4.30.2003
This guy has some really cool old amps to sell/trade - I wonder if he'd be interested in any of my stuff?
Dating Amplifiers by Potentiometers and Speakers
The best way to date an individual Gibson amplifier is to look for the EIA source-date codes stamped or printed on potentiometers. This code also appears on speakers and other components.
The best way to date an individual Gibson amplifier is to look for the EIA source-date codes stamped or printed on potentiometers. This code also appears on speakers and other components.
4.29.2003
Mission Amps
Bruce Collins of Mission Amps, coordinated a project to build a tweed Deluxe 5E3 style guitar amp. The goal of the project was to build high quality, great-sounding clones of the immensely popular narrow panel Fender tweed Deluxe 5E3 circuit at a significant savings over boutique prices. This model is ideally suited for both the beginner and advanced builder due to its relative ease of construction and killer tone.
He received about 50 responses from people interested in joining the project, many for whom, including myself, this would be their first homebrew amp. Since he is a custom amp builder and repairman with a relationship with parts suppliers, he offered to gather the chassis, transformers, and all other electronic parts in the form of a kit. Project members were on their own as to cabinet and speaker options. He also supplied a high quality schematic, color-coded layout and help via email as needed.
Bruce Collins of Mission Amps, coordinated a project to build a tweed Deluxe 5E3 style guitar amp. The goal of the project was to build high quality, great-sounding clones of the immensely popular narrow panel Fender tweed Deluxe 5E3 circuit at a significant savings over boutique prices. This model is ideally suited for both the beginner and advanced builder due to its relative ease of construction and killer tone.
He received about 50 responses from people interested in joining the project, many for whom, including myself, this would be their first homebrew amp. Since he is a custom amp builder and repairman with a relationship with parts suppliers, he offered to gather the chassis, transformers, and all other electronic parts in the form of a kit. Project members were on their own as to cabinet and speaker options. He also supplied a high quality schematic, color-coded layout and help via email as needed.
4.28.2003
4.27.2003
True "Secret" of Amp Tone - EQ>Dist and Power Attenuators
Boozehound Labs Tube HiFi Primer - I think I've posted this link before but I like it
This guy sells little amps based on the 5F1 for $800 - $1200
Vintage Tube Services has a cool page with lots of interesting info including:
Histories of Tube Companies
The RCA pages have lots of pictures of the factory back in the day
Histories of Tube Companies
The RCA pages have lots of pictures of the factory back in the day
4.26.2003
4.23.2003
DIY guitar tube amp-related information, as well as a selection of components and tube amp parts for sale or trade.
4.22.2003
4.20.2003
4.19.2003
Motorboating is mostly likely caused by
1. insufficient decoupling between stages
2. insufficient capacitance or bad caps in the B+ filters
1. insufficient decoupling between stages
2. insufficient capacitance or bad caps in the B+ filters
...Motorboating is usually the result of an insufficient power supply bipass - so your gain stages talk to each other through the supply rail. So look at the supply distibution, making sure gain stages are isolated from each other...
...I would also replace the 0.047 uf/400 coupling caps (2 of them) w/orange drop 715/716P caps and get some silver mylars for other 2 coupling caps...
Possible cure for my motorboating problem in the Magnavox: Resistance-Coupled Amplifiers (from RCA manual)
I'm still having motorboating issues with the Magnavox when I have all 4 6V6 tubes installed. It seems that if I swap the tubes around it sometimes goes away for a while. Sometimes it occurs even with only 2 tubes installed. The 4 new 6V6GT's I got are marked with their test values, so I have been trying to match pairs with close values in each channel. I thought I had it sorted, listened with no problems for an hour or so, then turned off the amp, then turned it back on and it started motorboating immediately.
So I got it on the bench and bypassed the power supply filter caps with new individual capacitors, since several folks on audioasylum.comsaid it was probably the problem. Still motorboats. Argh. Hopefully implementing resistance coupling will help.
I'm still having motorboating issues with the Magnavox when I have all 4 6V6 tubes installed. It seems that if I swap the tubes around it sometimes goes away for a while. Sometimes it occurs even with only 2 tubes installed. The 4 new 6V6GT's I got are marked with their test values, so I have been trying to match pairs with close values in each channel. I thought I had it sorted, listened with no problems for an hour or so, then turned off the amp, then turned it back on and it started motorboating immediately.
So I got it on the bench and bypassed the power supply filter caps with new individual capacitors, since several folks on audioasylum.comsaid it was probably the problem. Still motorboats. Argh. Hopefully implementing resistance coupling will help.
4.18.2003
In Reply to: Tube Amp, Preamp, or both? posted by Twodawgs on June 16, 2001 at 10:51:05:
"[Tube guys] look at the audio system in a different way. The source, preamp(do we need it ?), and power amp pre-driver should be consider[sic] as one section that should be as neutral and transparent as possible. This section is where low signal is tranferred. Any deiviation or colouration will be greatly magnified by output section. The power amp and speaker combination is considered as another section since there is a lot more complicated interaction between power amp and speaker. This section is where we choose our personal preference."
