Search found 641 matches

by izzy wizzy
Thu Feb 21, 2019 3:45 pm
Forum: Everyones Projects
Topic: Looking for recommendation for Phono Stage
Replies: 62
Views: 1536

Re: Looking for recommendation for Phono Stage

This is from a D3A datasheet. I appreciate this is for operation as a pentode, but I'm struggling to understand why BOTH a cathode resistor and a positive grid bias are recommended ? With 22mA through the cathode a 400R will set the cathode to 8.8v, leaving G1 at +1.2V ? What am I missing ? Capture...
by izzy wizzy
Mon Feb 11, 2019 11:45 pm
Forum: Assorted Stuff
Topic: Black Gates
Replies: 13
Views: 315

Re: Black Gates

Reckon I might do some auditioning of other caps and sell mine on if even used ones get good money. They're good but not that good ... well from memory anyway.

Cheers,
Stephen
by izzy wizzy
Fri Jan 25, 2019 4:03 pm
Forum: Everyones Projects
Topic: Remember These?
Replies: 449
Views: 12883

Re: Remember These?

Whatever music sounded fab on the OTL, don't play the same music with the SS amp. Just play something else so you can't compare. Works for me ;)

Cheers,
Stephen
by izzy wizzy
Tue Jan 22, 2019 12:20 pm
Forum: Everyones Projects
Topic: Looking for recommendation for Phono Stage
Replies: 62
Views: 1536

Re: Looking for recommendation for Phono Stage

RhythMick wrote:
Mon Jan 21, 2019 6:09 pm
Perhaps 2 breadboards, winner stays on, keep trying to improve...
I do something similar on the one I use. Mono the input and output with a combining connector and then modify one channel - swap back and forth.

Cheers,
Stephen
by izzy wizzy
Sun Jan 20, 2019 7:52 pm
Forum: Everyones Projects
Topic: Looking for recommendation for Phono Stage
Replies: 62
Views: 1536

Re: Looking for recommendation for Phono Stage

I model in LTSPICE, make it, fiddle a bit with values, listen, remodel and round and round. I can't measure accurately enough so don't bother. I reckon getting the EQ right is only possible in a model (calculators aren't up to the job) and small changes can alter the character quite a bit hence it's...
by izzy wizzy
Sun Jan 20, 2019 5:58 pm
Forum: Everyones Projects
Topic: Looking for recommendation for Phono Stage
Replies: 62
Views: 1536

Re: Looking for recommendation for Phono Stage

This is excellent news as they are cheap. I'll give them a go soonish.

Cheers,
Stephen
by izzy wizzy
Sat Jan 19, 2019 6:14 pm
Forum: Everyones Projects
Topic: Looking for recommendation for Phono Stage
Replies: 62
Views: 1536

Re: Looking for recommendation for Phono Stage

A question for Nick and Mark. You both use RC cathode bias on the first valve. I'm beginning to think battery bias has a bit of an issue and a steeper LF rolloff with RC biasing might help. In the model, 1000u looks a good value on the cathode. How did you both arrive at the values you used? And Nic...
by izzy wizzy
Sat Jan 19, 2019 6:10 pm
Forum: Everyones Projects
Topic: Looking for recommendation for Phono Stage
Replies: 62
Views: 1536

Re: Looking for recommendation for Phono Stage

I like the D3a 5687 combo and a previous phono I really liked had 6072 mu follower with 6SL7 up front I think. Anything I had with the 6072 sounded nice. The first pairing are a bit more direct which I like these days but because I like lowish Z EQ and Tx coupling that rules out the 6072 unless it's...
by izzy wizzy
Sat Jan 19, 2019 4:56 pm
Forum: Everyones Projects
Topic: Looking for recommendation for Phono Stage
Replies: 62
Views: 1536

Re: Looking for recommendation for Phono Stage

Nick wrote:
Sat Jan 19, 2019 3:26 pm
By all means, I have sold a few of them and I am rather pleased with the design itself so happy to see what people think.
It's got 3 of my favourite small signal valves in it. If I could get a 6072 into mine somewhere I would :)

Cheers,
Stephen
by izzy wizzy
Sat Jan 19, 2019 1:46 pm
Forum: Everyones Projects
Topic: Looking for recommendation for Phono Stage
Replies: 62
Views: 1536

Re: Looking for recommendation for Phono Stage

Depends how complex you want to be, this is the front end of the ref phono, it makes use of the d3a as a pentode with feedback via g2 to reduce and stabilise the gain, then the 5687 cathode follower will drive any riaa stage you want. That looks fantastic and creative. How would you feel if I added...
by izzy wizzy
Fri Jan 18, 2019 7:17 pm
Forum: Everyones Projects
Topic: Looking for recommendation for Phono Stage
Replies: 62
Views: 1536

Re: Looking for recommendation for Phono Stage

D3a are silly prices now. There are I think some Russian valves that are similar that might be worth a try at more sensible prices. Would have to look up what they are though.

E810f is another super hi gm valve. Not sure of their prices.

Cheers,
Stephen
by izzy wizzy
Thu Jan 17, 2019 8:25 pm
Forum: Everyones Projects
Topic: Looking for recommendation for Phono Stage
Replies: 62
Views: 1536

Re: Looking for recommendation for Phono Stage

RhythMick wrote:
Thu Jan 17, 2019 8:10 pm
Oh I must be tired. Choke, cap, resistor. Sigh. I'll get me coat.
Or too excited about skiing. Where are you going? I'm off to 3 valleys beginning Feb. Can't wait.

cheers,
Stephen
by izzy wizzy
Thu Jan 17, 2019 6:36 pm
Forum: Everyones Projects
Topic: Looking for recommendation for Phono Stage
Replies: 62
Views: 1536

Re: Looking for recommendation for Phono Stage

Also - valve considerations should really start with what I have plenty of stock of ... 26 - plenty of ST, some Globe 71A - short on the Globe ones which I prefer 45 - plenty of both globe and ST The above are used in the power amp. I also have the following which are interesting and would like to ...
by izzy wizzy
Thu Jan 17, 2019 6:22 pm
Forum: Everyones Projects
Topic: Looking for recommendation for Phono Stage
Replies: 62
Views: 1536

Re: Looking for recommendation for Phono Stage

RhythMick wrote:
Thu Jan 17, 2019 10:34 am
So would this be better ...

1) kept balanced through the gain and EQ stages
2) balanced gain stages with SE EQ (perhaps transformer coupling)
3) SE with balanced output

Gut feel says 1 or 2.
Mine is option 3 :)

cheers,
Stephen