grounded grid

[joehpj]

Is there any benefit to raise rail voltage from 400V to 450V?

Tubes are said to be more linear when the voltages are higher. Though 400V seems enough.

Edited August 9, 2016 by joehpj

[UFN]

Been slowly plugging away at a pair of GG-boards for a while now and I'm getting ready to order the last parts (I hope...). Two questions though:

Kevin quoted 16W dissipation for the 10m90s a few pages back, but is that per board or per device (i.e. 32W per board)? I'm planning to use a 450V PSU, probably a BH-PSU since I have a board left over and I'm not sure I can fit a Carbon PSU in the intended chassis anyway.

Also, once the amp boards are done is there a way to verify that all voltages are OK before I plug in tubes? (or better still, before I even buy the tubes )

 

//UFN

[sorenb]

@UFN depends on the current setting and rails ....400V rails and 20mA will give you 16W for two 10m90 ...upping to 450V will give you 18W ...

Load the PSU with 5-10k power resistors

I have some cheapo EL34s for testing

[jose]

EL34? Is not the 6S4A better choice?  Sorry I´m mistake

 

Edited December 11, 2016 by jose

[UFN]

Thanks @sorenb, looks like my math was correct. I built a PSU dummyload a while ago, so that's not a problem.

If I have to start looking around for cheap EL34s for testing then so be it, but I was hoping I could maybe put my collection of Fluke meters to use instead 

[sorenb]

7 minutes ago, UFN said:

Thanks @sorenb, looks like my math was correct. I built a PSU dummyload a while ago, so that's not a problem.

If I have to start looking around for cheap EL34s for testing then so be it, but I was hoping I could maybe put my collection of Fluke meters to use instead 

not worth the hassle ...

[mwl168]

I bought a matched quad of NOS Winged C Svetlana EL34 from Upscale Audio in preparation for the Grounded Grid build. The 4 tubes have these spec's on their boxes:

Tube 1: Bias 40.8, Transconductance 5.80, G2 mA 7.07 

Tube 2: Bias 40.9, Transconductance 6.07, G2 mA 7.25 

Tube 3: Bias 40.9, Transconductance 6.07, G2 mA 6.70 

Tube 4: Bias 40.8, Transconductance 6.18, G2 mA 7.02

So based on the Grounded Grid circuit, how should I pair them up? Would the same pairing work for the Blue Hawaii?

Thanks! 

[fat joey]

@JoaMat Is it possible to use GGDHT as the dirver board plus the nanotube output board?

 

@kevin gilmore I've read that solid state amps including solid state electrostatics amps has their lowest distortion only at about 80% of their max output level (THD+N vs power level graph)

but when we turn the volume to let them achieve 80% of max output level our ears are already bleeding

Does that mean GGDHT running at 20ma has lower distortion than KGSSHV Carbon running at 20ma at normal listening level (ie. small level)?

[chinsettawong]

I've been trying to source 0.1uF 1KV capacitors which will fit into the board, but can't seem to find them.  Can someone please help me with the part number and where to buy them?

 

 

[G600]

Those are fine PHE426PB6100JR06

From Carbon BOM

[chinsettawong]

Oh, that was fast.  Thanks a lot.

[jose]

Yes, PHE426PB6100JR06 are OK

I used Carbon BOM to.

[xianghao]

for GG

[joehpj]

Just like Carbon we built. Same box, same PS.

Relay=120s. Separated filament transformer.

 

 

 

[Pars]

Looks really good. I like the case(s)... custom? Or off the shelf? Nice clean look.

[jose]

Please, What kind of resistor do you use for grid?

I used a KOA metal film (10K, 1 / 2w) but I can see that you used a different type (Carbon maybe???) . I'm in time to be able to change them and I would like be sure before pluging my GG.

[bbest]

Nice looking assembly! All components fits on their places. Only volume control raises the question. It is EIZZ and there is long wires to it through the whole case. Does GG deserved this Chinese volume control ...

[joehpj]

13 hours ago, Pars said:

Looks really good. I like the case(s)... custom? Or off the shelf? Nice clean look.

Semi-customized. The shape of front plate, depth, height, and heatsink was fixed. Others were customized.

11 hours ago, jose said:

Please, What kind of resistor do you use for grid?

I used a KOA metal film (10K, 1 / 2w) but I can see that you used a different type (Carbon maybe???) . I'm in time to be able to change them and I would like be sure before pluging my GG.

If you use my BOM, that would be 10k/.5w as you used. A experienced builder told me grid resistors were super hot because it was connected to the internal structure of tube. I later changed to 470R/3w, just because I have them in stock.  KG said the value doesn't really matter. T2 used 20k. BH used 470R.

4 hours ago, bbest said:

Nice looking assembly! All components fits on their places. Only volume control raises the question. It is EIZZ and there is long wires to it through the whole case. Does GG deserved this Chinese volume control ...

Those were not EIZZ. Those were indeed from China. Building quality was good enough for the price. No issues like pop or clicking . There weren't much choice for stepped VR that were cased and no clicking. It has more steps in low volume area than DACT. Khozmos clicks. Goldpoint is expensive. I've bought over 10 of these. 

For long wires, as you could see, there's no place for extension rod. Even I could move the amp boards a little bit, it would still need to redesign the back plate that means I have to throw away the whole batch. The wires were shielded and power supply were in another box. No worries. 

Edited March 19, 2017 by joehpj

[jose]

Thanks!

[bbest]

1 hour ago, joehpj said:

Those were not EIZZ. Those were indeed from China. Building quality was good enough for the price. No issues like pop or clicking . There weren't much choice for stepped VR that were cased and no clicking. It has more steps in low volume area than DACT. Khozmos clicks. Goldpoint is expensive. I've bought over 10 of these. 

I thought it was something like this http://www.eizz.cn/S24T-AMRS100K-700.html .

And the main question: as in fairy story ... someone whisper from the curves ... how GG sounds ... how GG sounds ...

[joehpj]

I think the final casing of the VR was done by same factory. Mine uses dale resistors. Or maybe they are really the same thing. I don't know (and don't care). I only care about the performance which was pretty nice for the asking price. I will have a chance to compare it with DACT. Will report if the difference is significant.

I haven't heard GG now. It has been back ordered for months.

According to the builder, both carbon and GG are TOTL amps. Overall performance are in the same league. Compared to carbon, GG has slightly recessed bass and tremble extension but sweeter mid and vocal. I've heard some people said 009 w/ carbon were too "clean". For those who think so, GG might be a better choice.

Edited March 19, 2017 by joehpj

[jose]

I want to turn on my GG now!!!!!

Ok, I have 15K/2W on my stock but I'm not sure if 2W is an adequate value. I have other values but only with 5W and the size is very large for use here.

[JoaMat]

Shouldn't 1/2 watt be enough?

[kevin gilmore]

where did you get the delay board?

 

[G600]

Is there any need of a a HV delay ?