• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

SE Triode amp for a newbie

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If DHT is not mandatory, costs can be held down by using a triode wired multigrid tube. 6AQ5s are inexpensive and 12AQ5s even more inexpensive, but not as plentiful. Either 'AQ5 variant will do fine driven by 1/2 of a 5965. Hammond 125ESE O/P trafos are about as low cost as can be, while offering OK performance.

SS B+ rectification by UF4007 diodes combined with a low cost snubber network is quite good sounding and will cost less than vacuum rectification.
 
Friends,
Thank all of you that have tried to give me a hand. What I've got in this moment is a pair of Russian made 6C33C. The wonderamp that I'll build around these tubes should make a pair of speakers made based on Fostex FE 206E drivers following the producer's cabinet design.
Again advises, suggestions, schematics etc. needed.
Thanks a lot and best regards,
TTA
 
Hi, I have a SET amp with 6C33C, it is designed by Dakesue who "discovered" the 6C33C and started to import it as EC33C to Japan. The circuit diagram can be found here: http://www.bonavolta.ch/hobby/en/audio/6c33c_5.htm

It is a relatively simple design but the sound is very good. My own amp that I bought as a kit by Dakesue use a Tango output transformer, which is of very high quality. As you are probably aware of the quality of the output transformer is very important in a tube amp, even more so in a SET so I would suggest to try finding something at least similar quality level.

Regards Hans
 
tubetvr schematic suggestion

Good schematic design. This should be a great sounding amp with careful attention to some components.

I would exchange the 12BH7 with a Sylvania 6SN7GT, 6SN7W or 6SN7GTA with 'T' shape plates. Same circuit components are ok. Just hard to beat those common Sylvania 6SN7s.

For a 12AX7, Mullard tall plate such as 10M series would be a great tube. 1950s era CBS 12AX7s are also a winner.

Use motor oil run caps or a polyproplyene type such as Solen in the amp & power supply. The huge capacitance of 400uF at the 6C33C PS filter is necessary- just use four 100uF motor oil caps in parallel.

I would also use a Mullard EZ80 rectifier tube in place of SS bridge at B2 supply.

UF4007 solid-state diodes are best at 6C33C position.

The .22uf @ 630 volts coupling cap at the 12BH7 (now a 6SN7) should be of best quality. Russian teflon type are good.

My 2 cents.
 
tta60 said:
Thank Hans and amperex.
As the next step of my project, I intend to buy a pair of James output transformers ... model 6130HS (350mA, 600§Ù, 30W, 12Hz~100KHz-2dB). ...
TTA


No experience with the 6130HS but I have used the 6123HS in a pair of SE KT88 monoblocks and they sound great. The fit and finish is superb and at almost the same price as a Hammond they are a great value. Overall I've heard nothing but good things about James OPTs.
 
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You will need 600 ohm output transformers, several vendors like ASL in HK make opts that would be suitable for relatively "small" money.

The James transformers imho are quite good, although I have experience of this specific model.

Look for a design using cathode bias, and with B+ delay to allow filaments to warm up fully before plate voltage is applied..

Google 6C33 se amplifier and see what comes up. You should be able to get almost 15Wrms out of a single tube in SE.

Driver stage design will depend on how much power you want to get out of this amplifier.

Avoid OTL designs unless you have a lot of electronics experience.
 
Please comment the attached schema.
 

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They both appear to be reasonable designs, the 6SL7 based design does not use global feedback, which to me is an advantage.

Both the 6J5 and 6SL7 are good sounding tubes.

The 6J5 version seems to be configured for lots of voltage gain, the 6SL7 is not, but will still have a full power sensitivity of less than 1Vrms I would guess.

I terms of reliability issues I am not sure there is a significant difference.

In terms of driving the 6C33 the 6SL7 CF will have lower source impedance than the 6J5, but due the relatively low operating current will probably have less large signal power bandwidth than the 6J5 which can be operated at much higher currents.
 
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