How much solid state in your amp?

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Paul Barker
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Post by Paul Barker » Sun Jan 20, 2008 2:50 pm

Boatanchors are just impractical. I praise the introduction of solid state to make things more possible, with a slight alteration in sonic, but not that bad.

I have done it all ways, including the full on boatanchor. At the end of the day, the boatanchor isn't really worth the gargantuan effort, even though it is the best which can be done. Do we have to have the best? There are weaker links in the chaon, such as speakers cartridges recording quality.

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Nick
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Post by Nick » Sun Jan 20, 2008 3:00 pm

I do wonder sometimes if some of use have lost their way
Well given that no two people are aiming at the same destination, who can say?
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Post by Max N » Thu Dec 18, 2008 11:23 am

Paul
I like your idea of a bridge of freds passed through a single schottky. I think I will give this a try. Do you do anything to delay the HT? Delay, slow start, seperate switching of the heaters or just not worry about it?

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Post by Paul Barker » Sun Sep 04, 2011 8:48 am

sorry Max missed this.

Actually my Ht is a very difficult kettle of fish to cope with.

If I let the 6em7 heat all the way up, it pulls sufficient current for the power supply ripple to be sufficiently dealt with by the first stage of shunt valve/VR combinations such that there isn't enough strike voltage for the second stage of shunt filtering. So it has to be judged by yours truly, generally when the 6em7 gets to about 4.5 volts (by the way it is a slow warm up valve so would make a good delay valve in itself) I can power up the Ht and there is sufficinet ripple for both stages of shunting to strike.

SO mine has to be manually switched on, heaters first then HT.

I don't want anyone else turning it on anyway, and when I am no longer on earth to turn it on what ever happens to it happens. I can't take it with me. Unlike the millionaire who specified in his will all his money to be buried with him. his wife wrote him a cheque saying "he can cash that if he wants to!"

The reason I use solid state diodes is that I have to start with 400mA of current pull and whereas I recognise that mercury vapour rectifiers might be optimal I can't get everything perfect right away. It is probably going to end up with mercury rectifiers one day.

Actually it did just occur to me that I could implement a very low current high voltage winding with an unfiltered half wave rectifier to use like a match to strike the FR tubes. Just flash them with HT, maybe have a bank of small scope capacitors on voltage doubler ie typical scope supply just to strike the VR's.

If anyone thinks it is easy to provide three direct coupled stages using VR tubes for seting the levels and two stages of vr tube behaviour in the power supply. BE MY GUEST!

i will give you a hint. every individual VR tube has it's own specific behaviour each has it's own preference for when it will strike and each has it's own level at which it will regulate, and that level differes depending on the current it is passing. Then when you have 8 in series you have to configure 8 individualistic critters to behave in unison predictably every time. Then the behaviour of that string of critters has to be made to akllow for the behavioour of another equally ornry string of critters, such that neither steals the show from the other. Then when you get to the amplifier you have to find a critter for each stage which makes room for the critters for the other stages and if you are really lucky you might find everntually that you can end up with an operating point which is on the same page as the spec sheet for the valve, memaybe even somewhere on the same graph, even some stages might be pushed over to a suitable vague area along that graph.. Along the way you will watch in despair as beautiful valves which will never be made ever again glow bright and burn up in front of your eyes. EVERY single valve and every single VRtube has to be tested for predictable performance at the specific scenaio you are planning (aided only with knowledge, similar experience and a calculator), then with a brave face on you try again and put all the parts into place and switch on, then hurry round the points to test what is happening and who is suffering or who is not getting enough. These are all my babies and I have just about tamed them. not many of them are set up at any so called perfect operating point, but there are no coupling caps there are no cathode resistors, no anode resistors and from the DAC to the output transformer the only things in the signal path are wire and three glass bottles containing a vacuum.

