|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
75.51.105.65
In Reply to: RE: Heath monoblocks complete, sounding very good (picture) posted by PeterI on June 27, 2012 at 13:02:22
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.
Follow Ups:
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.
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: