amplifier soon.

Offline stevenvalve

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Re: How to Build a killer Amp
« Reply #145 on: September 25, 2017, 12:54:46 AM »
Ha ha Rab, it is a fun journey. Perhaps we will have to build you one!
Steve has been such a great help, let alone a treasure trove of useful information.
I have updated the schematic and will post some images of the amplifier soon.
Best to run around 300v/0/300v to the rectifier. 400V/0/400v will probably have to much voltage, especially if you run the 15uf cap on the voltage out of the rectifier. The 15 uf cap is needed to lower the noise floor but it is a case of diminishing returns, a bigger cap will probably not lower it much more anyway, but it will not hurt. The other advantage of the 15uf cap is you get a voltage increase and that will allow you to run a lower voltage mains transformer. The UX250 or type 50 is good for 450 volts, but dont run that because that will shorten the life of your hard to find UX250 globes and could make them sound stressed. I run 250v/0/250v and that gives me around 280v-300v at the valve. the B+ switch is used to let the valves warm up before adding the currant, helps the valves last a lot longer. I must say my UX250 globe amplifier running this circuit is so good it is the end game for me, it really does sound real, but to get it there you must use the right bits and tune it correctly. My PX/4 amplifier is running the same circuit and same parts combination.
« Last Edit: September 25, 2017, 06:58:53 PM by stevenvalve »

Offline stevenvalve

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Re: How to Build a killer Amp
« Reply #146 on: September 25, 2017, 07:14:18 PM »
I have replaced the Jensen 4 pole 385v- 470uf electrolytic with an 680uf to lower the noise floor, but the 680uf has a lower voltage, so check your voltages. Remember the rule is, doubling the cap size means lowering the noise floor by half, that is important because with no feedback and direct AC heaters you want to lower the noise floor. Its always a battle to work out how to do that without hurting the sound.
« Last Edit: September 28, 2017, 03:29:17 PM by stevenvalve »

Offline kajak12

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Re: How to Build a killer Amp
« Reply #147 on: September 25, 2017, 09:00:14 PM »
I have replaced the Jensen 4 pole 385v- 470uf electrolytic with an 680uf to lower the noise floor, but the 680uf has a lower voltage, so check your voltages. Remember the rule is, doubling the cap size means lowering the noise floor by half, that is important because with no feedback and direct AC heaters you have to lower the noise floor without hurting the sound. Its always a battle the work out how to do that.
If i was anactive member on SNA i would post this and ask the almighty zb for advice :-*
still discovering the link between electronics and audio reproduction.so much to learn and so little time

Offline stevenvalve

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Re: How to Build a killer Amp
« Reply #148 on: November 02, 2017, 07:00:28 PM »
Just taken this picture of the internals of the PX4 amplifier as you see mechanically its finished. But are they ever finished, as i type i will be trying a new main transformer, well not new, but very vintage.
« Last Edit: November 02, 2017, 07:03:12 PM by stevenvalve »

Offline kajak12

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Re: How to Build a killer Amp
« Reply #149 on: November 03, 2017, 08:26:04 PM »
Just taken this picture of the internals of the PX4 amplifier as you see mechanically its finished. But are they ever finished, as i type i will be trying a new main transformer, well not new, but very vintage.
i feel so honoured you are looking after my future amplifier (put that in your will  :-* :-* :-* :-*)
still discovering the link between electronics and audio reproduction.so much to learn and so little time