12GT5-guitar amp.

davorin · 26th April 2010, 07:58 PM

Small, (~30W) and not expensive amplifier, but with "brand name" tubes. (12GT5-RCA)

Sal Brisindi · 27th April 2010, 12:12 PM

Very nice job done on your Guitar amp.

Sal

firechief · 27th April 2010, 04:03 PM

davorin
Hi I see that you are getting away from the more conventional choices for guitar amp tubes, fun experiment! Have you tried using the effects send yet?
I wonder if coming off of the tone stack, and right out to the effects send is going to work well. Conventional wisdom usally says put a buffer just befor the send out. On the other hand it may work just fine. I dont want to rain on your parade, just an observation. Also is that a re-cycled chassis?

davorin · 27th April 2010, 06:11 PM

Yes, chassis is from some HF-selector (HI!). I am not satisfied with quality of current tube production, conventional audio NOS tubes are very expensive, so I use non-conventional cheep tubes from the end of tubes evolution for my projects.
Maximum total distortion of this amplifier at is almost enough for punk or heavy-metal, and some pedal-effects works good at input (all I try). Line(effect) in/out work good with tube-reverb(diy), but I did not try any other effect here(in this amp.).
Maximum power is ~40W (very loud with only 320V-DC!), but clean power is ~30W.
This tubes (total cost ~16$) will work good next 5-10 years (maybe much more!), and current production of tubes cant work good 2-3 year!
HV-BIAS transformer is from old Sharp-B&W TV, heater transformer is for halogen 12V-light, CAN-elko is new, but cheep (for old TV-repair!) and 2x560uF are also new and cheep (for repair computer PS).
All other parts are new, but total cost is only ~80$ for very good guitar amplifier.
Many other cheep TV-sweep tubes can work here, maybe all with Pa>18. (with small modification: socket, anode cap, heater voltage and small bias correction)(Pa~18W is very conservative ratings; only for CCS as deflection tube! All that tubes can work with Pa22-25W in push-pull audio amplifier!).
Input, drive and PS tubes are cheep Russian military "Long-Life, SQ", but conventional 12AX7/ECC83 will work fine as input tubes, and 12AT7/ECC81 or 6AQ7/ECC85 for driver and PS (and 12AV7, 5965 or E180CC too!).
I was experimenting with very expensive "Müllard", "Brimar" and "Philips" small tubes, but sound was not much better with them.

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27th April 2010, 12:12 PM	#2
Sal Brisindi diyAudio Member Join Date: Nov 2006	Very nice job done on your Guitar amp. Sal

27th April 2010, 04:03 PM	#3
firechief diyAudio Member Join Date: Sep 2008 Location: Near Seattle Wa	davorin Hi I see that you are getting away from the more conventional choices for guitar amp tubes, fun experiment! Have you tried using the effects send yet? I wonder if coming off of the tone stack, and right out to the effects send is going to work well. Conventional wisdom usally says put a buffer just befor the send out. On the other hand it may work just fine. I dont want to rain on your parade, just an observation. Also is that a re-cycled chassis?

27th April 2010, 06:11 PM	#4
davorin diyAudio Member Join Date: Aug 2005 Location: Zadar, Croatia	Yes, chassis is from some HF-selector (HI!). I am not satisfied with quality of current tube production, conventional audio NOS tubes are very expensive, so I use non-conventional cheep tubes from the end of tubes evolution for my projects. Maximum total distortion of this amplifier at is almost enough for punk or heavy-metal, and some pedal-effects works good at input (all I try). Line(effect) in/out work good with tube-reverb(diy), but I did not try any other effect here(in this amp.). Maximum power is ~40W (very loud with only 320V-DC!), but clean power is ~30W. This tubes (total cost ~16$) will work good next 5-10 years (maybe much more!), and current production of tubes cant work good 2-3 year! HV-BIAS transformer is from old Sharp-B&W TV, heater transformer is for halogen 12V-light, CAN-elko is new, but cheep (for old TV-repair!) and 2x560uF are also new and cheep (for repair computer PS). All other parts are new, but total cost is only ~80$ for very good guitar amplifier. Many other cheep TV-sweep tubes can work here, maybe all with Pa>18. (with small modification: socket, anode cap, heater voltage and small bias correction)(Pa~18W is very conservative ratings; only for CCS as deflection tube! All that tubes can work with Pa22-25W in push-pull audio amplifier!). Input, drive and PS tubes are cheep Russian military "Long-Life, SQ", but conventional 12AX7/ECC83 will work fine as input tubes, and 12AT7/ECC81 or 6AQ7/ECC85 for driver and PS (and 12AV7, 5965 or E180CC too!). I was experimenting with very expensive "Müllard", "Brimar" and "Philips" small tubes, but sound was not much better with them.

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