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 Post subject: Re: 807 Williamson amp
PostPosted: Apr Mon 16, 2018 4:13 am 
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john8750 wrote:
Flipperhome wrote:
john8750 wrote:
I will guess this amp is costing around $500. I have a few parts on hand, about $15 for them. I am getting about the middle quality. The Edcors are about $250 alone. All caps are audio grade. All precision resistors are 1%. Getting the vented sockets for the 5pin 807's. Might go with a turret component mounting system. Thinking about building a custom heatsink for the MOSFET.
Where are you getting vented 807 sockets?



It is two pieces. The 5pin socket is separate.
https://www.ebay.com/itm/8pc-5pin-New-C ... 1438.l2649

The vented plate comes with an octal socket.
.https://www.ebay.com/itm/Ventilated-Alu ... 2749.l2648
I see. I got the 'large' ceramic ones. Just curious.


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 Post subject: Re: 807 Williamson amp
PostPosted: Apr Mon 16, 2018 6:41 pm 
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Is the 3.92ohm shunt resistor a set value?
I guess the 3 selection switch would read-left/off/right?

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 Post subject: Re: 807 Williamson amp
PostPosted: Apr Tue 17, 2018 12:29 am 
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john8750 wrote:
Is the 3.92ohm shunt resistor a set value?
I guess the 3 selection switch would read-left/off/right?
If you mean am I absolutely sure of the value, I tested the meter but I'm never "absolutely sure" about something I've not yet implemented. :wink: (My main concern was whether the meters are repeatable and accurate.) If you're asking if the value 'has' to be 3.92 Ohm, that's the value that should result in 50 mA reading '100%' on the meter's scale. I didn't include a 'trim' adjustment though. I kind of planned to 'adjust' the meters themselves for final 'trim' since the VU function is only for 'show'. I mean, it's not a recorder of any type so the 'VU' reading doesn't really mean anything.

The switch isn't clear because I was drawing it for 'me'. :mrgreen: It's left-right-VU (still somewhat TBD, depending on final layout). Also not shown is the "VU section" itself, which is a solid state VU meter board I bought that runs off 12 VAC. That is now a problem because the 12 VAC is elevated and I haven't worked out a solution for that (maybe a small 12 V transformer of it's own). I also am not sure where to physically put it and wasn't sure if I'd just abandon the idea completely, if it became cumbersome, and just use an external measurement for bias. It's all really just 'fluff' and not needed for the amplifier but I've already purchased the meters, VU meter board, and switch.


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 Post subject: Re: 807 Williamson amp
PostPosted: Apr Tue 17, 2018 1:01 am 
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Flipperhome wrote:
john8750 wrote:
Is the 3.92ohm shunt resistor a set value?
I guess the 3 selection switch would read-left/off/right?
If you mean am I absolutely sure of the value, I tested the meter but I'm never "absolutely sure" about something I've not yet implemented. :wink: (My main concern was whether the meters are repeatable and accurate.) If you're asking if the value 'has' to be 3.92 Ohm, that's the value that should result in 50 mA reading '100%' on the meter's scale. I didn't include a 'trim' adjustment though. I kind of planned to 'adjust' the meters themselves for final 'trim' since the VU function is only for 'show'. I mean, it's not a recorder of any type so the 'VU' reading doesn't really mean anything.

The switch isn't clear because I was drawing it for 'me'. :mrgreen: It's left-right-VU (still somewhat TBD, depending on final layout). Also not shown is the "VU section" itself, which is a solid state VU meter board I bought that runs off 12 VAC. That is now a problem because the 12 VAC is elevated and I haven't worked out a solution for that (maybe a small 12 V transformer of it's own). I also am not sure where to physically put it and wasn't sure if I'd just abandon the idea completely, if it became cumbersome, and just use an external measurement for bias. It's all really just 'fluff' and not needed for the amplifier but I've already purchased the meters, VU meter board, and switch.



I agree it is just 'frosting on the cake'
I think it will require an isolated power supply.
Are the cathode adjustment pots going to be mounted on the chassis?
What about using a mv meter?
I went ahead and ordered the 3.92ohms from Mouser anyway.

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 Post subject: Re: 807 Williamson amp
PostPosted: Apr Tue 17, 2018 2:08 am 
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john8750 wrote:
Flipperhome wrote:
If you mean am I absolutely sure of the value, I tested the meter but I'm never "absolutely sure" about something I've not yet implemented. :wink: (My main concern was whether the meters are repeatable and accurate.) If you're asking if the value 'has' to be 3.92 Ohm, that's the value that should result in 50 mA reading '100%' on the meter's scale. I didn't include a 'trim' adjustment though. I kind of planned to 'adjust' the meters themselves for final 'trim' since the VU function is only for 'show'. I mean, it's not a recorder of any type so the 'VU' reading doesn't really mean anything.