But you could never make one to sell.

i have torched a few 112a's a few 45's some balloon, copius VR tubes. But what I have ended up with is now stable, has good tone, perfect low level detail extraction, now the Black Gates are gone is void of sibilance or capacitor inspired tone control, has no bottom to the bass charactertistics or speed of response to crescendos (especially since the new opamp went in) and sounds best I have heard anywhere on planet earth. (Not that I've been out of my body to go anywhere off the planet! I imagine off planet there is better.)

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JackOfAll
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Post by JackOfAll » Sun Sep 04, 2011 11:14 am

deleted

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MrAcoustat
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Post by MrAcoustat » Mon Jul 16, 2012 10:14 am

Well for me it's 100% solid state Chord CPM-2600 integrated amplifier very decent and it does the job for ME on 81db speakers that's asking alot of an amplifier.
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floppybootstomp
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Post by floppybootstomp » Wed Jul 18, 2012 4:55 pm

Solid state devices in valve amp? Have just had a look at the cct diag to my Elektor pp amp and all it has is four diodes in HT line. Heater supply is AC.

That's the only valve amp I have apart from a headphone amp I recently bought from Hong Kong This one which I don't have a circuit diagram for and I haven't had a look inside yet.

For those curious, the headphone amp, in my opinion, sounds very good indeed and is well constructed. It does work very warm and if you want to use it with a speaker driving amplifier the way the audio signal is routed through the headphone amplifier means it's dependent on headphone amp volume control which means leaving headphone amp on all the time.

So I'm currently making a 2-way switcher based on the NWO relay switcher.
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floppybootstomp
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Post by floppybootstomp » Wed Jul 18, 2012 5:13 pm

Here's my psu as mentioned above, a very simple affair:

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Clive
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Post by Clive » Thu Jul 19, 2012 4:03 pm

All SS in this one:

Image

10W Class A monoblocks, floating quiescent current. Single Ended too, even if the pic makes you think there are 2 output transistors - there is only one.

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Paul Barker
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Post by Paul Barker » Thu Jul 19, 2012 7:24 pm

Doesn't seem much of a heat sink for 10W class A! Does it not get too hot?
I can do it right or I can do it now, but I can't do it right now.

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MrAcoustat
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Post by MrAcoustat » Thu Jul 19, 2012 7:34 pm

This is a Classé DR3-VHC PURE CLASS a 45 watts per channel with 4 12 inch heat sinks and a hefty 102 pounds.

[ Image ][/img]
Last edited by MrAcoustat on Thu Jul 19, 2012 7:35 pm, edited 1 time in total.

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pre65
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Post by pre65 » Thu Jul 19, 2012 7:35 pm

I had a much bigger heatsink when I did my mosfet single ended monoblocks , and they only had one mosfet per channel.
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chris661
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Post by chris661 » Thu Jul 19, 2012 8:13 pm

I have two set-ups.

One's the one most of you saw at Owston. 15w/ch switching amplifier for the Fostex FR drivers, and a pro amp of >120w/ch for the low-sensitivity bass drivers. During (loud) films and things, I reckon there's 10s of watts going into those bass drivers.

Check the heatsinks on this!! :roll:

Image

The other is (at the moment) completely valve-based. The thread's over in the Beginners section.
I plan on adding some silicon in the form of half of a bridge rectifier. This will allow me to use a transformer I've found on eBay to up the HT to somewhere near what it ought to be. I would've liked to keep it all-valve, but a high power dual diode would be needed, which would add more cost than a couple of bits of silicon.

Chris

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pre65
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Post by pre65 » Thu Jul 19, 2012 8:29 pm

A hybrid bridge is fine Chris, I use them on most of my amps. :wink:
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Post by Mike H » Fri Jul 20, 2012 1:51 pm

All-valve bridges always were possible, the reasons they weren't typically done are cost / power consumption / heat / space.

Plus, radios used to be taxed on how many valves it had got.

A full-wave CT winding solves a lot of these problems, hence I still maintain that that was the only real reason for having a full-wave winding
 
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