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Linn Lingo schematic
Linn Lingo schematic
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Old 26th January 2019, 09:14 AM   #11
nigel pearson is offline nigel pearson  United Kingdom
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R1 on original Valhalla was antisurge protection to the Vallhalla rectifier. It was 47R 300V 1/2 watt approximately. Later ones used a non linear resistor. This device often causes trouble. If you need to add an external resistance this is all to the good.

Looking at my notes R13 22K can be shunted by a 20K pot to get your 45 RPM without too much modification. I used a relay, DPDT with crystal one side and resistor the other. The crystal is 3.2768 MHz x 1.35. Some exist that are very close ( 67.7 Hz ). I averaged the error between 33/45 which was fine. The LP12 motor tilt is worth about 0.5%. 320 VDC is required if wanting full torque at 45 RPM using 100 VAC. Only do this if you understand the risks. Like with valve circuits this is highly dangerous. When removing the 47 uF they might hold a charge. Hard to say what is the best advice. Do not work on the Valhalla on the LP12. That's asking for trouble. I have tested the Valhalla at 350 VDC. If you do that by mistake it probably will be OK. Don't let it remain there as it's very close to the transistor limit. The amplifier seems to be class A!
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Old 26th January 2019, 09:40 AM   #12
nigel pearson is offline nigel pearson  United Kingdom
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Click the image to open in full size.

Here with 2 x 220 uF 250V. Sorry about image quality. Circa - 58 dB.
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Old 26th January 2019, 06:28 PM   #13
postpunk is online now postpunk  Germany
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Hello Nigel,

thanks for posting the instructions above! I went out and bought two 220uf 400v capacitors and an isolation transformer today. I will let you know how it works out.

Kind regards,
Evert
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Old 27th January 2019, 02:15 AM   #14
cakyol is offline cakyol  United States
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Thanks Nigel.

I like overdesigning things so I build once and dont worry for the next 30 years :-)

I am changing my rectifier to a 1kv 35 Amp device. The power resistors are now 30 Watts each, hanging to the side so the heat does not get trapped by the pcb. I am replacing the caps to 150uF 450 V Nichicons with 12000 hours at 105 degrees C.
Hopefully I will never have to worry about these components again :-)
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Old 27th January 2019, 10:56 AM   #15
nigel pearson is offline nigel pearson  United Kingdom
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You could use the old 47 uF with the 150 uF as it gives you about 200 uF. Every dB is worth it. Or you can use 4 x 150 uF. I like that idea. The risk of going higher is no improvement and greater surge current. 245/47 = circa 5 amps if factoring in R1. R1 reduces the risk. It's always worth saying the capacitors are 0 ohms initially. High grades especially. 220uF Nichicon 250 V is what I used. It's what I had.

Be sure you don't exceed 330 VDC especially if using an isolation transformer as they are rated at full load, higher when less. At my house I got 326 VDC ( - ve C1 +ve C2 ) at about 246 VAC ( 123 VAC were it USA, I'm told 130 VAC is known ), the UK is very high. The transistors are about 400 VDC rating. Equally below 300 VDC might mean the output wave is clipped. If so drop the output to 85 VAC on the red phase as did later LP12's. That's RV1 next to R13 R14. I really like the Valhalla power amp section. It has a bootsrap current source that has very good voltage swing. It can't exceed 1/2 VDC x 0.707. 150x0.7 = 105 VAC (rms ). 85 VAC is very OK. There is always loss in voltage swing. 93% would be excellent.

I had a Lingo. In some ways an improved Valhalla is more to my taste, more verve. If I remember the Lingo starts at 90 VAC then drops to 66 VAC. One could arrange Valhalla R13 RV1 to give both voltages. I suspect you will find out 85 VAC is best which will start the turntable well. 130 VAC is the design maximum of the motor. It gets hot and vibrates at that level. The Valhalla is good for 90 VAC maximum. 66 VAC is 1/4 full motor power, That's not much. A Garrard 301 is 16 watts and 28 watts used ( VA ). Even if 20% gets to the platter that's far more. The 301 is the LP12 you always wanted, I have a 401 and LP12 EKOS Valhalla. 401/LP12 are alike. LP12 is less than 1 watt to the motor.

A W08 800 V PIV rectifier is fine and W10 even better. First Valhalla's were 400PIV W04.

C19 0.22 uF can be tuned ( Blue phase ). You will drive yourself mad if you do. In theory if VAC red is 85VAC then red to blue is 120.2 VAC by pythagorous ( A^2+B^2=C^2 ). 1.414 times larger. It's not that simple and I found the supplied capacitor is about right. I mention this as many will insist it matters. Likely it does and likely it's not the mathamatical ideal. Try 0.18, 0.2, 0.22, 0.24, 0.26. Paralell caps add.