The switch isn't clear because I was drawing it for 'me'. :mrgreen: It's left-right-VU (still somewhat TBD, depending on final layout). Also not shown is the "VU section" itself, which is a solid state VU meter board I bought that runs off 12 VAC. That is now a problem because the 12 VAC is elevated and I haven't worked out a solution for that (maybe a small 12 V transformer of it's own). I also am not sure where to physically put it and wasn't sure if I'd just abandon the idea completely, if it became cumbersome, and just use an external measurement for bias. It's all really just 'fluff' and not needed for the amplifier but I've already purchased the meters, VU meter board, and switch.

I agree it is just 'frosting on the cake'
I think it will require an isolated power supply.
Are the cathode adjustment pots going to be mounted on the chassis?
What about using a mv meter?
I went ahead and ordered the 3.92ohms from Mouser anyway.
Why not just use an external meter? :wink: Btw, like most amplifiers did, if they even had a bias adjust at all.

Where else would the bias pots mount? Just exactly where I, again, hadn't worked out but one location was in the rear, which makes looking at the meters problematic, but mounting on the front creates (potential) wiring layout problems.

I'm beginning to think it was a nice idea but, in the end, not worth the bother.


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 Post subject: Re: 807 Williamson amp
PostPosted: Apr Tue 17, 2018 2:22 am 
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Did some amps have a meter on board? Maybe on top of chassis next to the adjustment pots. Wait, that wouldn't look very good. Maybe a plug-in jack on the rear panel. Maybe a trick CCS.

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 Post subject: Re: 807 Williamson amp
PostPosted: Apr Tue 17, 2018 2:48 am 
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john8750 wrote:
Did some amps have a meter on board? Maybe on top of chassis next to the adjustment pots. Wait, that wouldn't look very good. Maybe a plug-in jack on the rear panel. Maybe a trick CCS.
There may be a few others but the only one I am aware of is the Marantz 8.

Attachment:
Marantz 8.jpg
Marantz 8.jpg [ 116.07 KiB | Viewed 374 times ]


Attachment:
Bias Meter.jpg
Bias Meter.jpg [ 65.15 KiB | Viewed 374 times ]


A CCS would add too much complexity, which is another reason to ditch the VU meter idea (SS board).

Btw, one of the things I noticed is the 'bias' point on the Marantz is similar to "100% (0 VU) on the VU meters. That's where I got the idea to have them do double duty.
Attachment:
VU Meters.jpg
VU Meters.jpg [ 79.71 KiB | Viewed 374 times ]


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 Post subject: Re: 807 Williamson amp
PostPosted: Apr Tue 17, 2018 3:29 am 
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Btw, the switch I bought was a 4 pole 5 position (can be stopped down to any positions less than 5) ceramic wafer, with knob, off Ebay for $2.50.
Attachment:
4 pole 5 Pos Ceramic.jpg
4 pole 5 Pos Ceramic.jpg [ 6.02 KiB | Viewed 372 times ]

Unfortunately, the nearest thing I see now is this one for $8.55. https://www.ebay.com/itm/1-Switch-band- ... Ohq0S2RzLg


This is the VU meter board I got (although a different supplier) https://www.ebay.com/itm/Dual-Stereo-VU ... Sw4GVYNWSu

I got these multi-turn dials for the bias pots (although mine were cheaper). https://www.ebay.com/itm/3590S-4MM-Knob ... Sw-WFava~7

You found the same WXD3-13 2W 100 ohm Multi-Turn Wirewound pots that I bought.


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 Post subject: Re: 807 Williamson amp
PostPosted: Apr Tue 17, 2018 4:51 am 
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Flipperhome wrote:
Btw, the switch I bought was a 4 pole 5 position (can be stopped down to any positions less than 5) ceramic wafer, with knob, off Ebay for $2.50.
Attachment:
4 pole 5 Pos Ceramic.jpg

Unfortunately, the nearest thing I see now is this one for $8.55. https://www.ebay.com/itm/1-Switch-band- ... Ohq0S2RzLg


This is the VU meter board I got (although a different supplier) https://www.ebay.com/itm/Dual-Stereo-VU ... Sw4GVYNWSu

I got these multi-turn dials for the bias pots (although mine were cheaper). https://www.ebay.com/itm/3590S-4MM-Knob ... Sw-WFava~7

You found the same WXD3-13 2W 100 ohm Multi-Turn Wirewound pots that I bought.



I have the 3 position-4pole rotary switch.
Here is the VU meter kit I have, or very similar.
https://www.ebay.com/itm/2-PCS-AC-10-12 ... 5d7549f28f

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 Post subject: Re: 807 Williamson amp
PostPosted: Apr Tue 17, 2018 5:14 am 
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I saw this 0-100mv meter. It will work for adjusting the bias balance. Don't know about using it for anything else. I guess the shunt would be less than 1ohm.
https://www.ebay.com/itm/5pcs-100mV-Pan ... XQ8ABRkJQ2

Some of the Heathkits had an on-board meter used for alignment. It was under the chassis.