Paul Lam
P.L.C.Lam Consulting Inc.
"[Tube guys] look at the audio system in a different way. The source, preamp(do we need it ?), and power amp pre-driver should be consider[sic] as one section that should be as neutral and transparent as possible. This section is where low signal is tranferred. Any deiviation or colouration will be greatly magnified by output section. The power amp and speaker combination is considered as another section since there is a lot more complicated interaction between power amp and speaker. This section is where we choose our personal preference."
Paul Lam
P.L.C.Lam Consulting Inc.
4.17.2003
Tonight I installed a lighted switch into the Magnavox, as well as a fuse holder. It has a 1 amp fuse in it and so far so good, although it''s doing that motorboating thing again unless I pull one of the power tubes. It didn't do it when I had it hooked up as 16 ohms (2 8 ohm speakers in series per channel). Moved the Foreplay and the Mag into my workshop so I can play with it with different speaker configs. I'm not convinced the Magnavox is truly a stereo unit - I saw a post where someone mentioned the they made a version that had one channel for low frequencies and one for high frequencies, like for a TV, in mono. It may explain why it seems muted... but damn if it's mono it sounds gooood! I need to test it with an obviously stereo CD. if it is a mono unit I'll make it into a sweet-sounding guitar amp.
4.16.2003
So, I built my Foreplay pre-amp, and it sounded great with the Magnavox, but with the ST-35 it has WAY too much gain, and I can hear a lot of buzz and hum. It has been suggested:
What you will need to do to start with is lower the overall gain of the FP. There are wads of post on this subject in the archives. and VoltSecond's page in 'Loose Parts' has an excellent section on attenuators. The quickest, cheapest, easiest fix is the Simple Shunt.
Once you get the gain where you like it, you may need to tackle some other issues, such as grounding and noise reduction, but geting the "gain chain" right is the logical first step, IMO.
Jim
Simplified instructions for Simple Shunt for Simple guys like me:
1. Using a 100K resistor instead of a wire, connect right tab of left L-Pad to left inner contact of selector switch.
2. Connect center tab of left L-Pad to A-2.
3. Connect left tab of L-Pad to terminal 14.
4. Using a wire, connect center tab of left L-pad to Right tab of left L-pad.
more:
The Easy Way to make the Stock Foreplay Volume Control into a Shunt Mode Volume Control:
1. Remove the wire connection from the top (right terminal) of the volume pot to the selector switch at the volume pot end.
2. Insert a resistor between the volume pot top (right terminal) and the loose wire going to the selector switch.
This resistor is typically 47.0K (3.3 dB minimum attenuation) to 200K (9.5 dB minimum attenuation) metal film when using a 100K volume pot.
3. Run a short wire from the wiper (middle terminal) to the top (right terminal) of the volume pot.
Using this method (Shunt Mode Easy Way) will reduce the any noise you get when you adjust the volume when compared to (Shunt Mode Pot Typical). I have been told it sounds better this way too. I didn't notice too much of a change with the stock Foreplay pots, but I didn't have a hot rodded Paramour to drive my speakers at that time either.
From VoltSecond's web page
http://www.triodeel.com/tlinks.htm
4.15.2003
Voight pipe variants, zigmahornet - in German but good plans
4.14.2003
Thordarson Manuals and Schematics collection for $11.95
Here's some Thordarson data that's free: Thordarson Manuals (top of page)
Here's some Thordarson data that's free: Thordarson Manuals (top of page)
4.13.2003
4.11.2003
Desktop Reference of Hip Vintage Guitar Amps
I'm reading this book right now. It's pretty good at explaining stuff, but it is very dense, and the technical level changes a lot. I think he was trying to save space for all the schematics people have been bugging him for for years.
I'm reading this book right now. It's pretty good at explaining stuff, but it is very dense, and the technical level changes a lot. I think he was trying to save space for all the schematics people have been bugging him for for years.
Bitco Electronics
4 Hudson Street
Malden MA
David Greenberg bitco@tiac.net
781 322 5560
FAX 781 322 0601
www.bitcoelectronics.com
This place is right near me, and the website looked promising, so I sent them an e-mail about getting some training.
4 Hudson Street
Malden MA
David Greenberg bitco@tiac.net
781 322 5560
FAX 781 322 0601
www.bitcoelectronics.com
This place is right near me, and the website looked promising, so I sent them an e-mail about getting some training.
Circle Stereo in Austin, specializing in fixing old tube stuff
4.10.2003
4.08.2003
This tube database site has the tube data sheets from original tube manufacturers!
4.07.2003
Resistor value calculator for constructing attenuators
Ladder Type:
http://homepages.tcp.co.uk/~nroberts/atten.html
Shunt Type:
http://homepages.tcp.co.uk/~nroberts/shunt.html
Ladder Type:
http://homepages.tcp.co.uk/~nroberts/atten.html
Shunt Type:
http://homepages.tcp.co.uk/~nroberts/shunt.html
Some folks swear by cryogenically freezing their audio gear to improve it's sound. Sounds like a big waste of money to me, but here's the argument for Cryo