The Amp Garage

Hello- I am building a two channel amp (Bass, Normal) with a pair of KT-88 into a very good output transformer at back end. I wish to voice one channel for bass. In doing research the Peavey Alpha Bass preamp attracted my attention. I am considering using just the first two triodes and tone stack in...

Thanks Steve- Yes I have studied some of the Sunn amps, including the 200S. Since I have no playing experience, I sift through the comments I read on all the various forums and study the schematics to see if I see any hint of reasons for these comments. It seems I read too many unfavorable comments ...

Thank you Stevem- I appreciate the reply and comments. I am going into a head cab build that will have a very clean (near-HiFi) KT88 back end. I plan to have a bass voiced channel and a clean channel for pedals. I have two 12AX7 type tubes (4 triodes) for each channel's preamp. Have been looking for...

Hello- Studying bass amp circuits here for a good preamp section to put ahead of KT88 power section. Came across the Sound City B150 schematic (attached). I don't recall seeing a couple of features this amp has in any other amp. One feature is the configuration of the input stage V-1. The input trio...

Thank you, Steve-
I appreciate you taking the time to help. I use your Tremonator circuit in a lot of my builds. Thank you for that wonderful gift.
Byron

I have followed tubenits builds with great interest. Here is the schematic of 5879 with DC coupled C/F.

Martin- If you have time for a quick question - I have been studying the biasing of the 5879 as used in some of the amps on The Hoffman forum where it is the second stage. The loadline calculator I like to use has the EF-86 but not 5879. I have started a build, targeted to be used for bass and pedal...

Thank you Martin -
I really appreciate all the help you give, tnx!

Hello- In a recent octal build using 6SJ7 players commented the amp was a little too bassy even with bass pot all the way down. The amp used a parallel 6SL7 input stage driving Fender tone stack (as used in HRD ML-212) with 6SJ7 as second stage. There is a recent thread here where I described all th...

Hey Stevem-
Schematic is posted at beginning of this thread. I am using a CDE silver mica 470 pF cap.

One thing I forgot to mention -sorry- grounding the grid pin #2 of V-1A had no effect on the hum. I meant to include this to emphasize that the hum was coming from grid pin #7 of V-1B strictly.

I wanted to post this info as it may help others dealing with same issue - the issue was a low-level hum in speaker independent of control settings; hum level was acceptable to some players but I am not happy until I can achieve a dead quiet amp. I experienced this issue with a low-level hum pickup ...

I changed the cathode resistor from 910 ohms to 430 ohms and left the dropping resistor alone for this 6SN7 reverb driver, it is a 7.5K coming off of 415 v bus. At idle I measured 301 v on center tap of output transf. Showing 6.7 vdc difference between cathode and grid resistors. Looks to be drawing...

Martin- I cannot thank you enough for taking the time to help me here! This is exactly the info I was looking for. I have both Merlin Blencowe books and in the latest book he details how to draw load lines for push pull stages. I was struggling with trying to do it and sure needed this help. You are...

I meant to ask Mr. Steve (sluckey) - I have two unused 6SL7 triodes in this build. The input tube V-1 has only one triode in use, driving the tone stack. I did this deliberately in order to convert to a parallel input stage if desired. The other unused triode is in V-4, this tube is amplifying the s...