I will post the circuit if I find it. Quality isn't great.
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Old 27th January 2019, 11:15 AM   #16
nigel pearson is offline nigel pearson  United Kingdom
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Click the image to open in full size.

Lets go through the circuit. The crystal ( 3.2768 MHz ) is divided by a 4060 oscillator ripple counter. If Contrology had used another 4060, 4040 , 4020 they could have simplified the idea. Instead they use the element ciruits of the 4060 to get 2^16 division. They use another flip flop to do on off. Next a LM324N does filtering plus power amp preamp stage. To get good performance from a LM324N gets my respect. C17 ( ? ) is the bootstrap current source from the 1920's. Old ways sometimes are best. The sine waves are into the final stage. They start as square waves.

The 115 V input is a very unusual voltage muliplier of sorts. As these usually have more ripple 230 V from a transformer could be best.

The reason a floating transformer should be better is the Valhalla uses a 10 V and 320 V DC supply coupled to the same 0V. That's not great. Floating seems to minimise the imbalance. To be honest I don't know why except it sort of follows reason why we do it. All I know is it is worth about 6dB if floating. Many centre tap when doing this. That will not work here.

DC voltages should be right or close.
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Old 27th January 2019, 11:41 AM   #17
nigel pearson is offline nigel pearson  United Kingdom
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I should add the circuit above was an attempt to use an extra 10 VDC DC supply. I broke the PCB next to C1. It wasn't worthwhile. The 68K ( 15K original ) was due to that and the 220uF non standard ( was 47 uF ).

The 1.414 red to blue is when 90 degrees phase shift. I have measured that motor many times and never found out what it really likes. 85/75 red/blue is not too bad as was typical of later LP12's.
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Old 27th January 2019, 07:52 PM   #18
PRR is offline PRR  United States
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Quote:
Originally Posted by nigel pearson View Post
...The 115 V input is a very unusual voltage muliplier of sorts.....
Every desktop PC uses just that sort of affair (switch instead of fuse-as-jumper) and often the same 220uFd caps. And the turntable load is much less than a PC. There's no audio here and no user-touchable parts. I don't see a problem.
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Old 28th January 2019, 08:42 AM   #19
nigel pearson is offline nigel pearson  United Kingdom
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Whilst that's true in principle a switch mode power supply has a slightly different way of working. Read any discussion on voltage doublers and the high output impedance is quoted as the down side ( that's Valhalla USA ). The load is circa 30mA. Up to a certain point making the capacitor values larger fixes that.

When the UK version at US 60 Hz ( set by the fuse ) Delta V =i/fc to a good approximation. For USA at 230V via a transformer ripple is 30mA/120x23.5 = 10 V pk to pk more or less. We might hope that drops to just over 2 V pk to pk if 220 uF fitted. My graphs of PSU hum show - 40 db worse case. Or 1/100 of the motor output is not a sine wave. As the Valhalla has only 0.05% THD it seems reasonable to want it better. My best case - 58 dB is almost 1/1000. This when used with a floating transformer should cross that ideal -60 dB line I set myself.

As far as I can see regardless of what capacitors fitted the USA version will be worse as doublers generally have worse ripple. One also finds there is a point where more capacitance will not be a cure. Doubtless a choke could work or the famous Sid Smith LM317 regulator for his valve amps. As we want to reject 20 V peak to peak worse case it is a bit slim to get 85 Vrms.

All of this should not matter were it not for the engineering. The common mode rejection of the design is not as good as modern designs. My attempts to correct that proved it's the concept rather than parts used.

Notice in my version posted I use 68 K to discharge and to center the charging of the 2 x 220 uF I used. This is a great improvement over the 15 K of Linn. I could do that because I was using a battery for testing the oscillator side. None of it worked. You can not use 68K when the standard version. The unmarked resistors on the dia are the ones.

Click the image to open in full size.

I speculate 470 uF " might " be better for 115 V opperation. As I don't have a spare Valhalla I will have to do 320 VDC and 10K load. The circuit is very easy to clone. 2 x 1N4007 2 x 220 uF USA via a 115 V transformer. 4 x 1N4007 via UK mains 240V. Load 4 x 10K 3 watt ( 10 K ).
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Old 28th January 2019, 08:52 AM   #20
postpunk is online now postpunk  Germany
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I have been floating the Valhalla for about six records now. It seems that the sound has been improved. I live right next to some major industry and the power here is quite dirty, so that is probably an additional factor. I used a 65VA isolation transformer, turntable grounded to the preamp.

I recently replaced all electrolytic capacitors on the board, so it will be interesting to hear what happens when I put in the bigger ones.
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