Be careful of teflon loctal tube sockets. Teflon is very slippy. What happens is that the inner part comes up when you pull the tube out of its socket. At least it does on mine. I've stopped using them.
And of course, with loctal sockets you need to open up the bottom of this inner part where it locks the tube pin or you'll have hell taking it in and out. Use a thin nose pliers for instance.
And of course, with loctal sockets you need to open up the bottom of this inner part where it locks the tube pin or you'll have hell taking it in and out. Use a thin nose pliers for instance.
Thanks for advice Andy, BTW Ale teflon sockets looks very nice and don't seems to suffer the same problem like yours.
loctal socket | Bartola Valves
loctal socket | Bartola Valves
Damn - those are nice! Quite different from the usual teflon types. That central part, however, might still start to slip if it isn't held in pretty securely by the construction. I can't quite see if they lock or not. These days, locking is a just a pain and quite unnecessary.
They are very well made. Get in touch directly with Jakeband if you are interested, but they are not cheap as are handmade and by order.
A great socket is the NOS Russian ceramic one: it locks nicely and perfectly!Not sure how easy is to find these:
Ale
A great socket is the NOS Russian ceramic one: it locks nicely and perfectly!Not sure how easy is to find these:
Ale
10pcs ceramic B8G 8pin LOCTAL BOTTOM PCB MOUNT tube socket for 5B254 | eBay
The ones I use are Chinese as above. The ones I used to have a lot of and dislike intensely are these. They corroded, pins fell off, middle pulled up with the tube (2nd one down):
http://www.ebay.co.uk/sch/i.html?_trksid=p3984.m570.l1313&_nkw=loctal+socket&_sacat=0&_from=R40
These look interesting:
1 Tube Socket loctal for C3g C3m C3o Siemens Telefunken Post Rohre | eBay
These are the Russian type - they come shielded and unshielded.
Loctal sockets shielded used Lot of 8 | eBay
I don't know if a 4P1L goes into a shielded socket, and I'm even more unsure of how you'd get it out except by pushing it from the bottom!!!
The ones I use are Chinese as above. The ones I used to have a lot of and dislike intensely are these. They corroded, pins fell off, middle pulled up with the tube (2nd one down):
http://www.ebay.co.uk/sch/i.html?_trksid=p3984.m570.l1313&_nkw=loctal+socket&_sacat=0&_from=R40
These look interesting:
1 Tube Socket loctal for C3g C3m C3o Siemens Telefunken Post Rohre | eBay
These are the Russian type - they come shielded and unshielded.
Loctal sockets shielded used Lot of 8 | eBay
I don't know if a 4P1L goes into a shielded socket, and I'm even more unsure of how you'd get it out except by pushing it from the bottom!!!
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I ordered also a couple from Moscow, Russia, here:
''GSTube.com''. Tubes, sockets etc. Search result for <u>pl3-5-14</u>
''GSTube.com''. Tubes, sockets etc. Search result for <u>pl3-5-14</u>
Changing the subject a bit, have any of you guys used anything like dampeners around the bottle of the 4P1L? It's about 28mm diameter. A friend suggested this very cheap and useful box of O-rings. They include 25 x 3.5, 26.5 x 3.5, 28 x 3.5. For a preamp this looks useful:
419 PIECE RIC RUBBER O RING SEALS SET PLUMBING TAP WASHER ORING PLUMBERS | eBay
I've been using teflon plumbers tape. I'll see if I can upload a picture.
419 PIECE RIC RUBBER O RING SEALS SET PLUMBING TAP WASHER ORING PLUMBERS | eBay
I've been using teflon plumbers tape. I'll see if I can upload a picture.
I bought a 10 pack of 3mm x 26mm viton 75 high temp o rings, nice tight fit, didn't make much difference, they still sing along!
enzo
enzo
I'm looking for a DHT headphone amp for my Sennheiser HD600, I saw this schematic regal posted in other thread of moglia.
I have several questions:
-Can I use only one Salas SSHV2 for the two anodes?
-If yes how much current have to set plus de 20mA required for the reg?
-Value of interestage capacitor?
-Value of resistor for bias filament & Rod Coleman heaters reg?
-The OPT for my Senns must be 5K:300ohms or lower?
I have several questions:
-Can I use only one Salas SSHV2 for the two anodes?
-If yes how much current have to set plus de 20mA required for the reg?
-Value of interestage capacitor?
-Value of resistor for bias filament & Rod Coleman heaters reg?
-The OPT for my Senns must be 5K:300ohms or lower?
hi Felipe,
It's possible to use one shunt-regulator for power and driver stages. But if each stage draws 30mA each the standing-current will be 80mA or more at 150-250V (you must choose your B+ value in this range - draw some load lines for the output transformer you plan to use. Ale has some triode curves posted here somewhere, I think). Please check that your regulator can support this high power level (depends on power transistors, and size of heatsink).
