Author Topic: How to Build a killer Amp  (Read 58444 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

Offline stevenvalve

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Re: How to Build a killer Amp
« Reply #150 on: December 19, 2017, 08:19:01 PM »
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.
  At the moment this amp does have an Impedance to grid problem when using the 50 tube. As it is, the Impedance to grid is 100K and needs to be 10K. It is only a problem with the 50. It will work fine with 2A3 -245 -PX4  45 345 145 valve. There will be an update soon on fixing this problem. With the 45 dont run more than 250 Volts, with the PX4 1930s globe no more than 250volts, up to 300v is fine with the later 1950s ST PX/4 finned or non finned versions. I can run these different valves because i had filament transformers made with AC 2.5v 4v 5v 6.3v 7.5v.
« Last Edit: December 19, 2017, 08:33:20 PM by stevenvalve »

Offline fallsaudio

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Re: How to Build a killer Amp
« Reply #151 on: December 19, 2017, 08:39:41 PM »
Hello to all!
              This amplifier is a rock solid circuit to be use with 2A3, 6A3 , 245, 246 ,PX25 etc. It will provide you with a amazing sound stage and a hi quality sound that a lot of others SE amps fail to do .  But the ux250 a tube that require 10000 ohms or less resistance on the control grid . Yes it will work in there but it will stress the tube and shorten the life of the tube . You can be overcome the problem by remove the coupling capacitor and the plate load resistor to the driver tube and placing a Hi Quality inter stage transformer 1:1 ratio 10K to 10K works great . The primary winding is connect were the plate resistor was and the secondary goes across the grid leak resistor from the grid to the signal earth .I will over the day post a circuit for those who are not sure what to do . :D
Paul
Fallsaudio

If anyone has a problem and need help, I am more than willing to help . Just email me at fallsaudio@yahoo.com
« Last Edit: December 19, 2017, 10:01:11 PM by fallsaudio »

Offline stevenvalve

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Re: How to Build a killer Amp
« Reply #152 on: January 03, 2018, 01:01:10 AM »
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.
To help lower the AC filament noise run a 100R resistor from one 6.3v filament wire to ground as seen in the picture

Offline stevenvalve

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Re: How to Build a killer Amp
« Reply #153 on: January 03, 2018, 01:18:43 AM »
I needed less voltage to run the RCA 45 tubes max 250v, instead of 50s max 450v, so i used a .47uf Duelund capacitor instead of a 45uf solen on the output of the rectifier, the voltage went down from 280v to 218v prefect for the 45 valves. The .47 has little affect on increasing the voltage unlike the a 15uf, but still seems to lower the noise floor.
« Last Edit: January 03, 2018, 01:59:20 AM by stevenvalve »

Offline vitavoxdude

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Re: How to Build a killer Amp
« Reply #154 on: January 03, 2018, 12:12:24 PM »
Hi Steve.  Will the Dueland be happy at that voltage? those stacked copper foils do not have the greatest of reliability at anything over 100 or so volts.  I see the VSF DC copper caps have a 400v rating so maybe at UKP-165 each they should hold up.  Do you employ a delayed switch on for the B+ in your circuit?

The PC networking cable wiring you are using, what brand is it?  I bought 500m of the stuff, but it turns out what I thought was CAT6 cable was from china and recycled WW11 aircraft body parts coated in what appears to be darkly tarnished oxidized recycled copper...................bloody awful stuff, you can tell by just holding the stuff, proper copper has around 3 times the weight and is no where near as flexible.  Others be warned, go to the likes of Belden cables and avoid this SHeeeeeeeT.  Ozzy re sellers must make a packet on re selling it into our market.
V
We all like different things so lets all agree to disagree and if any common ground is found then worship it.  Mine is the KD hence being present on this forum.

Offline vitavoxdude

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Re: How to Build a killer Amp
« Reply #155 on: January 03, 2018, 12:19:40 PM »
ooops, just looked at the earlier post of the CD and I can see the B+ switch off to the LHS...my bad.
V
We all like different things so lets all agree to disagree and if any common ground is found then worship it.  Mine is the KD hence being present on this forum.

