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
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
Attachments
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.
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.
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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
AudioTropic
I would like to comment to the administrators on the handling of images in the new forum format. It sux. Big time.
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
AudioTropic
I would like to comment to the administrators on the handling of images in the new forum format. It sux. Big time.
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.
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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!
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!
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.
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
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
Hope this is not OT but can anyone explain the diodes in the screen feeds?
I have tried searching the Forum but without success. Is it to prevent any negative excursions at the OPT tapping from lowering the screen voltage? Perhaps a wild guess, I can understand the resistors limiting the screen current.
Les
(I know at my age I should know but there is always something to learn as the turns go slowly on the coil with the passing of time
)
P.S. Do they have to be 2 Amp rated!
I have tried searching the Forum but without success. Is it to prevent any negative excursions at the OPT tapping from lowering the screen voltage? Perhaps a wild guess, I can understand the resistors limiting the screen current.
Les
(I know at my age I should know but there is always something to learn as the turns go slowly on the coil with the passing of time
)P.S. Do they have to be 2 Amp rated!
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The diodes in the screen feeds give a little more drop to the screens under low current conditions, but especially they insure that no screen signal gets on the plate. The idea in a triode-connected pentode is to 'disappear' the screen. It should not be there at all.
I learned this trick from Al Marcy, and when I tried it I thought the sound a bit clearer. For a dime, why not? Use schottky barrier diodes, they are the quietest, by all reports.
Aloha,
Poinz
AudioTropic
I learned this trick from Al Marcy, and when I tried it I thought the sound a bit clearer. For a dime, why not? Use schottky barrier diodes, they are the quietest, by all reports.
Aloha,
Poinz
AudioTropic
Many thanks Poinz for the prompt reply. In my haste to find a suitable modification for my EL34 amplifier output stage, I did not catch on that the 6V6 circuit was triode connected doh! (63 and the grey matter is turning to stone!)
As you can see from the attached schematic, my amp has no screen resistors at all!
I was going to install something like 1K at 5W to each screen and the diode in your circuit caught my eye. I guess it would have no value in my particular case unless I was going to try connecting the EL34's in triode mode. I can now see how the diode keeps the screen lower than the anode as you explained and is certainly worth remembering for future reference. Many thanks, Les
As you can see from the attached schematic, my amp has no screen resistors at all!
I was going to install something like 1K at 5W to each screen and the diode in your circuit caught my eye. I guess it would have no value in my particular case unless I was going to try connecting the EL34's in triode mode. I can now see how the diode keeps the screen lower than the anode as you explained and is certainly worth remembering for future reference. Many thanks, Les
Attachments
thanks for all the help guys!fixed the problem...the machine is the best amplifier i've ever heard..heard a few dht sets and have spare se el84 amps.....there's just no comparison....though those amps really sound good i just prefer the 6v6 machine for its uncanny musicality and see through transparency.....great job poinz....
im having problems with my amp again when i took the 100k volume pot out and replaced it with 100k ressistor from grid to ground to convert it to a power amp so i would be able to use the lightspeed preamp.
1. there is a scratchy sound when i turn the volume pot of the lightspeed pre.
2. is it possible that the 6gk5 suffers from grid current?do i need to insert a cap between the pot and the grid?
pls help thanks
1. there is a scratchy sound when i turn the volume pot of the lightspeed pre.
2. is it possible that the 6gk5 suffers from grid current?do i need to insert a cap between the pot and the grid?
pls help thanks
I would suspect the pot. The 6GK5s are way far from grid current at their quiescent operating point, and the effect of grid current would rather be to strain the sound of the source component if it is not cap-coupled on its output.
Why did you want to insert an additional source of trouble into the component path? The lightspeed is just a volume control; if you think it fabulously famously superior to your volume pot, why not put it in the Machine in replacement? Save yourself some connections.
Aloha,
Poinz
AudioTropic
Why did you want to insert an additional source of trouble into the component path? The lightspeed is just a volume control; if you think it fabulously famously superior to your volume pot, why not put it in the Machine in replacement? Save yourself some connections.
Aloha,
Poinz
AudioTropic
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