Hi,
Would like advice before buying tubes. I am about to buy 4 6AN8A pairs (2 pairs/brand) and asked triode matching datas from the dealer.
Circuit uses a pair of 6AN8s for gain/phase splitting and has bias adjustment for each channel as well as test points and trimmer pots for DC and AC balance of each channel.
Is triode matching important in these conditions?
Here's the test data from the Zenith, Rogers valves.
Data is Triode / Pentode, in uMhos, measured/tested on Stark 9-66 Mutual Transconductance test set.
Rogers
4900/4100
4900/4700
4650/4200
4850/4250
4250/3800
3400/4100
Zenith (USA)
3400/3600
4500/3800
5000/4100
3900/3700
Zenith (UK)
5100/4100
5000/4050
3900/3650
4550/3850
3400/3950
As you can see, "matching" sets of triode-pentode tubes in brands is difficult.
Thanks for any and all help.
HugoR
Would like advice before buying tubes. I am about to buy 4 6AN8A pairs (2 pairs/brand) and asked triode matching datas from the dealer.
Circuit uses a pair of 6AN8s for gain/phase splitting and has bias adjustment for each channel as well as test points and trimmer pots for DC and AC balance of each channel.
Is triode matching important in these conditions?
Here's the test data from the Zenith, Rogers valves.
Data is Triode / Pentode, in uMhos, measured/tested on Stark 9-66 Mutual Transconductance test set.
Rogers
4900/4100
4900/4700
4650/4200
4850/4250
4250/3800
3400/4100
Zenith (USA)
3400/3600
4500/3800
5000/4100
3900/3700
Zenith (UK)
5100/4100
5000/4050
3900/3650
4550/3850
3400/3950
As you can see, "matching" sets of triode-pentode tubes in brands is difficult.
Thanks for any and all help.
HugoR
The circuit is a three-stage feedback amp employing a common 6AN8 triodepentode as the voltage amp and phase inverter. The input signal is applied to the 6AN8 penthode grid, after being coupled through a 15000 ohm isolating resistor. The penthode acts as a voltage amp and DC-couples the signal to the grid of the triode phase inverter.
HugoR
HugoR
SY,
I am sorry. Image was too big!
The link of the complete schema is bellow... Hope it will work.
I appreciate your help.
Hugor
I am sorry. Image was too big!
The link of the complete schema is bellow... Hope it will work.
I appreciate your help.
Hugor
An externally hosted image should be here but it was not working when we last tested it.
Retrying with the link
Don't know how to handle IMG If link doesn't work. Sorry.
Thanks alot.
H
An externally hosted image should be here but it was not working when we last tested it.
.Don't know how to handle IMG If link doesn't work. Sorry.
Thanks alot.
H
Hi Hugor,
SY is right, mostly does not matter much. There is feedback too so that will reduce the differences. I would match output sections.
I see there is a way of balancing the AC drive to the outputs. Won't matter much. What brand of 7591's are you going to use?
-Chris
SY is right, mostly does not matter much. There is feedback too so that will reduce the differences. I would match output sections.
I see there is a way of balancing the AC drive to the outputs. Won't matter much. What brand of 7591's are you going to use?
-Chris
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