It will work better if you use 1 shunt regulator for drivers, 1 for power stage, I think.
for e.g.: 200V B+, the filament-bias resistor is chosen like this:
- bias required at 200V: 15V approx for 30mA (Anode dissipation <6W - against max. of 7,5W).
- filament current 500-650mA (adjustable to suit 1,2V connexion)
- bias resistor = 15V/If = 24 to 33R
- resistor power dissipation: 7,5 to 10W. Use 3 or 4 parallel 100R 10W wirewound, eg Welwyn W23 or W24.
At 150V B+ the bias is about 10V so you can use about 20 ohms with 15W handling.
It's possible to use one shunt-regulator for power and driver stages. But if each stage draws 30mA each the standing-current will be 80mA or more at 150-250V (you must choose your B+ value in this range - draw some load lines for the output transformer you plan to use. Ale has some triode curves posted here somewhere, I think). Please check that your regulator can support this high power level (depends on power transistors, and size of heatsink).
It will work better if you use 1 shunt regulator for drivers, 1 for power stage, I think.
for e.g.: 200V B+, the filament-bias resistor is chosen like this:
- bias required at 200V: 15V approx for 30mA (Anode dissipation <6W - against max. of 7,5W).
- filament current 500-650mA (adjustable to suit 1,2V connexion)
- bias resistor = 15V/If = 24 to 33R
- resistor power dissipation: 7,5 to 10W. Use 3 or 4 parallel 100R 10W wirewound, eg Welwyn W23 or W24.
At 150V B+ the bias is about 10V so you can use about 20 ohms with 15W handling.
Thanks Rod, do you know if can handle high Z headphones? insterstage cap value 100nF or 47nF? do you kow secondary value of OPT?
Hi Felipe,
Grid resistor of 500K is specified, BUT the tubes are old and you are planning to use fixed bias, at least for the output stage. Maybe use 330K for the driver, 220K for the output stage (Anatoliy will have more experience of the actual 1st-grid leakage value).
In this case, 100n for the driver input coupling cap, 150nF for the output stage cap.
As for high Z headphones - should be OK, but the load line of the transformer-load must be plotted, to make a proper check.
Grid resistor of 500K is specified, BUT the tubes are old and you are planning to use fixed bias, at least for the output stage. Maybe use 330K for the driver, 220K for the output stage (Anatoliy will have more experience of the actual 1st-grid leakage value).
In this case, 100n for the driver input coupling cap, 150nF for the output stage cap.
As for high Z headphones - should be OK, but the load line of the transformer-load must be plotted, to make a proper check.
I'm looking for a DHT headphone amp for my Sennheiser HD600, I saw this schematic regal posted in other thread of moglia.
I have several questions:
-Can I use only one Salas SSHV2 for the two anodes?
-If yes how much current have to set plus de 20mA required for the reg?
-Value of interestage capacitor?
-Value of resistor for bias filament & Rod Coleman heaters reg?
-The OPT for my Senns must be 5K:300ohms or lower?
The intent was that the SSHV would supply the output tube only because the input tube has a DN2450 casode, prefiltering is CLC. Otherwie your case would be a big ugly heatsink.
The coupling cap is .5uf (copper foil PIO), I didn't draw the grid leak resistors, should be about 100k. Also would recommend the filament bias on both tubes.
But if you are as interested in hearing how this sounds as I am we both need to find a good output transformer. One that is designed from the ground up for headphones not speakers, this is what has been holding me back on the project. A good headphone transformer is more than just winding a long secondary on a speaker transformer.
We want to take advantage of the lower stepdown ratio but at the same time not end up with a ridiculous 12 ohms DCR in the secondary. Parafeed permalloy may be the best answer, this is why the project is at a standstill there are practically no output transformer designers left who are willing to work with an individual for a novel OPT design. For senns be very careful you don't end up with a crazy 200 ohm DCR secondary. If you have any help on that end let me know.
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I know one person in Spain how makes hand made grain orientated, can't be enough? what about Lundhal LL1689 http://www.lundahl.se/pdf/1689.pdf, can be wired 9:1 or 18:1?
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Sowter still offer custom OTs to any who fill out the form:
SOWTER TUBE VALVE OUTPUT TRANSFORMERS
Not exactly cheap, but no charge for the design work, so you can really get something optimised. They have a huge range of Prosound mixing desk, line & headphone trafos, too, so Brian will know just how to implement your requirements.
SOWTER TUBE VALVE OUTPUT TRANSFORMERS
Not exactly cheap, but no charge for the design work, so you can really get something optimised. They have a huge range of Prosound mixing desk, line & headphone trafos, too, so Brian will know just how to implement your requirements.