moo-fi

SET amps

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Super Wammer

I'm travelling through Yorkshire on Monday Fred (got a site visit in Bradford on Tuesday) .....I could bring the type 26 fir you to have a closer look at etc 

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1 hour ago, moo-fi said:

Heard Keith's at one of our Welsh bake off's along with his 845 power amps. This is one of the reasons I started looking at DHT's, the other is the aforementioned horns which are crying out to be used. 

Quiet power supplies are an art form, everything needs to be considered and is the area which I am most concerned about.

The basic amplifier circuit is about as basic as it gets, which also means there isn't any hiding place for poor PSU design. 

I love power supplies, as anyone who has been here will attest to. The issues really are that ideally a DHT needs constant current sources, but constant current for the heater (and therefore cathode) can damp the dynamics. A DHT with a choke plate load and an AC filament supply has absilutely stunning dynamics and sonic character, but more noise than a 747 at takeoff.

Goes back actually to James' first comment about tradeoffs. That said, the basics will be the same whatever you do. A clean B+ for a start, but here, just valve rectification and something like a good CLCRCRC chain will be fine. Start off with enough voltage obviously, as it's better to lose some through having enough resistance to get a proper filter. Experimenting is not really an issue here, because the costly bit is the output transformers, and they'll be the same no matter what you do. If you haven't already got it, download PSUd power supply design sim software. It's straightforward, not extensive, but gives accurate results for expected voltages and ripple with 'standard' formats of chokes, capacitors, resistors and current loads. It's saved me endless hours of wasted time.

The other big positive is that it's a power amp, not a preamp, so some of the noise issues are less of a problem because the noise floor can be significantly higher.

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The Bartola link seems very good news, particularly with regard to PSU's. I don't know if anyone has come across the Rod Coleman DHT supply, but it seems to be just the thing:  http://lyrima.co.uk/heatv7pdf/.

39 minutes ago, MF 1000 said:

I'm travelling through Yorkshire on Monday Fred (got a site visit in Bradford on Tuesday) .....I could bring the type 26 fir you to have a closer look at etc 

Thanks Keith, but I should be in Ireland actually doing some work, if I can get there, and at this stage it could involve driving back down to Pembroke to catch a ferry!

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I use both the tentlabs supply and ones which a few of the lads over on audio talk designed, there s a 70 page thread about them.. 

A few years ago we had a test at one of the audio talk diy meets at doncaster with some interesting results. I moved to dc filament supplies after that.

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28 minutes ago, moo-fi said:

The Bartola link seems very good news, particularly with regard to PSU's. I don't know if anyone has come across the Rod Coleman DHT supply, but it seems to be just the thing:  http://lyrima.co.uk/heatv7pdf/.

Thanks Keith, but I should be in Ireland actually doing some work, if I can get there, and at this stage it could involve driving back down to Pembroke to catch a ferry!

Rod Coleman boards are ideal Fred. I've used them for a few things. They're excellent value and Rod is very helpful as well.

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11 minutes ago, steve 57 said:

I use both the tentlabs supply and ones which a few of the lads over on audio talk designed, there s a 70 page thread about them.. 

A few years ago we had a test at one of the audio talk diy meets at doncaster with some interesting results. I moved to dc filament supplies after that.

I always forget Tentlabs stuff for some reason. It's ideal, but not the best value necessarily. If you can use a soldering iron, the Coleman boards are conspicuously good value.

In danger of going off topic, but it might be relevant and useful  in this regard anyway. Has anyone tried the Tentlabs E-chokes?

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Posted (edited)
36 minutes ago, rabski said:

Rod Coleman boards are ideal Fred. I've used them for a few things. They're excellent value and Rod is very helpful as well.

I use them in both of my DHT preamps, and yes Rod is very helpful.. Especially when you have killed one of his supplies!  :doh:

Edited by awkwardbydesign
  • Haha 2

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For a dht preamp it doesn't get much simpler than a bottlehead quickie. Pretty sure the schematic is available online with a search.  I paired one with a Nelson Pass 6w ACA total build was under £150 if I rember and that was using some nice components. Amazing sonics for peanuts. Sold it a while back but fancy building one again sometime.

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Super Wammer
5 hours ago, awkwardbydesign said:

I'm just starting to look into a Tubelabs 845 SE amp.  More power and complexity than you want, I think, but he does simpler designs.  Like this - http://tubelab.com/designs/tubelab-sse/

My question will be, can the  845 SE drive Quad 2805s properly?

Robin happily drove the 989s and his 2905s with 18w Mingda 845SE monos

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Super Wammer

Mind you he has said my full fat Icons (90wpc) have taken the 989s to another level and he'd never heard them sound so good. 

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For a dht preamp it doesn't get much simpler than a bottlehead quickie. Pretty sure the schematic is available online with a search.  I paired one with a Nelson Pass 6w ACA total build was under £150 if I rember and that was using some nice components. Amazing sonics for peanuts. Sold it a while back but fancy building one again sometime.
Kit is discontinued sadly, and I don't see the circuit released into the public domain, but it is very simple and sounds excellent!

Sent from my BLA-L09 using Tapatalk

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Super Wammer
34 minutes ago, awkwardbydesign said:

I've been looking at the MB90s, as I couldn't afford the 845s.  But they are PP.

As are my MB845SEs (the SE = Signature Edition) 

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Super Wammer
2 hours ago, awkwardbydesign said:

Damn, I was already regretting selling mine to Keith. >:(

You've been regretting selling them ...since you sold them to me.  I'm still treating them nicely 😀

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