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My Hk W-5M amp restoration has paid off. I'm hearing very good things. I haven't done a head-to-head comparison yet with my (on the shelf) Eico HF81. Maybe apples n oranges.
The new SDS board power supply settled ALL the voltages down, near spec. The tubes are happy, I'm happy. Things still breaking in, so to speak.
I wish I could get more gain - I seem to lose some with my passive preamp. At full volume, it's not quite as loud as it should be. Fewer resistors in the input to the first tube? (Mike said sumthin about 30uf bypass cap on cathode of 1st tube; was a concept I don't know about).
thanks for input (har, har)
Peter
Edits: 06/27/12Follow Ups:
Matching audio transformers? Heathkit had two versions with the larger audio transformer more reliable than the early audio transformer known for failure. Perhaps a shorted power tube takes out the audio transformer. A fast blow fuse in the B+ to audio transformer may be of some benefit.
Replace the octal rectifier socket and add those .1 630v bypass caps on the SDS board too.
Socket already done. Funny that Mr Stokes doesn't mention the .1 bypass capacitors in his instructions. I figured maybe he backed off supporting their purpose.
I can always add them; maybe for comparison's sake.
Peter
The .1 caps have no effect except on older filter caps where it can lower the effective esr that the cap sees...If you have good low esr eletrolytics like panasonics or nichicons,.1uf bypass caps are pretty much useless.
Where bypassing really became popular was in the 70s and 80s on the big solid state amps with 20,000uf and up computer grate electrolytics because of their high esr..People then starting putting them on older tube amps..A 2uf oil or film and foil can make a difference across an electrolytic..I use 5uf ploys in the citation 2 decoupling capacitance.
When problems become increasingly difficult,we can always rely on our collective knowledge and seek relief.
Edits: 06/29/12
yes, thanks for info. I've never really done the ~.1uf bypass caps on PS electrolytics. But companies like ARC put them in on their best tube preamps such as SP-3, in 2 stages. And I think they know a thing or two.
I can always get 630V-rated Solen caps in 2-5uf values. There may be room for their big diameters.
Pete
they can have a bright tinny sound. If they are used, bypassed with 10th value polypro works well and then I think they can do well. Just my opinion after working with the Solen in all types of gear. I advised them to Mike of Quicksilver years ago and he bought a bunch only to tell me they were terrible. I had told him they needed to be bypassed and then do a good job but for some reason he didn't want to do the bypass so he never heard what they can do. For an all in one cap though, there are others but it depends on available area of course.
The Elaborate DAC=Johnny's Balloon Meshplate 27 Balanced Preamp=Balanced Six Pacs=Newform Research 645
iRiver H140/MB Balanced dac/amp/Ultrasone Ed. 9/JH13 Pro IEM's
see images at: www.pbase.com/jamato8
John
You are right in that there are better caps than solens but for bypass and filtering,the larger solens are decent..I will not use them in the audio path but I use them in speaker crossovers where no DC is present and there the larger values sound ok also,,Martin Logan uses one big solen in their 130k dollar Statement speakers in the bass crossover..
When problems become increasingly difficult,we can always rely on our collective knowledge and seek relief.
Edits: 06/30/12
I understand what you are saying. From my work with them, once bypassed, they step up quite a bit and smooth out but in my experience, only if bypassed, which is inexpensive to do.
The Elaborate DAC=Johnny's Balloon Meshplate 27 Balanced Preamp=Balanced Six Pacs=Newform Research 645
iRiver H140/MB Balanced dac/amp/Ultrasone Ed. 9/JH13 Pro IEM's
see images at: www.pbase.com/jamato8
nt
with the polypropylene (the orange ones) in .1 and and I would sometimes also use .01, they sound pretty good. You also don't have too much invested.
The Elaborate DAC=Johnny's Balloon Meshplate 27 Balanced Preamp=Balanced Six Pacs=Newform Research 645
iRiver H140/MB Balanced dac/amp/Ultrasone Ed. 9/JH13 Pro IEM's
see images at: www.pbase.com/jamato8
It could be he sent the .1uF 630v bypass details in an email.
Peter
That amp is a fantastic williamson design.It has a bandwidth from 5hz to 160khz and at 25 watts its only .3% distortion.The 12au7s are run pretty hard and thats why I opted for the 6cg7 with a filament rewire..You won't increase gain but you do lower distortion by a lot being tube isn't saturated.
Now,if you want to increase gain without using a gain type presmp you have a couple options.One is to change V1 to a 12at7..You have to change plate load resistors as well as cathode resistors.The other option is to open the feedback loop more by changing the 4.7k to a 10k.You can also change the cathode resistor at V1 which is a 470 ohm to s 680 in series with a 100 ohm to ground.Insert the FB wire coming from the 16 ohm tap between the 680 and the 100 ohm.
I personally would use a gain preamp but I have done these things also.
Lastly,take out those 1uf polys from the 12au7s to the kt66s..The original black pyramid wax paper caps in there were gorgeous sounding.Get some .47 k40s and run two in parallel to each tube,or get some Jupiters because those little metallized caps will not give you the rich and layered original sound the amp was designed for.Those are gorgeous amps that you got for a steal so treat them to good stuff..You will hear a difference in the couplers.
When problems become increasingly difficult,we can always rely on our collective knowledge and seek relief.
I'm not sure what i would use for an active pre. Non-tube would be out of the question, I think. Maybe I shoulda kept my last Eico HF85. I would rather keep from putting new, extra stuff in the signal path.Apparently, the guitar amp crowd puts 20uf+ on the cathode of 1st tube to increase gain. Tone effect. The link below is to the calculator for values and frequencies. But is this a hi-fi use? and will it screw with feedback?
I have 12BH7 on phase splitter position . Hi-Q 5814 on input, for now.
Edits: 06/28/12
Try Brimar 13D5 or for even better performance Tungsram E80cc. I used the E80cc on my W-5Ms and extra .3 amp on the E80cc filament did not bother the power transformer. HF-85? These W-5M are more cool to me plus are monoblocks!
...tubes for the 12AU7 positions. I'd love to try E80CCs, but they're not cheap. I might have to cough up real money (gasp!). Meanwhile, I find 6CG7s down in my sofa cushions.I was referring to (sold) Eico HF-85 preamp that I could've used for these Heath monoblocks.
I still have my HF81, which I mentioned earlier. Sure digging some Stones on the Hk W5's now. 6P3S-E's from Mr McShane working very well, perfectly balanced and running 47.5V bias.Peter
Edits: 06/28/12
Thats a hell of a great tube,the 6p3se.
When problems become increasingly difficult,we can always rely on our collective knowledge and seek relief.
I just received some Brimar 13D6 blackplates (12BH7 equivalent).... man these are outstanding !!
Very high resolution like the truly refined Tungsram E80CC, except that these are less hi fi sounding-i.e: a whole lot more musical ;-)
13D6=12BH7- tnx for tip.
Underneath. Circuit unaltered, just a lotta new parts.
I think the CL-190 'inrush limiter' is worthless. Not sure it does its job.
Edits: 06/28/12
with a higher gain for your input tube.
The Elaborate DAC=Johnny's Balloon Meshplate 27 Balanced Preamp=Balanced Six Pacs=Newform Research 645
iRiver H140/MB Balanced dac/amp/Ultrasone Ed. 9/JH13 Pro IEM's
see images at: www.pbase.com/jamato8
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