Eli
I've just been re-reading through this post thinking about the heater; what is a CT transformer?
An externally hosted image should be here but it was not working when we last tested it.
Of Course! Cheers.
That is a very common myth. They still have a junction capacitance that stores and releases a charge when switching on / off. Here is a nice concise discussion of the same: http://www.irf.com/technical-info/appnotes/an-968p8.pdf
Do you probably mean his Super Symmetrical Cathode Follower ? He also mentions a possible “-20dB reduction of second and third harmonic distortion.” And there is a low voltage tube version included: More cathode follower stuff
A good cheap option for a heater supply is to use one of those wall block power supplies (the heavy ones - not the SMPS type). Every house has loads of redundant ones about. Child intercoms generally run at 6V. Many are either 6V,or 12V which is OK because heaters can be series or parallel connected.
Remember to tightly twist the heater wires - do a google search to find tips on correct routing.
Shoog
Remember to tightly twist the heater wires - do a google search to find tips on correct routing.
Shoog
HT Transformers - I have had great success from this UK industrial transformer builder.
1 PH Trans
They do custom stuff (just enter primary & secondary voltages in webshop checkout).
They do any voltage you like for the same price, and they don't hummm (ganz ohne brummen)!
I have used their 100VA (£12) 150VA (£18.66) and 250VA (£26.76) with all kinds of voltages and they have all been just the ticket. The larger ones had screened primaries, which I consider a big plus. Windings resistances have been low (about 10R for 240V 1A winding)
You can specify two windings ( I have used 0-340V and 0-30V for fixed-bias amps), but I haven't tried heater windings on them yet (only because I have a stash of 6V trafos)
Two things to watch out for:
1. Price is excluding VAT on the web - add £12 for (UK) shipping and VAT onto the total price - makes it worth ordering more than one to take advantage of the pricing.
2. The finish is industrial - "baked bean" coloured varnish and open frames, so not for a top-plate mounting, unless you like industrial style.
Other than that, I like them a great deal - O, I forgot, it only takes them a few days to ship custom designs, some of mine have arrived next day.
1 PH Trans
They do custom stuff (just enter primary & secondary voltages in webshop checkout).
They do any voltage you like for the same price, and they don't hummm (ganz ohne brummen)!
I have used their 100VA (£12) 150VA (£18.66) and 250VA (£26.76) with all kinds of voltages and they have all been just the ticket. The larger ones had screened primaries, which I consider a big plus. Windings resistances have been low (about 10R for 240V 1A winding)
You can specify two windings ( I have used 0-340V and 0-30V for fixed-bias amps), but I haven't tried heater windings on them yet (only because I have a stash of 6V trafos)
Two things to watch out for:
1. Price is excluding VAT on the web - add £12 for (UK) shipping and VAT onto the total price - makes it worth ordering more than one to take advantage of the pricing.
2. The finish is industrial - "baked bean" coloured varnish and open frames, so not for a top-plate mounting, unless you like industrial style.
Other than that, I like them a great deal - O, I forgot, it only takes them a few days to ship custom designs, some of mine have arrived next day.
I should be able to find a 9/6VDC Transformer at work before the end of next week; I'm one of a team of Traveling engineers most of us have are car boots full of PSUs, I was rummaging last night, loads of 12s and 24s but no 9s or 6s, typical.
Looks good for future ref', cheers Rod
Are there any golden rules/guidelines regarding the wire to be used?
I have some silver plated 24AWG PTFE coated wire i intend to use on short runs between the components and also twisted (as advised) for the heater power.
I also have some screened Van Damme install cable to carry the signals too and from the amplifier circuit.
Why twist the heater supply? Is it have some sort of noise rejection?
I have some silver plated 24AWG PTFE coated wire i intend to use on short runs between the components and also twisted (as advised) for the heater power.
I also have some screened Van Damme install cable to carry the signals too and from the amplifier circuit.
Why twist the heater supply? Is it have some sort of noise rejection?
It's noise cancellation. The heaters are energized by (sic) AC. Twisting the supply wires causes self cancellation of the oscillating magnetic field such a current implies. The unit will hum, like a SOB, should the twisting be omitted.
Randomly induced signals, at the power mains freq., are VERY bad.
It's only silver plated, it takes 5% Ag solder very nicely and whats really nice is PTFE coating does not shrink back at all when your soldering!
Mounted the valves and some lengths of Tag board into the chasis; my metal-work leaves a bit to be desired but as long as you dont look to close it's all looking good; I particually like the way the Tagboard screwed streight into the upstands left by the old Power Amp board and the valves lign up perfectly with the venting on the lid and base of the chassis:
Why would that be? how would silver coating even efect the sound?
I could only imagine the PTFE would have any effect on the sound if the cable is in close proximity to another as in the capacitance of an interconnect, and even then PTFE is often championed by the audiophools. But then the audiophools will tell you a 30 quid gold plated fuse "tightened up the mids and noticeably improved the bass response" so I take their opinions with a pinch of salt.
With JB's recent super triode article(mosfet/low voltage triode), I will expect the space charge tube will be rocket-high in ebay very soon
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