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 Post subject: Re: 807 Williamson amp
PostPosted: Apr Tue 17, 2018 5:31 am 
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john8750 wrote:
Flipperhome wrote:
Btw, the switch I bought was a 4 pole 5 position (can be stopped down to any positions less than 5) ceramic wafer, with knob, off Ebay for $2.50.
Attachment:
4 pole 5 Pos Ceramic.jpg

Unfortunately, the nearest thing I see now is this one for $8.55. https://www.ebay.com/itm/1-Switch-band- ... Ohq0S2RzLg


This is the VU meter board I got (although a different supplier) https://www.ebay.com/itm/Dual-Stereo-VU ... Sw4GVYNWSu

I got these multi-turn dials for the bias pots (although mine were cheaper). https://www.ebay.com/itm/3590S-4MM-Knob ... Sw-WFava~7

You found the same WXD3-13 2W 100 ohm Multi-Turn Wirewound pots that I bought.

I have the 3 position-4pole rotary switch.
Here is the VU meter kit I have, or very similar.
https://www.ebay.com/itm/2-PCS-AC-10-12 ... 5d7549f28f

It's basically the same but DC input (sans diode bridge) and those are the cheap Chinese knockoff meters. You can tell by the 'horizontal' lettering that causes the characters to not line up properly over their arc, most noticeable with the 30 50 on the percent scale, and I have no idea where "100 %" is supposed to be. They might have different electrical characteristics too. I'm sure they can be made to work, just saying the resistor value might not be right for those.

Btw, I don't know where you can get the real "Taiwan" version. I wasn't even sure the seller I got them from had the 'real' ones, since some show a picture of the 'real' one despite selling the cheap Chinese knockoffs, and was sweating bullets till they got here but, lo and behold, they WERE the Taiwan meters. He promptly vanished from Ebay though.


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 Post subject: Re: 807 Williamson amp
PostPosted: Apr Tue 17, 2018 5:37 am 
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john8750 wrote:
I saw this 0-100mv meter. It will work for adjusting the bias balance. Don't know about using it for anything else. I guess the shunt would be less than 1ohm.
https://www.ebay.com/itm/5pcs-100mV-Pan ... XQ8ABRkJQ2

Some of the Heathkits had an on-board meter used for alignment. It was under the chassis.
I thought about that one, and any number of others (I think they're all the same meter with just different faces) but the scale is wrong (mV, for example) or the 50 mA mark is lower on the scale than with the VU meter. It doesn't make all that much difference but I wanted the 'bias point' to be further up.


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 Post subject: Re: 807 Williamson amp
PostPosted: Apr Tue 17, 2018 5:49 am 
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Flipperhome wrote:
john8750 wrote:
I saw this 0-100mv meter. It will work for adjusting the bias balance. Don't know about using it for anything else. I guess the shunt would be less than 1ohm.
https://www.ebay.com/itm/5pcs-100mV-Pan ... XQ8ABRkJQ2

Some of the Heathkits had an on-board meter used for alignment. It was under the chassis.
I thought about that one, and any number of others (I think they're all the same meter with just different faces) but the scale is wrong (mV, for example) or the 50 mA mark is lower on the scale than with the VU meter. It doesn't make all that much difference but I wanted the 'bias point' to be further up.



I think you will be better at that decision Flip. I can only guess.
And the front mounted meters would look real neat just being there. We could power the panel lights with our 12volt supply.
Would the meters move at all, just being connected across the shunt?
Just some thoughts..

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 Post subject: Re: 807 Williamson amp
PostPosted: Apr Tue 17, 2018 5:55 am 
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john8750 wrote:
I think you will be better at that decision Flip. I can only guess.
And the front mounted meters would look real neat just being there. We could power the panel lights with our 12volt supply.
Would the meters move at all, just being connected across the shunt?
Just some thoughts..
I don't think so, or not much. VU, on the other hand, would, which was why I planned for that. Although, then the question is "what to meter?" I doubt the input impedance is high enough for the input so I figured on the output (speakers) and then the issue becomes "what's 0 VU?"


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 Post subject: Re: 807 Williamson amp
PostPosted: Apr Tue 17, 2018 6:08 am 
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Btw, I seriously considered building this one (figure 6). http://objectivesounds.co.uk/articles/d ... ac-meters/

Also note his comments on the "Chinese" meters just before the "AC Meter Drive Circuit" section.


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 Post subject: Re: 807 Williamson amp
PostPosted: Apr Tue 17, 2018 7:37 am 
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Flipperhome wrote:
Btw, I seriously considered building this one (figure 6). http://objectivesounds.co.uk/articles/d ... ac-meters/

Also note his comments on the "Chinese" meters just before the "AC Meter Drive Circuit" section.



