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Old 21st August 2009, 10:09 PM   #1
tubo is offline tubo  Philippines
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Default 6v6 music machine build help!

hi folks!

i just finished building the poinz 6v6 music machine with the 6gk5 version! it is sounding really good and is marginally better than the 5965 version! evrything is great except for the bass which is thin and does not go as low as the 5965 version! im using a pair of hitachi 6gk5....

here are the questions!

1. did i wire the ccs correctly! i wired the -66v to one end of the 100ohm resistor which goes to the wiper of the 100ohm 18 turn trim pot then one end of the 100ohm resistor to pin G of the 10m45s... the pin no.1 of the trim pot is not connected.

pin no.3 of the trimpot is then wired to one end of the 255ohm resistor then the other end is wired to pin K of the 10m45s.

pin A of the 10m45s is wired to the 6gk5 cathodes..

2. poinz recommended a bias of 4.5ma. where should i take the measurement?
im getting about 9ma on Pin K of the 10m45s..which i assume is for both the 6gk5 cathode giving 4.5ma each.

3. im using an amveco 62045 with two 22v secondary wired in series to get 44v for the bias supply! instead of the amveco 62035 that is on the schematic> is the transformer adequate for the job?

pls help....thanks in advance


tubo
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Old 22nd August 2009, 03:26 AM   #2
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I've breadboarded (and I am presently building a final copy) Poinz' 6GK5/EL34 music machine and the IXYS is wired as you have stated exactly. I emailed Poinz about adjusting the 10M45S and he replied to adjust it for roughly 195V on the anodes of the 6GK5's, although YMMV since the B+ is lower on the 6V6 version (306V vs 320V).

I'm using the Amveco 70035 (PC mount version of the 62035) shared between both channels with no problems. It's 7 VA compared to 10 VA for the one you are using so it should be fine, since yours is more VA, and the grids should draw a mousefart's worth of current.

I have a pair of Hashimoto 8K OPT's that I bought off of the swap meet page (thanks Jazzbo!) that are slated for Poinz's 6V6 build.

Last edited by boywonder; 22nd August 2009 at 03:48 AM.
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Old 22nd August 2009, 04:03 AM   #3
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BoyWonder, I did not tell you to adjust for 195V on the anodes of the 6GK5s, but for 195V drop across the 43K (composite) plate load resistors of the 6GK5. You should listen more carefully.

Tubo, I see nothing in the description of your circuit that could cause it to be bass shy. If the parameters of the circuit are anywhere in the neighborhood of the schematic, you should have a bandwidth of +0 -1dB from 10Hz - 30KHz. Have you built the circuit exactly according to the schem? Brands of components I don't care, but values. If the coupling caps are substantially smaller than 0.33μF, this can thin out the bass. Otherwise, I would suspect your output transformer. What are you using?

Aloha Kakou,

Poinz
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Old 22nd August 2009, 01:50 PM   #4
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Quote:
Originally Posted by Poindexter View Post
BoyWonder, I did not tell you to adjust for 195V on the anodes of the 6GK5s
Aloha Kakou,
Poinz/Tubo, sorry about that, it's been a while since getting the breadboard amp together....It's slowly coming back to me now....On the EL34 version with a B+ of 320 volts and adjusting the 10M45S for 195V drop across the anode load R, gets 135V at the anodes at the operating point as marked on the schematic.

So on the 6V6 version, adjust the 10M45S to set the drop across plate load R's for 204V, yielding 102V at the operating point (306V-204V=102V) as marked on the schema. Sanity check 204V/43.1KR=4.7ma Hopefully I have this correct.

Last edited by boywonder; 22nd August 2009 at 02:11 PM.
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Old 22nd August 2009, 02:36 PM   #5
tubo is offline tubo  Philippines
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hi poinz,

the coupling caps are .33uf pios. and the opts are from the bogen db110 which i believe are 11ks......
the amp right now has the voltage doubler power supply on your website.

i just converted the the old 5965 version to accommodate the 6gk5 version.and replaced the old 9k opts with the bogens....

ill try putting back the old 9k opts and see what happens.

is pin K of the 10m45s the place to get the bias of 4.5ma....which in my case is 9ma?

thanks you!
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Old 22nd August 2009, 02:41 PM   #6
tubo is offline tubo  Philippines
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Quote:
Originally Posted by boywonder View Post
Poinz/Tubo, sorry about that, it's been a while since getting the breadboard amp together....It's slowly coming back to me now....On the EL34 version with a B+ of 320 volts and adjusting the 10M45S for 195V drop across the anode load R, gets 135V at the anodes at the operating point as marked on the schematic.

So on the 6V6 version, adjust the 10M45S to set the drop across plate load R's for 204V, yielding 102V at the operating point (306V-204V=102V) as marked on the schema. Sanity check 204V/43.1KR=4.7ma Hopefully I have this correct.
hi boywonder,

your calculations are correct and are exactly whats on the schematic!
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Old 22nd August 2009, 02:46 PM   #7
tubo is offline tubo  Philippines
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hi poinz,

although the bass is not that deep...but boy oh boy...........the amp is wonderful...wow! strings and acoustic guitars are so life like on my OB speakers.
highs are crystal clear and mids that is SET like..........but most of all it is very musical.

tubo
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Old 22nd August 2009, 02:53 PM   #8
Salas is offline Salas  Greece
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Since you mentioned OB speakers, can it be the amp creates less bass grunge than others so the open back speakers show more of their inability there? Just a scenario. If you have a mic and some measurement software like ARTA is good to check VS another amp so to see if there is actual lack of SPL down low with the Machine or not. Did you check for polarities also? There may be an inversion in a primary or secondary in one channel.
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Old 22nd August 2009, 03:17 PM   #9
tubo is offline tubo  Philippines
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hi salas,

i checked and doubled check everything on my speakers and the orientations are correct! im a relative newbie so i don't have any idea on how to measure speakers!

i also used some of my friends tube amps and the obs are not bass shy...i also tried my ta2020 amp and the results are still the same....ill try putting the old opts asap...

tubo
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Old 22nd August 2009, 03:35 PM   #10
Salas is offline Salas  Greece
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Pay attention to the wiring of the OPTs between channels, so it is same colors going to same points both for primary and secondary, before changing.
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