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15th August 2012, 05:43 PM
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#1951 | |
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diyAudio Member
Join Date: Jul 2011
Location: Ukraine, Dnepropetrovsk
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Quote:
I build pre-amp, I have a question: 1. Why should (SSHV + CCS + Preamp)? I understand it - the sound is good, very little noise is 120Hz, Out THD is very small ... but 2. If you can only use (CCS + Preamp) - we have too - sounds good, Out THD is very small ... 3. use in the anode Cascode CCS (DN2540) - we always have - the sound is good, Out THD is very small (almost perfect) ... good rejection of power supply ... what improvements we have with the scheme (SSHV + CCS + Preamp), when compared with (Girator + CCS + Preamp)? any thoughts on this? Why complicate things? Vyacheslav. |
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24th August 2012, 02:06 PM
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#1952 |
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diyAudio Member
Join Date: Nov 2007
Location: athens
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I am about to begin a 26 linestage ...
got a bounch of tubes, sshv2 and waiting for rods regulators ... havent yet decided about the b+ ps, whether its gonna be ss or tube rectifier, and if its gonna be tube ... which tube .... I have one question, apart from the LL1660 and Thomas new LL2745 (8ma) are there any other ot suggestions to look at? thanks ! Pretty much I'll follow this schematic by Rod |
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24th August 2012, 03:45 PM
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#1953 | |
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работник
diyAudio Member
Join Date: Jul 2004
Location: Warwickshire UK
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Quote:
Transformer output is excellent choice in many ways - but the transformer must be a very high quality part to do justice to the 26 line amp. The LL1660 certainly meets the requirements, but the cost is quite high. Maybe others have tried different high quality trafos - anyone?? The alternative is some kind of cathode follower to give the necessary high-drive, low output impedance to suit cable-driving. Here's another circuit combining filament bias and a cathode follower - with the heater of the 6N6 forming the load of the filament bias for the 26 (saving you a heater supply). This should give very good sound for the cost! . |
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24th August 2012, 04:11 PM
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#1955 |
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diyAudio Member
Join Date: Nov 2007
Location: athens
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24th August 2012, 05:32 PM
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#1956 |
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diyAudio Member
Join Date: Sep 2003
Location: London
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I have some new Hammond 156C chokes right now I'm not using if anyone is interested - just send me a personal message.
Andy |
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24th August 2012, 07:46 PM
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#1957 |
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diyAudio Member
Join Date: Dec 2009
Location: London
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Gyrator with mu-follower output provides low output impedance. Good output cap and is a very simple and cost effective preamp...next step, as Rod suggested, you can add a source follower to increase the current driving capability...
Good filament bias preferd and quiet HT supply is required of course... Ale
__________________
"A mistake is always forgivable, rarely excusable and always unacceptable. " (Robert Fripp) http://www.bartola.co.uk/valves/ |
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24th August 2012, 08:11 PM
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#1958 |
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diyAudio Member
Join Date: Dec 2009
Location: London
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I've been testing the LL2745 OT in the workbench and now am planning to build the following incarnation of the 26 preamp. I will use the Gary Pimm's approach to CCS+VR as HT. I have done some tests recently and they perform really well (i.e. over 60dB attenuation at 50Hz). I'm re-using the HT and LT raw supplies but luckily can try the operating point that found in the workbench to be quite good for the 26 (after previous tests and preamps versions).
I don't have at the moment a balanced input amp, however I'd like to leave this preamp ready for future push-pull amp project which may have a balanced input. I can then wire a special set of cables with the pins 2 and 3 only... thoughts? Ale
__________________
"A mistake is always forgivable, rarely excusable and always unacceptable. " (Robert Fripp) http://www.bartola.co.uk/valves/ |
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26th August 2012, 12:32 AM
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#1959 |
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diyAudio Member
Join Date: Oct 2009
Location: New Jersey, USA
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Just received the panels from Front Panel Express. Everything came out great except for one minor glitch...the bottom panels were chromated on the wrong side...we're working that one out. The chromating gives a corrosion-free finish so I can use the bottom panels as ground planes. Other than that they look great! I've attached snapshots of the front and back panels of the linestage and power supply.
The front panels are 5mm thick aluminum, the back are 2.5mm thick aluminum. All are powder coated in jet black and engraved with ochre brown infill. The cutouts line up perfectly with the Bent Audio control and input selector panels, too. The top panels of both units have been dropped off at a local plating shop for triple chrome plating to a mirror finish for that extra little bling. Once I get the bottoms straightened out the build can be completed, hopefully within the next 2 weeks! |
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