Hey, I wan't VU's like these:
http://www.helios-electronics.com/More_Pics/more_pics.html
Where do I get them??
:sam: hejsan
http://www.helios-electronics.com/More_Pics/more_pics.html
Where do I get them??
:sam: hejsan
Help Support GroupDIY Audio Forum:
Viitalahde
Well-known member
Those are actually Sifams, they have a "retro" looking version.
Tekay
Well-known member
The Sifam meters are AL20SQ, Canford Audio use to stock them!
G
Guest
Guest
I see grayhill switches (I think I have sintech a load of these - ex-military surplus - from RAF cockpits)
Single gang Elma
Home made inductor?
BC box caps
Can anyone please explain to me what the "Card 1" and "Card 2" is which you see on the schematic diagram that you can download on vintag king. is card 2 the line amp which you can also download of the site. if so, what is card 1 and where can i find the diagramm for it.
ruffrecords
Well-known member
Hey everyone, what is the current status of this project? Seems to be a bit quiet since May?
I have made a few notes looking through this thread.
1. Several references to -20dB mic input achieved by the Lustraphone transformer secondary centre tap. Maybe I am just pedantic but it is not a centre tap. This is a 1:10 transformer and the -20dB setting is achieved by a 1:1 tap. Maybe this is FUD put out by those who would prefer we don't make our own clone?
2. -24V supply. This is probably a holdover from the original germanium designs. Even today it is well known that PNP transistors are less noisy than NPNs, so the original design would most likely have used a PNP as the first transistor. The various currently available schematics show an NPN as the first transistor which is probably the easiest way of updating the circuit to silicon without doing a complete redesign.
3. I have managed to simulate the amps and the EQ using switcherCAD. I can post swCAD files if anyone is interested. There is no sign of the fabled bump in the simulations I have done. Also the EQ gives the right bass boost frequencies with an inductor value of 10H.
4. Some people have noted the older cards sound 'smoother'. The 150pF at the card input seems to be the cause of this making the 20KHz response drop by 1.6dB. Reissues may use a different value; 50pF reduces this drop to 0.3dB
5. Asymmetric distortion is also mentioned as one of the well liked features. This appears to be due to the way the output is biassed. Generaly you aim to get the biggest possible output swing so you arrange the bias so the output collector is half way between the emitter and supply voltages. On the Helios 69 this is not the case; it is biassed somewhat lower than this which means the bottom of the waveform clips first. This produces lots of nice second harmonic (read musical) distortion. At first I thought there was an error in the schematic becuase if you swap the positions of the 680K and 820K bias resistors the output collector voltage is much more central. This produces symmetric distortion with loads of 3rd (read yukky) harmonic distortion. I don't know if Dick did this deliberately or accidentally but it certainly ties in with the reported 'sound'.
6. The simulations show a rather poor LF response of -2.1dB at 20Hz mainly caused by the 125uF gain capacitor. Raising this to 470uF brings the 20Hz response to -0.6dB.
7. Sowter now do their own version of the Lustraphone transformer type number 7490 with the 1:1 tap.
That's it for now. Just waiting for the parts to arrive before I start building a prototype.
Cheers
Ian
I have made a few notes looking through this thread.
1. Several references to -20dB mic input achieved by the Lustraphone transformer secondary centre tap. Maybe I am just pedantic but it is not a centre tap. This is a 1:10 transformer and the -20dB setting is achieved by a 1:1 tap. Maybe this is FUD put out by those who would prefer we don't make our own clone?
2. -24V supply. This is probably a holdover from the original germanium designs. Even today it is well known that PNP transistors are less noisy than NPNs, so the original design would most likely have used a PNP as the first transistor. The various currently available schematics show an NPN as the first transistor which is probably the easiest way of updating the circuit to silicon without doing a complete redesign.
3. I have managed to simulate the amps and the EQ using switcherCAD. I can post swCAD files if anyone is interested. There is no sign of the fabled bump in the simulations I have done. Also the EQ gives the right bass boost frequencies with an inductor value of 10H.
4. Some people have noted the older cards sound 'smoother'. The 150pF at the card input seems to be the cause of this making the 20KHz response drop by 1.6dB. Reissues may use a different value; 50pF reduces this drop to 0.3dB
5. Asymmetric distortion is also mentioned as one of the well liked features. This appears to be due to the way the output is biassed. Generaly you aim to get the biggest possible output swing so you arrange the bias so the output collector is half way between the emitter and supply voltages. On the Helios 69 this is not the case; it is biassed somewhat lower than this which means the bottom of the waveform clips first. This produces lots of nice second harmonic (read musical) distortion. At first I thought there was an error in the schematic becuase if you swap the positions of the 680K and 820K bias resistors the output collector voltage is much more central. This produces symmetric distortion with loads of 3rd (read yukky) harmonic distortion. I don't know if Dick did this deliberately or accidentally but it certainly ties in with the reported 'sound'.
