audio-talk

Hi Nick,

I'm not getting all of this, so I'll ask a silly question if that's OK?

What's the relationship between the triode's load and the load the pentode sees? For a phono like Simon's the load needs to be fixed as the pentode load and RIAA Z are matched.

cheers,

-- Andrew

Well, I'm no expert but what I looked for, as Nick said, was a combo of quiteness and a good impedance curve. I started, by having a search around to see what others recommended and ran into the one used on the Bottlehead C4S, the HLMP-6000. This is now made by Avago, ex-Agilent semiconductors and b...

Hi Simon,

Yes, I would suspect LEDs might be better. What's the rough cathode voltage with the diodes in?

cheers,

-- Andrew

Hi Shaun, The 6C45 should give you about 12-13db after RIAA eq, so you need a second stage that gives about 27db for the magic 40db. The C3g should give a gain of 15-16db, after RIAA eq, so you'd need about 24db; there really isn't much between the two gain-wise, about 3db. Simon might want to chip ...

Hi Shaun, Leave the RIAA as is, the 4k7 needs to be in series with the signal so take the signal off the 6C45 into the 4k7 the other end which goes to the start of the RIAA (see attached) You might find 4k7 is a tad high, 4k6 might be better, (edit more cross checking start a 4k1 and work your way u...

Hi Simon, Yes, sounds like the same TX, mine was labelled 0v-9v and 0v-9v, on separate windings, that was what attracted me, my plan was, by joining the lower 9v with the upper 0v I was going to make a 9v-0v-9v or put it another way a 9v center tap. That does give 18volts but the two windings are in...

We've been tweaking Simon's C3g input stage, but the RIAA seems pretty sorted. Simon would like more gain for his set up, so I have suggested using an LED for the C3g bias, thus eliminating the local feedback of the resistive bias and increasing gain accordingly. Its up to you what you prefer, knowi...

Simon and I have mostly been mucky around with the C3g on his phono to get more gain. The rest of Simon's RIAA + Aikido will be a good enough starter for you if you want to go down this road. Simon, thanks for posting the link. One thing Shaun, most folks seem to think that the ratio between Zout of...

OK doing some quickie sums... The Rp of the 6C45 is ~1100R, with a bypassed cathode, or when using battery bias. This will give a Zout of Rp || Rload or 1100 || 10000, about 990R so it you want you could use the 6C45 loaded with a 10K 300v B+ and Nicad battery, as per Jerermy's circuit. Now chop the...

Hi Shaun I haven't tried a 6C45pi as a phono front end, but I do have a design I did with James D for a 6C45 cascode, this has bags of drive so can deal with awful loads like say the 600R LCR phono, it be would instead of the E810F in something liks Nick's. I am now of the opinion that a pentode is ...

OK overheating solid state parts are not good, so I ordered just about the biggest heatsinks that Rapid had, tv40. I fitted them just a few days ago and have been away. In spare moment, now were back, and when the kids were otherwise occupied. I managed to get 225v steady through a 5k load, so 45mA,...

I meant to ask you both, what you're using the Tent heaters for 300B or GM70 and if they are clearly better for the 300B than an LM317-based current source?

cheers,

-- Andrew

A pity Steve, but on the positive side you now have a working amp, so when you are able to get some new valves you'll have cracked it and will have a beautiful looking and sounding amp. If I were to build a push pull then an OTL would have to be it. A 6C33C using a cricuit based upon Bruce's could b...

Oh that's a shame, to loose a pair of valves having got so far.

Can you run it with two pair of the best survivors and change the heaters?

cheers,

-- Andrew

I see in Bruce's patent.

http://patft.uspto.gov/netacgi/nph-Pars ... PN/5604461

He's talk's about using a 6C33C as an output device, hmmmmm

-- Andrew