Offline stevenvalve

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Re: How to Build a killer Amp
« Reply #156 on: January 03, 2018, 05:00:23 PM »
Hi Steve.  Will the Dueland be happy at that voltage? those stacked copper foils do not have the greatest of reliability at anything over 100 or so volts.  I see the VSF DC copper caps have a 400v rating so maybe at UKP-165 each they should hold up.  Do you employ a delayed switch on for the B+ in your circuit?

The PC networking cable wiring you are using, what brand is it?  I bought 500m of the stuff, but it turns out what I thought was CAT6 cable was from china and recycled WW11 aircraft body parts coated in what appears to be darkly tarnished oxidized recycled copper...................bloody awful stuff, you can tell by just holding the stuff, proper copper has around 3 times the weight and is no where near as flexible.  Others be warned, go to the likes of Belden cables and avoid this SHeeeeeeeT.  Ozzy re sellers must make a packet on re selling it into our market.
V
Will the Dueland be happy at that voltage, They are rated 400V but previous experience has shown he these caps are fragile regarding voltage. But still the voltage here is lower around 300 - 350v.
 My cat 5 is vintage solid core Belden cable for the filament wire. Jaycar has the newer Cat5 and it is made in china, looks OK, but does it sound good, it seems to sound OK. I always run a B+ switch, Love it.  The B+ switch is so important and has a huge effect on the sound, i have only found a few brands and types that really sound good, the big early vintage English ones are nice, they need to be cleaned out thoroughly, obviously go for brass or copper switches if you can find them. 

Offline stevenvalve

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Re: How to Build a killer Amp
« Reply #157 on: January 03, 2018, 05:08:49 PM »
The other wire in this amp is partly the wood coated yamamura. Its the same stuff as used in yamamura 5 interconnect, beware not all yamamura wire is brilliant. I also use 1930 to 1950s Hanley cloth covered solid core wire, Very good sounding wire. 
« Last Edit: January 04, 2018, 03:37:39 PM by stevenvalve »

Offline zenelectro

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Re: How to Build a killer Amp
« Reply #158 on: January 05, 2018, 10:45:30 PM »
Hello to all!
              This amplifier is a rock solid circuit to be use with 2A3, 6A3 , 245, 246 ,PX25 etc. It will provide you with a amazing sound stage and a hi quality sound that a lot of others SE amps fail to do .  But the ux250 a tube that require 10000 ohms or less resistance on the control grid . Yes it will work in there but it will stress the tube and shorten the life of the tube . You can be overcome the problem by remove the coupling capacitor and the plate load resistor to the driver tube and placing a Hi Quality inter stage transformer 1:1 ratio 10K to 10K works great . The primary winding is connect were the plate resistor was and the secondary goes across the grid leak resistor from the grid to the signal earth .I will over the day post a circuit for those who are not sure what to do . :D
Paul
Fallsaudio

If anyone has a problem and need help, I am more than willing to help . Just email me at fallsaudio@yahoo.com

Another way to do it is use a high value choke to ground to bias the OP tube. This one would be perfect
https://www.hificollective.co.uk/components/audio-note-chokes/choke-200.html
450 Henries..... that's a beast   :o ;D

Even at 20Hz the load only will be >50k but DC resistance = 2k, should keep the OP tube grid current happy.  :)

T

Offline fallsaudio

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Re: How to Build a killer Amp
« Reply #159 on: January 14, 2018, 03:22:36 PM »
 ;D
Here are two fixes for the grid resistance on the 50 tube. I will post two circuits later today .
I have been playing around with some grid chokes in place of the standard grid leak resistor . I experimented with a few different brands and different inductions. All worked very well and gave there own signature to the sound . The one that I only had one of seem to work best . That was a Lundah LL1670 choke. It may not be to every ones taste as I find Lundah transformers can be too clean sounding for my liking. But this one work very well.

The other way to fix this problem is to increase the current coupling cap from .47mfd to 1mfd by adding another .47 in parallel . You also need to decrease the grid leak resistor to 100K .
2w resistor sound better than the small wattage. I used a Allen Bradly
I hope this will help you all :D
« Last Edit: January 18, 2018, 11:34:09 PM by fallsaudio »