6. The simulations show a rather poor LF response of -2.1dB at 20Hz mainly caused by the 125uF gain capacitor. Raising this to 470uF brings the 20Hz response to -0.6dB.
7. Sowter now do their own version of the Lustraphone transformer type number 7490 with the 1:1 tap.
That's it for now. Just waiting for the parts to arrive before I start building a prototype.
Cheers
Ian
Wonderlandaudio
Well-known member
I have Tony Arnold´s ones in case you need any help.
I think the Sowter is the 8666x.
I think the Sowter is the 8666x.
Wonderlandaudio
Well-known member
I use mine with a B283 and Lo1166 as output stage. And took Tony´s transistor based phase reverse switch, which changes gain as well.
Card 1 and card 2 in the schematics are the same.
Card 1 and card 2 in the schematics are the same.
ruffrecords
Well-known member
[quote author="Wonderlandaudio"]I have Tony Arnold´s ones in case you need any help.[/quote]
That is interesting. It would be nice to know what silicon they use and whether the input transistor is a PNP or NPN. Also what value cap do they use in series with the first stage gain switch. The original circuits show 125uF but this gives poor LF response at max gain. 470uF would cure this. Lastly the HF perfomance is affected by the 150pF across the input of each 'card' in the original circuits. It would be interesting to know if they have changed these values.
Ian
That is interesting. It would be nice to know what silicon they use and whether the input transistor is a PNP or NPN. Also what value cap do they use in series with the first stage gain switch. The original circuits show 125uF but this gives poor LF response at max gain. 470uF would cure this. Lastly the HF perfomance is affected by the 150pF across the input of each 'card' in the original circuits. It would be interesting to know if they have changed these values.
I read somewhere that the Sowter 8666X is a custom design that is exclusive to Tony Arnold. Sowter cannot and will not sell it to you. Their own design of the lustraphone is the 7490.
Ian
Wonderlandaudio
Well-known member
Check the archive. The 8666 is also 200:20K with the 1:1 tap at the secondary. Suspicious...
Wonderlandaudio
Well-known member
220uF. Still 150pF.2TX214c,bc184c,bc184c, ip to op.[/b]
ruffrecords
Well-known member
[quote author="Wonderlandaudio"]220uF. Still 150pF.2TX214c,bc184c,bc184c, ip to op.[/b][/quote]
That is good. I see they are using a PNP input. Should that be a ZTX214C rather than 2TX214C??? I had already bought BC184s for the two NPNs. I'll check out 220uF on the simulation and see what it does to the LF response.
Ian
That is good. I see they are using a PNP input. Should that be a ZTX214C rather than 2TX214C??? I had already bought BC184s for the two NPNs. I'll check out 220uF on the simulation and see what it does to the LF response.
Ian
Wonderlandaudio
Well-known member
It IS ZTX214c. It was dark. Sorry
G
Guest
Guest
[quote author="Wonderlandaudio"]It IS ZTX214c. It was dark. Sorry[/quote]
That would be the amp I just sold a thousand of to various members of this forum
BTW - check my look see on the original Helios amps on this thread
http://www.groupdiy.com/index.php?topic=16647&highlight=helios
Cyril then starts pulling out old modules
A module from the FIRST Helios desk ever made
I spotted - Colvin Pots - the turret board with BIG mustard caps
Then - Veroboard/Stripboard
Lustraphone transformers and the inductor
Then he pulls out the module from the SECOND ever Helios desk
Now this one is quite different inside - two little RadioSpares (RS Components) Interstage transformer right behind the panel
That would be the amp I just sold a thousand of to various members of this forum
BTW - check my look see on the original Helios amps on this thread
http://www.groupdiy.com/index.php?topic=16647&highlight=helios
Cyril then starts pulling out old modules
A module from the FIRST Helios desk ever made
I spotted - Colvin Pots - the turret board with BIG mustard caps
Then - Veroboard/Stripboard
Lustraphone transformers and the inductor
Then he pulls out the module from the SECOND ever Helios desk
Now this one is quite different inside - two little RadioSpares (RS Components) Interstage transformer right behind the panel
Wonderlandaudio
Well-known member
I had the chance to meet Cyryl in Spain. We bought a Symphony and he came himself to help with the installation. Really nice man. An open book
Can someone send me one of those laundramat transformers or
whatever they are called? (chops a lickin!) :razz:
whatever they are called? (chops a lickin!) :razz:
Wonderlandaudio
Well-known member
Lustraphones???? Man, I´ve seen rare things but never a Lustraphone.... Sorry. I have Decca transformers, EMI´s,... but not Lustraphones.
ruffrecords
Well-known member
[quote author="uk03878"]That would be the amp I just sold a thousand of to various members of this forum][/quote]
What amp would that be then? Can you post a link?
Ian
What amp would that be then? Can you post a link?
Ian