Well. I have the wrong meters. For yours, building the driver in fig.6 looks about the only way to switch from ac/speakers to dc/bias adjustment. Or could you modify the driver included with the meters?
That article is very interesting and informative.

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 Post subject: Re: 807 Williamson amp
PostPosted: Apr Tue 17, 2018 7:58 am 
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john8750 wrote:
Flipperhome wrote:
Btw, I seriously considered building this one (figure 6). http://objectivesounds.co.uk/articles/d ... ac-meters/

Also note his comments on the "Chinese" meters just before the "AC Meter Drive Circuit" section.
Well. I have the wrong meters. For yours, building the driver in fig.6 looks about the only way to switch from ac/speakers to dc/bias adjustment. Or could you modify the driver included with the meters?
That article is very interesting and informative.
I'm not sure the 'meter' itself makes that much difference, as long as it 'works'. It's not as if we actualy 'need' a 'precision' VU meter, just a pleasant bouncing needle in time with the music.

Neither the Chinese or Taiwan meter has anything 'in the meter'. That's why they're not true VU meters despite the scale. It takes 'some circuit' to make them VU.

My plan was to switch the METERs, themselves (the + and- leads of each), from bias to VU, so it's irrelevant what the 'VU circuit' is. Well, except that could be a problem with "circuit 6" because the feedback loop is current through the meter, so it'll full scale when the meter is disconnected and slam the pointer against the stops when it's switched back. I don't think these Chinese boards work that way, though (never powered it up to see).


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 Post subject: Re: 807 Williamson amp
PostPosted: Apr Tue 17, 2018 8:16 am 
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Flipperhome wrote:
john8750 wrote:
Flipperhome wrote:
Btw, I seriously considered building this one (figure 6). http://objectivesounds.co.uk/articles/d ... ac-meters/

Also note his comments on the "Chinese" meters just before the "AC Meter Drive Circuit" section.
Well. I have the wrong meters. For yours, building the driver in fig.6 looks about the only way to switch from ac/speakers to dc/bias adjustment. Or could you modify the driver included with the meters?
That article is very interesting and informative.
I'm not sure the 'meter' itself makes that much difference, as long as it 'works'. It's not as if we actualy 'need' a 'precision' VU meter, just a pleasant bouncing needle in time with the music.

Neither the Chinese or Taiwan meter has anything 'in the meter'. That's why they're not true VU meters despite the scale. It takes 'some circuit' to make them VU.

My plan was to switch the METERs, themselves (the + and- leads of each), from bias to VU, so it's irrelevant what the 'VU circuit' is. Well, except that could be a problem with "circuit 6" because the feedback loop is current through the meter, so it'll full scale when the meter is disconnected and slam the pointer against the stops when it's switched back. I don't think these Chinese boards work that way, though (never powered it up to see).



OK. I sure do like the idea of the meters on the front. Looks like some mean equipment. So if they are used for the output level only, we could just install test points next to the adjustment pots and use a multimeter. Would be super cool to have the selectable bi-function though.

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 Post subject: Re: 807 Williamson amp
PostPosted: Apr Tue 17, 2018 8:35 am 
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john8750 wrote:
Flipperhome wrote:
john8750 wrote:
Well. I have the wrong meters. For yours, building the driver in fig.6 looks about the only way to switch from ac/speakers to dc/bias adjustment. Or could you modify the driver included with the meters?
That article is very interesting and informative.
I'm not sure the 'meter' itself makes that much difference, as long as it 'works'. It's not as if we actualy 'need' a 'precision' VU meter, just a pleasant bouncing needle in time with the music.

Neither the Chinese or Taiwan meter has anything 'in the meter'. That's why they're not true VU meters despite the scale. It takes 'some circuit' to make them VU.

My plan was to switch the METERs, themselves (the + and- leads of each), from bias to VU, so it's irrelevant what the 'VU circuit' is. Well, except that could be a problem with "circuit 6" because the feedback loop is current through the meter, so it'll full scale when the meter is disconnected and slam the pointer against the stops when it's switched back. I don't think these Chinese boards work that way, though (never powered it up to see).

OK. I sure do like the idea of the meters on the front. Looks like some mean equipment. So if they are used for the output level only, we could just install test points next to the adjustment pots and use a multimeter. Would be super cool to have the selectable bi-function though.
The front VU section is where all the problems are (transformer, SS board, where to fit everything in, etc.). If you do that it's almost trivial to add bias metering.


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 Post subject: Re: 807 Williamson amp
PostPosted: Apr Tue 17, 2018 5:51 pm 
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Let me know what your planning as soon as possible. I want to build my amp exactly, kind of, like yours.
I like the meters in front, as long as they move a little :roll:

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